Recitals

Fifth Supplemental Indenture

by Pioneer Natural Resources
January 2nd, 1998

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                                                                   EXHIBIT 10.14
                                                                                
                                                                                
                          FIFTH SUPPLEMENTAL INDENTURE                          
                                                                                
                                                                                
         THIS FIFTH SUPPLEMENTAL INDENTURE, dated as of December 30, 1997, among
PIONEER NEWSUB1, INC. (as successor to Pioneer Natural Resources USA, Inc.,   
formerly known as Mesa Operating Co.), a Texas corporation (the "Company"),    
PIONEER NATURAL RESOURCES COMPANY (as successor to MESA Inc.), a Delaware     
corporation ("Pioneer"), PIONEER DEBTCO, INC., a Texas corporation and         
wholly-owned subsidiary of Pioneer ("DebtCo"), and HARRIS TRUST AND SAVINGS    
BANK, an Illinois corporation, as trustee (the "Trustee"). Capitalized terms   
used herein and not otherwise defined have the meanings set forth in the       
Indenture referred to below.                                                   
                                                                               
                                    RECITALS                                   
                                                                               
         A. The Company, Pioneer and the Trustee are parties to that certain   
Indenture, dated as of July 2, 1996, as amended by the First Supplemental      
Indenture, dated as of April 15, 1997, as further amended by the Second        
Supplemental Indenture, dated as of August 7, 1997, as further amended by the  
Third Supplemental Indenture, dated as of December 18, 1997, as further amended
by the Fourth Supplemental Indenture, dated as of December 30, 1997 (the       
"Indenture"), pursuant to which the 11 5/8% Senior Subordinated Discount Notes
due July 1 2006 (the "Notes") were issued.
                                                                               
         B. In connection with a merger (the "Restructuring") as of the date   
hereof by and between the Company and DebtCo, DebtCo will assume and be        
responsible and liable for all obligations of the Company with respect to the  
Notes and the Indenture (collectively, the "Restructured Debt"), to the same   
extent as if the Restructured Debt had been incurred or contracted by DebtCo.  
                                                                               
         C. In connection with the Restructuring, the Company, Pioneer and     
DebtCo have duly determined to make, execute and deliver to the Trustee this   
Fifth Supplemental Indenture in order to reflect the results of the            
Restructuring as required by the Indenture.                                    
                                                                               
         NOW, THEREFORE, in consideration of the mutual agreements and
covenants set forth herein, the parties hereto agree, subject to the terms and
conditions hereinafter set forth, as follows for the benefit of the Trustee and
the Holders of the Notes:  
                                                                               
         1. The Restructuring is permitted by Section 5.1 of the Indenture and 
in connection therewith:                                                       
                                                                              
                  (a) DebtCo hereby expressly assumes all obligations of the   
         Company under the Notes and the Indenture;                           
                                                                              
                  (b) The Company, Pioneer and DebtCo hereby represent that   
         immediately before and after giving effect to the Restructuring, no  
         Default or Event of Default exists;                                  
                                                                               
                                                                               
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                  (c) The Company, Pioneer and DebtCo hereby represent that
         immediately after giving effect to the Restructuring on a pro forma
         basis (and treating any Indebtedness not previously an obligation of
         the Company which becomes the obligation of the Company as a result of
         the Restructuring as having been incurred at the time of such
         transaction), the Consolidated Net Worth of DebtCo, as the Surviving
         Entity with respect to the Restructured Debt, is equal to or greater
         than the Consolidated Net Worth of the Company immediately prior to the
         Restructuring; and

                  (d) The Company, Pioneer and DebtCo hereby represent that
         DebtCo will, at the time of the Restructuring and after giving pro
         forma effect thereto as if such transaction had occurred as of January
         1, 1997, be permitted to incur at least $1.00 of additional
         Indebtedness as set forth in the first paragraph of Section 4.9 of the
         Indenture.

         2. As of the effective date of this Fifth Supplemental Indenture,
DebtCo, as the Surviving Entity with respect to the Restructured Debt, shall
succeed to, and be substituted for, and may exercise every right and power of
the Company under the Indenture with the same effect as if DebtCo had been named
as the Company in the Indenture.

         3. This Fifth Supplemental Indenture is executed and shall be construed
as an indenture supplemental to the Indenture and, as provided in the Indenture,
this Fifth Supplemental Indenture forms a part of the Indenture. Except to the
extent amended by or supplemented by this Fifth Supplemental Indenture, the
Company, Pioneer, DebtCo and the Trustee hereby ratify, confirm and reaffirm the
Indenture in all respects.

         4. This Fifth Supplemental Indenture may be executed in any number of
counterparts, each of which so executed shall be an original, but all such
counterparts shall together constitute but one and the same instrument.

         5. The laws of the State of New York shall govern the construction and
interpretation of this Fifth Supplemental Indenture, without regard to
principles of conflicts of laws.


                                       -2-


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         IN WITNESS WHEREOF, the parties hereto have caused this Fifth
Supplemental Indenture to be signed on their behalf by their duly authorized
representatives as of the date first above written:

                                     PIONEER NEWSUB1, INC.                      
Attest:                                                                         
                                                                                
                                                                                
                                                                                
 /s/ Mark L. Withrow                 By: /s/ M. Garrett Smith                   
- --------------------------------        ----------------------------------------
Name: Mark L. Withrow                         M. Garrett Smith                  
         Secretary                            President                         
                                                                                
                                     PIONEER NATURAL RESOURCES                  
Attest:                              COMPANY                                    
                                                                                
                                                                                
                                                                                
 /s/ Mark L. Withrow                 By: /s/ M. Garrett Smith                   
- --------------------------------        ----------------------------------------
Name: Mark L. Withrow                         M. Garrett Smith                  
         Secretary                            Executive Vice President and Chief
                                              Financial Officer                 
                                                                                
                                     PIONEER DEBTCO, INC.                       
Attest:                                                                         
                                                                                
                                                                                
 /s/ Mark L. Withrow                 By: /s/ M. Garrett Smith                   
- --------------------------------        ----------------------------------------
Name: Mark L. Withrow                         M. Garrett Smith                  
         Secretary                            President                         
                                                                                
                                                                                
                                     HARRIS TRUST AND SAVINGS BANK,             
Attest:                              as Trustee                                 
                                                                                
 /s/ C. Potter                       By: /s/ J. Bartolini                       
- -------------------------------         ----------------------------------------
C. Potter                                     J. Bartolini                      
Assistant Secretary                           Vice President                    
                                                                                





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