As filed with the Securities and Exchange Commission on January 31, 2024

No. 333-     

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

APA CORPORATION

(Exact name of registrant as specified in its charter)

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

(713) 296-6000

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

P. Anthony Lannie

Executive Vice President and General Counsel

APA Corporation

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

(713) 296-6000

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies of all communications, including communications sent to agent for service, should be sent to:

Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable after this Registration Statement is declared effective and all other conditions to the proposed merger contemplated by the Agreement and Plan of Merger dated as of January 3, 2024, described in the joint proxy statement/prospectus contained herein, have been satisfied or waived.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this joint proxy statement/prospectus is not complete and may be changed. A registration statement relating to the securities described in this joint proxy statement/prospectus has been filed with the U.S. Securities and Exchange Commission. These securities may not be issued until the registration statement filed with the U.S. Securities and Exchange Commission is effective. This joint proxy statement/prospectus does not constitute an offer to sell or the solicitation of offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

PRELIMINARY—SUBJECT TO COMPLETION, DATED JANUARY 31, 2024

MERGER PROPOSAL—YOUR VOTE IS VERY IMPORTANT

Dear Stockholders of APA Corporation and Callon Petroleum Company:

On behalf of the boards of directors of APA Corporation (“APA”) and Callon Petroleum Company (“Callon”), we are pleased to enclose the accompanying joint proxy statement/prospectus relating to the merger of APA and Callon. We are requesting that you take certain actions as an APA or Callon stockholder.

On January 3, 2024, APA, Astro Comet Merger Sub Corp., a Delaware corporation and wholly owned, direct subsidiary of APA (“Merger Sub”), and Callon entered into an Agreement and Plan of Merger (as amended from time to time, the “Merger Agreement”), providing for the merger of Merger Sub with and into Callon, with Callon surviving the merger (the “merger”) as a wholly owned, direct subsidiary of APA. In the merger, Callon stockholders will be entitled to receive, without interest, in exchange for each share of Callon common stock, par value $0.01 per share (“Callon Common Stock”), owned by them immediately prior to such merger, 1.0425 shares of APA common stock, par value $0.625 per share (“APA Common Stock”), with cash paid in lieu of the issuance of any fractional shares, which we refer to collectively as the “merger consideration.”

APA and Callon will each hold special meetings of their respective stockholders in connection with the proposed merger (respectively, the “APA Special Meeting” and the “Callon Special Meeting”).

At the APA Special Meeting, the holders of APA Common Stock (the “APA stockholders”) will be asked to vote on proposals to (i) approve the issuance of shares of APA Common Stock to the holders of Callon Common Stock (the “Callon stockholders”) in connection with the merger pursuant to the terms of the Merger Agreement (the “Stock Issuance Proposal”) and (ii) approve the adjournment of the APA Special Meeting to solicit additional proxies if there are not sufficient votes cast at the APA Special Meeting to approve the Stock Issuance Proposal (the “APA Adjournment Proposal”). Assuming a quorum is present at the APA Special Meeting, approval of the Stock Issuance Proposal requires the affirmative vote of the holders of a majority of the shares of APA Common Stock properly cast on such proposal. Approval of the APA Adjournment Proposal requires the affirmative vote of the holders of a majority of the shares of APA Common Stock properly cast on such proposal.

The APA Special Meeting will be held virtually at [    ], on [    ], 2024, at [    ] [a.m./p.m.], Central Time. The board of directors of APA (the “APA Board”) unanimously recommends that APA stockholders vote “FOR” the Stock Issuance Proposal and “FOR” the APA Adjournment Proposal.

At the Callon Special Meeting, the Callon stockholders will be asked to vote on proposals to (i) adopt the Merger Agreement (the “Merger Proposal”), (ii) approve, on a non-binding advisory basis, the compensation that may be paid or become payable to Callon’s named executive officers that is based on or otherwise relates to the merger (the “Advisory Compensation Proposal”), and (iii) approve the adjournment of the Callon Special Meeting to solicit additional proxies if there are not sufficient votes cast at the Callon Special Meeting to approve the Merger Proposal (the “Callon Adjournment Proposal”). Approval of the Merger Proposal requires the affirmative vote of the holders of a majority of the outstanding shares of Callon Common Stock entitled to vote on the proposal. Approval of the Callon Adjournment Proposal and, assuming a quorum is present, the Advisory Compensation Proposal requires the affirmative vote of the holders of a majority of the Callon Common Stock entitled to vote thereon and present in person or represented by proxy at the Callon Special Meeting.

The Callon Special Meeting will be held at [    ], on [    ], 2024, at [    ] [a.m./p.m.], Central Time. The board of directors of Callon (the “Callon Board”) unanimously recommends that Callon stockholders vote “FOR” the Merger Proposal, “FOR” the Advisory Compensation Proposal, and “FOR” the Callon Adjournment Proposal.

If the merger is completed, at the effective time of the merger (the “Effective Time”), each issued and outstanding share of Callon Common Stock as of immediately prior to the Effective Time that is eligible to be converted into APA Common Stock in accordance with the terms of the Merger Agreement will convert automatically into the right to receive, without interest, 1.0425 shares of APA Common Stock (the “Exchange

Ratio”), with cash paid in lieu of the issuance of fractional shares, if any. Although the number of shares of APA Common Stock that Callon stockholders will receive in exchange for their shares of Callon Common Stock is fixed, the market value of the merger consideration will fluctuate with the market price of APA Common Stock and will not be known at the time Callon stockholders vote to adopt the Merger Agreement or at the time APA stockholders vote to approve the Stock Issuance Proposal. Based on the closing price of APA Common Stock on the Nasdaq Global Select Market (“Nasdaq”) on January 3, 2024, the last trading day before the public announcement of the parties entering into the Merger Agreement, the Exchange Ratio represented approximately $38.31 in value for each share of Callon Common Stock. Based on the closing price of APA Common Stock on the Nasdaq on [    ], 2024, the last practicable trading day before the date of the accompanying joint proxy statement/prospectus, the Exchange Ratio represented approximately $[    ] in value for each share of Callon Common Stock. Based on the estimated number of shares of APA Common Stock and estimated number of shares of Callon Common Stock, as well as the outstanding equity awards of the parties, that will be outstanding immediately prior to the consummation of the merger, we estimate that, upon consummation of the merger, APA stockholders as of immediately prior to the merger will hold approximately eighty-one percent (81%), and Callon stockholders as of immediately prior to the merger will hold approximately nineteen percent (19%), of the issued and outstanding shares of APA Common Stock (in each case based on fully diluted shares outstanding of each company). We urge you to obtain current market quotations for APA Common Stock (trading symbol “APA”) and Callon Common Stock (trading symbol “CPE”).

The obligations of APA and Callon to complete the merger are subject to the satisfaction or waiver of a number of conditions set forth in the Merger Agreement, a copy of which is attached as Annex A to the accompanying joint proxy statement/prospectus. The accompanying joint proxy statement/prospectus describes the APA Special Meeting and the proposals to be considered thereat, the Callon Special Meeting and the proposals to be considered thereat, the merger, and the documents and agreements related to the merger. It also contains or references information about APA and Callon and certain related agreements and matters. Please carefully read the entire accompanying joint proxy statement/prospectus, including “Risk Factors” beginning on page 27, for a discussion of the risks relating to the proposed merger. You also can obtain information about APA and Callon from documents that each has filed with the Securities and Exchange Commission (the “SEC”). Please see “Where You Can Find More Information” beginning on page 210 of the accompanying joint proxy statement/prospectus for how you may obtain such information.

Sincerely,

Neither the SEC nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger described in the accompanying joint proxy statement/prospectus or determined if the accompanying joint proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

The accompanying joint proxy statement/prospectus is dated [    ], 2024, and is first being mailed to APA stockholders of record and Callon stockholders of record on or about [    ], 2024.

APA CORPORATION

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

NOTICE OF SPECIAL MEETING OF

STOCKHOLDERS OF APA CORPORATION

TO BE HELD ON [    ], 2024

To the Stockholders of APA Corporation:

You are cordially invited to attend the special meeting of stockholders (the “APA Special Meeting”) of APA Corporation (“APA”) virtually, to be held at [    ] [a.m./p.m.], Central Time, on [    ], 2024, virtually at [    ] (advance registration required), for the following purposes:

APA will transact no other business at the APA Special Meeting or any adjournment or postponement thereof, except such business as may properly be brought before the APA Special Meeting by or at the direction of the board of directors of APA (the “APA Board”) in accordance with APA’s amended and restated bylaws. These items of business are described in the enclosed joint proxy statement/prospectus. The APA Board has designated the close of business on [    ], 2024 as the record date for the purpose of determining the holders of shares of APA Common Stock who are entitled to receive notice of, and to vote at, the APA Special Meeting and any adjournment or postponement of the special meeting, unless a new record date is fixed in connection with any adjournment or postponement of the special meeting. Only the holders of record of APA Common Stock at the close of business on the record date are entitled to notice of, and to vote at, the APA Special Meeting and at any adjournment or postponement of the special meeting.

The APA Board has unanimously (i) determined that it is in the best interest of APA and the holders of APA Common Stock (the “APA stockholders”) to enter into the Merger Agreement, (ii) declared entry into the Merger Agreement to be advisable, (iii) authorized and approved APA’s execution, delivery, and performance of the Merger Agreement in accordance with its terms and APA’s consummation of the transactions contemplated thereby, including the merger of Merger Sub and Callon contemplated thereby (the “merger”) and the issuance of APA Common Stock contemplated by the Stock Issuance Proposal, (iv) directed that the approval of the Stock Issuance Proposal be submitted to a vote at a meeting of the APA stockholders, and (v) resolved to recommend that the APA stockholders approve the Stock Issuance Proposal. The APA Board unanimously recommends that the APA stockholders vote “FOR” the Stock Issuance Proposal and “FOR” the APA Adjournment Proposal.

Properly executed proxy cards with no instructions indicated on the proxy card will be voted “FOR” the Stock Issuance Proposal and “FOR” the APA Adjournment Proposal. Even if you plan to attend the APA Special Meeting virtually, APA requests that you complete, sign, date, and return the enclosed proxy card in the

accompanying envelope prior to the APA Special Meeting to ensure that your shares will be represented and voted at the APA Special Meeting if you later decide not to or become unable to attend virtually.

You may also submit a proxy over the Internet using the Internet address on the enclosed proxy card or by telephone using the toll-free number on the enclosed proxy card. If you submit your proxy through the Internet or by telephone, you will be asked to provide the control number from the enclosed proxy card. If you are not a stockholder of record, but instead hold your shares in “street name” through a broker, bank, trust, or other nominee, you must provide a proxy executed in your favor from your broker, bank, trust, or other nominee in order to be able to vote at the APA Special Meeting.

Please vote as promptly as possible, whether or not you plan to attend the APA Special Meeting virtually. If your shares are held in the name of a broker, bank, or other nominee, please vote by following the instructions on the voting instruction form furnished by the broker, bank, or other nominee. If you hold your shares in your own name, submit a proxy to vote your shares as promptly as possible by (i) visiting the Internet site listed on the proxy card, (ii) calling the toll-free number listed on the proxy card, or (iii) submitting your proxy card by mail by using the self-addressed, stamped envelope provided. Submitting a proxy will not prevent you from voting virtually, but it will help to secure a quorum and avoid added solicitation costs. Any eligible APA stockholder entitled to vote thereon and who is virtually present at the APA Special Meeting may vote, thereby revoking any previous proxy. In addition, a proxy may also be revoked in writing before the APA Special Meeting in the manner described in the joint proxy statement/prospectus.

If you have any questions concerning the merger or the joint proxy statement/prospectus, would like additional copies, or need help voting your shares of APA Common Stock, please contact APA’s proxy solicitor:

1290 Avenue of the Americas, 9th Floor

New York, NY 10104

Toll-Free: 1-888-815-3892

Houston, Texas

[    ], 2024

CALLON PETROLEUM COMPANY

One Briarlake Plaza

2000 W. Sam Houston Parkway S., Suite 2000

Houston, Texas 77042

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

OF CALLON PETROLEUM COMPANY TO BE HELD

[    ], 2024

To the Stockholders of Callon Petroleum Company:

You are cordially invited to attend the special meeting of stockholders (the “Callon Special Meeting”) of Callon Petroleum Company (“Callon”), to be held at [    ] [a.m./p.m.], Central Time, on [    ], 2024, at [    ], for the following purposes:

Callon will transact no other business at the Callon Special Meeting, except such business as may properly be brought before the Callon Special Meeting or any adjournment or postponement thereof by or at the direction of the Callon board of directors (the “Callon Board”) in accordance with Callon’s amended and restated bylaws. The joint proxy statement/prospectus, of which this notice is a part, describes the proposals listed above in more detail. Please refer to the attached documents, including the Merger Agreement and all other annexes and any documents incorporated by reference, for further information with respect to the business to be transacted at the Callon Special Meeting. You are encouraged to read the entire document carefully before voting. In particular, please see the sections entitled “The Merger” beginning on page 42 for a description of the transactions contemplated by the Merger Agreement and “Risk Factors” beginning on page 27 for an explanation of the risks associated with the merger of Merger Sub with and into Callon, as contemplated pursuant to the Merger Agreement (the “merger”) and the other transactions contemplated by the Merger Agreement.

Approval of the Merger Proposal by the affirmative vote of the holders of a majority of the outstanding shares of Callon common stock, par value $0.01 per share (“Callon Common Stock”), entitled to vote on the proposal is required to complete the merger. Approval of the Callon Adjournment Proposal and, assuming a quorum is present, the Advisory Compensation Proposal requires the affirmative vote of the holders of a majority of the Callon Common Stock entitled to vote thereon and present in person or represented by proxy at the Callon Special Meeting.

The Callon Board has fixed the close of business on [    ], 2024 as the record date for the determination of the holders of Callon Common Stock (the “Callon stockholders”) entitled to receive notice of,

and to vote at, the Callon Special Meeting or any adjournment or postponement thereof. The Callon stockholders of record as of the close of business on the record date are the only Callon stockholders that are entitled to receive notice of, and to vote at, the Callon Special Meeting or any adjournment or postponement thereof. For additional information regarding the Callon Special Meeting, please see the section entitled “Callon Special Meeting” beginning on page 155 of the joint proxy statement/prospectus.

The Callon Board, at a meeting duly called and held, has by unanimous vote (i) declared that the Merger Agreement and the transactions contemplated thereby, including the merger, are fair to, and in the best interests of Callon and the Callon stockholders, (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the merger, and (iii) resolved to recommend that the Callon stockholders adopt the Merger Agreement and approve the transactions contemplated thereby, including the merger. The Callon Board unanimously recommends that holders of Callon Common Stock vote “FOR” the Merger Proposal, “FOR” the Advisory Compensation Proposal, and “FOR” the Callon Adjournment Proposal.

Please vote as promptly as possible, whether or not you plan to attend the Callon Special Meeting. If your shares are held in the name of a broker, bank, or other nominee, please vote by following the instructions on the voting instruction form furnished by the broker, bank, or other nominee. If you hold your shares in your own name, submit a proxy to vote your shares as promptly as possible by (i) visiting the Internet site listed on the proxy card, (ii) calling the toll-free number listed on the proxy card, or (iii) submitting your proxy card by mail by using the self-addressed, stamped envelope provided. Submitting a proxy will not prevent you from voting at the Callon Special Meeting, but it will help to secure a quorum and avoid added solicitation costs. Any eligible holder of Callon Common Stock entitled to vote thereon and who is present at the Callon Special Meeting may vote, thereby revoking any previous proxy. In addition, a proxy may also be revoked in writing before the Callon Special Meeting in the manner described in the joint proxy statement/prospectus.

If you have any questions concerning the Merger Proposal, the Advisory Compensation Proposal, the Callon Adjournment Proposal, the merger, or the joint proxy statement/prospectus, would like additional copies, or need help voting your shares of Callon Common Stock, please contact Callon’s proxy solicitor:

Innisfree M&A Incorporated

501 Madison Ave, 20^th Floor

New York, New York 10022

Banks and Brokerage Firms, please call: (212) 750-5833

Shareholders, please call toll-free: (877) 687-1865

Houston, Texas

[    ], 2024

ABOUT THIS JOINT PROXY STATEMENT/PROSPECTUS

This document, which forms part of a registration statement on Form S-4 filed with the U.S. Securities and Exchange Commission (the “SEC”) by APA, constitutes a prospectus of APA under Section 5 of the Securities Act of 1933 (as amended, the “Securities Act”) with respect to the shares of APA Common Stock to be issued to Callon stockholders pursuant to the Merger Agreement. This document also constitutes a proxy statement of each of APA and Callon under Section 14(a) of the Securities Exchange Act of 1934 (as amended, the “Exchange Act”). It also constitutes a notice of meeting with respect to the special meeting of Callon stockholders (the “Callon Special Meeting”) and the special meeting of APA stockholders (the “APA Special Meeting”).

You should rely only on the information contained in or incorporated by reference into this joint proxy statement/prospectus. APA and Callon have not authorized anyone to provide you with information that is different from that contained in or incorporated by reference into this joint proxy statement/prospectus. This joint proxy statement/prospectus is dated [    ], 2024. The information contained in this joint proxy statement/prospectus is accurate only as of that date or, in the case of information in a document incorporated by reference, as of the date of such document, unless the information specifically indicates that another date applies. Neither the mailing of this joint proxy statement/prospectus to APA stockholders and Callon stockholders nor the issuance by APA of shares of APA Common Stock pursuant to the Merger Agreement will create any implication to the contrary.

This joint proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. APA has supplied all information contained in this joint proxy statement/prospectus relating to APA, and Callon has supplied all such information relating to Callon. APA and Callon have both contributed to the information related to the merger contained in this joint proxy statement/prospectus.

Unless the context otherwise requires, all references in this joint proxy statement/prospectus to “APA” refer to APA Corporation, a Delaware corporation. Unless the context otherwise requires, all references in this joint proxy statement/prospectus to “Callon” refer to Callon Petroleum Company, a Delaware corporation. All references in this joint proxy statement/prospectus to “APA Common Stock” refer to the common stock of APA, par value $0.625 per share, and all references in this joint proxy statement/prospectus to “Callon Common Stock” refer to the common stock of Callon, par value $0.01 per share. All references in this joint proxy statement/prospectus to the “Callon stockholders” refer to the holders of Callon Common Stock and all references in this joint proxy statement/prospectus to the “APA stockholders” refer to the holders of APA Common Stock. All references in this joint proxy statement/prospectus to the “Merger Agreement” refer to the Agreement and Plan of Merger, dated as of January 3, 2024, by and among APA, Astro Comet Merger Sub Corp., a Delaware corporation and a wholly owned, direct subsidiary of APA (“Merger Sub”), and Callon, as it may be amended from time to time, a copy of which is attached as Annex A to this joint proxy statement/prospectus and incorporated by reference herein, and all references in this joint proxy statement/prospectus to the “merger” refer to the merger of Merger Sub with and into Callon, with Callon surviving the merger as a wholly owned subsidiary of APA. All references in this joint proxy statement/prospectus to the “Exchange Ratio” refer to the ratio of 1.0425 shares of APA Common Stock per outstanding share of Callon Common Stock that Callon stockholders are entitled to receive in connection with the merger, subject to the terms and conditions of the Merger Agreement.

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ADDITIONAL INFORMATION

This joint proxy statement/prospectus incorporates by reference important business and financial information about APA and Callon from other documents that are not included in or delivered with this joint proxy statement/prospectus. For a listing of the documents incorporated by reference into this joint proxy statement/prospectus, see “Where You Can Find More Information” beginning on page 210.

You may request copies of this joint proxy statement/prospectus and any of the documents incorporated by reference herein or other information concerning APA or Callon, without charge, upon written or oral request to the applicable company’s principal executive offices. The respective addresses and phone numbers of such principal executive offices are listed below.

If you would like to request any of the APA or Callon documents that are incorporated by reference into this joint proxy statement/prospectus, please do so by [    ], 2024, in order to receive them before the APA Special Meeting and the Callon Special Meeting.

You may also obtain any of the documents incorporated by reference into this joint proxy statement/prospectus without charge through the SEC’s website at www.sec.gov. In addition, you may obtain copies of documents filed by APA with the SEC by accessing APA’s website at https://investor.apacorp.com. You may also obtain copies of documents filed by Callon with the SEC by accessing Callon’s website at https://callon.com/investors.

We are not incorporating the contents of the websites of the SEC, APA, Callon, or any other entity into this joint proxy statement/prospectus. We are providing the information about how you can obtain certain documents that are incorporated by reference into this joint proxy statement/prospectus at these websites only for your convenience.

