FIFTH AMENDMENT TO SECOND AMENDED AND RESTATED SENIOR REVOLVING CREDIT AGREEMENT

Exhibit 10.1

Execution Version

FIFTH AMENDMENT

TO

SECOND AMENDED AND RESTATED

SENIOR REVOLVING CREDIT AGREEMENT

among

PETROHAWK ENERGY CORPORATION,

as the Borrower,

BNP PARIBAS,

as Administrative Agent,

BANK OF AMERICA, N.A. and

BMO CAPITAL MARKETS FINANCING, INC.,

as Co-Syndication Agents,

JPMORGAN CHASE BANK, N.A.,

WELLS FARGO BANK, N.A. and

FORTIS CAPITAL CORP.

as Co-Documentation Agents,

and

THE LENDERS PARTY HERETO

Effective as of February 5, 2008

FIFTH AMENDMENT TO

SECOND AMENDED AND RESTATED SENIOR REVOLVING CREDIT AGREEMENT

This FIFTH AMENDMENT TO SECOND AMENDED AND RESTATED SENIOR REVOLVING CREDIT AGREEMENT (this “ Fifth Amendment ”) executed effective as of February 5, 2008 (the “ Fifth Amendment Effective Date ”) is among PETROHAWK ENERGY CORPORATION, a corporation duly formed and existing under the laws of the State of Delaware (the “ Borrower ”); each of the Guarantors signatory hereto (the “ Guarantors ”); each of the Lenders from time to time party hereto; BNP PARIBAS (in its individual capacity, “ BNP Paribas ”), as administrative agent for the Lenders (in such capacity, together with its successors in such capacity, the “ Administrative Agent ”); Bank of America, N.A. and BMO Capital Markets Financing, Inc., as co-syndication agents for the Lenders (in such capacity, together with their successors in such capacity, the “ Co-Syndication Agents ”); and JPMorgan Chase Bank, N.A., Wells Fargo Bank, N.A. and Fortis Capital Corp. as co-documentation agents for the Lenders (in such capacity, together with their successors in such capacity, the “ Co-Documentation Agents ”).

Recitals

A. The Borrower, the Administrative Agent, the other Agents and Lenders named and defined therein as lenders and agents, are parties to that certain Second Amended and Restated Senior Revolving Credit Agreement dated as of July 12, 2006, as amended by the First Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of July 24, 2006, the Second Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of May 8, 2007, the Third Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of July 25, 2007 and the Fourth Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of October 15, 2007, pursuant to which such lenders and agents provided certain loans and extensions of credit to the Borrower (as amended, the “ Credit Agreement ”).

B. The Administrative Agent has requested, and the Borrower, the Administrative Agent, the Co-Syndication Agents, the Co-Documentation Agents and Lenders have agreed to amend certain provisions of the Credit Agreement.

C. NOW, THEREFORE, in consideration of the premises and the mutual covenants herein contained, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

Section 1. Defined Terms . Each capitalized term which is defined in the Credit Agreement, but which is not defined in this Fifth Amendment, shall have the meaning ascribed such term in the Credit Agreement. Unless otherwise indicated, all section references in this Fifth Amendment refer to sections in the Credit Agreement.

Section 2. Amendments to Credit Agreement .

2.1 Certain Defined Terms . The following defined terms in Section 1.02 are hereby amended and restated in their entirety as follows:

“ Agreement ” means this Second Amended and Restated Senior Revolving Credit Agreement, as amended by the First Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of July 24, 2006, the Second Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of May 8, 2007, the Third Amendment to Second Amended and Restated Senior Revolving Credit Agreement dated as of July 25, 2007, the Fourth Amendment to Second Amended and Restated Senior Revolving Credit Agreement, dated as of October 15, 2007 and the Fifth Amendment to Second Amended and Restated Senior Revolving Credit Agreement dated as of February 5, 2008, as the same may from time to time be further amended, modified, supplemented or restated.

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“ Applicable Margin ” means, for any day, with respect to any ABR Loan or Eurodollar Loan, or with respect to the Commitment Fee Rate, as the case may be, the rate per annum set forth in the Borrowing Base Utilization Grid below based upon the Borrowing Base Utilization Percentage then in effect:

Each change in the Applicable Margin or Commitment Fee Rate shall apply during the period commencing on the effective date of such change and ending on the date immediately preceding the effective date of the next such change, provided, however, that if at any time the Borrower fails to deliver a Reserve Report pursuant to Section 8.12(a), then the “ Applicable Margin ” or “ Commitment Fee Rate ” means the rate per annum set forth on the grid when the Borrowing Base Utilization Percentage is at its highest level.

