Exhibit 10.2

FIRST AMENDMENT

TO

STOCKHOLDERS’ AGREEMENT

This FIRST AMENDMENT, dated as of July 14, 2008 (the “Amendment”), to that
certain STOCKHOLDERS’ AGREEMENT (the “Agreement”) originally entered into as of
September 29, 2006, by and among Chaparral Energy, Inc., a Delaware corporation
(the “Company”), Fischer Investments, L.L.C., an Oklahoma limited liability
company (“Fischer”), Altoma Energy, an Oklahoma general partnership (“Altoma”),
and CHK Holdings, L.L.C., an Oklahoma limited liability company (“Chesapeake”),
each person named above being referred to individually as a “Party” and
collectively as the “Parties”. Capitalized terms used but not defined herein
shall have the respective meanings assigned to them in the Agreement.

RECITALS

WHEREAS, the Company intends to acquire Edge Petroleum Corporation, a Delaware
corporation (“Edge”), by merging Edge with and into a newly created, wholly
owned subsidiary of the Company (the “Merger”);

WHEREAS, in conjunction with the Merger, the Company will list its Common Stock
on the New York Stock Exchange or another national securities exchange; and

WHEREAS, the Parties desire to make changes to the Agreement appropriate for its
activities following the Merger;

NOW, THEREFORE, in consideration of the mutual covenants and obligations
hereinafter set forth, the parties hereto, intending to be legally bound, hereby
agree as follows:

1. Termination of Specified Sections of the Agreement. Concurrent with the
closing of the Merger (the “Effective Time”), the following Sections (or
portions thereof) in the Agreement will be deleted and be of no further force
and effect:

 

  a. The definitions set forth in Section 1.1 of the Agreement that relate only
to Sections (or portions thereof) of the Agreement that are deleted and of no
further force and effect pursuant to this Amendment;

 

  b. Sections 3.1 through 3.10 of the Agreement;

 

  c. Sections 4.1 through 4.9 of the Agreement; and

 

  d. Section 5.1(b) of the Agreement.

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2. Amendment of Specified Sections of the Agreement. Immediately prior to the
effective time of the Merger, the following Sections in the Agreement will be
amended as follows:

a. The beginning phrase of Section 5.1(a), which reads “At any time after a
Qualified IPO (the “Demand Period”),” is hereby deleted and of no further force
and effect.

 

  b. Section 8.4 shall read in its entirety as follows:

“Stock Subject to this Agreement. All shares of Common Stock and Common Stock
Equivalents now owned or hereafter acquired by any of the Parties (other than
the Company) shall be subject to, and entitled to the benefits of, the terms of
this Agreement. Any transferee or recipient of the Common Stock or Common Stock
Equivalents of a Party (other than the Company), other than a transferee or
recipient who acquires a Party’s Common Stock or Common Stock Equivalents in a
registered offering or a bona fide open market sale in accordance with Rule 144,
shall become a Party and be bound as if an original Party hereto upon the
execution of an Adoption Agreement substantially in the form attached hereto as
Exhibit B.

 

  c. Section 8.6 shall be amended to replace Andrews Kurth LLP as recipient of
copies of any notice to the Company with the following:

McAfee & Taft A Professional Corporation

10th Floor, Two Leadership Square

211 North Robinson

Oklahoma City, Oklahoma 73102

Attn: David J. Ketelsleger

Phone: (405) 235-9621

Fax: (405) 235-0439

IN WITNESS WHEREOF, the Parties hereto have executed this First Amendment to
Stockholders’ Agreement as of the date first above written, and shall become
effective immediately prior to the effective time of the Merger.

 

Chaparral Energy, Inc. By:  

/s/ Mark A. Fischer

Name:   Mark A. Fischer Title:   Chief Executive Officer and President Fischer
Investments, L.L.C. By:  

/s/ Mark A. Fischer

Name:   Mark A. Fischer Title:   Manager Altoma Energy By:  

/s/ Charles A. Fischer, Jr.

Name:   Charles A. Fischer, Jr. Title:   Managing General Partner CHK Holdings,
L.L.C. By:  

/s/ Marcus C. Rowland

Name:   Marcus C. Rowland Title:   Executive Vice President