In addition, if you have questions about the merger or this joint proxy statement/prospectus, would like additional copies of this joint proxy statement/prospectus or need to obtain proxy cards or other information related to the proxy solicitation, contact Georgeson LLC (“Georgeson”), the proxy solicitor for APA, toll-free at 1-888-815-3892 or Innisfree M&A Incorporated (“Innisfree”), the proxy solicitor for Callon, toll-free at (877) 687-1865 or, for brokers and banks, collect at (212) 750-5833. You will not be charged for any of these documents that you request.

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TABLE OF CONTENTS

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QUESTIONS AND ANSWERS

The following questions and answers briefly address some commonly asked questions about the Callon Special Meeting, the APA Special Meeting, and the merger. They may not include all the information that is important to Callon stockholders and APA stockholders. Callon stockholders and APA stockholders should carefully read this entire joint proxy statement/prospectus, including the annexes and the other documents referred to herein.

You are receiving this joint proxy statement/prospectus because APA and Callon have agreed for APA to acquire Callon in an all-stock transaction. At the Effective Time, Merger Sub will merge with and into Callon, the separate corporate existence of Merger Sub will cease, and Callon will continue as the surviving corporation in the merger as a wholly owned, direct subsidiary of APA (the “Surviving Corporation”). As referred to in this joint proxy statement/prospectus, the “Effective Time” means the effective time of the merger and as set forth in the Merger Agreement. The Merger Agreement governs the terms of the merger of Merger Sub and Callon and is attached to this joint proxy statement/prospectus as Annex A.

In order to complete the merger, among other things, Callon stockholders must adopt the Merger Agreement in accordance with the General Corporation Law of the State of Delaware (the “DGCL”), and APA stockholders must approve the issuance of shares of APA Common Stock in connection with the merger.

This joint proxy statement/prospectus serves as both the proxy statement through which APA and Callon will solicit proxies to obtain the necessary stockholder approvals for the merger and the prospectus by which APA will issue shares of APA Common Stock as consideration in the merger.

This joint proxy statement/prospectus, which you should carefully read in its entirety, contains important information about the Callon Special Meeting and APA Special Meeting, the merger, and other matters.

The Merger Agreement is attached to this joint proxy statement/prospectus as Annex A. For a more complete discussion of the proposed merger, its effects, and the other transactions contemplated by the Merger Agreement, please see “The Merger” elsewhere in this joint proxy statement/prospectus.

Callon stockholders will also be asked to (1) approve, on a non-binding advisory basis, the compensation that may be paid or become payable to Callon’s named executive officers that is based on or otherwise relates to the merger (the “Advisory Compensation Proposal”) and (2) approve the proposal to adjourn the Callon Special Meeting to solicit additional proxies if there are not sufficient votes at the time of the Callon Special Meeting to approve the Merger Proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Callon stockholders (the “Callon Adjournment Proposal”).

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Your vote is very important, regardless of the number of shares that you own. The approval of the Merger Proposal is a condition to the obligations of APA and Callon to complete the merger.

APA stockholders will also be asked to approve the proposal to adjourn the APA Special Meeting to solicit additional proxies if there are not sufficient votes at the time of the APA Special Meeting to approve the Stock Issuance Proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to APA stockholders (the “APA Adjournment Proposal”).

Your vote is very important, regardless of the number of shares that you own. The approval of the Stock Issuance Proposal is a condition to the obligations of each of APA and Callon to complete the merger.

Approval of the Callon Adjournment Proposal and, assuming a quorum is present, the Advisory Compensation Proposal requires the affirmative vote of the holders of a majority of the Callon Common Stock entitled to vote thereon and present in person or represented by proxy at the Callon Special Meeting. Accordingly, with respect to a Callon stockholder who is present in person or represented by proxy at the Callon Special Meeting, such stockholder’s abstention from voting or the failure of a Callon stockholder to vote will have the same effect as a vote “against” the Advisory Compensation Proposal and Callon Adjournment Proposal. The failure of a Callon stockholder who holds shares in “street name” through a bank, broker, or other nominee to give voting instructions to the bank, broker, or other nominee will have no effect on the outcome of the Advisory Compensation Proposal and Callon Adjournment Proposal. However, if a Callon stockholder instructs its bank, broker, or other nominee regarding some but not all of the proposals, such broker non-vote will have the same effect as voting “against” any proposal for which no instruction is provided. Under the Callon Bylaws, regardless of whether there is a quorum, the chair of the Callon Special Meeting may also adjourn the Callon Special Meeting.

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Assuming a quorum is present at the APA Special Meeting, approval of the Stock Issuance Proposal requires the affirmative vote of holders of a majority of the shares of APA Common Stock properly cast on such proposal. Assuming a quorum is present at the APA Special Meeting, abstentions will have no effect on the Stock Issuance Proposal. The failure of an APA stockholder who holds shares in “street name” through a bank, broker, or other nominee to give voting instructions to the bank, broker, or other nominee will have no effect on the outcome of the Stock Issuance Proposal.

Approval of the APA Adjournment Proposal requires the affirmative vote of holders of a majority of the shares of APA Common Stock properly cast on such proposal. Abstentions will have no effect on the APA Adjournment Proposal. The failure of an APA stockholder who holds shares in “street name” through a bank, broker, or other nominee to give voting instructions to the bank, broker, or other nominee will have no effect on the outcome of the APA Adjournment Proposal. Under APA’s bylaws, regardless of whether there is a quorum, the chair of the APA Special Meeting may also adjourn the APA Special Meeting.

Because APA will issue a fixed number of shares of APA Common Stock in exchange for each share of Callon Common Stock, the value of the merger consideration that Callon stockholders will receive in the

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merger will depend on the market price of shares of APA Common Stock at the Effective Time. The market price of shares of APA Common Stock that Callon stockholders receive at the Effective Time could be greater than, less than, or the same as the market price of shares of APA Common Stock on the date of this joint proxy statement/prospectus or at the time of the Callon Special Meeting. Accordingly, you should obtain current market quotations for APA Common Stock and Callon Common Stock before deciding how to vote with respect to the Merger Proposal or the Stock Issuance Proposal, as applicable. APA Common Stock is traded on the Nasdaq under the symbol “APA.” Callon Common Stock is traded on the New York Stock Exchange (“NYSE”) under the symbol “CPE.”

For more information regarding the merger consideration to be received by Callon stockholders if the merger is completed, please see “The Merger Agreement—Merger Consideration.”

For additional information regarding the right of Callon to appoint one individual to the APA Board following the completion of the merger, please see “The Merger—Board of Directors After Completion of the Merger.”

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If you are a Callon stockholder of record as of the close of business on the Callon Record Date, you may submit your proxy before the special meeting in one of the following ways:

If you decide to attend the Callon Special Meeting and vote at the meeting, your vote will revoke any proxy previously submitted.

The Callon Special Meeting will begin promptly at [    ] [a.m./p.m.], Central Time, on [    ], 2024 at [    ]. Callon encourages its stockholders to arrive at the meeting prior to the start time to leave ample time for check-in.

Even if you plan to attend the Callon Special Meeting, Callon recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to or become unable to attend the Callon Special Meeting.

Additional information on voting procedures can be found under “Callon Special Meeting.”

If you are an APA stockholder of record, you may also cast your vote virtually at the special meeting by registering in advance at [     ]. To register, APA stockholders (or their authorized representatives) will need the control number provided on their proxy card, voting instruction form, or notice. If you do not have a control number, you will not be able to vote at the meeting. Once registered, you will receive an email prior to the start of the meeting at the email address provided during registration, which will contain a unique link to access the virtual meeting. Further instructions and contact information for technical support will be provided in the email. If you decide to attend the APA Special Meeting virtually and vote at the meeting, your vote will revoke any proxy previously submitted.

The APA Special Meeting will begin promptly at [   ] [a.m./p.m.], Central Time, on [     ] , 2024. APA encourages its stockholders to access the meeting prior to the start time to leave ample time for check-in. Please follow the instructions as outlined in this joint proxy statement/prospectus.

Even if you plan to attend the APA Special Meeting virtually, APA recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to or become unable to attend the APA Special Meeting.

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Additional information on voting procedures can be found under “APA Special Meeting.”

Even if you plan to attend the Callon Special Meeting, Callon recommends that you vote your shares in advance as described above so that your vote will be counted if you later decide not to or become unable to attend the special meeting.

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Record Holders. For shares held directly, please complete, sign, date, and return each proxy card, or you may cast your vote by telephone or Internet as provided on each proxy card, or otherwise follow the voting instructions provided in this joint proxy statement/prospectus in order to ensure that all of your shares of Callon Common Stock or APA Common Stock are voted.

“Street name” Holders. For shares held in “street name” through a bank, broker, or other nominee, you should follow the procedures provided by your bank, broker, or other nominee to vote your shares.

If you sign, date, and return your proxy card and do not indicate how you want your shares of APA Common Stock to be voted, then your shares of APA Common Stock will be voted “FOR” the Stock Issuance Proposal and “FOR” the APA Adjournment Proposal.

Your attendance at the Callon Special Meeting will not revoke your proxy unless you give written notice of revocation to Callon’s Corporate Secretary before your proxy is exercised or unless you vote your shares in person at the Callon Special Meeting.

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Execution or revocation of a proxy will not in any way affect your right to attend the Callon Special Meeting and vote. Written notices of revocation and other communications with respect to the revocation of proxies should be addressed to:

Callon Petroleum Company

Attn: Corporate Secretary

One Briarlake Plaza

2000 W. Sam Houston Parkway S., Suite 2000

Houston, Texas 77042

For more information, please see “Callon Special Meeting—Revocation of Proxies.”

Your attendance at the APA Special Meeting will not revoke your proxy unless you give written notice of revocation to APA’s Corporate Secretary before your proxy is exercised or unless you vote your shares virtually at the APA Special Meeting.

Execution or revocation of a proxy will not in any way affect your right to attend the APA Special Meeting and vote. Written notices of revocation and other communications with respect to the revocation of proxies should be addressed to:

APA Corporation

Attn: Corporate Secretary

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

For more information, please see “APA Special Meeting—Revocation of Proxies.”

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APA and Callon also may be required to reimburse banks, brokers, and other custodians, nominees, and fiduciaries or their respective agents for their expenses in forwarding proxy materials to beneficial owners of Callon Common Stock. APA’s directors, officers, and employees and Callon’s directors, officers, and employees also may solicit proxies by telephone, by electronic means, or in person. They will not be paid any additional amounts for soliciting proxies.

APA and Callon also may be required to reimburse banks, brokers, and other custodians, nominees, and fiduciaries or their respective agents for their expenses in forwarding proxy materials to beneficial owners of APA Common Stock. APA’s directors, officers, and employees and Callon’s directors, officers, and employees also may solicit proxies by telephone, by electronic means, or in person. They will not be paid any additional amounts for soliciting proxies.

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All holders of Callon Common Stock should consult with their own tax advisor to determine the particular U.S. federal, state, or local or non-U.S. income or other tax consequences of the merger to them. See “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 185 for additional information.

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Callon Petroleum Company

Attn: Corporate Secretary

One Briarlake Plaza

2000 W. Sam Houston Parkway S., Suite 2000

Houston, Texas 77042

If you are an APA stockholder and have questions about the APA Special Meeting or the merger, or desire additional copies of this joint proxy statement/prospectus or additional proxy cards, you may contact:

APA Corporation

Attn: Corporate Secretary

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

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RISK FACTORS

In deciding how to vote, stockholders of APA and Callon, respectively, should carefully consider the following risk factors and all of the information contained in or incorporated by reference herein, including, but not limited to, the matters addressed in the section entitled “Cautionary Statement Regarding Forward-Looking Statements,” as well as Callon’s and APA’s other filings with the SEC incorporated herein by reference. Please see the section entitled “Where You Can Find More Information.”

Risks Relating to the Merger

Because the market price of APA Common Stock will fluctuate, Callon stockholders cannot be sure of the value of the shares of APA Common Stock they will receive in the merger. In addition, because the Exchange Ratio is fixed, the number of shares of APA Common Stock to be received by Callon stockholders in the merger will not change between now and the time the merger is completed to reflect changes in the trading prices of APA Common Stock or Callon Common Stock.

As a result of the merger, each eligible share of Callon Common Stock will be converted automatically into the right to receive, without interest, 1.0425 shares of APA Common Stock, with cash paid in lieu of the issuance of any fractional shares of APA Common Stock. The Exchange Ratio is fixed, which means that it will not change between now and the closing date, regardless of whether the market price of either APA Common Stock or Callon Common Stock changes. Therefore, the value of the merger consideration will depend on the market price of APA Common Stock at the Effective Time. The market price of APA Common Stock has fluctuated since the date of the announcement of the parties’ entry into the Merger Agreement and will continue to fluctuate from the date of this joint proxy statement/prospectus to the date of the Callon Special Meeting, the date of the APA Special Meeting, the date the merger is completed, and thereafter. The market price of APA Common Stock, when received by Callon stockholders after the merger is completed, could be greater than, less than, or the same as the market price of APA Common Stock on the date of this joint proxy statement/prospectus or at the time of the Callon Special Meeting. Accordingly, you should obtain current stock price quotations for APA Common Stock and Callon Common Stock before deciding how to vote or abstain from voting on any of the proposals described in this joint proxy statement/prospectus.

The market price for APA Common Stock following the closing may be affected by factors different from those that historically have affected or currently affect APA Common Stock and Callon Common Stock.

Upon the completion of the merger, Callon stockholders will receive shares of APA Common Stock. APA’s financial position may differ from its financial position before the completion of the merger, and the results of operations of the combined company may be affected by some factors that are different from those currently affecting the results of operations of APA and those currently affecting the results of operations of Callon. Accordingly, the market price and performance of APA Common Stock is likely to be different from the performance of Callon Common Stock in the absence of the merger. In addition, general fluctuations in stock markets could have a material adverse effect on the market for, or liquidity of, APA Common Stock, regardless of APA’s actual operating performance. For a discussion of the businesses of APA and Callon and important factors to consider in connection with those businesses, see the documents incorporated by reference herein and referred to in “Where You Can Find More Information.”

APA stockholders and Callon stockholders, in each case as of immediately prior to the merger, will have reduced ownership in the combined company.

Based on the number of issued and outstanding shares of Callon Common Stock as of [    ], 2024, and the number of outstanding Callon equity awards currently estimated to be payable in shares of APA Common Stock in connection with the merger, APA anticipates issuing approximately [    ] shares of APA Common Stock pursuant to the Merger Agreement. The actual number of shares of APA Common Stock to

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be issued pursuant to the Merger Agreement will be determined at the completion of the merger based on the number of shares of Callon Common Stock outstanding immediately prior to such time. The issuance of these new shares could have the effect of depressing the market price of APA Common Stock, through dilution of earnings per share or otherwise. Any dilution of, or delay of any accretion to, APA’s earnings per share could cause the price of APA Common Stock to decline or increase at a reduced rate.

Immediately after the completion of the merger, it is expected that APA stockholders as of immediately prior to the merger will own approximately eighty-one percent (81%), and Callon stockholders as of immediately prior to the merger will own approximately nineteen percent (19%), of the issued and outstanding shares of APA Common Stock (in each case based on fully diluted shares outstanding of each company). As a result, APA’s current stockholders and Callon’s current stockholders will have less influence on the policies of the combined company than they currently have on the policies of APA and Callon, respectively.

APA and Callon must obtain certain regulatory approvals and clearances to consummate the merger, which, if delayed, not granted, or granted with unacceptable conditions, could prevent, substantially delay, or impair consummation of the merger, result in additional expenditures of money and resources, or reduce the anticipated benefits of the merger.

At any time before or after consummation of the merger, the DOJ or the FTC, or any state, could take such action under the antitrust laws as it deems necessary or desirable in the public interest, including seeking to enjoin the completion of the merger, seeking divestiture of substantial assets of the parties, or requiring the parties to license, or hold separate, assets or terminate existing relationships and contractual rights. Such action could include seeking to enjoin the completion of the merger or seeking divestiture of substantial assets of the parties. Private parties may also seek to take legal action under the antitrust laws under certain circumstances.

The merger is subject to a number of conditions to the obligations of both APA and Callon to complete the merger, which, if not fulfilled, or not fulfilled in a timely manner, may delay completion of the merger or result in termination of the Merger Agreement.

The respective obligations of each of Callon and APA to consummate the merger are subject to the satisfaction at or prior to the Effective Time of numerous conditions, including the following:

Many of the conditions to completion of the merger are not within either APA’s or Callon’s control, and neither company can predict when, or if, these conditions will be satisfied. If any of these conditions are not satisfied or waived prior to October 3, 2024 (or such date as extended pursuant to the terms set forth in the Merger Agreement), it is possible that the Merger Agreement may be terminated. In addition, satisfying the conditions to and completion of the merger may take longer, and could cost more, than APA and Callon expect. Neither APA nor Callon can predict whether and when these other conditions will be satisfied. Furthermore, the

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requirements for obtaining the required clearances and approvals could delay the completion of the merger for a significant period of time or prevent them from occurring. Any delay in completing the merger may adversely affect the cost savings and other benefits that APA and Callon expect to achieve if the merger and the integration of the companies’ respective businesses are not completed within the expected timeframe. There can be no assurance that all required regulatory approvals will be obtained or obtained prior to the termination date.

Uncertainties associated with the merger may cause a loss of management personnel and other key employees of APA and Callon, which could adversely affect the future business and operations of APA following the merger.

APA and Callon are dependent on the experience and industry knowledge of their officers and other key employees to execute their business plans. APA’s success after the merger will depend in part upon its ability to retain key management personnel and other key employees. Current and prospective employees of APA and Callon may experience uncertainty about their roles within APA following the merger or other concerns regarding the timing and completion of the merger or the operations of APA following the merger, any of which may have an adverse effect on the ability of APA and Callon to retain or attract key management and other key personnel. If APA or Callon is unable to retain personnel, including APA’s or Callon’s key management, who are critical to the future operations of the companies, APA and Callon could face disruptions in their operations, loss of existing customers, loss of key information, expertise, or know-how, and unanticipated additional recruitment and training costs. In addition, the loss of key APA and Callon personnel could diminish the anticipated benefits of the merger. No assurance can be given that APA, following the merger, will be able to retain or attract key management personnel and other key employees of APA and Callon to the same extent that APA and Callon have previously been able to retain or attract their own employees.

The business relationships of APA and Callon may be subject to disruption due to uncertainty associated with the merger, which could have a material adverse effect on the results of operations, cash flows, and financial position of APA or Callon pending and following the merger.

Parties with which APA or Callon do business may experience uncertainty associated with the merger, including with respect to current or future business relationships with APA or Callon following the merger. APA’s and Callon’s business relationships may be subject to disruption as customers, distributors, suppliers, vendors, landlords, joint venture partners, and other business partners may attempt to delay or defer entering into new business relationships, negotiate changes in existing business relationships, or consider entering into business relationships with parties other than APA or Callon following the merger. These disruptions could have a material and adverse effect on the results of operations, cash flows, and financial position of APA or Callon, regardless of whether the merger is completed, as well as a material and adverse effect on APA’s ability to realize the expected cost savings and other benefits of the merger. The risk, and adverse effect, of any disruption could be exacerbated by a delay in completion of the merger or termination of the Merger Agreement.

APA or Callon may waive one or more of the closing conditions without re-soliciting stockholder approval.

APA or Callon may determine to waive, in whole or part, one or more of the conditions to closing the merger prior to APA or Callon, as the case may be, being obligated to consummate the merger. Each of APA and Callon currently expects to evaluate the materiality of any waiver and its effect on its respective stockholders in light of the facts and circumstances at the time, to determine whether any amendment of this joint proxy statement/prospectus or any re-solicitation of proxies is required in light of such waiver. Any determination whether to waive any condition to the merger or to re-solicit stockholder approval or amending or supplementing this joint proxy statement/prospectus as a result of a waiver will be made by APA or Callon at the time of such waiver based on the facts and circumstances as they exist at that time.

Callon stockholders will not be entitled to appraisal rights in the merger.

Under Delaware law, holders of Callon Common Stock do not have appraisal rights in connection with the merger, as more fully described in “The Merger—No Appraisal Rights.”

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The Merger Agreement subjects APA and Callon to restrictions on their respective business activities prior to the Effective Time.

The Merger Agreement subjects APA and Callon to restrictions on their respective business activities prior to the Effective Time. The Merger Agreement obligates each of APA and Callon to generally use reasonable best efforts to conduct its businesses in all material respects in the ordinary course until the Effective Time. These restrictions could prevent APA and Callon from pursuing certain business opportunities that arise prior to the Effective Time. See “The Merger Agreement—Covenants” for additional details.

