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                                                                     EXHIBIT 4.4

This Instrument was prepared by,
and when recorded should be returned to:
Vinson & Elkins L.L.P.
2001 Ross Avenue, Suite 3700
Dallas, Texas 75201
Attn: Susan D. Hamilton

                     ASSIGNMENT OF AND AMENDMENT TO MORTGAGE

      This Assignment of and Amendment to Mortgage (this "ASSIGNMENT") is
executed to be effective as of July __, 2004, by BANK ONE, NA, a national
banking association having its principal office in Chicago, Illinois ("BANK
ONE"), acting in its capacity as Collateral Agent for Existing Lenders (as
herein defined) (in such capacity, "EXISTING MORTGAGEE"), UBS AG, STAMFORD
BRANCH ("UBS"), acting in its capacity as Collateral Agent for Secured Parties
(as defined in the Successor Credit Agreement [defined below]) (in such
capacity, "SUCCESSOR MORTGAGEE"), and QUEST CHEROKEE, LLC, a Delaware limited
liability company ("MORTGAGOR").

                                    RECITALS:

      WHEREAS, Mortgagor, Bank One, as Administrative Agent, and the financial
institutions party thereto (collectively, the "EXISTING LENDERS", and each
individually, an "EXISTING LENDER") are parties to (a) that certain Revolving
Credit Agreement dated as of December 22, 2003, and (b) that certain Senior Term
Second Lien Secured Credit Agreement dated as of December 22, 2003
(collectively, as each may have been amended, modified or restated from time to
time, the "EXISTING CREDIT AGREEMENTS"), pursuant to which the Existing Lenders
have made the Revolving Loan and the Term Loan (as each such term is defined in
the Existing Credit Agreements, respectively, and such Revolving Loan and Term
Loan are collectively referred to herein as the "EXISTING LOANS") to Mortgagor,
as borrower; and

      WHEREAS, as security for the payment and the performance of the
obligations and indebtedness (collectively, the "EXISTING OBLIGATIONS") of
Mortgagor under the Existing Credit Agreements and the other Loan Papers (as
respectively defined in each Existing Credit Agreement, and as referred to
herein, the "EXISTING LOAN PAPERS"), including, without limitation, as security
for the payment of the Existing Notes, Mortgagor executed and delivered to
Existing Mortgagee that certain Mortgage, Deed of Trust, Security Agreement,
Financing Statement and Assignment of Production in favor of Existing Mortgagee,
counterparts of which were filed and/or recorded in the various counties in
Kansas and Oklahoma as more particularly described in Schedule 1 hereto
(collectively, and, where applicable, as amended, the "EXISTING MORTGAGE"); and

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      WHEREAS, to the extent provided in the Existing Mortgage, the Existing
Mortgage attaches to and creates liens in and to the Mortgaged Property therein
defined and described (and referred to herein as the "MORTGAGED PROPERTY"); and

      WHEREAS, Existing Mortgagee has agreed to assign its right, title and
interest to the Existing Obligations, and certain of the liens securing the
payment of the Existing Obligations, including, without limitation, the Existing
Mortgage, to Successor Mortgagee for the ratable benefit of the Secured Parties
(as provided in the Successor Credit Agreement); and

      WHEREAS, as a result of giving effect to this Assignment, Successor
Mortgagee will succeed to all rights of Existing Mortgagee as described in
Section 1.1 hereof; and

      WHEREAS, contemporaneously with the execution and delivery hereof,
Mortgagor, as borrower, the Guarantors, the Lenders (each as defined in the
Successor Credit Agreement), UBS Securities LLC, as lead arranger, documentation
agent and syndication agent, UBS Loan Finance LLC, as swingline lender, and
Successor Mortgagee, as issuing bank, LC Facility issuing bank, administrative
agent for the Lenders and collateral agent for the Secured Parties, will each
enter into that certain Credit Agreement (the "SUCCESSOR CREDIT AGREEMENT")
dated as of the date hereof; and

      WHEREAS, pursuant to the Successor Credit Agreement, UBS is being
appointed as the Collateral Agent for the Secured Parties; and

      WHEREAS, in furtherance of the foregoing, (a) Existing Mortgagee,
Successor Mortgagee and Mortgagor desire to provide for the assignment of record
of all right, title and interest of Existing Mortgagee in, to and under the
Existing Mortgage to Successor Mortgagee, and (b) Successor Mortgagee and
Mortgagor desire to provide for the amendment of the Existing Mortgage to
evidence and reflect the assignment of all of the rights and obligations of Bank
One, in its individual capacity as an Existing Lender, and certain of the other
Existing Lenders under the Existing Credit Agreements and Existing Loan Papers
to UBS, in its individual capacity as a Lender under the Successor Credit
Agreement, and certain of the other Secured Parties under the Successor Credit
Agreement.

