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                                                                 EXHIBIT 10.22.4

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                      FOURTH AMENDMENT TO CREDIT AGREEMENT

                                     BETWEEN

                             PRIMEENERGY CORPORATION
                       PRIMEENERGY MANAGEMENT CORPORATION
                             PRIME OPERATING COMPANY
                        EASTERN OIL WELL SERVICE COMPANY
                     SOUTHWEST OILFIELD CONSTRUCTION COMPANY
                              EOWS MIDLAND COMPANY

                                      AND

                          GUARANTY BANK, FSB, AS AGENT
                                  AND A LENDER

                       EFFECTIVE AS OF DECEMBER 28, 2004

                       ---------------------------------

             REDUCING REVOLVING LINE OF CREDIT OF UP TO $50,000,000
                   REDUCING REVOLVING TERM LOAN OF $3,599,998

                       ---------------------------------

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                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                             PAGE
                                                             ----
<S>                                                          <C>
  ARTICLE I    DEFINITIONS.................................    1
    1.01       Terms Defined Above.........................    1
    1.02       Terms Defined in Agreement..................    1
    1.03       References..................................    1
    1.04       Articles and Sections.......................    2
    1.05       Number and Gender...........................    2
 ARTICLE II    AMENDMENTS..................................    2
    2.01       Amendment of Section 1.2....................    2
    2.02       Amendment of Section 2.9....................    2
ARTICLE III    CONDITIONS..................................    2
    3.01       Receipt of Documents........................    2
    3.02       Accuracy of Representations and Warranties..    3
    3.03       Matters Satisfactory to Lenders.............    3
 ARTICLE IV    REPRESENTATIONS AND WARRANTIES..............    3
 ARTICLE V     RATIFICATION................................    3
 ARTICLE VI    MISCELLANEOUS...............................    3
    6.01       Scope of Amendment..........................    3
    6.02       Agreement as Amended........................    3
    6.03       Parties in Interest.........................    3
    6.04       Rights of Fourth Parties....................    3
    6.05       ENTIRE AGREEMENT............................    3
    6.06       GOVERNING LAW...............................    4
    6.07       JURISDICTION AND VENUE......................    4
</TABLE>

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                      FOURTH AMENDMENT TO CREDIT AGREEMENT

      This FOURTH AMENDMENT TO CREDIT AGREEMENT (this "Fourth Amendment") is
made and entered into effective as of December 28, 2004, between PRIMEENERGY
CORPORATION, a Delaware corporation ("PEC"), PRIMEENERGY MANAGEMENT CORPORATION,
a New York corporation, PRIME OPERATING COMPANY, a Texas corporation, EASTERN
OIL WELL SERVICE COMPANY, a West Virginia corporation, SOUTHWEST OILFIELD
CONSTRUCTION COMPANY, an Oklahoma corporation, and EOWS MIDLAND COMPANY, a Texas
corporation (collectively, the "Borrower"), with each other lender that is a
signatory hereto or becomes a signatory hereto as provided in Section 9.1,
(individually, together with its successors and assigns, a "Lender" and
collectively together, with their respective successors and assigns, the
"Lenders") and GUARANTY BANK, FSB, a federal savings bank, as agent for the
Lenders (in such capacity, together with its successors in such capacity
pursuant to the terms hereof, the "Agent").

                               W I T N E S S E T H

      WHEREAS, the above named parties did execute and exchange counterparts of
that certain Credit Agreement dated December 19, 2002, as amended by First
Amendment to Credit Agreement dated effective as of June 1, 2003, as further
amended by Second Amendment to Credit Agreement dated effective as of September
22, 2003, and as further amended by Third Amendment to Credit Agreement dated
effective as of February 17, 2004 (the "Agreement"), to which reference is here
made for all purposes;

      WHEREAS, the parties subject to and bound by the Agreement are desirous of
amending the Agreement in the particulars hereinafter set forth;

      NOW, THEREFORE, in consideration of the mutual covenants and agreements of
the parties to the Agreement, as set forth therein, and the mutual covenants and
agreements of the parties hereto, as set forth in this Fourth Amendment, the
parties hereto agree as follows:

                                   ARTICLE I
                                  DEFINITIONS

      1.01 Terms Defined Above. As used herein, each of the terms "Agent,"
"Agreement," "Borrower," "Fourth Amendment," and "Lenders" and shall have the
meaning assigned to such term hereinabove.

