Exhibit 10.5(f)

EXECUTION VERSION

AMENDMENT NO. 2 TO

INTERCREDITOR AGREEMENT

THIS AMENDMENT NO. 2 TO INTERCREDITOR AGREEMENT (this “Amendment”), dated as of
October 29, 2008, is made by and among the institutional investors listed under
the caption “Noteholders” on the signature pages hereto (collectively, together
with the other holders from time to time of the hereinafter described NPA Notes
and their successors and assigns, the “Noteholders”); Capital One, National
Association, Union Bank of California, N.A., BNP Paribas, Compass Bank and
Fortis Capital Corp. (collectively, together with the other lenders from time to
time party to the hereinafter described Bank Loan Agreement and their successors
and assigns, the “Banks”); Capital One, National Association, as agent for the
Banks (in such capacity, the “Bank Agent”), and The Bank of New York Trust
Company, N.A., as collateral agent for the Noteholders (together with its
successors and assigns in such capacity, the “Noteholder Collateral Agent”).

RECITALS

A. The Noteholders, the Banks, the Bank Agent and the Noteholder Collateral
Agent are parties to an Intercreditor Agreement dated as of July 31, 2007, as
amended by Amendment No. 1 to Intercreditor Agreement dated as of June 12, 2008
(as so amended, the “Agreement”).

B. The parties hereto have agreed to amend the Agreement as described herein.

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

Section 1. Existing Defined Term. Effective as of the date hereof, the defined
term “Senior Indebtedness” in Article I of the Intercreditor Agreement is hereby
amended by (a) deleting each reference to “$185,000,000” occurring therein and
(b) substituting “$200,000,000” in lieu of each occurrence thereof.

Section 2. Miscellaneous.

(i) Except as expressly amended by this Amendment, the Agreement shall remain in
full force and effect. This Amendment shall be binding upon and inure to the
benefit of the Noteholders, the Banks, the Collateral Agent, any other parties
to the Agreement from time to time, and their respective successors and
permitted assigns.

(ii) THIS AMENDMENT SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, AND THE
RIGHTS OF THE PARTIES SHALL BE GOVERNED BY, THE LAW OF THE STATE OF NEW YORK.

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(iii) This Amendment may be executed in any number of counterparts, each of
which shall be deemed an original and all of which taken together shall
constitute one and the same document. Delivery of this Amendment may be made by
telecopy or electronic transmission of a duly executed counterpart copy hereof;
provided that any such delivery by electronic transmission shall be effective
only if transmitted in .pdf format, .tif format or other format in which the
text is not readily modifiable by any recipient thereof.

[Remainder of Page Intentionally Left Blank; Signature Pages Follow]

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly
executed by their respective officers hereunto duly authorized as of the date
first above set forth.

 

NOTEHOLDER COLLATERAL AGENT: THE BANK OF NEW YORK TRUST COMPANY, N.A. By:  

/s/ Geraldine Creswell

Name:   Geraldine Creswell Title:   Assistant Treasurer Address:   10161
Centurion Parkway 2nd Floor Jacksonville, FL 32256 Fax No: (904) 645-1921 Attn:
Corporate Trust Ms. Geraldine Creswell Assistant Treasurer BANK AGENT: CAPITAL
ONE, NATIONAL ASSOCIATION By:  

/s/ Eric Broussard

Name:   Eric Broussard Title:   Senior Vice President BANKS: CAPITAL ONE,
NATIONAL ASSOCIATION By:  

/s/ Eric Broussard

Name:   Eric Broussard Title:   Senior Vice President UNION BANK OF CALIFORNIA,
N.A. By:  

/s/ Jarrod Bourgeois

Name:   Jarrod Bourgeois Title:   Vice President

 

Signature Page to Amendment No. 2 to Intercreditor Agreement

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BNP PARIBAS

By:  

/s/ Edward Pak

   

/s/Courtney Kubesch

Name:   Edward Pak     Courtney Kubesch Title:   Vice President     Vice
President COMPASS BANK     By:  

/s/Kathleen J. Bowen

    Name:   Kathleen J. Bowen     Title:   Senior Vice President     FORTIS
CAPITAL CORP.     By:  

/s/ David Montgomery

    Name:   David Montgomery     Title:   Director     By:  

/s/ Ilene Fowler

    Name:   Ilene Fowler     Title:   Director    

 

Signature Page to Amendment No. 2 to Intercreditor Agreement

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NOTEHOLDERS: THE PRUDENTIAL INSURANCE COMPANY OF AMERICA By:  

/s/ Brian Thomas

  Vice President Address: c/o Prudential Capital Group 2200 Ross Avenue, Suite
4200E Dallas, Texas 75201 Fax No: (214) 720-6299 Attn: Managing Director

 

Signature Page to Amendment No. 2 to Intercreditor Agreement

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CONSENTED AND AGREED TO AS OF THE DATE FIRST ABOVE WRITTEN: GMX RESOURCE INC.
By:  

/s/ James A. Merrill

  James A. Merrill   Chief Financial Officer and Treasurer Address: 9400 N.
Broadway, Suite 600 Oklahoma City, Oklahoma 73114 ENDEAVOR PIPELINE INC. By:  

/s/ Keith Leffel

  Keith Leffel   President Address: 9400 N. Broadway, Suite 600 Oklahoma City,
Oklahoma 73114 DIAMOND BLUE DRILLING CO. By:  

/s/ Richard Q. Hart

  Richard Q. Hart   President Address:   9400 N. Broadway, Suite 600   Oklahoma
City, Oklahoma 73114

 

Signature Page to Amendment No. 2 to Intercreditor Agreement