Directors and executive officers of Callon have interests in the merger that may be different from, or in addition to, the interests of Callon stockholders generally.

In considering the recommendation of the Callon Board that Callon stockholders vote in favor of the Merger Proposal and the Advisory Compensation Proposal, Callon stockholders should be aware of and take into account the fact that certain Callon directors and executive officers have interests in the merger that may be different from, or in addition to, the interests of Callon stockholders generally. The interests of Callon’s directors and executive officers include, among others, treatment of Callon long-term incentive awards, severance rights, and rights to continuing indemnification and directors’ and officers’ liability insurance. See “The Merger—Interests of Callon’s Directors and Executive Officers in the Merger” for a more detailed description of these interests. The Callon Board was aware of and carefully considered the interests of its directors and officers, among other matters, in evaluating the terms and structure, and overseeing the negotiation of the merger, in approving the Merger Agreement and the transactions contemplated thereby, including the merger, and the recommendation of the Callon Board that Callon stockholders adopt the Merger Agreement.

The Merger Agreement limits APA’s and Callon’s respective ability to pursue alternatives to the merger, may discourage certain other companies from making a favorable alternative transaction proposal, and, in specified circumstances, could require APA or Callon to pay the other party a termination fee.

The Merger Agreement contains certain provisions that restrict each of APA’s and Callon’s ability to initiate, solicit, knowingly encourage, or knowingly facilitate any inquiry or the making of any proposal or offer that constitutes, or would reasonably be expected to result in, a competing proposal with respect to APA or Callon, as applicable, and APA and Callon have each agreed to certain terms and conditions relating to their ability to engage in, continue, or otherwise participate in any discussions with respect to, provide any third party confidential information with respect to, or enter into any acquisition agreement with respect to certain unsolicited proposals that constitute or are reasonably likely to lead to a competing proposal. Further, even if the APA Board or the Callon Board changes, withdraws, modifies, or qualifies its recommendation with respect to the Stock Issuance Proposal or the Merger Proposal, as applicable, unless the Merger Agreement has been terminated in accordance with its terms, both parties will still be required to submit the Stock Issuance Proposal and the Merger Proposal, as applicable, to a vote at their respective special meetings. In addition, APA and Callon generally have an opportunity to offer to modify the terms of the Merger Agreement in response to any competing acquisition proposals or intervening events before the Callon Board or APA Board, respectively, may withdraw or qualify their respective recommendations. The Merger Agreement further provides that under specified circumstances, including after receipt of certain alternative acquisition proposals, each of APA and Callon may be required to pay the other a cash termination fee equal to $170 million (if APA is the payor) or $85 million (if Callon is the payor). See “The Merger Agreement—Termination Fee” for additional details.

These provisions could discourage a potential third party acquirer or other strategic transaction partner that might have an interest in acquiring all or a significant portion of Callon or APA from considering or pursuing an alternative transaction with either party or proposing such a transaction, even if it were prepared, in Callon’s case, to pay consideration with a higher per share value than the total value proposed to be paid or received in the merger. These provisions might also result in a potential third-party acquirer or other strategic transaction partner proposing to pay a lower price than it might otherwise have proposed to pay because of the added expense of the termination fee or expense reimbursement that may become payable in certain circumstances.

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Failure to complete the merger could negatively impact APA’s or Callon’s stock price and have a material adverse effect on their results of operations, cash flows, and financial position.

If the merger is not completed for any reason, including as a result of failure to obtain all requisite regulatory approvals, or if the APA stockholders or Callon stockholders fail to approve the applicable proposals, the ongoing businesses of APA and Callon may be materially adversely affected and, without realizing any of the benefits of having completed the merger, APA and Callon would be subject to a number of risks, including the following:

If the merger is not completed, the risks described above may materialize and they may have a material adverse effect on APA’s or Callon’s results of operations, cash flows, financial position, and stock prices.

The shares of APA Common Stock to be received by Callon stockholders upon the completion of the merger will have different rights from shares of Callon Common Stock.

Upon the completion of the merger, Callon stockholders will no longer be stockholders of Callon. Instead, former Callon stockholders will become APA stockholders and while their rights as APA stockholders will continue to be governed by the laws of the State of Delaware, their rights will be subject to and governed by the terms of the amended and restated certificate of incorporation of APA (the “APA Charter”) and the amended and restated bylaws of APA (the “APA Bylaws”). The terms of the APA Charter and the APA Bylaws are in some respects different than the terms of the certificate of incorporation of Callon (the “Callon Charter”) and the Callon Bylaws, which currently govern the rights of Callon stockholders. See “Comparison of Stockholders’ Rights” for a discussion of the different rights associated with shares of APA Common Stock and shares of Callon Common Stock.

Completion of the merger may trigger change in control or other provisions in certain agreements to which Callon is a party.

The completion of the merger may trigger change in control or other provisions in certain agreements to which Callon is a party. If APA and Callon are unable to negotiate waivers of those provisions, the counterparties may exercise their rights and remedies under the agreements, potentially terminating the agreements, or seeking monetary damages. Even if APA and Callon are able to negotiate waivers, the counterparties may require a fee for such waivers or seek to renegotiate the agreements on terms less favorable to Callon.

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APA and Callon are expected to incur significant transaction costs in connection with the merger, which may be in excess of those anticipated by them.

APA and Callon have incurred and are expected to continue to incur a number of non-recurring costs associated with negotiating and completing the merger, integrating the operations of the two (2) companies, and achieving desired synergies. These costs have been, and will continue to be, substantial and, in many cases, will be borne by APA and Callon whether or not the merger is completed. A substantial majority of non-recurring expenses will consist of transaction costs and include, among others, fees paid to financial, legal, accounting, and other advisors, employee retention, severance and benefit costs, and filing fees. APA will also incur costs related to formulating and implementing integration plans, including facilities and systems consolidation costs and other employment-related costs. APA and Callon will continue to assess the magnitude of these costs and additional unanticipated costs may be incurred in connection with the merger and the integration of the two (2) companies’ businesses. While APA and Callon have assumed that a certain level of expenses would be incurred, there are many factors beyond their control that could affect the total amount or the timing of the expenses. The elimination of duplicative costs, as well as the realization of other efficiencies related to the integration of the businesses, may not offset integration-related costs and achieve a net benefit in the near term, or at all. The costs described above and any unanticipated costs and expenses, many of which will be borne by APA or Callon even if the merger is not completed, could have an adverse effect on APA’s or Callon’s financial condition and operating results.

Litigation relating to the merger could result in an injunction preventing the completion of the merger and/or substantial costs to APA and Callon.

Securities class action lawsuits and derivative lawsuits are often brought against public companies that have entered into acquisition, merger, or other business combination agreements. Even if such a lawsuit is without merit, defending against these claims can result in substantial costs and divert management time and resources. An adverse judgment could result in monetary damages, which could have a negative impact on APA’s and Callon’s respective liquidity and financial condition.

Lawsuits that may be brought against APA, Callon, or their respective directors could also seek, among other things, injunctive relief or other equitable relief, including a request to rescind parts of the Merger Agreement already implemented and to otherwise enjoin the parties from consummating the merger.

There can be no assurance that any of the defendants will be successful in the outcome of any pending or any potential future lawsuits. The defense or settlement of any lawsuit or claim that remains unresolved at the time the merger is completed may adversely affect APA’s or Callon’s business, financial condition, results of operations, and cash flows.

Risks Relating to APA and Callon

The combined company may not be able to retain customers or suppliers, and customers or suppliers may seek to modify contractual obligations with the combined company, either of which could have an adverse effect on the combined company’s business and operations. Third parties may terminate or alter existing contracts or relationships with APA or Callon as a result of the merger.

As a result of the merger, the combined company may experience impacts on relationships with customers and suppliers that may harm the combined company’s business and results of operations. Certain customers or suppliers may seek to terminate or modify contractual obligations following the merger whether or not contractual rights are triggered as a result of the merger. There can be no guarantee that customers and suppliers will remain with or continue to have a relationship with the combined company or do so on the same or similar contractual terms following the merger. If any customers or suppliers seek to terminate or modify contractual obligations or discontinue their relationships with the combined company, then the combined company’s business and results of operations may be harmed. Furthermore, the combined company will not have long-term

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arrangements with many of its significant suppliers. If the combined company’s suppliers were to seek to terminate or modify an arrangement with the combined company, then the combined company may be unable to procure necessary supplies or services from other suppliers in a timely and efficient manner and on acceptable terms, or at all.

APA and Callon also have contracts with vendors, landlords, licensors, and other business partners which may require APA or Callon, as applicable, to obtain consent from these other parties in connection with the merger. If these consents cannot be obtained, the combined company may suffer a loss of potential future revenue, incur costs, and lose rights that may be material to the business of the combined company. In addition, third parties with whom APA or Callon currently have relationships may terminate or otherwise reduce the scope of their relationship with either party in anticipation of the merger. Any such disruptions could limit the combined company’s ability to achieve the anticipated benefits of the merger. The adverse effect of any such disruptions could also be exacerbated by a delay in the completion of the merger or by a termination of the Merger Agreement.

The combined company may fail to realize the anticipated benefits of the merger.

The success of the merger will depend on, among other things, the combined company’s ability to combine the APA and Callon businesses in a manner that realizes anticipated synergies and benefits and meets or exceeds the forecasted stand-alone cost savings anticipated by the combined company. The combined company anticipates it will benefit from significant synergies, based on, among other things, increased scale. If the combined company is not able to successfully achieve these synergies, or the cost to achieve these synergies is greater than expected, then the anticipated benefits of the merger may not be realized fully or at all or may take longer to realize than expected.

The failure to successfully integrate the businesses and operations of APA and Callon in the expected time frame may adversely affect the combined company’s future results.

APA and Callon have operated and, until the completion of the merger, will continue to operate independently; however, their respective businesses may not be integrated successfully. It is possible that the integration process could result in the loss of key APA employees or key Callon employees, the loss of customers, providers, vendors, or business partners, the disruption of either company’s or both companies’ ongoing businesses, inconsistencies in standards, controls, procedures, and policies, potential unknown liabilities and unforeseen expenses, delays, or regulatory conditions associated with and following completion of the merger, or higher-than-expected integration costs and an overall post-completion integration process that takes longer than originally anticipated. Specifically, the following issues, among others, must be addressed in integrating the operations of APA and Callon in order to realize the anticipated benefits of the merger:

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In addition, at times the attention of certain members of either company’s or both companies’ management and resources may be focused on completion of the merger and the integration of the businesses of the two (2) companies and diverted from day-to-day business operations or other opportunities that may have been beneficial to such companies, which may disrupt each company’s ongoing business and the business of the combined company.

The unaudited pro forma combined financial information contained in this joint proxy statement/prospectus may not be an indication of the combined company’s results of operations or financial condition following the closing of the merger.

This joint proxy statement/prospectus includes unaudited pro forma combined financial information for the combined company, which gives effect to the merger and should be read in conjunction with the financial statements and accompanying notes of APA and Callon, which are incorporated by reference into this joint proxy statement/prospectus. The unaudited pro forma combined financial information contained in this joint proxy statement/prospectus should not be considered to be an indication of the combined company’s results of operations or financial condition following the closing of the merger. The unaudited pro forma combined financial information has been derived from the historical financial statements of APA and Callon, and adjustments, assumptions, and preliminary estimates have been made in connection with the preparation of this information. The information upon which these adjustments and assumptions have been made is preliminary, and these kinds of adjustments, assumptions, and estimates are difficult to make with accuracy.

Moreover, the unaudited pro forma combined financial information does not reflect all costs that are expected to be incurred by the combined company in connection with the merger. For example, the impact of any incremental costs incurred in coordinating the operations of APA and Callon are not reflected in the unaudited pro forma combined financial information. In addition, the unaudited pro forma combined financial information does not include, among other things, estimated cost synergies, adjustments related to restructuring or integration activities, future acquisitions or disposals not yet known or probable, or impacts of merger-related change in control provisions that are currently not factually supportable or probable of occurring.

As a result, the actual results of operations and financial condition of the combined company following the closing of the merger may not be consistent with, or evident from, the unaudited pro forma combined financial information. The assumptions used in preparing the unaudited pro forma combined financial information may not prove to be accurate, and other factors may affect the combined company’s results of operations or financial condition following the closing of the merger. Any potential decline in the combined company’s financial condition or results of operations may cause significant variations in the price of the APA Common Stock following the closing of the merger.

The unaudited pro forma combined financial information in this joint proxy statement/prospectus is based on the best information available, which in part includes a number of estimates and assumptions. These estimates and assumptions may prove not to be accurate, and accordingly, the unaudited pro forma combined financial information should not be assumed to be indicative of what the combined company’s financial condition, results of operations, or cash flows actually would have been as a standalone company or to be a reliable indicator of what the combined company’s financial condition or results of operations may actually be in the future.

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The financial forecasts relating to APA and Callon prepared in connection with the merger may not be realized, which may adversely affect the market price of the APA Common Stock following the closing of the merger.

This joint proxy statement/prospectus includes certain financial forecasts considered by APA and Callon in connection with their respective businesses. None of the financial forecasts prepared by APA or Callon were prepared with a view towards public disclosure or compliance with the published guidelines of the SEC, GAAP, or the guidelines established by the American Institute of Certified Public Accountants for preparation and presentation of financial forecasts. These forecasts are inherently based on various estimates and assumptions that are subject to the judgment of those preparing them. These forecasts are also subject to significant economic, competitive, industry, and other uncertainties and contingencies, all of which are difficult or impossible to predict and many of which are beyond the control of APA and Callon. Important factors that may affect the actual results of APA and Callon and cause the internal financial forecasts to not be achieved include risks and uncertainties relating to APA’s and Callon’s businesses, industry performance, the regulatory environment, general business and economic conditions, and other factors described under the section entitled “Cautionary Statement Regarding Forward-Looking Statements” in this joint proxy statement/prospectus.

In addition, the financial forecasts also reflect assumptions that are subject to change and do not reflect revised prospects for APA’s and Callon’s businesses, changes in general business or economic conditions, or any other transaction or event that has occurred or that may occur and that was not anticipated at the time the financial forecasts were prepared. In addition, since such financial forecasts cover multiple years, the information by its nature becomes less predictive with each successive year. There can be no assurance that APA’s, Callon’s, or the combined company’s financial condition or results of operations will be consistent with those set forth in such forecasts.

The trading price and volume of the APA Common Stock may be volatile following the merger.

The trading price and volume of the APA Common Stock may be volatile following completion of the merger. The stock markets in general have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. These broad market fluctuations may adversely affect the trading price of the APA Common Stock. As a result, you may suffer a loss on your investment.

The market for APA Common Stock will depend on a number of conditions, most of which the combined company cannot control, including:

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These and other factors may impair the market for the APA Common Stock and the ability of investors to sell shares at an attractive price. These factors also could cause the market price and demand for the APA Common Stock to fluctuate substantially, which may negatively affect the price and liquidity of the APA Common Stock. Many of these factors and conditions are beyond the control of the combined company or the combined company’s stockholders.

Future sales or issuances of APA Common Stock could have a negative impact on the APA Common Stock price.

The APA Common Stock that APA will issue to Callon stockholders if the merger is consummated generally may be sold immediately in the public market. It is possible that some Callon stockholders will decide to sell some or all of the shares of APA Common Stock that they receive in the merger. Any disposition of a significant number of shares of APA Common Stock, or the perception in the market that such dispositions could occur, may cause the price of APA Common Stock to fall. Any such decline could impair the combined company’s ability to raise capital through future sales of APA Common Stock.

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Combined company stockholders may experience dilution in the future.

The percentage ownership of the combined company’s stockholders may be diluted in the future because of equity issuances for acquisitions, capital market transactions, or otherwise, including, without limitation, equity awards that the combined company may grant to its directors, officers, and employees. Such issuances may have a dilutive effect on the combined company’s earnings per share, which could adversely affect the market price of the APA Common Stock.

In addition, the combined company’s certificate of incorporation will authorize the combined company to issue, without the approval of stockholders, one or more classes or series of preferred stock having such designations, powers, preferences, and relative, participating, optional, and other special rights, including preferences over APA Common Stock with respect to dividends and distributions, as the APA Board generally may determine. The terms of one or more classes or series of preferred stock could dilute the voting power or reduce the value of the APA Common Stock. For example, the repurchase or redemption rights or liquidation preferences that could be assigned to holders of preferred stock could affect the residual value of the APA Common Stock. For more information, see “Description of APA Capital Stock.”

The combined company may record goodwill and other tangible and intangible assets that could become impaired and result in material non-cash charges to the results of operations of the combined company in the future.

The combined company will account for the merger as an acquisition of a business in accordance with GAAP. Under the acquisition method of accounting, the assets and liabilities of Callon and its subsidiaries will be recorded, as of completion, at their respective fair values and added to APA’s. The combined company’s reported financial condition and results of operations for periods after completion of the merger will reflect Callon’s balances and results after completion of the merger but will not be restated retroactively to reflect the historical financial position or results of operations of Callon and its subsidiaries for periods prior to the merger.

Under the acquisition method of accounting, the total purchase price is allocated to Callon’s identifiable tangible and intangible assets acquired and liabilities assumed based on their respective fair market values as of the date of completion of the merger, with any excess purchase price allocated to goodwill. To the extent the value of goodwill, tangibles, or intangibles, if any, becomes impaired in the future, the combined company may be required to incur material non-cash charges relating to such impairment. The combined company’s operating results may be significantly impacted from both the impairment and the underlying trends in the business that triggered the impairment.

Following the closing of the merger, APA will incorporate Callon’s hedging activities into APA’s business, and APA may be exposed to additional commodity price risks arising from such hedges.

To mitigate its exposure to changes in commodity prices, Callon hedges oil, natural gas, and NGL prices from time to time, primarily through the use of certain derivative instruments, including fixed price swaps, basis swaps, and costless collars. APA will bear the economic impact of all of Callon’s current hedges following the closing of the merger. Actual crude oil, natural gas, and NGL prices may differ from the combined company’s expectations and, as a result, such hedges may or may not have a negative impact on APA’s business.

Risks Relating to Callon’s Business

You should read and consider risk factors specific to Callon’s business that will also affect the combined company after the merger. These risks are described in the section entitled “Risk Factors” in Callon’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, and in other documents incorporated by reference into this joint proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 210 of this document for the location of information incorporated by reference into this joint proxy statement/prospectus.

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Risks Relating to APA’s Business

You should read and consider risk factors specific to APA’s business that will also affect the combined company after the merger. These risks are described in the section entitled “Risk Factors” in APA’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, and in other documents incorporated by reference into this joint proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 210 of this document for the location of information incorporated by reference into this joint proxy statement/prospectus.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Certain statements and information in this joint proxy statement/prospectus may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. The words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “predict,” “budget,” “should,” “would,” “could,” “attempt,” “appears,” “forecast,” “outlook,” “estimate,” “continue,” “project,” “projection,” “goal,” “model,” “target,” “potential,” “may,” “will,” “objective,” “guidance,” “outlook,” “effort,” “are likely,” and other similar expressions are intended to identify forward-looking statements, which are generally not historical in nature, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements are based on APA’s and Callon’s current expectations and beliefs concerning future developments and their potential effect on their respective businesses.

The forward-looking statements contained in this document are largely based on APA’s and Callon’s expectations for the future, which reflect certain estimates and assumptions made by their respective managements. These estimates and assumptions reflect APA’s and Callon’s best judgment based on currently known market conditions, operating trends, and other factors. Although APA and Callon believe such estimates and assumptions to be reasonable, they are inherently uncertain and involve a number of risks and uncertainties that are beyond APA’s and Callon’s control. As such, management’s assumptions about future events may prove to be inaccurate. For a more detailed description of the risks and uncertainties involved, see “Risk Factors” in APA’s and Callon’s most recently filed Annual Reports on Form 10-K, subsequent Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and other SEC filings. Except as required by law, APA and Callon do not intend to publicly update or revise any forward-looking statements as a result of new information, future events, changes in circumstances, or otherwise.

These cautionary statements qualify all forward-looking statements attributable to APA or Callon, or persons acting on either’s behalf. APA management and Callon management caution you that the forward-looking statements contained in this joint proxy statement/prospectus are not guarantees of future performance, and neither APA nor Callon can assure you that such statements will be realized or that the events and circumstances they describe will occur. Factors that could cause actual results to differ materially from those anticipated or implied in the forward-looking statements herein include, but are not limited to:

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All subsequent written and oral forward-looking statements concerning APA, Callon, the merger, the combined company, or other matters and attributable to APA or Callon or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements above. Except as required by law, APA and Callon assume no duty to update or revise their respective forward-looking statements based on new information, future events, or otherwise.