      1.02 Terms Defined in Agreement. As used herein, each term defined in the
Agreement shall have the meaning assigned thereto in the Agreement, unless
expressly provided herein to the contrary.

      1.03 References. References in this Fourth Amendment to Article or Section
numbers shall be to Articles and Sections of this Fourth Amendment, unless
expressly stated herein to the contrary. References in this Fourth Amendment to
"hereby," "herein," hereinafter," hereinabove," "hereinbelow," "hereof," and
"hereunder" shall be to this Fourth Amendment in its entirety and not only to
the particular Article or Section in which such reference appears.

                                       1
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      1.04 Articles and Sections. This Fourth Amendment, for convenience only,
has been divided into Articles and Sections and it is understood that the
rights, powers, privileges, duties, and other legal relations of the parties
hereto shall be determined from this Fourth Amendment as an entirety and without
regard to such division into Articles and Sections and without regard to
headings prefixed to such Articles and Sections.

      1.05 Number and Gender. Whenever the context requires, reference herein
made to the single number shall be understood to include the plural and likewise
the plural shall be understood to include the singular. Words denoting sex shall
be construed to include the masculine, feminine, and neuter, when such
construction is appropriate, and specific enumeration shall not exclude the
general, but shall be construed as cumulative. Definitions of terms defined in
the singular and plural shall be equally applicable to the plural or singular,
as the case may be.

                                   ARTICLE II
                                   AMENDMENTS

      The Borrower and the Lender hereby amend the Agreement in the following
particulars:

      2.01 Deletion of F-W Oil Exploration L.L.C. F-W Oil Exploration L.L.C. is
hereby deleted from the Agreement and released from all Obligations hereunder.

      2.02 Amendment of Section 2.9(a). Section 2.9(a) of the Agreement shall be
amended to read as follows:

      "2.9 Borrowing Base Determinations. (a) The Borrowing Base as of December
      28, 2004, is acknowledged by the Borrower and the Lenders to be
      $33,880,000."

      2.03 Amendment of Exhibit I. Exhibit I, i.e., the Form of Promissory Note,
shall be as set forth on Exhibit I to this Fourth Amendment.

                                  ARTICLE III
                                   CONDITIONS

      The obligation of the Lenders to amend the Agreement as provided herein is
subject to the fulfillment of the following conditions precedent:

      3.01 Receipt of Documents. The Agent shall have received, reviewed, and
approved the following documents and other items, appropriately executed when
necessary and in form and substance satisfactory to the Lender:

      (a)   multiple counterparts of this Fourth Amendment as requested by the
            Agent;

      (b)   the Note;

      (c)   such other agreements, documents, items, instruments, opinions,
            certificates, waivers, consents, and evidence as the Agent may
            reasonably request.

                                       2
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      3.02 Accuracy of Representations and Warranties. The representations and
warranties contained in Article IV of the Agreement and this Fourth Amendment
shall be true and correct.

      3.03 Matters Satisfactory to Lenders. All matters incident to the
consummation of the transactions contemplated hereby shall be satisfactory to
the Lenders.

                                   ARTICLE IV
                         REPRESENTATIONS AND WARRANTIES

      The Borrower hereby expressly re-makes, in favor of the Lenders, all of
the representations and warranties set forth in Article IV of the Agreement, and
represents and warrants that all such representations and warranties remain true
and unbreached.

