CHESAPEAKE ENERGY CORPORATION 1999 STOCK OPTION PLAN

Exhibit 10.1.5

CHESAPEAKE ENERGY CORPORATION

1999 STOCK OPTION PLAN

(as amended through June 6, 2008)

CHESAPEAKE ENERGY CORPORATION

1999 STOCK OPTION PLAN

Table of Contents

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ARTICLE I

PURPOSE

Section 1.1 Purpose . This Stock Option Plan is established by Chesapeake Energy Corporation (the “Company”) to create incentives which are designed to motivate Eligible Employees to put forth maximum effort toward the success and growth of the Company and to enable the Company to attract and retain experienced individuals who by their position, ability and diligence are able to make important contributions to the Company’s success. Toward these objectives, the Plan provides for the granting of Options to Eligible Employees on the terms and subject to the conditions set forth in the Plan.

Section 1.2 Establishment . The Plan is effective as of March 5, 1999 and for a period of 10 years from such date. The Plan will terminate on March 4, 2009; however, it will continue in effect until all matters relating to the exercise of Options and administration of the Plan have been settled.

Section 1.3 Shares Subject to the Plan . Subject to Articles IV, VII and IX of this Plan, shares of stock covered by Options shall consist of Three Million (3,000,000) shares of Common Stock.

Section 1.4 Shareholder Approval . Nonqualified Stock Options under the Plan may be granted to Participants prior to Shareholder Approval of the Plan, but no Incentive Stock Options may be granted prior to Shareholder Approval. In the event Shareholder Approval is not obtained within the twelve-month period following the date the Plan is adopted by the Board, no Incentive Stock Options may be granted under the Plan.

ARTICLE II

DEFINITIONS

Section 2.1 “Board” means the Board of Directors of the Company.

Section 2.2 “Code” means the Internal Revenue Code of 1986, as amended. Reference in the Plan to any Section of the Code shall be deemed to include any amendments or successor provisions to such Section and any regulations under such Section.

Section 2.3 “Committee” has the meaning set forth in Section 3.1.

Section 2.4 “Common Stock” means the common stock, par value $.01 per share, of the Company and, after substitution, such other stock as shall be substituted therefor as provided in Article VII or Article IX of the Plan.

Section 2.5 “Date of Grant” means the date on which the granting of an Option is authorized by the Committee or such later date as may be specified by the Committee in such authorization.

Section 2.6 “Disability” has the meaning set forth in Section 22(e)(3) of the Code.

Section 2.7 “Eligible Employee” means any employee of the Company, a Subsidiary or a partnership or limited liability company which the Company controls.

Section 2.8 “Exchange Act” means the Securities Exchange Act of 1934, as amended.

Section 2.9 “Executive Officer Participants” means Participants who are subject to the provisions of Section 16 of the Exchange Act.

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Section 2.10 “Fair Market Value” means (A) during such time as the Common Stock is listed on the New York Stock Exchange or other national securities exchanges or the Nasdaq National Market (each, an “exchange”), the closing price of the Common Stock on the New York Stock Exchange or, if no sale of the Common Stock shall have been made on the New York Stock Exchange, such other principal exchange on the day for which such value is to be determined, or if no sale of the Common Stock shall have been made on any such exchange that day, on the next preceding day on which there was a sale of such Common Stock or (B) during any such time as the Common Stock is not listed upon an exchange, the mean between dealer “bid” and “ask” prices of the Common Stock in the over-the-counter market on the day for which such value is to be determined, as reported by the National Association of Securities Dealers, Inc.

Section 2.11 “Incentive Stock Option” means an Option within the meaning of Section 422 of the Code.

Section 2.12 “Non-Executive Officer Participants” means Participants who are not subject to the provisions of Section 16 of the Exchange Act.

Section 2.13 “Nonqualified Stock Option” means an Option which is not an Incentive Stock Option.

Section 2.14 “Option” means an Option granted under Article VI of the Plan and includes both Nonqualified Stock Options and Incentive Stock Options to purchase shares of Common Stock.

Section 2.15 “Option Agreement” means any written instrument that establishes the terms, conditions, restrictions, and/or limitations applicable to an Option in addition to those established by this Plan and by the Committee’s exercise of its administrative powers.

Section 2.16 “Participant” means an Eligible Employee to whom an Option has been granted by the Committee under the Plan.

Section 2.17 “Plan” means the Chesapeake Energy Corporation 1999 Stock Option Plan.

Section 2.18 “Regular Stock Option Committee” means the Employee Compensation and Benefits Committee designated by the Board which shall consist of not less than one member of the Board.

Section 2.19 “Shareholder Approval” means approval by the holders of a majority of the outstanding shares of Common Stock, present, or represented, and entitled to vote at a meeting called for such purposes.