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

                                       I.
                                   ASSIGNMENT

      SECTION 1.1 Existing Mortgagee has GRANTED, BARGAINED, SOLD, TRANSFERRED,
CONVEYED, and does hereby GRANT, BARGAIN, SELL, TRANSFER AND CONVEY unto
Successor Mortgagee for the ratable benefit of the Secured Parties, the Existing
Mortgage and all other mortgages, deeds of trust, security agreements,
assignments and amendments to mortgages, assignments of notes and liens,
assignments, chattel mortgages, security interests or other documents,
instruments and agreements of any nature securing the Existing Obligations in
any way (collectively, the "ASSIGNED RIGHTS"), without recourse to, or warranty
or representation, either expressed or implied, by, Existing Mortgagee (except
as

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expressly provided in Section 1.2 hereof) TO HAVE AND TO HOLD the same unto
Successor Mortgagee, and its successors and assigns forever. Notwithstanding
anything to the contrary contained herein, neither Existing Mortgagee nor any
Existing Lender is assigning to Successor Mortgagee, and Existing Mortgagee and
each Existing Lender is, to the extent contemplated by the terms of such
documents, hereby expressly reserving to itself (and the "Assigned Rights" shall
not include) any and all rights and benefits accruing to it or any related
persons or parties in connection with any indemnity and reimbursement
obligations owed by Mortgagor under the Existing Credit Agreements and the
Existing Loan Papers.

      SECTION 1.2 Existing Mortgagee hereby represents and warrants to Successor
Mortgagee that (a) Existing Mortgagee has full power and authority to execute,
deliver and perform its obligations under this Assignment, including, without
limitation, the assignment of the Assigned Rights to Successor Mortgagee
hereunder, (b) this Assignment has been duly authorized, executed and delivered
by Existing Mortgagee and constitutes the valid and binding obligation of
Existing Mortgagee, enforceable against Existing Mortgagee in accordance with
its terms, (c) Existing Mortgagee has not executed any prior release,
termination or cancellation with respect to the Existing Mortgage, and (d)
Existing Mortgagee has not executed any prior assignment or pledge of the
Assigned Rights. Notwithstanding the foregoing, neither Existing Mortgagee nor
Bank One in its individual capacity as an Existing Lender (i) assumes any
responsibility with respect to any statements, warranties or representations
made in or in connection with the Existing Mortgage, the Existing Credit
Agreements or any of the other Existing Loan Papers or the execution, legality,
validity, enforceability, genuineness, sufficiency, existence of, or value of,
the Existing Credit Agreements, the Existing Mortgage, any of the other Existing
Loan Papers or title to any property intended as collateral thereunder, (ii)
makes any representation or warranty or assumes any responsibility with respect
to the financial condition of Mortgagor or any of its subsidiaries, or (iii)
makes any representation or warranty, express or implied, except as expressly
set forth in the foregoing sentence.

                                       II.
                         AMENDMENTS TO EXISTING MORTGAGE

      SECTION 2.1 The Existing Mortgage is hereby amended, effective as of the
date hereof, as expressly set forth in this Section 2.1:

            (a) Each reference in the Existing Mortgage to "Mortgagee",
including, without limitation, the reference contained in Section 7.14, shall be
deemed to refer to Successor Mortgagee, with an address of 677 Washington
Boulevard, Stamford, Connecticut 06901, and an Employer Identification Number of
980186363.

            (b) Each reference in the Existing Mortgage to the "Trustee" shall
be deleted and deemed of no further force and effect.

      SECTION 2.2 Successor Mortgagee hereby removes each person acting as
Trustee under the Existing Mortgage.