                                   ARTICLE V
                                  RATIFICATION

      Each of the parties hereto does hereby adopt, ratify, and confirm the
Agreement and the other Loan Documents, in all things in accordance with the
terms and provisions thereof, as amended by this Fourth Amendment.

                                   ARTICLE VI
                                  MISCELLANEOUS

      6.01 Scope of Amendment. The scope of this Fourth Amendment is expressly
limited to the matters addressed herein and this Fourth Amendment shall not
operate as a waiver of any past, present, or future breach, Default, or Event of
Default under the Agreement. except to the extent, if any, that any such breach,
Default, or Event of Default is remedied by the effect of this Fourth Amendment.

      6.02 Agreement as Amended. All references to the Agreement in any document
heretofore or hereafter executed in connection with the transactions
contemplated in the Agreement shall be deemed to refer to the Agreement as
amended by this Fourth Amendment.

      6.03 Parties in Interest. All provisions of this Fourth Amendment shall be
binding upon and shall inure to the benefit of the Borrower, the Lender and
their respective successors and assigns.

      6.04 Rights of Fourth Parties. All provisions herein are imposed solely
and exclusively for the benefit of the Lender and the Borrower, and no other
Person shall have standing to require satisfaction of such provisions in
accordance with their terms and any or all of such provisions may be freely
waived in whole or in part by the Lender at any time if in its sole discretion
it deems it advisable to do so.

      6.05 ENTIRE AGREEMENT. THIS FOURTH AMENDMENT CONSTITUTES THE ENTIRE
AGREEMENT BETWEEN THE PARTIES HERETO WITH RESPECT TO THE SUBJECT HEREOF AND
SUPERSEDES ANY PRIOR AGREEMENT, WHETHER WRITTEN OR ORAL, BETWEEN SUCH PARTIES
REGARDING THE SUBJECT HEREOF. FURTHERMORE IN THIS REGARD, THIS FOURTH AMENDMENT,
THE AGREEMENT, THE NOTE, THE SECURITY INSTRUMENTS, AND THE OTHER

                                       3
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WRITTEN DOCUMENTS REFERRED TO IN THE AGREEMENT OR EXECUTED IN CONNECTION WITH OR
AS SECURITY FOR THE NOTE REPRESENT, COLLECTIVELY, THE FINAL AGREEMENT AMONG THE
PARTIES THERETO AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
UNWRITTEN ORAL AGREEMENTS AMONG THE PARTIES.

      6.06 GOVERNING LAW. THIS FOURTH AMENDMENT, THE AGREEMENT AND THE NOTE
SHALL BE DEEMED TO BE CONTRACTS MADE UNDER AND SHALL BE CONSTRUED IN ACCORDANCE
WITH AND GOVERNED BY THE LAWS OF THE STATE OF TEXAS. THE PARTIES ACKNOWLEDGE AND
AGREE THAT THIS AGREEMENT AND THE NOTE AND THE TRANSACTIONS CONTEMPLATED HEREBY
BEAR A NORMAL, REASONABLE, AND SUBSTANTIAL RELATIONSHIP TO THE STATE OF TEXAS.

      6.07 JURISDICTION AND VENUE. ALL ACTIONS OR PROCEEDINGS WITH RESPECT TO,
ARISING DIRECTLY OR INDIRECTLY IN CONNECTION WITH, OUT OF, RELATED TO, OR FROM
THIS FOURTH AMENDMENT, THE AGREEMENT OR ANY OTHER LOAN DOCUMENT MAY BE LITIGATED
IN COURTS HAVING SITUS IN HARRIS COUNTY, TEXAS. EACH OF THE BORROWER AND THE
LENDER HEREBY SUBMITS TO THE JURISDICTION OF ANY LOCAL, STATE, OR FEDERAL COURT
LOCATED IN HARRIS COUNTY, TEXAS, AND HEREBY WAIVES ANY RIGHTS IT MAY HAVE TO
TRANSFER OR CHANGE THE JURISDICTION OR VENUE OF ANY LITIGATION BROUGHT AGAINST
IT BY THE BORROWER OR THE LENDER IN ACCORDANCE WITH THIS SECTION.