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THE PARTIES TO THE MERGER

APA Corporation

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

(713) 296-6000

APA is an independent energy company that explores for, develops, and produces natural gas, crude oil, and natural gas liquids in the United States, Egypt, and the United Kingdom and explores for oil and natural gas in offshore Suriname. Shares of APA Common Stock are listed and traded on the Nasdaq under the ticker symbol “APA.” Additional information about APA and its subsidiaries, including, but not limited to, information regarding its business, properties, legal proceedings, financial statements, financial condition and results of operations, market risk, executive compensation, and related party transactions is set forth in APA’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, and APA’s Quarterly Reports on Form 10-Q for the quarters ended March 31, 2023, June 30, 2023, and September 30, 2023, which are each incorporated by reference into this joint proxy statement/prospectus.

For more information about APA, please visit APA’s website at www.apacorp.com. The information contained on APA’s website or accessible through it does not constitute a part of this joint proxy statement/prospectus.

Callon Petroleum Company

One Briarlake Plaza

2000 W. Sam Houston Parkway S., Suite 2000

Houston, Texas 77042

(281) 589-5200

Callon has been engaged in the exploration, development, acquisition, and production of oil and natural gas properties since 1950. Callon is an independent oil and natural gas company focused on the acquisition, exploration, and sustainable development of high-quality assets in the Permian Basin in West Texas. Its activities are primarily focused on horizontal development in the Midland and Delaware Basins, both of which are part of the larger Permian Basin in West Texas. Callon’s primary operations in the Permian reflect a high-return, oil-weighted drilling inventory with multiple prospective horizontal development intervals. Shares of Callon Common Stock are listed and traded on the NYSE under the ticker symbol “CPE.” Additional information about Callon and its subsidiaries, including, but not limited to, information regarding its business, properties, legal proceedings, financial statements, financial condition and results of operations, executive compensation, and related party transactions is set forth in Callon’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, and Callon’s Quarterly Reports on Form 10-Q for the quarters ended March 31, 2023, June 30, 2023, and September 30, 2023, which are each incorporated by reference into this joint proxy statement/prospectus.

For more information about Callon, please visit Callon’s website at www.callon.com. The information contained on Callon’s website or accessible through it does not constitute a part of this joint proxy statement/prospectus.

Astro Comet Merger Sub Corp.

2000 Post Oak Boulevard, Suite 100

Houston, Texas 77056

(713) 296-6000

Merger Sub is a wholly owned, direct subsidiary of APA. Merger Sub was formed by APA solely in contemplation of the merger, has not conducted any business, and has no assets, liabilities, or other obligations of any nature other than as set forth in the Merger Agreement.

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THE MERGER

The following discussion contains certain information about the proposed merger. This discussion is subject, and qualified in its entirety by reference, to the Merger Agreement attached as Annex A to this joint proxy statement/prospectus. You are urged to carefully read this entire joint proxy statement/prospectus, including the Merger Agreement, before making any investment or voting decision.

Transaction Structure

Upon the terms and subject to the conditions set forth in the Merger Agreement, and in accordance with the DGCL, at the Effective Time, Merger Sub will be merged with and into Callon, the separate corporate existence of Merger Sub will cease, and Callon will continue as the Surviving Corporation in the merger as a wholly owned, direct subsidiary of APA.

Consideration to Callon Stockholders

At the Effective Time, by virtue of the merger and without any further action on the part of APA, Merger Sub, Callon, or any holder of capital stock thereof:

In addition, each outstanding Callon equity award in respect of Callon Common Stock will be treated as described in “The Merger Agreement—Treatment of Callon Long-Term Incentive Awards.”

Background of the Merger

The terms of the Merger Agreement are the result of arm’s-length negotiations between representatives of Callon and APA. The following is a summary of the events leading up to the signing of the Merger Agreement and the key meetings, negotiations, discussions, and actions by and between Callon and APA and their respective advisors that preceded the public announcement of the merger. However, this summary does not purport to catalog every conversation or interaction among the representatives of APA, Callon, and other parties.

The Callon Board, in the ordinary course and consistent with its fiduciary duties, continually evaluates Callon’s operations and future business prospects with a focus on generating long-term value for its stockholders by leveraging assets to create sustainable value, extend inventory life, and grow free cash flow to reduce long-term debt and return cash to stockholders. In connection with such ongoing evaluation, the Callon Board and Callon management team also review and assess potential strategic alternatives available to Callon, including mergers and acquisitions (“M&A”) and asset acquisitions and dispositions. During the past several years, the Callon Board and Callon management team have sought to execute strategies that would improve Callon’s position as a scaled, Permian Basin-focused exploration and production (“E&P”) company. Callon’s commitment to develop over a decade of high-quality, oil-rich inventory, improve capital efficiency, and control costs permitted the Callon Board to deliberately evaluate strategic M&A opportunities that would maximize stockholder returns.

The APA Board and APA’s management periodically review the strategic direction of APA and evaluate potential opportunities to enhance shareholder value, including through potential transactions involving

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acquisitions and combinations. From time to time, senior executives of APA, including Mr. John J. Christmann IV, Chief Executive Officer and Director of APA, have had informal and preliminary conversations about potential strategic transaction opportunities with senior executives of other companies. APA’s senior executives have updated the APA Board regarding these interactions during regularly scheduled and special meetings of the APA Board.

On October 5, 2021, Callon announced the closing of its acquisition of leasehold interests and related oil, gas, and infrastructure assets of Primexx Energy Partners and its affiliates in the Southern Delaware Basin and a simultaneous debt-for-equity exchange, which strengthened Callon’s financial position by reducing leverage, increasing current production, and extending inventory.

In November 2021, the chief executive officer of a publicly traded E&P company with operations outside of the Permian Basin (“Company A”), approached Mr. Joseph C. Gatto, Jr., President, Chief Executive Officer, and Director of Callon, to discuss a potential merger transaction among three E&P companies, including Company A and Callon, that would result in a larger, more diversified E&P company. The chief executive officer of Company A and Mr. Gatto discussed the merits of increasing oil-rich inventory as a scaled company, but specific details of a transaction were not discussed.

Consistent with its ongoing evaluation of future business prospects, subsequent to Mr. Gatto’s meeting with Company A, the Callon Board discussed a spectrum of various alternatives for Callon’s strategy and the underlying rationale at each of its regularly scheduled meetings throughout 2022 and 2023. Following discussions at its regularly scheduled meeting in January 2022, including an update regarding Mr. Gatto’s contact with Company A, the Callon Board instructed Mr. Gatto and the Callon management team to explore all alternatives, including remaining a standalone company and engaging in additional asset acquisitions and divestitures, combining with another pure-play Permian Basin E&P company, or combining with an E&P company with diversified assets with multi-basin operations.

Throughout the first quarter of 2022 and prior to the regularly scheduled meeting of the Callon Board on March 9, 2022, Mr. Gatto continued to engage in exploratory communications with a number of E&P companies with operations in North America, including maintaining discussions with Company A regarding a potential business combination and evaluating other potential transaction opportunities.

In February 2022, Mr. Gatto also commenced discussions with a privately held pure-play Permian operator (“Company B”) regarding a potential business combination. Callon and Company B entered into a mutual confidentiality agreement that contained a customary “standstill” provision that restricted the activities of Company B, a fallaway provision and a modified “don’t ask, don’t waive” provision that did not restrict the ability of Company B to make a private proposal regarding a business combination to the Callon Board. Callon and Company B subsequently commenced the exchange of financial and operational due diligence materials. At the invitation of Company B, Callon later submitted a non-binding indication of interest.

In February 2022, at a meeting between Mr. Gatto and the chief executive officer of Company A, Company A’s chief executive officer proposed that Company A acquire Callon in an at-the-market transaction. Mr. Gatto did not respond to the proposal except to note that the next regularly scheduled Callon Board meeting was in March, and such proposal would be considered at that meeting.

Later that month, Mr. Gatto met with the chief executive officer of a publicly traded, pure-play E&P operator in the Permian Basin (“Company C”), and they engaged in high-level discussions regarding the merits of a potential combination. After initial discussions, the CEO of Company C said they could be interested in continuing discussions depending on the outcome of another strategic opportunity they were evaluating.

In early March 2022, Mr. Gatto met with the Chief Executive Officer of a publicly traded company with operations in the Permian Basin (“Company D”), and they discussed their views of the E&P industry, generally.

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They also discussed the perceived merits and risks of a combination of the two companies under the prevailing market conditions as well as potential synergies that could result from a combination between the two companies based on their complementary acreage positions in parts of the Permian Basin and agreed to stay in contact.

On March 9, 2022, at a regularly scheduled meeting, the Callon Board continued discussions regarding the spectrum of alternatives for the company in the context of investor priorities for the sector. The Callon management team provided updates on their recent discussions with potential counterparties regarding strategic opportunities for Callon, including the verbal expression of interest from Company A for an at-the-market acquisition of Callon. They also discussed with the Callon Board the potential combination with Company B and the recent submission of a non-binding indication of interest for Company B. Given the preliminary nature of each of the opportunities discussed, the Callon Board instructed the Callon management team to continue its efforts and did not make any decisions regarding the relative merits and risks of any specific opportunity, other than to conclude that Company A’s proposal was not in the best interests of Callon and its stockholders given the absence of a premium and Company A’s focus entirely outside of the Permian Basin.

Over the ensuing months, Callon and Company B continued to exchange financial and technical due diligence materials, and they participated in reciprocal management presentations. In the second quarter of 2022, Company B publicly announced entry into a strategic transaction and ceased discussions with Callon in compliance with the terms of its definitive transaction agreement.

In May 2022, Mr. Gatto and Mr. Kevin Haggard, Senior Vice President and Chief Financial Officer of Callon, met with the chief executive officer and chief financial officer of Company D to discuss, among other matters, the perceived strategic rationale for a transaction between Company D and Callon based on each party’s evaluation of the other party’s publicly available information. The representatives of each of Callon and Company D agreed that there could be benefits to both companies resulting from the scaled positions in Texas basins, as well as an opportunity to deleverage the combined company’s balance sheet and improve the return of capital to stockholders. Later that month, Callon and Company D entered into a mutual confidentiality agreement with a mutual and customary “standstill” provision, including a fallaway and a modified “don’t ask, don’t waive” provision that did not restrict the ability of a party to make a private proposal regarding a business combination to the other party’s board of directors (the “Company D NDA”). Thereafter, the management teams of each of Callon and Company D exchanged detailed financial and operational due diligence materials.

On May 25, 2022, at a regularly scheduled meeting of the Callon Board, with members of the Callon management team in attendance, Mr. Gatto discussed with the Callon Board the macro industry environment and evolving investor preferences. He then provided an update to the Callon Board regarding management’s ongoing efforts in evaluating the strategic options reasonably available to Callon and provided an overview of a potential combination with Company D. After discussion, the Callon Board expressed support for continuing to evaluate a potential transaction with Company D as well as Callon’s other strategic options within the context of industry consolidation.

Throughout the ensuing months, Callon and Company D continued exchanging due diligence materials and also provided reciprocal management presentations. Throughout that time period, Mr. Gatto and Company D’s chief executive officer periodically discussed the progression of each party’s due diligence efforts and the merits and risks of a potential transaction.

At a meeting held on July 25, 2022, the Callon Board, with members of the Callon management team in attendance, invited representatives of its then-current financial advisor to present a macro overview of industry trends, investor priorities, and Callon’s financial and stock price performance. Mr. Gatto then updated the Callon Board on the progress of financial and operational due diligence on Company D, noting that Company D and Callon had jointly focused on technical due diligence matters and, with support from members of the Callon management team, discussed each company’s inventory and perceived synergies, risks, and opportunities. The financial advisor discussed in detail the current relative valuations of the two companies, perceived valuation

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drivers, and potential near-term catalysts for both companies. After discussion in executive session, the Callon Board expressed support for continuing to evaluate a potential transaction with Company D along with considering other strategic opportunities.

In mid-August of 2022, the chief executive officer of Company D and Mr. Gatto convened by phone to discuss the potential transaction, their respective perceptions of the market volatility affecting E&P companies generally and each of their companies specifically, and both agreed to pause discussions until later that year.

On August 24, 2022, at a regularly scheduled meeting of the Callon Board, the Callon Board discussed Callon’s performance on various financial and operational metrics. The Callon Board further discussed its near-term priorities, the E&P industry landscape, and longer-term optionality regarding strategic opportunities available to Callon. The Callon Board discussed various steps to best position Callon but did not make any decisions regarding the relative merits or risks of any strategic opportunity at that time.

Throughout the remainder of 2022 and into 2023, Mr. Gatto and members of the Callon management team continued to evaluate potential strategic transactions available to Callon, and the Callon Board received regular updates. As part of such evaluation, the Callon management team had exploratory discussions with several public and private companies from time to time which led to more advanced dialogue with select parties based on strategic and financial merits but, other than as described below, no specific transaction terms were discussed.

In September 2022, Mr. Gatto and Mr. Haggard met with their counterparts from a publicly traded E&P company with operations outside of the Permian Basin (“Company E”) to discuss the strategic merits and considerations of a potential combination. Over the ensuing weeks, Callon and Company E entered into a mutual confidentiality agreement with a mutual and customary “standstill” provision, a fallaway provision and a modified “don’t ask, don’t waive” provision that did not restrict the ability of a party to make a private proposal regarding a business combination to the other party’s board of directors, exchanged financial and technical due diligence materials, and participated in reciprocal management presentations. Throughout that time period, Mr. Gatto and the chief executive officer of Company E periodically discussed the ongoing due diligence efforts as well as the strategic merits and risks of a potential combination, including the financial strength of the combined company and optionality for capital allocation. They also discussed potential investor receptivity to a proposed multi-basin combination with the majority of operations outside of the Permian Basin.

On October 27, 2022, the Callon Board met to consider the potential transaction with Company E, with members of the Callon management team and representatives from one of Callon’s financial advisors in attendance. The Board discussed with management and its advisors the potential benefits of the transaction as well as the risks, including the lack of operational industrial logic for the potential cross-basin combination with limited opportunities for synergies. Subsequently, the parties mutually agreed to pause discussions until financial results for the year ended December 31, 2022, for each company had been announced.

In late 2022 and into 2023, as part of its ongoing assessment of strategy, Callon evaluated a series of Permian Basin asset acquisitions, as well as the potential disposition of its assets in the Eagle Ford Shale, with the objective of advancing Callon’s strategic objectives and focusing the organization entirely on the Permian Basin. Mr. Gatto and the management team periodically convened the Callon Board to discuss the asset opportunities under evaluation as well as the evolving landscape for E&P transactions.

On February 9, 2023, at a regularly scheduled meeting of the Callon Board, the management team provided updates for the Callon Board on the ongoing evaluation of Permian Basin asset acquisition opportunities, as well as the potential disposition of the Eagle Ford assets. At the invitation of the Callon Board and the management team, representatives from a financial advisor presented a broad overview of the energy landscape and offered perspectives on how certain factors, including capital allocation, inventory, and scale, had been influencing trading multiples in the sector. The advisors also discussed recent upstream transactions, investor reactions thereto, and the implications for Callon, and then reviewed potential strategic opportunities for Callon to consider. Following discussions, the Callon Board reiterated its guidance to the management team to continue exploring all alternatives for long-term shareholder value creation.

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On March 21, 2023, Mr. Gatto and Company E’s chief executive officer met to renew discussions about a potential combination. Mr. Gatto emphasized the need to develop strong industrial logic for a transaction of this nature with a diversified operational profile, and he also proposed the concept of a multi-party transaction to increase the Permian weighting of the combined company. Neither party proposed any commercial terms for a potential transaction, but they agreed to maintain a dialogue.

In the spring of 2023, Mr. Gatto spoke several times with the chief executive officer of a publicly traded, pure-play E&P operator in the Permian Basin (“Company F”) to discuss the merits of a potential strategic combination.

At a regularly scheduled meeting of the Callon Board on April 26, 2023, the management team updated the Callon Board on the advancing discussions for a potential disposition of Callon’s Eagle Ford position and a contingent acquisition of a Delaware Basin asset, which transactions were intended to strengthen Callon’s financial position and support the adoption of a return of capital program. The management team also provided the Callon Board with a high-level overview of a potential corporate combination with Company F. Following discussions, the Callon Board expressed its support for management to evaluate a combination with Company F as well as other strategic opportunities.

On May 3, 2023, Callon announced its entry into two definitive agreements to acquire Delaware Basin assets from Percussion Petroleum Operating II, LLC and to divest of its non-core Eagle Ford assets to Ridgemar Energy Operating, LLC (the “Percussion-Ridgemar Transactions”). Callon also announced the initiation of a $300 million share buyback program over a two-year period, subject to the closing of the transactions.

Following the announcement of the Percussion-Ridgemar Transactions, Mr. Gatto re-engaged with the chief executive officer of Company F to discuss a potential combination of the pure-play Permian companies. Shortly thereafter, Callon and Company F entered into a mutual confidentiality agreement, which included a mutual and customary “standstill” provision, including a provision that did not restrict the ability of a party to make a private proposal regarding a business combination to the other party’s CEO or board of directors. In the months that followed, the management teams of Callon and Company F exchanged detailed financial and operational due diligence materials and participated in reciprocal management presentations. Mr. Gatto and the chief executive officer of Company F periodically discussed the ongoing due diligence efforts and potential strategic merits and risks of a combination. Mr. Gatto expressed some concern about the relative positioning of a combined company in the evolving E&P landscape. Neither party proposed formal terms for a proposed transaction.

On July 3, 2023, each of the Percussion-Ridgemar Transactions closed, which solidified Callon’s approach as a focused, scaled Permian Basin E&P company.

At a regularly scheduled meeting of the Callon Board on July 24, 2023, the Callon Board continued discussions with the management team regarding the macro industry landscape, current themes in upstream public market investments, recent transaction activity in the space, and strategic opportunities for Callon.

In the third quarter of 2023, Company F publicly announced entry into a strategic transaction and thereafter ceased discussions with Callon in compliance with the terms of its definitive transaction agreement.

On September 13, 2023, the APA Board held a regularly scheduled board meeting, which was attended by members of senior management of APA, during which the APA Board and management discussed APA’s strategy, including a review of recent merger and acquisition activity in the upstream oil and gas industry and potential acquisition or other transaction opportunities for APA. The APA Board was supportive of management continuing its review of potential transactions and directed management to keep the APA Board apprised of any material developments.

In September 2023, APA engaged Citi and WFS as financial advisors for APA, in light of their experience and qualifications, in connection with its review of a potential transaction with Callon and other strategic alternatives.

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Also in September 2023, Mr. Gatto and the chief executive officer of Company A met in the ordinary course and discussed, among other matters, the ongoing M&A activity in the E&P industry, including their views on the Permian Basin.

Later that month, the chief executive officer of Company D called Mr. Gatto to discuss resuming discussions regarding a potential transaction. Mr. Gatto indicated that the market timing for a potential transaction may be more conducive than when the parties were last in discussions in August 2022, but indicated that the Callon Board was scheduled to meet in October, and he would receive guidance from the Callon Board on re-engaging at that time.

In October 2023, representatives of the Callon management team contacted Kirkland & Ellis LLP (“Kirkland”) to discuss Kirkland’s engagement in connection with a potential M&A transaction and Morgan Stanley to discuss its potential engagement as lead financial advisor in connection with Callon’s consideration of potential transactions.

On October 16, 2023, Mr. Christmann and other members of APA’s management provided an update to the APA Board during an optional board call on the work completed since the September strategy discussion, including a preliminary analysis of a potential transaction with Callon. The analysis included APA management’s views on Callon’s value, potential synergies, and the possible benefits and risks of a transaction with Callon, as well as other strategic alternatives. The APA board members present for the call expressed support for Mr. Christmann making an approach to Mr. Gatto for an introductory meeting to explore a potential transaction.

On October 17, 2023, Mr. Christmann contacted Mr. Gatto by telephone to arrange meeting over dinner to discuss a potential transaction between APA and Callon, and in a following call, Mr. Gatto agreed to meet for dinner on October 23, 2023.