      SECTION 2.3 Except as expressly set forth in Section 2.1 and Section 2.2
above, the Existing Mortgage shall not be modified or amended in any respect and
nothing contained herein

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shall be deemed to release, modify or impair the liens, security interests,
assignments and pledges intended to be created by the Existing Mortgage in any
respect, all of which shall continue to secure the obligations and indebtedness
under the Existing Credit Agreements, including, without limitation, the
Existing Obligations and all of which liens, security interests, assignments and
obligations are hereby ratified and confirmed. Mortgagor hereby acknowledges
that the Successor Credit Agreement represents a renewal, extension, amendment
and modification of the Existing Obligations, but does not represent a
satisfaction or novation thereof.

                                      III.
                  REPRESENTATIONS AND WARRANTIES; REAFFIRMATION

      SECTION 3.1 Mortgagor hereby represents and warrants to Successor
Mortgagee and Existing Mortgagee that the execution, delivery and performance by
Mortgagor of this Assignment is within Mortgagor's corporate powers, has been
duly authorized by all necessary corporate action, requires no action by or
filing with, any governmental body, agency or official and does not violate or
constitute a default under any provision of applicable laws, rules, regulations
or orders of any governmental authority applicable to Mortgagor or its property,
or any material agreement binding upon Mortgagor, or result in the creation or
imposition of any lien upon any of the assets of Mortgagor other than the liens
securing the Obligations under and as defined in the Successor Credit Agreement.

      SECTION 3.2 Mortgagor hereby represents and warrants to Successor
Mortgagee and Existing Mortgagee that this Assignment constitutes the valid and
binding obligation of Mortgagor enforceable in accordance with its terms, except
as the enforceability thereof may be limited by bankruptcy, insolvency or
similar laws affecting creditors' rights generally, and the availability of
equitable remedies may be limited by equitable principles of general
application.

      SECTION 3.3 Successor Mortgagee hereby represents and warrants to Existing
Mortgagee that it has received such documents and information as it has deemed
appropriate to make its own credit analysis and decision to enter into this
Assignment and to acquire the interest in the Assigned Rights granted to it
hereunder, and it has made such credit analysis and decision independently
without reliance on any Existing Lender or Existing Mortgagee.

      SECTION 3.4 Mortgagor hereby ratifies, readopts and reaffirms all of
Mortgagor's agreements and covenants contained in the Existing Mortgage,
including, without limitation, all of its grants, warrants, assignments,
mortgages, pledges, transfers and conveyances of the Mortgaged Property
contained in the granting clauses of the Existing Mortgage to secure all of the
indebtedness described in the Existing Mortgage (as amended hereby), including,
without limitation, all of the Existing Obligations.

                                       IV.
                                     RELEASE

      Mortgagor for itself and its successors and assigns (collectively, the
"RELEASING PARTIES") hereby forever releases, discharges and acquits each
Existing Lender, Existing Mortgagee and each of their respective officers,
directors, shareholders, employees, agents, successors, assignees

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(including, without limitation, the Lenders under the Successor Credit
Agreement), representatives and affiliates (collectively, the "RELEASED
PARTIES") from any and all claims, demands, actions, remedies, causes of action,
debts, liabilities, contracts, damages, costs (including, without limitation,
attorney's fees and all costs of court or other proceedings), expenses and
losses of every kind or nature (INCLUDING, WITHOUT LIMITATION, OFFSETS,
REDUCTIONS, REBATES OR CLAIMS OF USURY AND CLAIMS WITH RESPECT TO THE NEGLIGENCE
OF ANY OF THE RELEASED PARTIES) at this time known or unknown, direct or
indirect, fixed or contingent, in law, by statute, admiralty or equity which the
Releasing Parties ever had, now have, or hereafter can, shall or may have, for,
upon or by reason or arising out of any act, occurrence, transaction or omission
occurring from the beginning of time to the date of execution of this
Assignment.

                                       V.
                                  MISCELLANEOUS

      SECTION 5.1 All of the terms and provisions of this Assignment shall,
where applicable, run with the land and shall apply to, bind, and inure to the
benefit of, the parties hereto and their respective successors and assigns.

      SECTION 5.2 This Assignment may be executed in as many counterparts as may
be deemed necessary or convenient, and by the different parties hereto on
separate counterparts, each of which when so executed shall be deemed an
original, but all such counterparts shall constitute but one and the same
instrument; provided, that, the counterparts of this instrument filed for record
in any jurisdiction in which any of the Mortgaged Property is located shall have
annexed thereto (as applicable) as "Exhibit A" only the portions or divisions
containing specific descriptions of the real estate located in such
jurisdiction.

