Exhibit 10.3

FIRST AMENDMENT TO

SECURITIES PURCHASE AGREEMENT

for

CALUMET OIL COMPANY

J.M. GRAVES L.L.C.

and

JMG OIL & GAS, LP

Dated as of October 31, 2006

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FIRST AMENDMENT TO SECURITIES PURCHASE AGREEMENT

This First Amendment to Securities Purchase Agreement (the “Amendment”), is made
and entered into this 31st day of October, 2006, among the parties identified on
Exhibit A-1 (collectively, the “Shareholders” and individually a “Shareholder”),
the parties identified on Exhibit A-2 (collectively, the “Partners” and
individually a “Partner”), the parties identified on Exhibit A-3 (collectively,
the “Members” and individually a “Member”) (the Shareholders, the Partners and
the Members in their respective capacities sometimes being collectively referred
to herein as the “Sellers” and individually as a “Seller”), Calumet Oil Company,
an Oklahoma corporation (the “Company”), JMG Oil & Gas, LP, an Oklahoma limited
partnership (the “Partnership”), J.M. Graves L.L.C., an Oklahoma limited
liability company (the “General Partner”, and together with the Partnership, the
“Partnership Entities”) (the Company, the Partnership and the General Partner
being sometimes referred to collectively as the “Entities”), Chaparral Energy,
Inc., a Delaware corporation (the “Purchaser”), and Chaparral Energy, L.L.C., a
Delaware limited liability company and wholly-owned subsidiary of the Purchaser
(“Assignee”). The Sellers, the Company, the Partnership, the General Partner and
the Purchaser are each sometimes referred to herein as a “Party” and are
sometimes collectively referred to herein as the “Parties.”

RECITALS

WHEREAS, the Parties are party to that certain Securities Purchase Agreement
(the “Agreement”), dated as of September 16, 2006, whereby the Purchaser agreed
to purchase (i) all of the capital stock, warrants, options and any other rights
to acquire the capital stock of the Company owned by the Shareholders, (ii) all
of the partnership interests, warrants, options and any other rights to acquire
partnership interests in the Partnership (other than the general partner
interest owned by the General Partner) owned by the Partners and (iii) all of
the membership interests, warrants, options and any other rights to acquire
membership interests in the General Partner owned by the Members;

WHEREAS, the Parties desire to amend certain terms of the Agreement; and

WHEREAS, the Purchaser desires to assign all of its rights and obligations under
the Agreement to Assignee, a wholly owned subsidiary of the Purchaser, and
Assignee desires to assume such rights and obligations.

AGREEMENT

NOW, THEREFORE, in consideration of the foregoing recitals, the agreements
contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Parties agree as follows:

 

1. Definitions. All capitalized terms used in the recitals above and the
succeeding provisions of this Amendment which are not defined herein shall have
the meaning ascribed to such terms in the Agreement, as amended by this
Amendment. All sections referred to in this Amendment shall be references to
sections in the Agreement unless otherwise noted.

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2. Section 2.a of the Agreement is hereby deleted in its entirety and replaced
as follows:

 

  a. Purchase Price. Subject to the terms and conditions contained in this
Agreement, on the Closing Date, the Purchaser shall pay to the Sellers, in the
aggregate, an amount equal to $500,000,000.00 (the “Aggregate Purchase Price”),
subject to adjustment as provided in Section 2(b), Section 10(e), and Section 3
in consideration for the Interests. The Aggregate Purchase Price as adjusted
pursuant to Section 2(b), Section 10(e) and Section 3 is herein referred to as
the “Interest Purchase Price.” The parties hereto agree that the Interest
Purchase Price shall be allocated as set forth on Exhibit C.

 

3. Environmental Defects.

 

  a. The parties hereby agree that the reduction in the Aggregate Purchase Price
reflected in this Amendment of $10,000,000 from $510,000,000 to $500,000,000 is
made in lieu of, and as consideration for the elimination of, all of the
obligations and rights under Section 3.b. of the Agreement relating to the
Environmental Escrow Agreement.

 

  b. Section 11.b.IX is hereby amended and restated in its entirety as follows:

Environmental Compliance. Except as would not, individually or in the aggregate,
constitute a Material Adverse Change, the Company, its Subsidiaries and the
Partnership shall (1) be in possession of all Environmental Approvals needed to
carry on their current operations, (2) except as set forth on Schedules 5(g) and
6(f) of the Seller Disclosure Schedules, be in compliance with all Environmental
Laws and (3) except as set forth on Schedule 5(j) and (6)(i) of the Seller
Disclosure Schedules, not have received any demand or notice with respect to any
Environmental Claims or non-compliance with Environmental Laws; provided, the
existence of any of the foregoing, together with any other Environmental
Defects, that would not reasonably be estimated to represent an aggregate
liability in excess of $15.0 million or such other estimated amounts known to
Purchaser as of the Closing Date (including environmental inspection reports
prepared for Purchaser prior to the Closing Date), shall not be deemed to
represent a Material Adverse Change solely due to the estimated cost of such
liabilities.