On the evening of October 23, 2023, Mr. Gatto met with Mr. Christmann. During the meeting, Mr. Christmann delivered a written, non-binding proposal (the “APA October Proposal”) to Mr. Gatto specifying APA’s interest in acquiring all of the outstanding capital stock of Callon in exchange for a number of shares of APA Common Stock that would represent $42.00 per share of Callon Common Stock. The proposal package included a draft confidentiality agreement, which did not contain a standstill provision, and an approach deck that outlined the strategic merits of the proposed combination. The APA October Proposal implied a premium of 7.6% to the closing price of Callon Common Stock on October 23, 2023, and an exchange ratio of 1.020x.

On October 26, 2023, Mr. Christmann followed up with Mr. Gatto on the letter APA provided on October 23, 2023, stating that APA was ready to advance the negotiation and due diligence processes and that Mr. Christmann was available to discuss the transaction. Mr. Gatto replied, confirming receipt of the letter and that it would be reviewed with the Callon Board after further preparation.

On October 26, 2023, at a regularly scheduled meeting of the Callon Board, with members of the Callon management team and representatives from Morgan Stanley in attendance, the Callon Board considered, among other matters, the APA October Proposal. During this meeting, Ms. Michol L. Ecklund, Senior Vice President, Chief Sustainability Officer, and General Counsel of Callon, reviewed with the Callon Board its fiduciary duties in considering strategic alternatives. In addition, representatives of Morgan Stanley provided an overview of macro industry trends and then discussed with the Callon Board the APA October Proposal, relevant background information on APA and its assets and operations, and preliminary, high-level financial analyses related to the APA October Proposal. Mr. Gatto also updated the Callon Board on the status of discussions with Company D and other recent contacts. After discussion, including regarding the potential benefits of a combination with APA and its strategic logic, the Callon Board generally agreed that the Callon management team should engage with APA to exchange due diligence materials, but not in a manner preclusive of other offers.

On November 1, 2023, Callon and APA each released their respective quarterly results for the third quarter of 2023.

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On November 3, 2023, Mr. Gatto called Mr. Christmann regarding the APA October Proposal to convey that the Callon Board had expressed support for evaluating a potential transaction with APA and that Callon was prepared to enter into a confidentiality agreement to facilitate financial and operational due diligence. That same day, Mr. Gatto provided to Mr. Christmann a revised version of the mutual confidentiality agreement, which included changes to several provisions and the addition of customary standstill restrictions, with a customary “fall-away” provision and a modified “don’t ask, don’t waive” that did not restrict the ability of a party to make a private proposal regarding a business combination to the other party’s chief executive officer or board of directors.

On November 4, 2023, Mr. Scott Grandt, APA’s Senior Vice President of Corporate Development, sent a request to Ms. Ecklund and Mr. Liam Kelly, Callon’s Vice President of Corporate Development and Land, for a conference call amongst APA’s and Callon’s corporate development teams to discuss due diligence. That same day, Mr. Grandt provided a revised draft of the mutual confidentiality agreement with only minor changes. On November 6, 2023, Callon and APA entered into a mutual confidentiality agreement, which included the mutual and customary “standstill,” fallaway, and modified “don’t ask, don’t waive” provisions discussed above. Thereafter, the management teams of each of Callon and APA began exchanging detailed financial and operational due diligence materials.

Also on November 6, 2023, Mr. Gatto and the chief executive officer of Company D had a call to continue their discussion from September. On that call, Company D’s chief executive officer verbally communicated a non-binding proposal to acquire all of the outstanding capital stock of Callon in exchange for Company D’s common stock at an exchange ratio that implied a premium of 12.7% to the closing price of Callon Common Stock on November 3, 2023. That same day, Company D sent a non-binding written proposal to Mr. Gatto confirming the terms discussed on the call (the “Company D Nov. 6 Proposal”).

On November 10, 2023, the Callon Board held a meeting to consider the APA October Proposal and the Company D Nov. 6 Proposal with members of the Callon management team and representatives from Kirkland and Morgan Stanley in attendance. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives. Representatives of Morgan Stanley then provided an update on discussions with APA, as well as the volatility in commodity prices and relative share price performances since the Callon Board’s most recent meeting in late October. They discussed the potential implications for the APA October Proposal and the market for transactions in general. They then provided a review of the Company D Nov. 6 Proposal and discussed other potential counterparties for Callon, including Company A and Company C based on their relative scale, Permian Basin acreage positions, and overall strategic alignment. After discussion, the Callon Board instructed the Callon management team, with assistance from Morgan Stanley, to continue to engage with each of APA and Company D while continuing to evaluate other strategic options and monitor the macro-level market factors.

On November 13, 2023, Mr. Gatto called Mr. Christmann to clarify the terms of the APA October Proposal in light of recent fluctuations to each of Callon’s and APA’s stock price. Mr. Christmann noted that APA’s financial and operational due diligence were ongoing and that such work streams would need to progress before APA could provide a more certain economic proposal.

The following day, on November 14, 2023, Mr. Christmann and Mr. Gatto convened by telephone to confirm the details of the exchange of financial and operational due diligence materials. Mr. Christmann also reiterated that APA expected to be in a position to provide a refined proposal after scheduling and hosting in-person due diligence meetings.

On November 16, 2023, Mr. Gatto called the chief executive officer of Company D to clarify the terms of the Company D Nov. 6 Proposal, including whether Company D had any expectations regarding governance and whether the proposal remained subject to any key due diligence matters. Company D’s chief executive officer indicated that representatives of Callon should expect to have some governance role in the combined company,

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but no specific terms to supplement the Company D Nov. 6 Proposal were provided. In the same discussion, the chief executive officers discussed plans for Callon and Company D to exchange updated non-public information under a confidentiality agreement.

On November 19, 2023, Company D and Callon agreed to extend the term of the Company D NDA.

On November 20, 2023, Mr. Gatto met with the chief executive officer of Company E in the ordinary course to discuss the E&P industry generally. Company E’s chief executive officer indicated that Company E intended to scale within the basins it already operated in. Neither party proposed any terms of a proposed transaction.

On November 21, 2023, Mr. Gatto met with the chief executive officer of Company A in the ordinary course. Company A’s chief executive officer gave Mr. Gatto an update on Company A’s recent acquisition activities and stated his expectation that the E&P industry would continue to consolidate at a rapid pace. Each agreed on the merits of a scaled company with a strong Permian Basin presence and an improved cost of capital. Neither party proposed any terms of a proposed transaction.

Also on November 21, 2023, Mr. Gatto and the chief executive officer of Company D convened by phone to confirm the logistics of exchanging each party’s confidential information and agree to meet at the end of November to discuss pro forma capital allocation and review.

On November 27, 2023, at the direction of the Callon management team and in accordance with the guidance of the Callon Board, representatives of Morgan Stanley separately contacted representatives of each of Company C and Company A to invite each such company to formally consider a potential strategic transaction with Callon. Following these discussions, Morgan Stanley provided each of Company C and Company A with a form confidentiality agreement.

Also on November 27, 2023, Messrs. Gatto and Christmann convened by telephone to discuss the management presentation by APA’s management team contemplated later that week. In the same discussion, Mr. Christmann noted that it was his expectation that APA could confirm a comparable exchange ratio to that set forth in the APA October Proposal based on relative trading prices at that time.

Later that day, Callon contacted RBC Capital Markets, LLC (“RBCCM”) to discuss its engagement as a financial advisor in connection with Callon’s consideration of a potential M&A transaction.

On November 29, 2023, Mr. Gatto met with the chief executive officer of Company D to discuss the strategic rationale for the transaction and key financial metrics, including free cash flow generation that would be driven in part by a reduction in pro forma drilling activity. During this call, Company D’s chief executive offer noted that Company D anticipated at least $100 million in synergies to result from a combination with Callon and that he hoped the parties could execute definitive transaction documentation by mid-December.

Also on November 29, 2023, Callon entered into a confidentiality agreement with each of Company C and Company A, both of which included a mutual and customary “standstill” provision, including a fallaway and a modified “don’t ask, don’t waive” provision that did not restrict the ability of a party to make a private proposal regarding a business combination to the other party’s board of directors. Thereafter, Callon began to exchange operational and financial due diligence information with each of Company C and Company A.

On November 30, 2023, Callon received an unsolicited draft merger agreement from representatives of Company D, including, among other terms, a condition to closing that neither Callon nor Company D would be subject to an impermissible regulatory condition relating to their respective operations. Further, the terms of the merger agreement included that the termination fees that would be payable by either party under certain circumstances be calculated to equal 4.5% of Callon’s implied equity value at the proposed exchange ratio, and each party would be required to reimburse the other party’s transaction expenses under certain circumstances in an amount equal to 1.0% of Callon’s equity value; and the combined company board would include two members from the Callon Board selected by Callon.

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On December 1, 2023, members of APA’s and Callon’s management teams presented to each other a detailed discussion of their respective operations and financial condition. Representatives of the parties’ respective financial advisors were present.

On December 4, 2023, the APA Board met to discuss the proposed transaction with Callon. APA management provided an update on recent developments and presented information on potential exchange ratios and associated implied premiums. The APA Board was supportive of Mr. Christmann sending a revised offer to Callon and specifying an exact exchange ratio.

On December 4, 2023, Mr. Christmann called Mr. Gatto to convey a revised proposal specifying APA’s interest in acquiring all of the outstanding capital stock of Callon in exchange for 0.975 shares of APA Common Stock. The revised proposal implied a premium of 12.9% to the closing price of Callon Common Stock on December 1, 2023. Mr. Christmann informed Mr. Gatto that it was the view of the APA Board that such a premium was comparable to that of recent transactions in the E&P industry and noted the potential risk of market reception for greater premiums. Later that same day, APA sent a written, non-binding proposal to Callon confirming the terms discussed as well as a draft merger agreement. APA’s draft merger agreement specified, among other terms, that neither Callon nor APA would be permitted to terminate the merger agreement in order to accept a “superior proposal” unless one of the party’s stockholders had voted on and failed to approve the transaction (a “force the vote provision”); the termination fees that would be payable by either party under certain circumstances be equal to $125 million; and neither party would be obligated to reimburse the other’s expenses in the event that the transaction was not approved by such party’s stockholders.

On December 6, 2023, members of Company D’s management team and members of the Callon management team made presentations to the other party regarding such company’s operations and financial condition.

On December 8, 2023, Mr. Gatto and the chief executive officer of Company D convened via telephone to discuss the strategic logic of a potential transaction and to discuss details regarding Company D’s estimation of synergies. Company D’s chief executive officer noted the pro forma combined company would be expected to have very strong positioning with financial strength and significant technical capabilities. Mr. Gatto requested detailed support for Company D’s evaluation of potential synergies, and Company D’s chief executive officer noted he would discuss with his team.

Also on December 8, 2023, the chief executive officer of Company A called Mr. Gatto to preview that Company A intended to submit a proposal later that day specifying Company A’s interest in acquiring all of the outstanding capital stock of Callon in exchange for shares of Company A common stock, with an implied premium of up to 10%. Later that same day, Company A sent a written, non-binding proposal to Callon confirming the terms discussed.

On December 9, 2023, Mr. Gatto provided a brief update to the Callon Board regarding the status of discussions with the potential counterparties.

On December 12, 2023, Company D provided a one-page summary of its synergy analysis, which illustrated a material increase in anticipated synergies from the $100 million in anticipated synergies provided by Company D on November 29, 2023.

On December 13, 2023, Mr. Gatto and the chief executive officer of Company A convened by telephone to discuss logistics for the planned management presentations. Later that day, at the direction of the Callon management team and in accordance with the guidance of the Callon Board, representatives of Morgan Stanley spoke with Company A’s financial advisors to convey that Company A’s proposal was trailing the proposals of other interested parties and advised Company A to improve its proposal to remain competitive.

Also on December 13, 2023, Mr. Gatto and the chief executive officer of Company C met to discuss a potential transaction. Company C expressed that its priorities were focused on executing its strategic plan, but

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there were clear synergies in the Permian Basin so would be prepared to proceed with a no-to-low premium transaction.

On December 14, 2023, a member of Company A’s management team contacted Morgan Stanley to provide the update that Company A was no longer interested in evaluating a transaction with Callon.

Also on December 14, 2023, the Callon Board convened with members of the Callon management team to review and approve Callon’s 2024 capital budget, which reflected an improving well cost structure, shorter cycle times, and optimized capital allocation across Callon’s portfolio. Thereafter, representatives from Kirkland, Morgan Stanley, and RBCCM joined to discuss with the Callon Board, among other matters, the ongoing discussions between Callon and each potential counterparty. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives. Representatives of Morgan Stanley, together with Mr. Gatto, summarized discussions with each of the potential counterparties, including that Company A no longer intended to pursue a transaction with Callon and Company C would be prepared to discuss a no-to-low premium transaction. After discussion, the Callon Board instructed Morgan Stanley to (i) continue to engage with Company A and Company C, and convey they were welcome to continue to participate in discussions if they improved their respective offers, and (ii) continue to engage with each of APA and Company D, including to solicit additional back-up for Company D’s estimation of potential synergies, so as to enable the Callon Board to better compare each offer.

Also on December 14, 2023, Mr. Gatto and the chief executive officer of Company D convened by telephone and agreed to meet, together with Callon’s and Company D’s respective chairmen in attendance, to discuss synergies and the pro forma combined company’s governance and growth prospects. On behalf of Callon, Morgan Stanley contacted Company C to discuss its interest in continuing to pursue a potential transaction. Company C indicated that it did not intend to continue pursuing a transaction and would not be sending a written offer.

On December 15, 2023, Bloomberg published an article (the “Bloomberg article”) speculating that Callon was considering strategic options amid takeover interest from other E&P companies.

Also on December 15, 2023, Messrs. Gatto and Christmann convened by telephone to discuss the potential transaction, including outstanding due diligence matters, in order to refine each of Callon’s and APA’s net asset value analysis and update their respective boards. Both estimated that the financial and operational due diligence matters would be substantially complete prior to the year-end holidays. The two also decided to have their respective financial advisors connect with each other to discuss the proposed transaction.

On December 18, 2023, Mr. Gatto was contacted by the chief executive officer of a publicly-traded company (“Company G”), a peer with whom he had periodic discussions regarding macro industry and Permian Basin trends. The chief executive officer of Company G conveyed interest in discussing a potential strategic combination with Callon and proposed to engage in January to provide information on Company G’s evolving strategy and asset base.

Later that day, Mr. Gatto and Mr. Matthew R. Bob, Chairman of the Callon Board, met with their counterparts of Company D to discuss the potential transaction, including Company D’s strategy. Despite multiple requests, Company D had not yet provided support for its materially increased estimated synergies or its original estimate provided in November, and Mr. Gatto reiterated Callon’s request for such support. Company D’s chief executive officer described the technical model that Company D’s management team utilized in evaluating Callon’s assets and proposed that Callon enter into exclusivity with Company D in furtherance of reaching a definitive agreement by the beginning of the second week of January. At this meeting, the representatives of Company D indicated that a downward adjustment to the exchange ratio outlined in the Company D Nov. 6 Proposal may be warranted if the implied premium reached 20% as a result of the relative trading volatility.

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On December 19, 2023, Mr. Gatto and members of the Callon management team met with representatives of each of Kirkland and Morgan Stanley to discuss process in order to deliver to the Callon Board more complete information on each of APA’s and Company D’s interest in a potential transaction with Callon. After discussion of the uncertainty associated with the Company D Nov. 6 Proposal that was presented without the benefit of updated, non-public due diligence, including the underlying market conditions that resulted in Company D’s inability to confirm its willingness to proceed with a transaction on the terms of the Company D Nov. 6 Proposal, and lack of engagement on substantive financial and operational due diligence as compared to APA, Mr. Gatto instructed the outside advisors to implement a process to better compare the terms on which each party was amenable to engage in a potential transaction.

Also on December 19, 2023, Mr. Gatto and the chief executive officer of Company D convened by phone to discuss Callon’s specific information requests in respect of Company D’s proposal, including understanding any outstanding financial or operational due diligence requests, providing meaningful support of Company D’s estimated synergies, and affirming the exchange ratio proposed in the Company D Nov. 6 Proposal, and Callon’s desire to receive responses to such requests in advance of the Callon Board meeting scheduled for December 27, 2023. Mr. Gatto also stated that Company D should expect a formal process letter from Callon’s financial advisors.

Later that same day, on behalf of Callon, Morgan Stanley issued a process letter to each of APA and Company D requesting that each such party submit a proposal on or prior to December 26, 2023, outlining the consideration, any contingencies or outstanding due diligence requests, governance expectations, and the strategic rationale for the transaction, including synergies. The process letter also requested that each party provide comments to a merger agreement to be provided by Callon in executable form.

On December 20, 2023, the chief executive officer of Company D confirmed the exchange ratio proposed in the Company D Nov. 6 Proposal but conditioned Company D’s continued participation in the process on Callon entering into exclusivity with Company D. Company D provided no additional detail regarding its outstanding due diligence requests or support for its estimated synergies, as requested by Mr. Gatto.

Also on December 20, 2023, Callon made available a draft merger agreement to each of Company D and APA, including the terms that (i) each of Callon and the other party would be permitted to terminate the merger agreement in order to accept a “superior proposal,” (ii) a to-be-determined termination fee would be payable by each of Callon and the other party under certain customary circumstances, (iii) either party could terminate the merger agreement if the transactions were not consummated within a to-be-specified number of months from the execution thereof, and (iv) governance matters would be specified at a later time in negotiations.

On December 22, 2023, the APA Board met to discuss the proposed transaction. Mr. Christmann provided the APA Board with an update on the ongoing negotiations with Callon regarding a potential transaction, including the process set up by Callon. After discussion, the APA Board authorized Mr. Christmann to offer an increased exchange ratio of 1.020 APA shares for each Callon share and the appointment of one Callon Board member to the APA Board following the closing of the transaction.

On December 26, 2023, APA provided to Callon an updated non-binding proposal specifying APA’s interest in acquiring all of the outstanding capital stock of Callon in exchange for 1.020 shares of APA Common Stock, an increase from its prior proposal, with an implied premium of 10% to the closing price of Callon Common Stock on December 22, 2023. APA’s proposal indicated that one member of the Callon Board would be appointed to the APA Board following closing, affirmed that the proposal was not subject to any additional due diligence, included a detailed strategic rationale, including approximately $50 million per year of immediately available synergies from overhead reductions and operational and financial synergies, and proposed that the parties work to announce entry into definitive transaction documentation by January 8, 2024. In furtherance of that timeline, APA provided to Callon commitment papers for a bridge facility, the proceeds of which were expected to be used to repay all of Callon’s outstanding indebtedness and, as requested by the process letter, a

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markup to Callon’s draft merger agreement. APA’s marked draft of the merger agreement proposed that (i) both Callon and APA would be bound by a force the vote provision, (ii) a termination fee would be payable by Callon, in an amount equal to $95 million, and by APA, in an amount equal to $115 million, in each case following termination of the merger agreement under certain circumstances, (iii) either party could terminate the merger agreement if the transactions were not consummated within a to-be-specified number of months from the execution thereof, and (iv) APA would not be obligated to make any divestitures or agree to any restrictive covenants in order to obtain applicable regulatory approvals if such action would result in a material adverse effect on the combined company, if the combined company were the size of Callon.

Also on December 26, 2023, another publicly traded company (“Company H”) reached out to Morgan Stanley to indicate that it may be interested in a low- to no-premium deal with Callon, and subsequently indicated it was not sufficiently interested and would not be submitting a proposal.

On December 27, 2023, and in response to Mr. Gatto’s request for clarification as to whether Company D intended to submit information responsive to the letter of December 19, 2023, the chief executive officer of Company D again reaffirmed the economic terms of the Company D Nov. 6 Proposal but did not respond to the formal request for additional due diligence items or comments to the draft merger agreement.

