13D Filing: Corvex Capital and Energen Corporation (EGN)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 11)*

ENERGEN
CORPORATION

(Name of Issuer)

COMMON STOCK, $0.01 PAR VALUE

(Title of Class of Securities)

29265N108

(CUSIP Number)

Keith Meister

Patrick J. Dooley, Esq.

Corvex Management LP

667
Madison Avenue

New York, NY 10065

(212) 474-6700

Jeffrey
L. Kochian

Akin Gump Strauss Hauer & Feld LLP

One Bryant Park

New
York, NY 10036

(212) 872-8069

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

March 6, 2018

(Date
of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ☐

Note: Schedules filed in paper format shall
include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

CUSIP No. 29265N108

CUSIP No. 29265N108

This Amendment No. 11 supplements the information set forth in the Schedule 13D filed by Corvex Management
LP and Keith Meister with the United States Securities and Exchange Commission (the SEC) on May 31, 2017, as previously amended (the Schedule 13D), relating to the shares of common stock, par value $0.01 per share
(the Shares), of Energen Corporation, an Alabama corporation (the Issuer). Capitalized terms used but not defined herein shall have the meanings ascribed to them in the Schedule 13D.

The information set forth in response to each separate Item below shall be deemed to be a response to all Items where such information is relevant. The
Schedule 13D is supplementally amended as follows.

This statement on Schedule 13D is filed on behalf of Corvex Management LP, a
Delaware limited partnership (Corvex) and Keith Meister, a U.S. citizen (collectively, the Reporting Persons). This statement relates to Shares held for the accounts of certain private investment funds for which
Corvex acts as investment adviser, including Corvex Master Fund LP and Corvex Select Equity Master Fund LP, each a Cayman Islands limited partnership, the general partner of each of which is controlled by Mr. Meister (collectively, the
Corvex Funds). The general partner of Corvex is controlled by Mr. Meister.

Following the entry into the Letter Agreement (as
defined below), because Vincent J. Intrieri is no longer a Corvex Nominee, he will no longer be jointly filing this Schedule 13D with the Reporting Persons. There is no agreement or understanding in any way between the Reporting Persons and
Mr. Intrieri with respect to the voting, nor any restriction on the acquisition or disposition, of Shares of the Issuer held by such persons.

The
principal business address of the Reporting Persons is 667 Madison Avenue, New York, NY 10065. The principal business of Corvex is serving as the investment adviser of private investment funds, whose principal business is investing in
securities. Mr. Meisters principal occupation is serving as the Managing Partner of Corvex.

A joint filing agreement of Corvex and
Mr. Meister is attached hereto as Exhibit 12.

During the last five years, none of Corvex, Mr. Meister, or any of the Corvex Funds has
been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or has been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is
subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

On March 6, 2018, Corvex and the Issuer entered into a Letter Agreement
(the Letter Agreement). Pursuant to the terms of the Letter Agreement, the Issuer agreed as follows: (i) concurrently with the execution of the Letter Agreement, the Board shall expand the size of the Board from nine to 11 members
and not increase the size of the Board beyond 11 members at any time prior to the Issuers 2019 annual meeting of shareholders (the 2019 Annual Meeting) and (ii) appoint Jonathan Z. Cohen and Vincent J. Intrieri (the New
Directors) as members of the Board to fill the two vacancies created by the Board expansion, each with terms to expire at the Issuers 2018 annual meeting of shareholders (the 2018 Annual Meeting). In addition, the Issuer
agreed to include the New Directors in the slate of nominees recommended by the Board in the proxy statement and proxy card relating to the 2018 Annual Meeting, with Mr. Cohen nominated to serve in the class of directors with terms expiring at
the Issuers 2021 annual meeting of shareholders (the 2021 Annual Meeting) and Mr. Intrieri nominated to serve in the class of directors with terms expiring at the Issuers 2020 annual meeting of shareholders (the
2020 Annual Meeting), and the Issuer shall recommend that the Issuers shareholders vote for the election of the New Directors. Further, the Issuer agreed that four directors will stand for election at the 2019 Annual Meeting, four
directors will stand for election at the 2020 Annual Meeting, three directors will stand for election at the 2021 Annual Meeting and, other than as set forth in the Letter Agreement, the Issuer will not change or seek to change the classes on which
the directors (or their replacements) serve. The Issuer also agreed to hold the 2018 Annual Meeting no later than May 31, 2018.