 

  c. The requirements in Sections 12.a.IV and 12.b.III of the Agreement relating
to the delivery of an Environmental Escrow Agreement are hereby eliminated and
no longer required.

 

4. Schedules 9(c), 9 (g), 5(v) and 6 (u) are hereby amended and restated in
their entirety as set forth on such Schedules attached hereto.

 

5. Section 10.b.III of the Agreement is hereby deleted in its entirety and
replaced as follows:

 

  III. Spin-Off, Amendment and Merger of the Company’s 401(k) Plan.

(A) Spin-Off. Among other Benefit Plans, the Company sponsors a pension benefit
plan that is intended to meet the requirements

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of Sections 401(a) and 401(k) of the Code (“Company 401(k) Plan”). Green Country
Supply, Inc. (“GCSI”) co-sponsors the Company 401(k) Plan. Effective as of the
Closing Date, Sellers shall cause the Company 401(k) Plan to be split-up into
two separate, substantially identical plans. One such plan will cover
participants employed by the Company prior to or on the Closing Date and will
continue to be referred to as the Company 401(k) Plan. The other plan will cover
participants employed by GCSI prior to, on or after the Closing Date (“GCSI
401(k) Plan”).

(B) Amendment. Effective as of the Closing Date, Sellers shall cause the Company
401(k) Plan as it relates to participants (employed by the Company prior to or
on the Closing Date) to be amended, as appropriate, to (i) cease all
contributions for periods on or after the Closing Date, except to the extent
required by the top-heavy provisions of Section 416 of the Code or other
applicable law and (ii) fully vest amounts credited to the account of any such
participant who was not already fully vested in his or her account under the
Company Plan as of the Closing Date.

(C) Merger. As of a date (the “Account Transfer Date”) as soon as practicable
after the Closing Date, the Company shall cause to be transferred from the
Company 401(k) Plan to the 401(k) plan sponsored by the Purchaser (the
“Purchaser’s 401(k) Plan”) cash or property acceptable to Purchaser in an amount
equal to the aggregate account balances of all participants in the Company
401(k) Plan as of such Account Transfer Date, including actual investment
earnings or losses through the Account Transfer Date, except that all promissory
notes and any related documentation reflecting participant loans to such
participants outstanding as of such Account Transfer Date shall be transferred
in kind (the “Transferred Assets”). As of the Account Transfer Date, the
Purchaser shall assume all liabilities applicable to participants under the
Company 401(k) Plan to pay benefits, consistent with the terms of the Company
401(k) Plan, equal to the amount transferred. In the event any participant under
the Company 401(k) Plan has a qualified domestic relations order pending or
approved in the Company 401(k) Plan at the time of transfer, all documentation
concerning such qualified domestic relations order shall be assigned to the
Purchaser’s 401(k) Plan. Sellers, Company, GCSI and the Purchaser agree to
cooperate fully with respect to any governmental filings, including but not
limited to the filing of any Internal Revenue Service Form 5310A reporting
obligations, information and procedures necessary to effect the transactions
contemplated by this Section 10.b.III. Pending the transfer of the Transferred
Assets, the accounts of the participants under the Company 401(k) Plan shall
remain in the trust fund for the Company 401(k) Plan and the Company shall cause
the trustee of the Company 401(k) Plan to pay any current benefits or make any
distributions to participants under the Company 401(k) Plan, including such
benefits as may be payable to such participants on account

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of termination of employment with the Purchaser and its ERISA Affiliates, as
they become due. Sellers, Company, GCSI and the Purchaser agree to provide each
other with such records and information as they may reasonably request relating
to their respective obligations under this Section 10.b.III or the
administration of the Company 401(k) Plan, GCSI 401(k) Plan or the Purchaser’s
401(k) Plan.

 

6. Section 10.e of the Agreement is hereby deleted in its entirety and replaced
as follows:

 

  a. Section 338(h)(10) Election; Tax Adjustment.

I. At the request of Purchaser, the shareholders of the Company will cause the
Company to join with Purchaser in making an election under Section 338(h)(10) of
the Code (and any corresponding election under state, local, and foreign tax
law) with respect to the purchase and sale of the Shares of the Company
hereunder (a “Section 338(h)(10) Election”). Seller and the Purchaser shall
cooperate fully with each other and make available to each other as soon as
practicable after the Closing Date (but in not event more than 270 days after
the Closing Date) such Tax data and other information as may be reasonably
required by Purchaser to determine whether to make the Section 338(h)(10)
Election (including, without limitation, a good faith determination of the
actual amount of ordinary income recapture allocable to the Sellers on a
property-by-property basis that would result from the Section 338(h)(10)
Election). Each Seller will include any income, gain, loss, deduction, or other
Tax item resulting from the Section 338(h)(10) Election on its Tax Returns to
the extent permitted by applicable law. The allocation of the Purchase Price
among the assets of the Company shall be made in accordance with Section 338 of
the Code and the Treasury Regulations promulgated thereunder. The Sellers shall,
unless it would be unreasonable to do so, accept Purchaser’s determination of
such allocations of the Purchase Price and shall report, act and file in all
respects and for all purposes consistent with such determination of Purchaser.
To facilitate such election, all of the “S corporation shareholders” as defined
in Treasury Regulation Section 1.338(h)(10)-1(b)(5) shall, not later than 270
days after the Closing Date, execute and deliver to Purchaser such forms as
Purchaser shall request or as required by applicable law for effective
Section 338(h)(10) Elections, including IRS Form 8023 (together with any
schedules or attachments thereto.