Also on December 27, 2023, the Callon Board held a meeting to consider a potential transaction, with members of the Callon management team and representatives from Kirkland, Morgan Stanley, and RBCCM in attendance. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives, and representatives of Morgan Stanley and RBCCM provided an update on the status of discussions with APA and Company D and presented a side-by-side comparison of the terms and status of each potential counterparty’s interest in a potential transaction with Callon. Representatives of Morgan Stanley and RBCCM presented financial analyses for Callon, APA, and Company D, and the Callon Board considered Callon’s outlook and prospects as a standalone company based on the capital budget and development plan approved by the Callon Board on December 14, 2023. Representatives of Kirkland then summarized the terms of APA’s proposed merger agreement submitted to Callon on December 26, 2023. The Callon Board discussed the potential risk-adjusted relative economic values of each of APA’s and Company D’s proposals, including on the one hand, the potential opportunity for a positive increase to the premium to Callon stockholders that may have been achieved if the Callon Board waited until Company D was able to provide additional clarity regarding the total value proposition of its proposal (and Company D ultimately completed its due diligence of Callon and decided to provide a higher valued proposal) and, on the other hand, the perceived risks that Company D’s representatives had not yet conducted sufficient financial and operational due diligence, the high likelihood that Callon and APA could execute definitive documentation as currently proposed by APA in a shorter time frame relative to the time it would take to negotiate definitive documentation with Company D given that Company D had not yet submitted comments to Callon’s form of merger agreement as previously requested, as well as the overwhelming engagement of APA and its outside financial and legal advisors to expeditiously and decisively participate in the process. With respect to each of APA’s and Company D’s operations and financial standing, the Callon Board discussed the fact that a merger with APA would result in Callon stockholders owning equity of a company with a diversified asset base with exposure to both conventional and unconventional play types, a larger market capitalization, and an investment grade credit rating, while a merger with Company D would result in Callon stockholders owning equity in a small-mid capitalization company with a less diverse asset base. The Callon Board discussed that a potential transaction with Company D may not achieve sufficient scale. In addition, the Callon Board discussed whether Company D’s materially increased anticipated synergies were supportable in light of the fact that such synergies would be meaningfully greater than the anticipated synergies in precedent transactions that Callon used for benchmarking. With respect to APA, the Callon Board discussed with its advisors the additional complexity and commodity and geopolitical risks accompanying APA’s diversified asset portfolio. Notwithstanding the additional complexity and risks, the Callon Board believed that APA’s global assets presented opportunities for free cash flow stability and future growth. In addition, the pro forma Permian Basin footprint would represent the majority of APA’s production profile and provide the opportunity for additional capital allocation to the Callon asset base over time. The Callon Board also discussed

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the performance history of APA’s Common Stock and trading multiples and the potential impact of a more scaled Permian Basin presence. In order to maximize the consideration reasonably available to Callon’s stockholders, the Callon Board determined that it would be prudent to remain engaged with APA, while also soliciting clarity from Company D. To that end, the Callon Board requested that Callon management provide a counterproposal to APA contemplating an exchange ratio of 1.065 shares of APA Common Stock for each share of Callon Common Stock outstanding and certain modifications to the terms of the merger agreement. The exchange ratio of 1.065 implied a premium of 16.7% to the closing price of Callon Common Stock on December 26, 2023.

Also on December 27, 2023, Mr. Gatto and the chief executive officer of Company D convened by telephone to discuss the potential transaction. Company D’s chief executive officer reiterated that Company D remained interested in pursuing a transaction. Mr. Gatto acknowledged Company D’s interest and affirmation of the terms of the Company D Nov. 6 Proposal and reiterated that Company D’s outstanding due diligence, unsupported synergies estimates, lack of financing plan, and failure to return comments to Callon’s form merger agreement were matters that would need to be expeditiously resolved.

On December 27, 2023, Mr. Christmann contacted Mr. Gatto requesting that the two discuss the proposed transaction during the following morning. On December 28, 2023, Mr. Gatto called Mr. Christmann to discuss the potential transaction. During the conversation, Mr. Gatto conveyed that the Callon Board would be willing to proceed with a transaction on the basis of an exchange ratio of 1.065 shares of APA Common Stock for each share of Callon Common Stock outstanding. Mr. Christmann indicated that such an exchange ratio was beyond what the APA Board had authorized. Mr. Gatto also acknowledged APA’s constructive comments to Callon’s proposed form of merger agreement, but noted that Callon’s proposed revisions to the merger agreement would include, among other matters, the removal of the force the vote provision. Later that same day, Mr. Christmann advised Mr. Gatto that the APA Board would meet the following morning to discuss the proposed transaction and Callon’s counteroffer on the exchange ratio. The two agreed to reconnect via telephone after the APA Board meeting.

On December 29, 2023, the APA Board met to discuss the proposed transaction with Callon, with APA management and representatives of APA’s financial advisors and Wachtell, Lipton, Rosen & Katz (“Wachtell Lipton”) in attendance. At this meeting, APA’s management provided an update on recent discussions with Callon, and representatives of APA’s financial advisors reviewed with the APA Board certain financial aspects and other information regarding the proposed transaction. Representatives of Wachtell Lipton advised the APA Board of their fiduciary duties relating to the proposed transaction and certain terms of the proposed merger. After discussion, the APA Board authorized Mr. Christmann to offer an increased exchange ratio of 1.0425.

Also on December 29, 2023, Mr. Christmann called Mr. Gatto to update him on the APA Board’s discussions regarding the proposed transaction, including that APA would be willing to proceed on the basis of an exchange ratio of 1.0425 shares of APA Common Stock for each share of Callon Common Stock outstanding, which implied a premium of approximately 13.7% to the closing price of Callon Common Stock on December 28, 2023, based on the closing price of APA Common Stock on December 28, 2023. Further, Mr. Christmann indicated that the increased exchange ratio was APA’s best and final offer and that APA expected to be in a position to execute definitive documentation on January 4, 2024. Following the telephone call, Mr. Christmann confirmed APA’s updated proposal in a letter to Mr. Gatto. That same day, representatives of Kirkland communicated key issues in the merger agreement to representatives of Wachtell Lipton, including, among other matters, Callon’s intention to remove the force the vote provision.

Also on December 29, 2023, the chief executive officer of Company D called Mr. Gatto to inform him that Company D was considering submission of a formal response to Callon’s letter of December 19, 2023, by January 2, 2024. Company D’s chief executive officer indicated that Company D would need additional time to conduct due diligence, including in respect of financial and legal due diligence matters, and expected to be in a position to execute definitive documentation no earlier than January 15, 2024, with the ability to provide slightly more detailed, but not granular, synergies support.

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In advance of the meeting of the Callon Board on December 30, 2023, each of Mr. Gatto and representatives of Morgan Stanley had previously confirmed Company G would not be in a position to discuss a potential transaction until January 2024, Company H did not intend to pursue a proposal, and Company C declined to participate in further discussions.

On December 30, 2023, the Callon Board held a meeting to consider a potential transaction, with members of the Callon management team and representatives from Kirkland, Morgan Stanley, and RBCCM in attendance. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives, and representatives of Morgan Stanley provided an update on the status of discussions with each of APA and Company D. The Callon Board again discussed with its advisors the potential risk-adjusted relative economic values of each of APA’s and Company D’s proposals, including the factors discussed during the December 27th Callon Board meeting, as well as the fact that APA appeared ready to imminently sign a merger agreement offering a market premium while Company D was not providing a similar level of assurance. After discussion, the Callon Board instructed Kirkland to proceed with negotiating the terms of the Merger Agreement, on the basis discussed at the prior meeting of the Callon Board, with APA.

Also on December 30, 2023, Kirkland sent a revised draft of the merger agreement to Wachtell Lipton. The revised draft of the merger agreement included, among other terms, that (i) no force the vote provision would apply to either of Callon or APA, (ii) a termination fee would be payable by each of Callon, in an amount equal to $75 million, and APA, in an amount equal to $170 million, under certain circumstances, and (iii) either party could terminate the merger agreement if the transactions were not consummated within a to-be-specified number of months from the execution thereof.

On December 31, 2023, Wachtell Lipton sent a revised draft of the merger agreement to Kirkland. The revised draft of the merger agreement included, among other terms, that (i) each of APA and Callon would be subject to a force the vote provision, (ii) the termination fee that would be payable by Callon would be equal to $85 million under certain circumstances (and accepted that the termination fee payable by APA would be $170 million), and (iii) either party could terminate the merger agreement if the transactions were not consummated within 12 months from the execution thereof, subject to a six month extension if all conditions other than antitrust review had been satisfied.

Throughout the days of January 1, 2024, and January 2, 2024, certain members of Callon’s and APA’s management teams discussed the various open issues in the merger agreement and facilitated the exchange of information relating to operational and financial support. On a call between Mr. Kelly and Mr. Grandt, Mr. Grandt noted that APA would be willing to agree to remove the force the vote provision in the interest of seeking resolution on the remaining outstanding matters.

Also on January 1, 2024, Kirkland sent a revised draft of the merger agreement to Wachtell Lipton. The revised draft of the merger agreement included, among other terms, that (i) neither Callon nor APA would be subject to a force the vote provision and (ii) either party could terminate the merger agreement if the transactions were not consummated within nine months from the execution thereof, subject to a three-month extension if all conditions other than competition law approvals had been satisfied.

On January 2, 2024, the Callon Board held a meeting to consider a potential transaction, with members of the Callon management team and representatives from Kirkland, Morgan Stanley, and RBCCM in attendance. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives, and representatives of Morgan Stanley provided their preliminary pro forma financial analyses related to a potential business combination with APA, including the key financial metrics of net asset value, selected trading comparables, and weighted-average cost of capital. Representatives of Kirkland reviewed the material terms of the merger agreement, including that the parties had agreed on termination fees payable by Callon and APA in the amounts of $85 million and $170 million, respectively, so long as APA agreed to the removal of the force the vote provision. The Callon Board asked its advisors to confirm whether Company D had

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submitted any additional information or otherwise initiated contact. After confirming that Company D had not done either, the Callon Board discussed the procedure to reach definitive documentation and announce a transaction with APA prior to markets opening on January 4, 2024, should the Callon Board approve the potential transaction the following day.

Also on January 2, 2024, and following the meeting of the Callon Board, Company D submitted a revised proposal affirming the exchange ratio set forth in the Company D Nov. 6 Proposal and specifying, among other matters, that (i) Company D proposed to pay any cash required to consummate the potential transaction out of cash on hand and undrawn capacity on its revolver, (ii) Callon would appoint two members of the Callon Board to the board of directors of Company D after closing, (iii) additional due diligence would be required to refine synergies and financial attributes of the combined company, and (iv) Company D would be prepared to execute definitive transaction documentation in two weeks. The proposal also noted the need for further discussions regarding the public communication of the merits of the transaction, including synergies and pro forma guidance related to an operational plan that contemplated reduced overall drilling activity.

Also on January 2, 2024, the APA Board met to discuss the proposed transaction with Callon, with APA management and representatives of APA’s financial advisors and Wachtell Lipton in attendance. APA management provided an update on recent developments regarding the proposed transaction and the ongoing negotiations with Callon. Representatives of APA’s financial advisors provided the APA Board with certain financial analyses relating to the proposed transaction. Representatives of Wachtell Lipton advised the APA Board on certain provisions in the merger agreement and the status of negotiations with Callon with respect to such provisions. The APA Board was supportive of finalizing the terms of the merger with Callon and proceeding with entering into a definitive agreement, subject to APA management’s ongoing negotiations to finalize the terms of the draft merger agreement.

Also on January 2, 2024, Wachtell Lipton sent a revised draft of the merger agreement to Kirkland. The revised draft of the merger agreement included, among other terms, (i) agreement that neither Callon nor APA would be subject to a force the vote provision and (ii) that either party could terminate the merger agreement if the transactions were not consummated within nine months from the execution thereof, subject to two automatic, three-month extensions if all conditions other than antitrust review had been satisfied.

On January 3, 2024, Wachtell Lipton and Kirkland exchanged revised drafts of the merger agreement. The revised draft of the merger agreement included, among other terms, agreement that either party could terminate the merger agreement if the transactions were not consummated within nine months from the execution thereof, subject to one automatic, three-month extension and an additional three-month extension upon mutual agreement of the parties, in either such extension, if all conditions other than antitrust review had been satisfied.

On January 3, 2024, the Callon Board held a meeting to consider a potential transaction with members of the Callon management team and representatives from Kirkland, Morgan Stanley, and RBCCM in attendance. During this meeting, Ms. Ecklund reviewed with the Callon Board its fiduciary duties in considering strategic alternatives. Mr. Gatto reviewed with the Callon Board the terms of Company D’s proposal received the prior evening with assistance from each of Kirkland and Morgan Stanley. Representatives of Kirkland then summarized the changes to the terms of the draft merger agreement with APA from those reviewed with the Callon Board on January 2, 2024. Representatives of Morgan Stanley then reviewed its financial analysis of the exchange ratio. The Callon Board resumed its discussion regarding the potential risk-adjusted relative economic values of each of APA’s and Company D’s proposals, including on the one hand, the potential opportunity for a positive increase to the premium to Callon stockholders that could be sought relative to APA offer if the Callon Board continued to wait until Company D was able to refine its analysis and provide a more definitive view of the complete value proposition of the offer, and, on the other hand, the potential market reaction to announcement of a transaction with Company D as compared to one with APA, the perceived risk that APA may withdraw its interest and whose proposal had tangible synergies and certainty of execution, among other positive factors that would be expected to be catalysts for future value creation. In this regard, the Callon Board also believed that the quality of the synergy analysis was an

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important consideration in analyzing the proposals by APA and Company D. Morgan Stanley then delivered its oral opinion to the Callon Board, which opinion was subsequently confirmed in a written opinion dated January 3, 2024, that, as of the date of such opinion, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the scope of review undertaken by Morgan Stanley as set forth in its written opinion, the exchange ratio pursuant to the Merger Agreement was fair from a financial point of view to the holders of Callon Common Stock (other than APA, Merger Sub and their respective affiliates). The opinion of Morgan Stanley is further discussed in the section entitled “—Opinion of Morgan Stanley, Callon’s Financial Advisor.” After discussion, the Callon Board unanimously determined that the Merger Agreement, the merger, and the other transactions contemplated by the Merger Agreement to be in the best interests of, and are advisable to, Callon and the holders of Callon Common Stock, approved and declared advisable the Merger Agreement, the merger, and the other transactions contemplated by the Merger Agreement, and resolved to recommend that the holders of Callon Common Stock adopt and approve the Merger Agreement, the merger, and the other transactions contemplated by the Merger Agreement.

On the evening of January 3, 2024, the APA Board convened a special meeting, which was attended by representatives of Citi, WFS, Wachtell Lipton, and members of APA’s senior management. Mr. Christmann provided an update on discussions with Callon and the proposed terms of the merger. During the meeting, representatives from Citi and WFS each reviewed with the APA Board their financial analyses summarized below under “—Opinion of Citi, APA’s Financial Advisor” and “—Opinion of WFS, APA’s Financial Advisor,” respectively, and each rendered to the APA Board its oral opinion, which was subsequently confirmed by delivery of a written opinion, dated January 3, 2024, copies of which are attached to this joint proxy statement/prospectus as Annex B and Annex C, to the effect that, as of such date, and based upon and subject to the factors and assumptions set forth in each written opinion, the exchange ratio pursuant to the Merger Agreement was fair from a financial point of view to APA. During the meeting, representatives from Wachtell Lipton reviewed with the APA Board its fiduciary duties and materials summarizing the proposed terms of the Merger Agreement, which had previously been provided to the APA Board. Following discussion, and after carefully considering the proposed terms of the transaction with Callon, and taking into consideration the matters discussed during that meeting and prior meetings of the APA Board and the factors described below under “—Recommendation of the APA Board and Its Reasons for the Merger,” the APA Board unanimously (i) determined that the Merger Agreement and the transactions contemplated by the Merger Agreement, including the issuance of shares of APA Common Stock in connection with the merger, are fair to, and in the best interests of, APA stockholders, (ii) approved and declared advisable the Merger Agreement and the transactions contemplated by the Merger Agreement, including the issuance of shares of APA Common Stock in connection with the merger, and (iii) resolved to recommend that APA stockholders approve the issuance of shares of APA Common Stock in connection with the merger.

That same day, representatives of each of Kirkland and Wachtell Lipton finalized the Merger Agreement and disclosure schedules. That night, the parties executed the Merger Agreement and, prior to markets opening on January 4, 2024, issued a joint press release announcing the transaction.

Recommendation of the APA Board and Its Reasons for the Merger

This section summarizes the principal potential strategic and financial benefits that APA expects to realize in the merger. For a discussion of various factors that could prevent or limit the parties from realizing some or all of these benefits, see “Risk Factors” beginning on page 27. In evaluating the merger, the APA Board consulted with APA’s management, as well as APA’s legal and financial advisors, and, in reaching its conclusion, considered a variety of factors, including:

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The APA Board also considered potential risks and potentially negative factors concerning the merger in connection with its deliberations of the proposed transaction, including:

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The foregoing discussion of the information and factors considered by the APA Board is not exhaustive. In view of the APA Board’s consideration of a wide variety of factors in connection with its evaluation of the Merger Agreement and the transactions contemplated thereby, including the merger, and the complexity of these matters, the APA Board did not consider it practical to, nor did it attempt to, quantify, rank, or otherwise assign relative weights to the specific factors that it considered in reaching its decision. The actual benefits from the merger could be different from the foregoing estimates and those differences could be material. Accordingly, there can be no assurance that any of the potential benefits described above or included in the factors considered by the APA Board will be realized. See “Risk Factors” beginning on page 27.

The foregoing discussion of the information and factors considered by the APA Board is forward-looking in nature and should be read in light of the factors described in “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 39.

Opinion of Citi, APA’s Financial Advisor

APA engaged Citi as its financial advisor in connection with the proposed merger. On January 3, 2024, Citi rendered its oral opinion to the APA Board (which was subsequently confirmed in writing by delivery of Citi’s written opinion addressed to the APA Board dated the same date) as to the fairness, from a financial point of view and as of the date of the opinion, to APA of the Exchange Ratio provided for pursuant to the Merger Agreement.

The full text of Citi’s written opinion, which describes, among other things, the assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken, is attached as Annex B to this joint proxy statement/prospectus. The description of Citi’s opinion contained in this joint proxy statement/prospectus is qualified in its entirety by reference to the full text of the opinion. Citi’s opinion was directed to the APA Board, in its capacity as such, and addressed only the fairness from a financial point of view to APA of the Exchange Ratio in the merger pursuant to the Merger Agreement as of the date of such opinion. Citi’s opinion did not address any other terms, aspects, or implications of the merger. Citi expressed no view as to, and its opinion did not address, the underlying business decision of APA to effect or enter into the merger, the relative merits of the merger as compared to any alternative business strategies that might exist for APA, or the effect of any other transaction which APA might engage in or consider. Citi’s opinion did not in any manner address the price at which APA Common Stock would trade following the consummation of the merger or at any time. Citi’s opinion is not intended to be and does not constitute a recommendation as to how the APA Board or any securityholder should vote or act on any matters relating to the proposed merger or otherwise.

In arriving at its opinion, Citi, among other things:

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In rendering its opinion, Citi assumed and relied, without independent verification, upon the accuracy and completeness of all financial and other information and data publicly available or provided to or otherwise reviewed by or discussed with Citi and upon the assurances of the management of APA that they are not aware of any relevant information that has been omitted or that remains undisclosed to Citi. With respect to the Callon Projections, the APA Projections, and the other financial information and data relating to Callon, APA, and the merger provided to or otherwise reviewed by or discussed with Citi, Citi had been advised by the management of APA that such forecasts and other information and data were reasonably prepared on bases reflecting the best currently available estimates and judgments of the management of APA as to the future financial performance of Callon and APA (as the case may be), the potential strategic implications and operational benefits (including the amount, timing, and achievability thereof) anticipated to result from the merger, and the other matters covered thereby. With respect to the Street Estimates, Citi had assumed, with the consent of the APA Board, that such estimates and assumptions were also a reasonable basis upon which to evaluate the merger. Citi expressed no view or opinion with respect to any financial forecasts and other information or data used in its analyses (or the underlying assumptions upon which any such financial forecasts and other information or data are based) and Citi assumed, with the consent of the APA Board, that the financial results, including with respect to the potential strategic implications and financial and operational benefits anticipated to result from the merger, reflected in such financial forecasts and other information and data would be realized in the amounts and at the times projected.

Citi relied, at APA’s direction, upon the assessments of the management of APA as to, among other things, (i) the oil, natural gas, and natural gas liquids reserves, reservoir characteristics, undeveloped well inventory, drilling and well development, gathering and transportation, refining, and other exploration, development, and production activities, as applicable, of Callon and APA, including related costs and expenditures and capital funding requirements, (ii) the potential impact on Callon and APA of macroeconomic, geopolitical, market, competitive, seasonal, and other conditions, trends, and developments in and prospects for, and governmental, regulatory, and legislative matters relating to or otherwise affecting, the oil, natural gas, and natural gas liquids industry, including with respect to the geographic regions and basins in which Callon and APA operate, environmental regulations, and commodity pricing and supply and demand for oil, natural gas, natural gas liquids, and refined energy and petrochemical products, which are subject to significant volatility and which, if different than as assumed, could have a material impact on Citi’s analyses or opinion, (iii) existing and future agreements and other arrangements involving, and the ability to attract, retain, and/or replace, key employees, customers, service providers, and other commercial relationships of Callon and APA, and (iv) the ability to integrate the operations of Callon with those of APA and to realize the potential strategic implications and financial and operational benefits as contemplated. Citi assumed, with APA’s consent, that there would be no developments with respect to any such matters that would have an adverse effect on Callon, APA, or the merger (including the contemplated benefits thereof) or that otherwise would be meaningful in any respect to Citi’s analyses or opinion.