“ Borrowing Base Equalization Date ” means February 5, 2009.

“ Borrowing Base Utilization Percentage ” means, as of any day, the fraction expressed as a percentage, the numerator of which is the sum of the Revolving Credit Exposures of the Lenders on such day, and the denominator of which is (a) prior to the Borrowing Base Equalization Date, the Conforming Borrowing Base in effect on such day and (b) on and after the Borrowing Base Equalization Date, the Borrowing Base in effect on such day.

“ Conforming Borrowing Base ” means at any time an amount equal to the amount determined in accordance with Section 2.07, as the same may be adjusted from time to time pursuant to Section 8.13(c) or Section 9.13.

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“ Fifth Amendment Effective Date ” shall mean February 5, 2008.

2.2 Section 2.03 . Section 2.03(v) shall be amended and restated in its entirety as follows:

“(v) the amount of the then effective Borrowing Base and the then effective Conforming Borrowing Base (if applicable), the current total Revolving Credit Exposures (without regard to the requested Borrowing) and the pro form a total Revolving Credit Exposures (giving effect to the requested Borrowing); and”

2.3 Section 2.07 . Section 2.07 is hereby amended and restated in its entirety as follows:

“Section 2.07 Borrowing Base .

(a) Initial Borrowing Base . For the period from and including the Fifth Amendment Effective Date to but excluding the next Redetermination Date, the amount of the Borrowing Base shall be $1,000,000,000 and the amount of the Conforming Borrowing Base shall be $900,000,000. Notwithstanding the foregoing, the Borrowing Base and the Conforming Borrowing Base may be subject to further adjustments from time to time pursuant to Section 8.13(c) or Section 9.13. As of the Borrowing Base Equalization Date, the Borrowing Base shall equal the Conforming Borrowing Base and all references to the “Conforming Borrowing Base” in this Agreement shall mean the Borrowing Base.

(b) Scheduled and Interim Redeterminations . The Borrowing Base (and, if applicable, the Conforming Borrowing Base) shall be redetermined semi-annually in accordance with this Section 2.07 (a “ Scheduled Redetermination ”), and, subject to Section 2.07(d), such redetermined Borrowing Base (and, if applicable, Conforming Borrowing Base) shall become effective and applicable to the Borrower, the Agents, the Issuing Bank and the Lenders on May 1st and November 1st of each year. In addition, the Borrower may, by notifying the Administrative Agent thereof, and the Administrative Agent may, at the direction of the Majority Lenders, by notifying the Borrower thereof, one time during any 12-month period, each elect to cause the Borrowing Base to be redetermined between Scheduled Redeterminations (an “ Interim Redetermination ”) in accordance with this Section 2.07.

(c) Scheduled and Interim Redetermination Procedure .

(i) Each Scheduled Redetermination and each Interim Redetermination shall be effectuated as follows: Upon receipt by the Administrative Agent of (A) the Reserve Report and the certificate required to be delivered by the Borrower to the Administrative Agent, in the case of a Scheduled Redetermination, pursuant to Section 8.12(a) and (c), and, in the case of an Interim Redetermination, pursuant to Section 8.12(b) and (c), and (B) such other reports, data and supplemental information, including, without limitation,

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the information provided pursuant to Section 8.12(c), as may, from time to time, be reasonably requested by the Majority Lenders (the Reserve Report, such certificate and such other reports, data and supplemental information being the “ Engineering Reports ”), the Administrative Agent shall evaluate the information contained in the Engineering Reports and shall, in its sole discretion, propose a new Borrowing Base and which shall, prior to the Borrowing Base Equalization Date, also specify a new Conforming Borrowing Base (the “ Proposed Borrowing Base ”) based upon such information and such other information (including, without limitation, the status of title information with respect to the Oil and Gas Properties as described in the Engineering Reports and the existence of any other Debt) as the Administrative Agent deems appropriate and consistent with its normal oil and gas lending criteria as it exists at the particular time. In no event shall the Proposed Borrowing Base exceed the Aggregate Maximum Credit Amounts.