Section 2.20 “Special Stock Option Committee” means a committee designated by the Board which shall consist of not less than two members of the Board who meet the definition of “non-employee directors” pursuant to Rule 16b-3, or any successor rule, promulgated under Section 16 of the Exchange Act.

Section 2.21 “Subsidiary” shall have the same meaning set forth in Section 424 of the Code.

ARTICLE III

ADMINISTRATION

Section 3.1 Administration of the Plan; the Committee . For purposes of administration, the Plan shall be deemed to consist of two separate stock option plans, a “Non-Executive Officer Participant Plan” which is limited to Non-Executive Officer Participants, and an “Executive Officer Participant Plan” which is limited to Executive Officer Participants. Except for administration and the category of Participants eligible to receive Options, the terms of the Non-Executive Officer Participant Plan and the Executive Officer Participant Plan are identical.

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The Non-Executive Officer Participant Plan shall be administered by the Regular Stock Option Committee, and the Executive Officer Participant Plan shall be administered by either the Special Stock Option Committee or the Board. Accordingly, with respect to decisions relating to Non-Executive Officer Participants, including the grant of Options, the term “Committee” shall mean only the Regular Stock Option Committee; and, with respect to all decisions relating to Executive Officer Participants, including the grant of Options, the term “Committee” shall mean either the Special Stock Option Committee or the Board.

Unless otherwise provided in the by-laws of the Company or resolutions adopted from time to time by the Board establishing the Committee, the Board may from time to time remove members from, or add members to, the Committee. Vacancies on the Committee, however caused, shall be filled by the Board. The Committee shall hold meetings at such times and places as it may determine. A majority of the Committee shall constitute a quorum, and the acts of a majority of the members present at any meeting at which a quorum is present or acts reduced to or approved by the Committee in writing by a majority of the members of the Committee shall be the valid acts of the Committee.

Subject to the provisions of the Plan, the Committee shall have exclusive power to:

(a) Select the Eligible Employees to participate in the Plan.

(b) Determine the time or times when Options will be granted.

(c) Determine the form of an Option, whether an Incentive Stock Option or a Nonqualified Stock Option, the number of shares of Common Stock subject to the Option, all the terms, conditions (including performance requirements), restrictions and/or limitations, if any, of an Option, including the time and conditions of exercise or vesting, and the terms of any Option Agreement, which may include the waiver or amendment of prior terms and conditions or acceleration of the vesting or exercise of an Option under certain circumstances determined by the Committee.

(d) Determine whether Options will be granted singly or in combination.

(e) Take any and all other action it deems necessary or advisable for the proper operation or administration of the Plan.

Section 3.2 Committee to Make Rules and Interpret Plan . The Committee in its sole discretion shall have the authority, subject to the provisions of the Plan, to establish, adopt, or revise such rules and regulations and to make all such determinations relating to the Plan as it may deem necessary or advisable for the administration of the Plan. The Committee’s interpretation of the Plan or any Options granted pursuant hereto and all decisions and determinations by the Committee with respect to the Plan shall be final, binding, and conclusive on all parties.

ARTICLE IV

GRANT OF OPTIONS

The Committee may, from time to time, grant Options to one or more Participants, provided, however, that:

(a) Any shares of Common Stock related to Options which terminate by expiration, forfeiture, cancellation or otherwise without the issuance of shares of Common Stock shall be available again for grant under the Plan.

(b) Common Stock delivered by the Company upon exercise of an Option under the Plan may be authorized and unissued Common Stock or Common Stock held in the treasury of the Company or may be purchased on the open market or by private purchase.

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(c) The Committee shall, in its sole discretion, determine the manner in which fractional shares arising under this Plan shall be treated.

(d) Upon the exercise of any Option, the Company shall issue and deliver to the Participant who exercised the Option a certificate representing the number of shares of Common Stock purchased thereby.

ARTICLE V

ELIGIBILITY

Subject to the provisions of the Plan, the Committee shall, from time to time, select from the Eligible Employees those to whom Options shall be granted and shall determine the type or types of Options to be granted and shall establish in the related Option Agreements the terms, conditions, restrictions and/or limitations, if any, applicable to the Options in addition to those set forth in the Plan and the administrative rules and regulations issued by the Committee.

ARTICLE VI

STOCK OPTIONS

Section 6.1 Grant of Options . The Committee may, from time to time, subject to the provisions of the Plan and such other terms and conditions as it may determine, grant Options to Eligible Employees. These Options may be Incentive Stock Options or Nonqualified Stock Options, or a combination of both. Each grant of an Option shall be evidenced by an Option Agreement executed by the Company and the Participant, and shall contain such terms and conditions and be in such form as the Committee may from time to time approve, subject to the requirements of Section 6.2.

Section 6.2 Conditions of Options . Each Option so granted shall be