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Citi did not make and was not provided with an independent evaluation or appraisal of the assets or liabilities (contingent, accrued, derivative, off-balance sheet, or otherwise) of Callon, APA, or any other entity nor had Citi made any physical inspection of the properties or assets of Callon, APA, or any other entity. Citi expressed no view or opinion as to reserve quantities, or the exploration, development, or production (including, without limitation, as to the feasibility or timing thereof and associated expenditures), of any properties of Callon, APA, or any other entity. Citi did not evaluate the solvency or fair value of Callon, APA, or any other entity under any state, federal, or other laws relating to bankruptcy, insolvency, or similar matters. Citi also expressed no view or opinion as to any actual or potential litigation, claims, or governmental, regulatory, or other proceedings, enforcement actions, consent, or other orders or investigations or the potential impact thereof on Callon, APA, or any other entity.

Citi assumed, with APA’s consent, that the merger would be consummated in accordance with its terms, without waiver, modification, or amendment of any material term, condition, or agreement and that, in the course of obtaining the necessary regulatory or third-party approvals, consents, and releases for the merger, no delay, limitation, restriction, or condition would be imposed that would have an adverse effect on Callon, APA, or the contemplated benefits of the merger. Representatives of APA advised Citi, and Citi further assumed, that the final terms of the Merger Agreement would not vary materially from those set forth in the draft reviewed by Citi. Citi also assumed, with APA’s consent, that the merger would be treated as a tax-free reorganization for federal income tax purposes. Citi’s opinion relates to the relative values of Callon and APA. Citi did not express any opinion as to what the value of APA Common Stock actually would be when issued pursuant to the merger or the price at which APA Common Stock would trade at any time. Citi did not express any view or opinion with respect to accounting, tax, regulatory, legal, or similar matters, including, without limitation, as to tax or other consequences of the merger or otherwise or changes in, or the impact of, accounting standards or tax and other laws, regulations, and governmental and legislative policies affecting Callon, APA, or the merger (including the contemplated benefits thereof), and Citi relied, with APA’s consent, upon the assessments of representatives of APA as to such matters. Citi’s opinion does not address the underlying business decision of APA to effect the merger, the relative merits of the merger as compared to any alternative business strategies that might exist for APA, or the effect of any other transaction in which APA might engage. Citi expressed no view as to, and Citi’s opinion does not address, the fairness (financial or otherwise) of the amount or nature or any other aspect of any compensation to any officers, directors, or employees of any parties to the merger, or any class of such persons, relative to the Exchange Ratio. Citi’s opinion is necessarily based upon information available to Citi, and financial, stock market, and other conditions and circumstances existing, as of the date of its opinion. Citi did not undertake, and is under no obligation, to update, revise, reaffirm, or withdraw its opinion, or otherwise comment on or consider events occurring or coming to Citi’s attention after the date of its opinion. The issuance of Citi’s opinion was authorized by an opinion committee of Citi.

In preparing its opinion, Citi performed a variety of financial and comparative analyses, including those described below. The summary of the analyses below is not a complete description of Citi’s opinion or the analyses underlying, and factors considered in connection with, Citi’s opinion. The preparation of a financial opinion is a complex analytical process involving various determinations as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances and, therefore, a financial opinion is not readily susceptible to summary description. Citi arrived at its ultimate opinion based on the results of all analyses and factors assessed as a whole, and it did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis. Accordingly, Citi believes that the analyses must be considered as a whole and in context and that selecting portions of its analyses and factors or focusing on information presented in tabular format, without considering all analyses and factors or the narrative description of the analyses, could create a misleading or incomplete view of the processes underlying such analyses and its opinion.

In its analyses, Citi considered business, economic, industry, and market conditions, financial and otherwise, and other matters as they existed on, and could be evaluated as of, the date of its opinion. No company, business, or transaction used in Citi’s analyses for comparative purposes is identical to APA, Callon,

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or the proposed merger. While the results of each analysis were taken into account in reaching its overall conclusion with respect to fairness to APA from a financial point of view of the Exchange Ratio in the merger, Citi did not make separate or quantifiable judgments regarding individual analyses. The reference ranges indicated by Citi’s financial analyses are illustrative and not necessarily indicative of actual values nor predictive of future results or values, which may be significantly more or less favorable than those suggested by the analyses. In addition, any analyses relating to the value of assets, businesses, or securities do not purport to be appraisals or to reflect the prices at which businesses or securities actually may be sold, which may depend on a variety of factors, many of which are beyond APA’s control and the control of Citi. Much of the information used in, and accordingly the results of, Citi’s analyses are inherently subject to substantial uncertainty.

Citi was selected by APA to act as its financial advisor based on Citi’s qualifications, experience, and reputation. Citi was not requested to, and it did not, recommend or determine the specific consideration payable in the merger or opine that any specific exchange ratio constituted the only appropriate exchange ratio for the merger. The type and amount of consideration payable in the merger were determined through negotiations between APA and Callon and the decision of APA to enter into the Merger Agreement was solely that of the APA Board.

Citi’s opinion to the APA Board was one of many factors taken into consideration by the APA Board in deciding to consider, approve, and declare the advisability of the Merger Agreement and the transactions contemplated thereby and to recommend the approval of the Stock Issuance Proposal by the holders of APA Common Stock. Consequently, the analyses described above should not be viewed as determinative of the opinion of the APA Board with respect to the Exchange Ratio pursuant to the Merger Agreement or of whether the APA Board or management would have been willing to agree to a different exchange ratio.

Summary of Financial Analyses of Citi

The following is a summary of the material financial analyses performed by Citi in connection with its oral opinion and the preparation of its written opinion to the APA Board, both provided as of January 3, 2024. The following summary is not a complete description of the financial analyses performed and factors considered by Citi in connection with its opinion, nor does the order of analyses described represent the relative importance or weight given to those analyses. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on or before January 3, 2024. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by Citi, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The analyses listed in the tables and described below must be considered as a whole. Assessing any portion of such analyses and of the factors reviewed, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Citi’s opinion. Furthermore, mathematical analysis is not in itself a meaningful method of using the data referred to below.

In calculating implied exchange ratio reference ranges as reflected in the financial analyses described below, except as otherwise noted, Citi divided the low-ends (or high-ends, as the case may be) of the approximate implied per share equity value reference ranges derived for Callon from such analyses by the high-ends (or low-ends, as the case may be) of the approximate implied per share equity value reference ranges derived for APA from such analyses in order to calculate the low-ends (or high-ends) of the implied exchange ratio reference ranges. For its analyses, Citi utilized and relied upon the number of issued and outstanding shares of Callon and APA provided or approved by the management of APA.

Net Asset Value Analysis

Citi performed a separate net asset value analysis for each of APA and Callon by calculating the estimated net present value, as of September 30, 2023, of the projected unlevered, after-tax free cash flows of each of APA

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and Callon after September 30, 2023, based on the APA Projections and the Callon Projections, which reflected APA management’s estimates of oil and gas reserves and resources.

APA – Net Asset Value Analysis. With respect to APA, Citi applied discount rates of 8.9% to 9.6%, representing the range of discount rates for APA selected by Citi based on APA’s weighted average cost of capital. Citi deducted from the resulting net present value calculation the net debt of APA as of September 30, 2023, and made certain other adjustments to account for, among other things, certain liabilities and other items not reflected in net debt, cash taxes, and equity investments, each as provided by APA management, to derive an implied equity value range. This analysis indicated an approximate implied per share equity value reference range for APA of $36.40 to $39.10.

Callon – Net Asset Value Analysis. With respect to Callon, Citi applied discount rates of 9.4% to 10.3%, representing the range of discount rates for Callon selected by Citi based on Callon’s weighted average cost of capital. Citi also estimated the present value, based on the discount rates noted above, of the synergies anticipated by APA management to result from the merger. Citi deducted from the resulting net present value calculation the net debt of Callon as of September 30, 2023, and made certain other adjustments to account for, among other things, certain liabilities and other items not reflected in net debt and cash taxes, each as provided by APA management, to derive an implied equity value range. This analysis indicated approximate implied per share equity value reference ranges for Callon of $37.05 to $40.45 (without synergies) and $44.05 to $47.65 (including synergies).

The net asset value analysis indicated the following implied exchange ratio reference ranges of (x) 0.948 to 1.111 shares of APA Common Stock for each share of Callon Common Stock (without synergies) and (y) 1.127 to 1.309 shares of APA Common Stock for each share of Callon Common Stock (including synergies), as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Discounted Cash Flow Analysis

Citi performed a separate discounted cash flow analysis for each of APA and Callon as described below.

APA – Discounted Cash Flow Analysis. Citi performed a discounted cash flow analysis of APA by calculating the estimated present value (as of September 30, 2023) of the standalone unlevered free cash flows that APA was forecasted to generate for the quarter ended December 31, 2023, and during the fiscal years ending December 31, 2024, through December 31, 2028, based on the APA Projections. Citi calculated an implied terminal value range for APA by applying to APA’s fiscal year 2028 estimated EBITDA (based on the APA Projections) a selected range of EBITDA multiples of 3.6x to 4.3x. The present values (as of September 30, 2023) of the cash flows and terminal values were then calculated using a selected range of discount rates of 8.9% to 9.6%. This analysis indicated an approximate implied per share equity value reference range for APA of $33.25 to $40.70.

Callon – Discounted Cash Flow Analysis. Citi performed a discounted cash flow analysis of Callon by calculating the estimated present value (as of September 30, 2023) of the standalone unlevered free cash flows that Callon was forecasted to generate for the quarter ended December 31, 2023, and during the fiscal years ending December 31, 2024, through December 31, 2028, based on the Callon Projections. Citi also estimated the present value of the synergies anticipated by APA management to result from the merger. Citi calculated an implied terminal value range for Callon by applying to Callon’s fiscal year 2028 estimated EBITDA (based on the Callon Projections) a selected range of EBITDA multiples of 2.8x to 3.7x. The present values (as of September 30, 2023) of the cash flows and terminal values were then calculated using a selected range of discount rates of 9.4% to 10.3%. This analysis indicated approximate implied per share equity value reference ranges for Callon of $31.00 to $40.70 (without synergies) and $35.40 to $45.60 (including synergies).

The discounted cash flow analysis indicated the following implied exchange ratio reference ranges of (x) 0.762 to 1.224 shares of APA Common Stock for each share of Callon Common Stock (without synergies) and (y) 0.971 to 1.510 shares of APA Common Stock for each share of Callon Common Stock (including

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synergies), as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Selected Public Company Analysis

Citi performed separate selected public companies analyses of APA and Callon in which Citi reviewed certain financial and stock market information relating to APA, Callon, and the selected publicly traded companies listed below.

APA – Selected Public Company Analysis. In its selected public companies analysis of APA, Citi reviewed certain financial and stock market information relating to APA and the following three (3) selected publicly traded oil and gas exploration and production companies, with operations in the same or similar basins in which APA operates, that Citi considered generally relevant for purposes of analysis (collectively referred to as the “APA selected companies”):

Citi reviewed, among other information, enterprise values, calculated as implied equity values based on closing stock prices on January 3, 2024, plus total debt and non-controlling interests (as applicable) and less cash, cash equivalents, and investments in unconsolidated affiliates, as a multiple of calendar year 2024 estimated adjusted EBITDA (earnings before interest, taxes, depreciation, amortization and exploration expenses). Financial data of the APA selected companies were based on publicly available Wall Street research analysts’ estimates. For purposes of Citi’s analyses, in deriving ranges of implied values for APA, Citi used the estimates for APA reflected in the APA Projections, as well as the Street Estimates.

The overall low to high, median, and 25^th and 75^th percentiles of calendar year 2024 estimated adjusted EBITDA multiples for the APA selected companies were: low of 3.8x to high of 4.5x (with a median of 4.0x) and 25^th and 75^th percentiles of 3.9x and 4.2x, respectively.

Citi noted that, based on market data as of January 3, 2024, the calendar year 2024 estimated adjusted EBITDA multiple observed for APA was 3.1x (based on Street Estimates). Citi then applied selected ranges of calendar year 2024 estimated adjusted EBITDA multiples of 3.1x to 4.0x to APA’s calendar year 2024 estimated adjusted EBITDA (based on the APA Projections and the Street Estimates). This analysis indicated approximate implied per share equity value reference ranges for APA of $30.05 to $42.80 (APA Projections) and $36.75 to $51.20 (Street Estimates).

Callon – Selected Public Company Analysis. In its selected public companies analysis of Callon, Citi reviewed certain financial and stock market information relating to Callon and the following seven (7) selected publicly traded oil and gas exploration and production companies, with operations in the same or similar basins in which Callon operates, that Citi considered generally relevant for purposes of analysis (collectively referred to as the “Callon selected companies”):

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Citi reviewed, among other information, enterprise values, calculated as implied equity values based on closing stock prices on January 3, 2024, plus total debt and non-controlling interests (as applicable) and less cash, cash equivalents, and investments in unconsolidated affiliates, as a multiple of calendar year 2024 estimated adjusted EBITDA. Financial data of the Callon selected companies were based on publicly available Wall Street research analysts’ estimates. For purposes of Citi’s analyses, in deriving ranges of implied values for Callon, Citi used the estimates for Callon reflected in the Callon Projections, as well as the Street Estimates.

The overall low to high, median and 25th and 75th percentiles of calendar year 2024 estimated adjusted EBITDA multiples for the Callon selected companies were: low of 2.7x to high of 4.6x (with a median of 3.6x) and 25th and 75th percentiles of 3.0x and 3.9x, respectively.

Citi noted that, based on market data as of January 3, 2024, the calendar year 2024 estimated adjusted EBITDA multiple observed for Callon was 3.1x (based on Street Estimates). Citi then applied selected ranges of calendar year 2024 estimated adjusted EBITDA multiples of 2.7x to 3.6x to Callon’s calendar year 2024 estimated adjusted EBITDA (based on the Callon Projections and the Street Estimates). This analysis indicated approximate implied per share equity value reference ranges for Callon of $21.60 to $37.45 (Callon Projections) and $25.90 to $43.05 (Street Estimates).

The selected companies analysis indicated the following implied exchange ratio reference ranges of (x) 0.505 to 1.246 shares of APA Common Stock for each share of Callon Common Stock (based on the APA Projections and Callon Projections) and (y) 0.506 to 1.171 shares of APA Common Stock for each share of Callon Common Stock (based on Street Estimates), as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Selected Precedent Transactions Analysis

Citi performed for Callon a selected precedent transactions analysis, which is designed to derive an implied value of a company based on publicly available financial terms for selected transactions. In connection with its analysis, Citi reviewed publicly available statistics for certain transactions involving exploration and production targets in 2022 and 2023.

The financial data reviewed included the implied transaction value as a multiple of EBITDA for the next twelve months following announcement of the transaction, or Forward EBITDA.

Citi noted that the low and high transaction value to Forward EBITDA multiples for the selected transactions was 2.7x and 3.2x, respectively. Based on the application of its professional judgment and experience, Citi applied a multiple range of 2.7x to 3.2x to Callon’s 2024E EBITDA (based on the Callon Projections). This analysis indicated an approximate implied per share equity value reference range for Callon of $25.55 to $35.75.

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Certain Additional Information

Citi also observed certain additional information that was not considered part of its financial analyses with respect to its opinion but was noted for informational purposes, including the following:

Illustrative Has/Gets Analysis

Citi compared the approximate implied per share equity value reference ranges derived for APA on a standalone basis described above under “—Net Asset Value Analysis” and “—Discounted Cash Flow Analysis” relative to illustrative approximate implied per share equity values for the combined company on a pro forma basis derived from a net asset value analysis and a discounted cash flow analysis of the combined company after taking into account the synergies anticipated by APA management to result from the merger. Citi utilized (i) in the case of the net asset value analysis, a selected range of discount rates of 8.9% to 9.6% and (ii) in the case of the discounted cash flow analysis, a selected range of terminal year adjusted EBITDA multiples of 3.6x to 4.3x and a selected range of discount rates of 8.9% to 9.6%. Financial data of APA was based on the APA Projections. Financial data of the pro forma combined company was based on the APA Projections, the Callon Projections and the synergies estimates of APA management.

Citi observed that this analysis indicated that the merger could result in approximate implied per share equity values for the combined company on a pro forma basis derived from the net asset value analysis and the discounted cash flow analysis of $37.60 to $40.30 and $36.25 to $43.90, respectively (relative to $36.40 to $39.10 and $33.25 to $40.70, respectively, for APA on a standalone basis). Actual results achieved by APA, Callon, and the pro forma combined company may vary from forecasted results and variations may be material.

Historical Trading Prices

Citi reviewed the historical closing trading ranges of the APA Common Stock and the Callon Common Stock for the 52-week period through January 3, 2024. Citi noted that the low and high closing prices for APA and Callon, and the low and high of the daily exchange ratios (based on daily trading), were as follows:

Equity Research

APA – Citi reviewed sell-side analyst price targets for shares of APA Common Stock published by 17 equity research analysts during the time period from November 2, 2023, through January 2, 2024. These targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of APA Common Stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of APA Common Stock was $36.00 per share to $61.00 per share. The resulting discount indicated an implied range of equity values for shares of APA Common Stock of $32.40 per share to $54.95 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of APA Common Stock and these estimates are subject to uncertainties, including the future financial performance of APA and future financial market conditions.

Callon – Citi reviewed sell-side analyst price targets for shares of Callon Common Stock published by 11 equity research analysts during the time period from November 2, 2023, through January 2, 2024. These targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of Callon Common Stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of Callon Common Stock was $34.00 per share to $54.00 per share. The resulting discount indicated an implied range of equity values for shares of Callon Common Stock of $30.45 per share to

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$48.35 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of Callon Common Stock and these estimates are subject to uncertainties, including the future financial performance of Callon and future financial market conditions.

Citi noted that the exchange ratio range implied by the undiscounted target price range was 0.727x to 1.149x.

Selected Precedent Transaction Premiums

Utilizing public filings and other publicly available information, for selected transactions involving publicly traded oil and gas companies announced from 2021 through 2023, Citi reviewed the one-day premiums implied by the transaction consideration paid or proposed to be paid to the last closing stock price of the target common stock prior to announcement of the transaction (or the last closing stock price on an unaffected date in the event of published reports of a possible transaction prior to announcement). Citi observed that these transactions reflected premiums ranging from 0.4% to 17.8% and that application of such range of premiums to the closing stock price for Callon Common Stock as of January 3, 2024, indicated an approximate implied per share equity value for Callon of $33.80 to $39.65.

Certain Other Pro Forma Effects

Citi observed certain illustrative potential pro forma financial effects of the merger on, among other things, APA’s fiscal years 2024 and 2025 estimated cash flow per share (referred to as “CFPS”) and estimated free cash flow per share (referred to as “FCFPS”), taking into account potential synergies anticipated by the management of APA to result from the merger, which indicated that the merger could be accretive to APA’s fiscal years 2024 and 2025 estimated CFPS and estimated FCFPS based on the APA Projections, the Callon Projections, and the synergies anticipated by the management of APA to result from the merger.

Miscellaneous

APA has agreed to pay Citi for its services in connection with the proposed merger a fee of up to $15 million, of which $2 million became payable upon the delivery of Citi’s fairness opinion and the remainder of which is contingent upon completion of the merger. APA agreed to reimburse Citi for its expenses, including fees and expenses of counsel, incurred in connection with its engagement. In addition, APA agreed to indemnify Citi and related parties against certain liabilities, including liabilities under the federal securities laws, relating to, or arising out of Citi’s engagement. An affiliate of Citi engaged in the commercial lending business is acting as lender for a credit facility to be used by APA in connection with the merger, for which services such entity would receive compensation.