(ii) The Administrative Agent shall notify the Borrower and the Lenders of the Proposed Borrowing Base (the “ Proposed Borrowing Base Notice ”):

(A) in the case of a Scheduled Redetermination (1) if the Administrative Agent shall have received the Engineering Reports required to be delivered by the Borrower pursuant to Section 8.12(a) and (c) in a timely and complete manner, then on or before April 15th and October 15th of such year following the date of delivery or (2) if the Administrative Agent shall not have received the Engineering Reports required to be delivered by the Borrower pursuant to Section 8.12(a) and (c) in a timely and complete manner, then promptly after the Administrative Agent has received complete Engineering Reports from the Borrower and has had a reasonable opportunity to determine the Proposed Borrowing Base in accordance with Section 2.07(c)(i); and

(B) in the case of an Interim Redetermination, promptly, and in any event, within fifteen (15) days after the Administrative Agent has received the required Engineering Reports.

(iii) Any Proposed Borrowing Base that would increase the Borrowing Base (or, if applicable, the Conforming Borrowing Base) then in effect must be approved or deemed to have been approved by the Required Lenders as provided in this Section 2.07(c)(iii); and any Proposed Borrowing Base that would decrease or maintain the Borrowing Base (or, if applicable, the Conforming Borrowing Base) then in effect must be approved or be deemed to have been approved by the Majority Lenders as provided in this Section 2.07(c)(iii). Upon receipt of the Proposed Borrowing Base Notice, each Lender shall have fifteen (15) days to agree with the Proposed Borrowing Base or disagree with the Proposed Borrowing Base by proposing an alternate Borrowing Base (which proposal must also propose, if applicable, a Conforming Borrowing Base). If at the end of such fifteen (15) days, any Lender has not communicated its approval or disapproval in writing to the Administrative Agent, such silence shall be

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deemed to be an approval of the Proposed Borrowing Base. If, at the end of such 15-day period, the Required Lenders, in the case of a Proposed Borrowing Base that would increase the Borrowing Base (or, if applicable, the Conforming Borrowing Base) then in effect, or the Majority Lenders, in the case of a Proposed Borrowing Base that would decrease or maintain the Borrowing Base (or, if applicable, the Conforming Borrowing Base) then in effect, have approved or deemed to have approved, as aforesaid, then the Proposed Borrowing Base shall become the new Borrowing Base (and, if applicable, the Conforming Borrowing Base), effective on the date specified in Section 2.07(d). If, however, at the end of such 15-day period, the Required or Majority Lenders, as applicable, have not approved or deemed to have approved, as aforesaid, then the Administrative Agent shall poll the Lenders to ascertain the highest Borrowing Base (and, if applicable, the Conforming Borrowing Base) then acceptable to the Majority Lenders for purposes of this Section 2.07 and, so long as such amount does not increase the Borrowing Base (or, if applicable, the Conforming Borrowing Base) then in effect, such amount shall become the new Borrowing Base (and, if applicable, the new Conforming Borrowing Base), effective on the date specified in Section 2.07(d). While the Conforming Borrowing Base is in effect, the foregoing procedures shall apply to each proposed Borrowing Base and each proposed Conforming Borrowing Base separately.

(iv) The Borrowing Base shall not be more than $100,000,000 greater than the Conforming Borrowing Base. If the Conforming Borrowing Base is adjusted and the Borrowing Base is more than $100,000,000 greater than the Conforming Borrowing Base, then the Borrowing Base shall automatically be reduced to an amount that is equal to $100,000,000 greater than the Conforming Borrowing Base.

(d) Effectiveness of a Redetermined Borrowing Base . After a redetermined Borrowing Base (and, if applicable, the Conforming Borrowing Base) is approved or is deemed to have been approved by the Required Lenders or the Majority Lenders, as applicable, pursuant to Section 2.07(c)(iii), the Administrative Agent shall notify the Borrower and the Lenders of the amount of the redetermined Borrowing Base (and, if applicable, the Conforming Borrowing Base) (the “ New Borrowing Base Notice ”), and such amount shall become the new Borrowing Base (and, if applicable, the new Conforming Borrowing Base), effective and applicable to the Borrower, the Agents, the Issuing Bank and the Lenders:

(i) in the case of a Scheduled Redetermination, (A) if the Administrative Agent shall have received the Engineering Reports required to be delivered by the Borrower pursuant to Section 8.12(a) and (c) in a timely and complete manner, then on May 1st or November 1st, as applicable, following such notice, or (B) if the Administrative Agent shall not have received the Engineering Reports required to be delivered by the Borrower pursuant to Section 8.12(a) and (c) in a timely and complete manner, then on the Business Day next succeeding delivery of such notice; and

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(ii) in the case of an Interim Redetermination, on the Business Day next succeeding delivery of such notice.

Such amount shall then become the Borrowing Base (and, if applicable, the Conforming Borrowing Base) until the next Scheduled Redetermination Date, the next Interim Redetermination Date or t