Pursuant to the Letter Agreement, as long as Corvex continues to beneficially own 5% or more of the Issuers
outstanding Shares, if there is a vacancy or vacancies on the Board, for any reason, as a result of the removal or resignation of one or both of the New Directors or any other event resulting in one or both of the New Directors no longer being a
director prior to the Issuers mailing of definitive proxy materials with respect to the 2019 Annual Meeting, then, provided José Maria Alapont satisfies applicable director criteria at the time, Corvex will be entitled to designate him
to fill such vacancy, or if Mr. Alapont is no longer able or willing to serve as a director, Corvex may designate another individual or two other individuals reasonably acceptable to the Issuer if there are two vacancies to replace the New
Director or New Directors. In addition, the Issuer agreed that the New Directors will each be added to one or more committees of the Board and if any new committees or subcommittees of the Board are formed, the Board shall offer membership on such
committee or subcommittee to the New Directors.

Corvex agreed in the Letter Agreement to the following: (i) to cause all Shares owned of record or
beneficially by it and its affiliates to be present for quorum purposes at the 2018 Annual Meeting, and (ii) to vote such Shares at the 2018 Annual Meeting in favor of each director candidate nominated by the Issuer, in favor of the
ratification of the appointment of PricewaterhouseCoopers LLP as the Issuers independent registered public accounting firm to audit the Issuers financial statements for calendar year 2018, and in favor of any say-on-pay
proposal. In addition, Corvex agreed to promptly cause the appeal captioned Corvex Management LP, Appellant, v. Energen Corporation, Appellee, docket No. 1170200, pending before the Supreme Court of Alabama to be voluntarily dismissed
with prejudice. Further, Corvex agreed concurrently with the execution of the Letter Agreement to cause Corvex Master Fund LP to withdraw the Notice of Intent to Bring Business Before, and Nominate Individuals for Election as Directors at, the
2018 Annual Meeting of Stockholders of Energen Corporation submitted by Corvex Master Fund LP to the Issuer on January 31, 2018.

The foregoing
description of the Letter Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Letter Agreement, which is incorporated by reference as Exhibit 13 and is incorporated herein by
reference.

On March 6, 2018, Messrs. Cohen and Intrieri were appointed to the Board in connection with the Letter Agreement. Mr. Cohen was
appointed to the Boards Compensation Committee and Mr. Intrieri was appointed to the Boards Audit Committee.

On March 7, 2018,
Corvex and the Issuer jointly issued a press release to announce that they have entered into the Letter Agreement.

The Reporting Persons intend to review
their investment in the Issuer on a continuing basis and may from time to time and at any time in the future depending on various factors, including, without limitation, the Issuers financial position and strategic direction, actions taken by
the Board, price levels of the Shares, other investment opportunities available to the Reporting Persons, conditions in the securities market and general economic and industry conditions, take such actions with respect to their investments in the
Issuer as they deem appropriate, which may include further discussions with the Issuer regarding matters previously disclosed in this Schedule 13D, as well as seeking direct discussions with, and changes or additions to, the Board. These actions may
include, without limitation: (i) acquiring additional Shares and/or other equity, debt, notes, other securities, or derivative or other instruments that are convertible into Shares, or are based upon or relate to the value of the Shares or the
Issuer (collectively, Securities) in the open market or otherwise; (ii) disposing of any or all of their Securities in the open market or otherwise; (iii) engaging in any hedging or similar transactions with respect to the
Securities; or (iv) proposing or considering one or more of the actions described in subsections (a) through (j) of Item 4 of Schedule 13D.

(a)-(b) Corvex may be deemed to be the beneficial owner of
9,710,474 Shares, which represent approximately 9.9% of the Issuers outstanding Shares. By virtue of his position as control person of the general partner of Corvex, Mr. Meister may be considered to beneficially own such Shares. The
Reporting Persons may be deemed to have sole power to vote and sole power to dispose of 9,710,474 Shares.

The percentage calculated in the immediately
foregoing paragraph and below is calculated based on a total of 97,404,730 Shares outstanding as of February 20, 2018, as reported in the Issuers Annual Report on Form 10-K filed with the SEC on February 28, 2018.

(c) Except as set forth in this Schedule 13D, there have been no transactions in the Shares during the sixty days prior to the date hereof by any of the
Reporting Persons.

(d) The limited partners of (or investors in) each of the private investment funds for which Corvex or its affiliates acts as general
partner and/or investment adviser have the right to participate in the receipt of dividends from, or proceeds from the sale of, the Shares held for the accounts of their respective funds in accordance with their respective limited partnership
interests (or investment percentages) in their respective funds.

(e) Not applicable.

The
Letter Agreement is incorporated by reference as Exhibit 13 hereto and is incorporated by reference herein.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.