Citi and its affiliates in the past provided, and currently provide, services to Callon and APA unrelated to the proposed merger, for which services Citi and such affiliates have received and expect to receive compensation, including, without limitation, during the approximately two (2)-year period prior to the date of Citi’s opinion, (x) for Callon, having acted as a financial advisor in connection with Callon’s acquisition of Primexx Energy Partners announced in August 2021, having acted as an underwriter or initial purchaser of senior notes in June 2021 and June 2022, and having provided a lending commitment to Callon’s credit facility and (y) for APA, having provided lending commitments to various credit facilities of APA. In the ordinary course of our business, Citi and its affiliates may actively trade or hold the securities of Callon and APA for its own account or for the account of its customers and, accordingly, may at any time hold a long or short position in such securities. In addition, Citi and its affiliates (including Citigroup Inc. and its affiliates) may maintain relationships with Callon, APA, and their respective affiliates. In the approximately two (2)-year period prior to the date of Citi’s opinion, for investment banking services, Citi and its affiliates received aggregate fees of approximately $7.5 million from Callon and $2.5 million from APA. Citi may seek to provide financial advisory and financing services to APA, Callon, and their respective affiliates in the future and would expect to receive fees for the rendering of these services.

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Opinion of WFS, APA’s Financial Advisor

APA retained WFS to provide it with financial advisory services in connection with the merger. On January 3, 2024, WFS rendered its oral opinion to the APA Board (which was subsequently confirmed in writing by delivery of WFS’s written opinion addressed to the APA Board dated the same date) as to, as of January 3, 2024, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the scope of the review undertaken by WFS as set forth in its written opinion, the fairness, from a financial point of view, to APA of the Exchange Ratio in the merger pursuant to the Merger Agreement.

The full text of WFS’s written opinion, which describes, among other things, the assumptions made, procedures followed, matters considered, and qualifications and limitations on the scope of review undertaken, is attached as Annex C to this joint proxy statement/prospectus. The summary of WFS’s opinion contained in this joint proxy statement/prospectus is qualified in its entirety by reference to the full text of the opinion. WFS’s opinion was directed to the APA Board, in its capacity as such, and addressed only the fairness from a financial point of view to APA of the Exchange Ratio in the merger pursuant to the Merger Agreement as of the date of such opinion. WFS’s opinion did not address any other aspects or implications of the merger. WFS expressed no view as to, and its opinion did not address, the underlying business decision of APA to effect or enter into the merger or the relative merits of the merger as compared to any alternative business strategies that might exist for APA. WFS’s opinion did not in any manner address the price at which APA Common Stock would trade following the consummation of the merger or at any time. WFS’s opinion is not intended to be and does not constitute a recommendation as to how the APA Board or any securityholder should vote or act on any matters relating to the proposed merger or otherwise.

For purposes of rendering its opinion, WFS, among other things:

In giving its opinion, WFS assumed and relied upon the accuracy and completeness of all information that was publicly available or was furnished to or discussed with WFS by APA or Callon or otherwise reviewed by

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WFS. WFS did not independently verify any such information, and pursuant to the terms of its engagement by the APA, WFS did not assume any obligation to undertake any such independent verification. In relying on the Callon Projections and the APA Projections, WFS assumed, with APA’s consent, that they have been reasonably prepared on bases reflecting the best currently available estimates and judgments of APA’s management as to the future performance and financial condition of Callon and APA, respectively. In relying on the Synergies Estimates, WFS assumed, with APA’s consent, that they have been reasonably prepared on bases reflecting the best currently available estimates and judgments of APA’s management as to the matters addressed thereby. WFS expressed no view or opinion with respect to the Callon Projections, the APA Projections, or the Synergies Estimates, or the assumptions upon which they are based. WFS assumed that any representations and warranties made by Callon and APA in the Merger Agreement or in other agreements relating to the merger will be true and accurate in all respects that are material to WFS’s analyses.

For purposes of WFS’s analyses and opinion, WFS assumed that, for U.S. federal income tax purposes, the merger would qualify as a reorganization within the meaning of Section 368 of the Internal Revenue Code of 1986, as amended. WFS also assumed that the merger would have the tax consequences described in discussions with, and materials provided to WFS by, APA and its representatives. WFS assumed that, in the course of obtaining any regulatory or third-party consents, approvals, or agreements in connection with the merger, no delay, limitation, restriction, or condition would be imposed that would have an adverse effect on Callon, APA, or the contemplated benefits of the merger. WFS also assumed that the merger would be consummated in compliance with all applicable laws and regulations and in accordance with the terms of the Merger Agreement without waiver, modification, or amendment of any term, condition, or agreement thereof that is material to WFS’s analyses or opinion. In addition, WFS did not make any independent evaluation, inspection, or appraisal of the assets or liabilities (contingent or otherwise) of Callon or APA, nor had WFS been furnished with any such evaluations or appraisals. WFS did not evaluate the solvency of Callon or APA under any state or federal laws relating to bankruptcy, insolvency, or similar matters. WFS further assumed that the final form of the Merger Agreement, when executed by the parties thereto, would conform to the draft reviewed by WFS in all respects material to its analyses and opinion.

WFS’s opinion only addresses the fairness, from a financial point of view, to APA of the Exchange Ratio in the merger, and WFS expressed no opinion as to the fairness of any consideration paid in connection with the merger to the holders of any other class of securities, creditors, or other constituencies of Callon. Furthermore, WFS expressed no opinion as to any other aspect or implication (financial or otherwise) of the merger, or any other agreement, arrangement, or understanding entered into in connection with the merger or otherwise, including, without limitation, the fairness of the amount or nature of, or any other aspect relating to, any compensation or consideration to be received by or otherwise payable to any officers, directors, or employees of any party to the merger, or class of such persons, relative to the Exchange Ratio or otherwise. Furthermore, WFS did not express any advice or opinion regarding matters that require legal, regulatory, accounting, insurance, tax, environmental, executive compensation, or other similar professional advice and relied upon the assessments of APA and its advisors with respect to such matters and advice.

WFS’s opinion was necessarily based upon information made available to WFS as of the date of its opinion and financial, economic, market, and other conditions as they existed and could be evaluated on the date thereof. WFS did not undertake, and are under no obligation, to update, revise, reaffirm, or withdraw its opinion, or otherwise comment on or consider events occurring or coming to its attention after the date thereof, notwithstanding that any such subsequent developments may affect the opinion. WFS’s opinion did not address the relative merits of the merger as compared to any alternative transactions or strategies that might be available to APA, nor did it address the underlying business decision of the APA Board or APA to proceed with or effect the merger. WFS did not express any opinion as to the prices at which Callon Common Stock or APA Common Stock may be traded at any time. The issuance of WFS’s opinion was approved by a fairness committee of WFS.

In preparing its opinion, WFS performed a variety of financial and comparative analyses, including those described below. The summary of the analyses below is not a complete description of WFS’s opinion or the

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analyses underlying, and factors considered in connection with, WFS’s opinion. The preparation of a financial opinion is a complex analytical process involving various determinations as to the most appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances and, therefore, a financial opinion is not readily susceptible to summary description. WFS arrived at its ultimate opinion based on the results of all analyses and factors assessed as a whole, and it did not draw, in isolation, conclusions from or with regard to any one factor or method of analysis. Accordingly, WFS believes that the analyses must be considered as a whole and in context and that selecting portions of its analyses and factors or focusing on information presented in tabular format, without considering all analyses and factors or the narrative description of the analyses, could create a misleading or incomplete view of the processes underlying such analyses and its opinion.

In performing its analyses, WFS considered business, economic, industry, and market conditions, financial and otherwise, and other matters as they existed on, and could be evaluated as of, the date of its opinion. No company, business, or transaction used in WFS’s analyses for comparative purposes is identical to APA, Callon, or the proposed merger. While the results of each analysis were taken into account in reaching its overall conclusion with respect to fairness to APA from a financial point of view of the Exchange Ratio in the merger, WFS did not make separate or quantifiable judgments regarding individual analyses. The reference ranges indicated by WFS’s financial analyses are illustrative and not necessarily indicative of actual values nor predictive of future results or values, which may be significantly more or less favorable than those suggested by the analyses. In addition, any analyses relating to the value of assets, businesses, or securities do not purport to be appraisals or to reflect the prices at which businesses or securities actually may be sold, which may depend on a variety of factors, many of which are beyond APA’s control and the control of WFS. Much of the information used in, and accordingly the results of, WFS’s analyses are inherently subject to substantial uncertainty.

WFS was selected by APA to act as its financial advisor based on WFS’s qualifications, experience, and reputation. WFS was not requested to, and it did not, recommend or determine the specific consideration payable in the merger or opine that any specific exchange ratio constituted the only appropriate exchange ratio for the merger. The type and amount of consideration payable in the merger were determined through negotiations between APA and Callon and the decision of APA to enter into the Merger Agreement was solely that of the APA Board.

WFS’s opinion to the APA Board was one of many factors taken into consideration by the APA Board in deciding to consider, approve, and declare the advisability of the Merger Agreement and the transactions contemplated thereby and to recommend the approval of the Stock Issuance Proposal by the holders of APA Common Stock. Consequently, the analyses described above should not be viewed as determinative of the opinion of the APA Board with respect to the Exchange Ratio pursuant to the Merger Agreement or of whether the APA Board or management would have been willing to agree to a different exchange ratio.

Summary of Financial Analyses of WFS

The following is a summary of the material financial analyses performed by WFS in connection with its oral opinion and the preparation of its written opinion to the APA Board, both provided as of January 3, 2024. The following summary is not a complete description of the financial analyses performed and factors considered by WFS in connection with its opinion, nor does the order of analyses described represent the relative importance or weight given to those analyses. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data as it existed on or before January 3, 2024. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by WFS, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The analyses listed in the tables and described below must be considered as a whole. Assessing any portion of such analyses and of the factors reviewed, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying WFS’s opinion. Furthermore, mathematical analysis is not in itself a meaningful method of using the data referred to below.

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In calculating implied exchange ratio reference ranges as reflected in the financial analyses described below, except as otherwise noted, WFS divided the low-ends (or high-ends, as the case may be) of the approximate implied per share equity value reference ranges derived for Callon from such analyses by the high-ends (or low-ends, as the case may be) of the approximate implied per share equity value reference ranges derived for APA from such analyses in order to calculate the low-ends (or high-ends) of the implied exchange ratio reference ranges. For its analyses, WFS utilized and relied upon the number of issued and outstanding shares of Callon and APA provided by the management of APA.

Selected Public Company Analysis

WFS performed separate selected public companies analyses of Callon and APA for which WFS reviewed certain financial and stock market information relating to Callon, APA, and the selected publicly traded companies listed below that WFS deemed comparable to Callon and APA, respectively, in one or more respects.

For each of the selected companies noted below, WFS considered, among other things, the ratio of enterprise value (defined as market capitalization plus net debt, preferred equity, and minority interests) to estimated EBITDA (calculated as earnings before interest, taxes, depreciation, amortization and exploration expenses) for 2024 and 2025 based on research consensus estimates. For purposes of WFS’s analyses, in deriving ranges of implied values for Callon and APA, WFS used the estimates reflected in the Callon Projections and the APA Projections, respectively, for the applicable financial data for Callon and APA.

Selected Public Company Analysis – Callon. The selected companies considered by WFS for its analysis of Callon were:

WFS noted that, based on market data as of January 3, 2024, the median Enterprise Value to 2024E EBITDA multiple for the selected publicly traded companies was 3.1x and the median Enterprise Value to 2025E EBITDA multiple for the selected publicly traded companies was 3.1x. Based upon the application of its professional judgment and experience, WFS selected for Callon a reference range of multiples of 3.00x to 3.75x to be applied to estimated 2024E EBITDA and 2025E EBITDA (based on the Callon Projections). This analysis indicated an approximate implied per share equity value reference range for Callon of $23.83 to $39.84.

Selected Public Company Analysis – APA. The selected companies considered by WFS for its analysis of APA were:

WFS noted that, based on market data as of January 3, 2024, the median Enterprise Value to 2024E EBITDA multiple for the selected publicly traded companies was 4.0x and the median Enterprise Value to 2025E EBITDA multiple for the selected publicly traded companies was 4.1x. Based upon the application of its

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professional judgment and experience, WFS selected for APA a reference range of multiples of 3.00x to 4.00x to be applied to estimated 2024E EBITDA and 2025E EBITDA (based on the APA Projections). This analysis indicated an approximate implied per share equity value reference range for APA of $33.51 to $51.27.

The selected companies analysis indicated the following implied exchange ratio reference range of 0.4647 to 1.1888 shares of APA Common Stock for each share of Callon Common Stock, as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Net Asset Value Analysis

WFS performed a separate net asset value analysis for each of Callon and APA by calculating the estimated net present value, as of September 30, 2023, of the projected unlevered, after-tax free cash flows of each of Callon and APA after September 30, 2023, based on the Callon Projections and the APA Projections, which reflected APA management’s estimates of oil and gas reserves and resources.

Callon Net Asset Value Analysis

With respect to Callon, WFS applied discount rates of 9.5% to 12.0%, representing the range of discount rates for Callon selected by WFS based on Callon’s weighted average cost of capital. WFS also estimated the present value, based on the discount rates noted above, of the synergies anticipated by APA management to result from the merger. WFS deducted from the resulting net present value calculation the net debt of Callon as of September 30, 2023, and made certain other adjustments to account for, among other things, certain liabilities and other items not reflected in net debt, cash taxes and share repurchases undertaken in the quarter ended December 31, 2023, each as provided by APA management, to derive an implied equity value range. This analysis indicated an approximate implied per share equity value reference range for Callon of $30.19 to $38.73 (without synergies) and $36.29 to $45.44 (including synergies).

APA Net Asset Value Analysis

With respect to APA, WFS applied discount rates of 8.0% to 9.5%, representing the range of discount rates for APA selected by WFS based on APA’s weighted average cost of capital. WFS deducted from the resulting net present value calculation the net debt of APA as of September 30, 2023, and made certain other adjustments to account for, among other things, certain liabilities and other items not reflected in net debt, cash taxes, equity investments, and share repurchases undertaken in the quarter ended December 31, 2023, each as provided by APA management, to derive an implied equity value range. This analysis indicated an approximate implied per share equity value reference range for APA of $36.73 to $42.81.

The net asset value analysis indicated the following implied exchange ratio reference ranges of (x) 0.7052 to 1.0545 shares of APA Common Stock for each share of Callon Common Stock (without synergies) and (y) 0.8476 to 1.2372 shares of APA Common Stock for each share of Callon Common Stock (including synergies), as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Pro Forma Net Asset Value Analysis

WFS performed a net asset value analysis for the combined company by calculating the estimated net present value, as of September 30, 2023, of the projected unlevered, after-tax free cash flows of the combined company after September 30, 2023, based on the APA Projections and the Callon Projections, which reflected APA management’s estimates of oil and gas reserves and resources. WFS applied discount rates of 8.0% to 9.5%, representing the range of discount rates selected by WFS based on APA’s weighted average cost of capital. WFS added the estimated the present value, based on the same discount rates of 8.0% to 9.5%, of the synergies anticipated by APA management to result from the merger. WFS deducted from the resulting net present value

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calculation the net debt of APA and Callon as of September 30, 2023, and made certain other adjustments to account for, among other things, certain liabilities and other items not reflected in net debt, cash taxes, equity investments, share repurchases undertaken in the quarter ended December 31, 2023, and APA’s estimate of transaction expenses, each as provided by APA management, to derive an implied equity value range for the pro forma combined company. This analysis indicated an approximate implied per share equity value reference range for the pro forma combined company of $37.75 to $43.90, as compared to the approximate implied per share equity value reference range for APA indicated by the standalone net asset value analysis for APA ($36.73 to $42.81).

Certain Additional Information

WFS also observed certain additional information that was not considered part of its financial analyses with respect to its opinion but was noted for informational purposes, including the following:

Selected Precedent Transactions Analysis. WFS performed with respect to Callon a selected precedent transactions analysis, which is designed to derive an implied value of a company based on publicly available financial terms for selected transactions. In connection with its analysis, WFS reviewed publicly available statistics for certain transactions involving exploration and production targets from 2018 through 2023. The financial data reviewed included the implied transaction value as a multiple of EBITDA for the target for the next twelve months following announcement of the transaction, or Forward EBITDA, based on research analyst estimates or forward-looking estimates reflected in public filings. WFS noted that the low and high transaction value to Forward EBITDA multiples for the selected transactions was 2.9x and 10.0x, respectively. Based on the application of its professional judgment and experience, WFS applied a multiple range of 3.0x to 3.75x to Callon’s 2024E EBITDA (based on the Callon Projections). This analysis indicated a range of implied per share value of Callon Common Stock of $27.55 to $41.73. Using the implied range for shares of APA Common Stock indicated by the selected companies analysis, this analysis indicated the following implied exchange ratio reference ranges of 0.5373 to 1.2451 shares of APA Common Stock for each share of Callon Common Stock, as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Historical Trading Prices. WFS reviewed the historical closing trading ranges of the APA Common Stock and the Callon Common Stock for the 52-week period through January 3, 2024.

WFS noted that this analysis indicated an exchange ratio reference range of 0.6285 to 1.3876 shares of APA Common Stock for each share of Callon Common Stock, as compared to the Exchange Ratio in the merger of 1.0425 shares of APA Common Stock for each share of Callon Common Stock.

Equity Research

Callon – WFS reviewed sell-side analyst price targets for shares of Callon Common Stock published by six (6) equity research analysts during the time period from November 2, 2023, through January 2, 2024. These targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of Callon Common Stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of Callon Common Stock was $34.00 per share to $54.00 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of Callon Common Stock and these estimates are subject to uncertainties, including the future financial performance of Callon and future financial market conditions.

APA – WFS reviewed sell-side analyst price targets for shares of APA Common Stock published by 13 equity research analysts during the time period from November 2, 2023, through January 2, 2024. These

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targets generally reflect each analyst’s estimate of the 12-month future public market trading price per share of APA Common Stock and were not discounted to reflect present values. The range of undiscounted price targets for shares of APA Common Stock was $36.00 per share to $61.00 per share. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of APA Common Stock and these estimates are subject to uncertainties, including the future financial performance of APA and future financial market conditions.

Miscellaneous

APA has agreed to pay WFS for its services in connection with the proposed merger a fee of up to $15 million, of which $2 million became payable upon the announcement of the merger and the remainder of which is contingent upon completion of the merger. APA agreed to reimburse WFS for its expenses, including fees and expenses of counsel, incurred in connection with its engagement. In addition, APA agreed to indemnify WFS and related parties against certain liabilities, including liabilities under the federal securities laws, relating to or arising out of WFS’s engagement.

During the two (2) years preceding the date of WFS’s opinion, WFS and its affiliates have had investment or commercial banking relationships with Callon and APA, for which WFS and its affiliates have received customary compensation. Such relationships included acting as joint dealer manager on an offering of debt securities by APA in March 2022, as joint bookrunner on an offering of debt securities by Callon in June 2022, and as joint lead arranger, joint bookrunner, and syndication agent in connection with a facility agreement by Callon in October 2022. In the two (2) years prior to the date of WFS’s opinion, for investment banking services, WFS and its affiliates received fees of approximately $500,000 from APA and $2.5 million from Callon. WFS and its affiliates are also an agent and a lender in one or more of the credit facilities of Callon and APA and certain of their affiliates. WFS is also arranging and/or providing financing to APA in connection with the merger for customary compensation. WFS and its affiliates hold, on a proprietary basis, less than one percent (1%) of the outstanding common stock of each of Callon and APA. In the ordinary course of business, WFS and its affiliates may trade or otherwise effect transactions in the securities or other financial instruments (including bank loans or other obligations) of Callon, APA, and certain of their affiliates for WFS’s own account and for the accounts of WFS’s customers and, accordingly, may at any time hold a long or short position in such securities or financial instruments.

Recommendation of the Callon Board and Its Reasons for the Merger

By unanimous vote, the Callon Board, at a meeting held on January 3, 2024, among other things, (i) determined that the Merger Agreement and the transactions contemplated thereby, including the merger, are fair to, and in the best interests of, Callon and the Callon stockholders, (ii) approved and declared advisable the Merger Agreement and the consummation of the transactions contemplated thereby, including the merger, and (iii) resolved to recommend that the Callon stockholders adopt and approve the Merger Agreement and the transactions contemplated thereby, including the merger. The Callon Board unanimously recommends that Callon stockholders vote “FOR” the Merger Proposal.

In evaluating the Merger Agreement, the merger, and the other transactions contemplated by the Merger Agreement, the Callon Board consulted with Callon’s management team, outside legal counsel, and financial advisors. The Callon Board determined that entering into the Merger Agreement with APA provided a superior path for maximizing stockholder value reasonably available to Callon and mitigating risk, compared to remaining a standalone company or pursuing an alternative transaction. In arriving at this determination and in recommending that the Callon stockholders vote their shares of Callon Common Stock in favor of the adoption and approval of the Merger Agreement, the Callon Board considered a number of factors, including the following factors (not necessarily in order of relative importance) that the Callon Board viewed as being generally positive or favorable in coming to its determination, approval, and related recommendation:

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