                  (REMAINDER OF PAGE INTENTIONALLY LEFT BLANK)

                                       4
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      IN WITNESS WHEREOF, this Fourth Amendment to Credit Agreement is executed
effective the date first hereinabove written.

                             BORROWER

                             PRIMEENERGY CORPORATION
                             PRIMEENERGY MANAGEMENT
                             CORPORATION, PRIME OPERATING
                             COMPANY, EASTERN OIL WELL SERVICE
                             COMPANY, SOUTHWEST OILFIELD
                             CONSTRUCTION COMPANY
                             EOWS MIDLAND COMPANY

                             By: /s/ Beverly A. Cummings
                                 ---------------------------------------
                                 Beverly A. Cummings
                                 Executive Vice President, Treasurer, and
                                 Chief Financial Officer

                                       5
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                                     AGENT AND LENDER

                                     GUARANTY BANK, FSB

                                     By: /s/  Arthur R. Gralla
                                         ---------------------------------------
                                         Arthur R. Gralla, Jr.
                                         Managing Director

                                       6
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                                 PROMISSORY NOTE

$50,000,000                      Houston, Texas                December 28, 2004

      FOR VALUE RECEIVED and WITHOUT GRACE, the undersigned ("Maker") promises
to pay to the order of GUARANTY BANK, FSB ("Payee"), at its banking quarters in
Houston, Harris County, Texas, the sum of FIFTY MILLION DOLLARS ($50,000,000),
or so much thereof as may be advanced against this Note pursuant to the Credit
Agreement dated of even date herewith by and between Maker and Payee (as
amended, restated, or supplemented from time to time, the "Credit Agreement"),
together with interest at the rates and calculated as provided in the Credit
Agreement.

      Reference is hereby made to the Credit Agreement for matters governed
thereby, including, without limitation, certain events which will entitle the
holder hereof to accelerate the maturity of all amounts due hereunder.
Capitalized terms used but not defined in this Note shall have the meanings
assigned to such terms in the Credit Agreement.

      This Note is issued pursuant to, is the "Note" under, and is payable as
provided in the Credit Agreement. Subject to compliance with applicable
provisions of the Credit Agreement, Maker may at any time pay the full amount or
any part of this Note without the payment of any premium or fee, but such
payment shall not, until this Note is fully paid and satisfied, excuse the
payment as it becomes due of any payment on this Note provided for in the Credit
Agreement.

      Without being limited thereto or thereby, this Note is secured by the
Security Instruments.

      THIS NOTE SHALL BE GOVERNED AND CONTROLLED BY THE LAWS OF THE STATE OF
TEXAS WITHOUT GIVING EFFECT TO PRINCIPLES THEREOF RELATING TO CONFLICTS OF LAW;
PROVIDED, HOWEVER, THAT CHAPTER 345 OF THE TEXAS FINANCE CODE (WHICH REGULATES
CERTAIN REVOLVING CREDIT LOAN ACCOUNTS AND REVOLVING TRIPARTY ACCOUNTS) SHALL
NOT APPLY TO THIS NOTE.

                             PRIMEENERGY CORPORATION
                             PRIMEENERGY MANAGEMENT
                             CORPORATION, PRIME OPERATING
                             COMPANY, EASTERN OIL WELL SERVICE
                             COMPANY, SOUTHWEST OILFIELD
                             CONSTRUCTION COMPANY
                             EOWS MIDLAND COMPANY

                             By: /s/ Beverly A. Cummings
                                -----------------------------------------
                                 Beverly A. Cummings
                                 Executive Vice President, Treasurer, and
                                 Chief Financial Officer