      SECTION 5.3 THIS ASSIGNMENT SHALL BE CONSTRUED IN ACCORDANCE WITH AND
GOVERNED BY THE LAWS OF THE STATE OF NEW YORK AND THE LAWS OF THE UNITED STATES
OF AMERICA, EXCEPT TO THE EXTENT THAT THE LAWS OF ANY STATE IN WHICH THE
MORTGAGED PROPERTY IS LOCATED NECESSARILY GOVERNS THE VALIDITY, PERFECTION,
PRIORITY AND ENFORCEABILITY OF THE EXISTING MORTGAGE AND THE EXERCISE OF ANY
REMEDIES WITH RESPECT TO THE MORTGAGED PROPERTY LOCATED IN SUCH STATE.

                [SIGNATURE PAGES AND ACKNOWLEDGEMENTS TO FOLLOW]

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      EXECUTED on the date of the notary certification below to be effective as
of the date first above written.

                                           EXISTING MORTGAGEE:

                                           BANK ONE, NA, as collateral agent

                                           By: /s/ STEPHEN L. LESCHER
                                              ----------------------------------
                                                  Stephen L. Lescher
                                                  Director, Capital Markets

                                 Signature Page
                    Assignment of and Amendment to Mortgages

<PAGE>

                                           SUCCESSOR MORTGAGEE:

                                           UBS AG, STAMFORD BRANCH, as
                                           collateral agent

                                           By: /s/ WILFRED V. SAINT
                                              ----------------------------------
                                                  Wilfred V. Saint
                                                  Director Banking Products
                                                  Services, U.S.

                                           By: /s/ JOSELIN FERNANDES
                                              ----------------------------------
                                                  Joselin Fernandes
                                                  Associate Director Banking
                                                  Products Services, U.S.

                                 Signature Page
                    Assignment of and Amendment to Mortgages

<PAGE>

                                           MORTGAGOR:

                                           QUEST CHEROKEE, LLC

                                           By: /s/ JERRY D. CASH
                                              ----------------------------------
                                                  Jerry D. Cash
                                                  Manager

                                 Signature Page
                    Assignment of and Amendment to Mortgages

<PAGE>

                                   SCHEDULE 1

                               Mortgage Documents

Mortgage, Deed of Trust, Security Agreement, Financing Statement and Assignment
of Production by Quest Cherokee, LLC in favor of Bank One, NA, as Collateral
Agent, or alternatively, J. Scott Fowler, Trustee, for the benefit of Bank One,
NA, as Collateral Agent, counterparts of which were filed as follows:

KANSAS

CHATAUQUA COUNTY, KANSAS

1.    Counterpart filed with the County Clerk of Chatauqua County, Kansas on
      January 7, 2004, in Volume 117, Page 336.

ELK COUNTY, KANSAS

2.    Counterpart filed with the County Clerk of Elk County, Kansas on December
      30, 2003, in Volume 112, Page 513.

LABETTE COUNTY, KANSAS

3.    Counterpart filed with the County Clerk of Labette County, Kansas on
      December 31, 2003, in Volume 33, Page 70.

MONTGOMERY COUNTY, KANSAS

4.    Counterpart filed with the County Clerk of Montgomery County, Kansas on
      December 30, 2003, in Volume 536, Page 519.

NEOSHO COUNTY, KANSAS

5.    Counterpart filed with the County Clerk of Neosho County, Kansas on
      December 30, 2003, in Volume 326, Page 245.

WILSON COUNTY, KANSAS

6.    Counterpart filed with the County Clerk of Wilson County, Kansas on
      December 30, 2003, in Volume 267, Page 88.

WOODSON COUNTY, KANSAS

7.    Counterpart filed with the County Clerk of Woodson County, Kansas on
      December 30, 2003, in Volume 95, Page 72.

OKLAHOMA

CRAIG COUNTY, OKLAHOMA

                                  Schedule 1-1

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8.    Counterpart filed with the County Clerk of Craig County, Oklahoma on
      December 29, 2003, in Volume 521, Page 158.

NOWATA COUNTY, OKLAHOMA

9.    Counterpart filed with the County Clerk of Nowata County, Oklahoma on
      January 2, 2004, in Volume 709, Page 1.

                                  Schedule 1-2