II. If Purchaser chooses to make a Section 338(h)(10) Election, Purchaser shall
pay to the Shareholders not later than 45 days after such Section 338(h)(10)
Election is filed, in cash as an adjustment to the Purchase Price, the amount of
additional consideration the parties agree is necessary to cause the
Shareholders’ after-Tax net proceeds from the sale of the Shares with the
Section 338(h)(10) Election to be equal to the after-Tax net proceeds that the
Shareholders would have received had the Section 338(h)(10) Election not been
made, taking into account all appropriate state, federal and local Tax
implications (the “Tax Adjustment”); provided, however, the maximum amount of
the Tax Adjustment shall in no event exceed $17 million in the aggregate.

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7. Assignment and Assumption of Agreement. Effective as of the date hereof,
Purchaser does hereby assign, sell, transfer and convey to Assignee all of its
right, title and interest in and to the Agreement. Assignee does hereby assume
and shall subsequently discharge and perform when lawfully due the obligations
of Assignee under the Agreement from and after the date hereof. Each of the
Purchaser and Assignee shall execute such documents and other instruments and
perform such further acts, as may be reasonably required or desirable to effect
the provisions of this Section 7 and the transactions contemplated hereby. The
assumption by Assignee of the rights and obligations as herein provided is not
intended by the Purchaser or the Assignee to expand the rights or remedies of
any third party against Assignee as compared to the rights and remedies which
such third party would have had against the Purchaser had Assignee not
consummated the transactions contemplated by the Agreement. Assignee shall have
all rights that Purchaser may have, or have had, to defend or contest any third
party claim or demand.

 

8. General Provisions.

 

  a. Entire Agreement. This Amendment together with the Schedules and Exhibits
contains the entire understanding of the Parties with regard to the subject
matter hereof and no warranties, representations, promises or agreements have
been made between the Parties other than as expressly herein set forth. This
Amendment supersedes any previous agreement or understanding between the Parties
and cannot be modified or amended except in a writing executed by the Purchaser
and the Majority of Sellers.

 

  b. Binding Effect. Upon execution, this Amendment shall be binding and fully
enforceable and shall inure to the benefit of the Parties hereto, their
successors, assigns, personal representatives and heirs.

 

  c. Notices. All communications and notices to the Parties hereunder shall be
given as provided in the Agreement.

 

  d. Severability. In the event that any of the provisions, or portions thereof,
of this Amendment are held to be unenforceable or invalid by any court of
competent jurisdiction, the validity and enforceability of the remaining
provisions, or portions thereof, shall not be affected thereby and effect shall
be given to the intent manifested by the provisions, or portions thereof, held
to be enforceable and valid.

 

  e. Governing Law; Waiver of Jury Trial. This Amendment shall be governed by
and construed under the laws of the State of Oklahoma without regard to its
choice of law provisions that would apply the law of any other state. EACH OF
THE PARTIES TO THIS AMENDMENT HEREBY IRREVOCABLY WAIVES ALL RIGHT TO A TRIAL BY
JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM ARISING OUT OF OR RELATING TO
THIS AMENDMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY.

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  f. Counterparts; Facsimile Signatures. This Amendment may be executed in any
number of counterparts and each such counterpart shall be considered an original
and an enforceable agreement. Facsimile and electronic signatures to this
Amendment shall be valid.

[SIGNATURES ON NEXT PAGE]

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IN WITNESS WHEREOF, the undersigned parties have executed this Agreement as of
the date first set forth above.

 

PURCHASER Chaparral Energy, Inc. By:  

/s/ Mark A. Fischer

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

/s/ Mark A. Fischer

Name:   Mark A. Fischer Title:   Manager SELLERS John Milton Graves Trust UTA
6/11/2004 By:  

/s/ Paul Korte

Name:   Paul Korte, Co-Trustee By:  

/s/ E. Ann Graves

Name:   E. Ann Graves, Co-Trustee J.M Graves, L.L.C. By:  

/s/ Michael L. Graves

Name:   Michael L. Graves Title:   Managing Member

/s/ E. Ann Graves

E. Ann Graves

/s/ John Graves

John Graves

/s/ Michael L. Graves

Michael L. Graves

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ENTITIES CALUMET OIL COMPANY By:  

/s/ Michael L. Graves

  Michael L. Graves, President J.M. GRAVES L.L.C. By:  

/s/ Michael L. Graves

  Michael L. Graves, Managing Member JMG OIL & GAS, LP By:   J.M. Graves L.L.C.,
its general partner By:  

/s/ Michael L. Graves

  Michael L. Graves, Managing Member