Exhibit 10.13
Base Contract for Sale and Purchase of Natural Gas
This Base Contract is entered into as of the following date: September 1, 2004.
The parties to this Base Contract are the following:

              SEMPRA ENERGY TRADING CORP. and ULTRA RESOURCES, INC. 58 Commerce
Road, Stamford, CT 06902   363 N. Sam Houston Pkwy., E., Suite 1200, Houston, TX
77060 Duns Number: 60-9746565

  Duns Number: 07-110-9974

Contract Number:

  Contract Number:

U.S. Federal Tax ID Number: 13-3653551

  U.S. Federal Tax ID Number: 83-0320643

 
            Notices:   Notices, Confirmations, Invoices and Payments: 58
Commerce Road, Stamford, CT 06902   363 N. Sam Houston Pkwy., E., Suite 1200,
Houston, TX 77060 Attn: Legal Dept.

  Attn: Natural Gas Marketing

Phone: 203 355-5000

  Fax: 203 355-5410

  Phone: 281.876.0120 x.307

  Fax: 281.876.2831

 
            Confirmations:         58 Commerce Road, Stamford, CT 06902        
Attn:
Operations

       
Phone: 203 355-5626

  Fax: 203 355-6631

       
 
            Invoices and Payments:         58 Commerce Road, Stamford, CT 06902
        Attn:
Operations

                 
Phone: 203 355-5626

  Fax: 203 355-6604

       
 
            Wire Transfer or ACH Numbers (If applicable):   Wire Transfer or ACH
Numbers (if applicable): BANK: JP Morgan Chase Bank, NY, NY, USA

  BANK: Bank One N.A.

ABA: 021000021 (Swift Code: CHASUS33) (Chips #: 0002)

  ABA: 102001017

ACCT:
323308090

  ACCT: 192 648 101

Other Details: for the acct of Sempra Energy Trading Corp.

  Other Details: For the Account of Ultra Resources, Inc.

This Base Contract incorporates by reference for all purposes the General Terms
and Conditions for Sale and Purchase of Natural Gas published by the North
American Energy Standards Board. The parties hereby agree to the following
provisions offered in said General Terms and Conditions. In the event the
parties fail to check a box, the specified default provision shall apply. Select
only one box from each section:

                                 
Section 1.2
Transaction
Procedure
þ
o Oral (default) 
Written     Section 7.2
Payment Date þ

o 25th Day of Month following Month of
delivery (default)
_____ Day of Month following Month of delivery                
Section 2.5
Confirm
Deadline
þ
o 2 Business Days after receipt (default)
_____ Business Days after receipt     Section 7.2
Method of
Payment þ
o
o Wire transfer (default)
Automated Clearinghouse Credit (ACH)
Check                
Section 2.6
Confirming
Party
o
o
þ Seller (default)
Buyer
Sempra Energy Trading Corp

    Section 7.7
Netting þ
o Netting applies (default)
Netting does not apply                
Section 3.2 Performance Obligation
þ
o Cover Standard (default) 
Spot Price Standard     Section 10.3.1
Early Termination
Damages þ
o Early Termination Damages Apply (default)
Early Termination Damages Do Not Apply                     Note: The following
Spot Price Publication applies to both of the immediately preceding.    
Section 10.3.2
Other Agreement
Setoffs þ
o Other Agreement Setoffs Apply (default)
Other Agreement Setoffs Do Not Apply                    
Section 2.26
Spot Price
Publication
þ Gas Daily Midpoint (default)     Section 14.5
Choice Of Law  

New York

               
Section 6
Taxes
þ

o Buyer Pays At and After Delivery Point
(default)
Seller Pays Before and At Delivery Point     Section 14.10
Confidentiality þ
o Confidentiality applies (default)
Confidentiality does not apply                 þ  Special Provisions Number of
sheets attached: 3     o  Addendum(s):

   
 
                           

IN WITNESS WHEREOF, the parties hereto have executed this Base Contract in
duplicate.

                SEMPRA ENERGY TRADING CORP.

Party Name
    ULTRA RESOURCES, INC.

Party Name
      By   /s/ Mara Kent     By   /s/ Stuart Nance      Name:   Mara Kent     
Name:   Stuart Nance      Title:   Vice President      Title:   Director   

        Copyright © 2002 North American Energy Standards Board, Inc.
All Rights Reserved   NAESB Standard 6.3.1
April 19, 2002