<PAGE>

                                 EXHIBIT 10.2


                       AMENDMENT TO GAS SALES AGREEMENT
                                       
                                       
     This Amendment made and entered into this 30th day of January, 1998, 
between Colorado Power Partners (a/k/a Colorado Power Partnership), a 
Colorado general partnership, with its principal place of business located at 
4845 Pearl East Circle, Suite 300, Boulder, Colorado  80301 ("Buyer") and 
Prima Oil & Gas Company ("Prima"), a Colorado corporation, with its principal 
place of business at 1801 Broadway, Suite 500, Denver, Colorado 80202.

Recitals:

   A.  Buyer, Prima, and KN Marketing, Inc., a Colorado corporation, successor 
in interest to KN Production Company, a Delaware corporation which was in 
turn successor in interest to Fuel Resources Development Co., a Colorado 
corporation, entered into that certain Gas Sales Agreement dated May 24, 
1989, as amended October 12, 1990, December 17, 1992, February 1, 1994 and 
December 31, 1997, providing for the sale of gas from Prima and KN Marketing, 
Inc. to Buyer for consumption in Phase I at Buyer's co-generation facility 
located near Brush, Colorado (the "Agreement").

   B.  KN Marketing, Inc., by amendment to the Agreement dated December 31, 
1997, terminated its obligations under the Agreement as mutually agreed by 
Prima and Buyer.

   C.  Buyer and Prima desire to enter into this Amendment to provide for an 
early termination of Buyer's and Prima's rights, responsibilities and 
obligations under the Agreement and to modify certain terms and provisions 
relating to purposes and pricing as well as other matters related to the 
Agreement.

   Now therefore, in consideration of the mutual covenants and agreements
contained herein, the parties agree as follows:

   1.  Article I, PURPOSE AND COMMITMENTS, shall be modified by deleting 
paragraph (d) and replacing it with the following new paragraph (d):

     "(d) The parties agree that the sale of natural gas by Prima to Buyer shall
          primarily be for consumption in Phase I at Buyer's co-generation
          facility located near Brush, Colorado.  Nothing however, shall be
          construed to limit Buyer's ability to resell or otherwise dispose of
          gas purchased hereunder at its sole option for those purchases on and
          after March 31, 1998.


<PAGE>

     2.   Article III, QUANTITY, shall be modified by adding a new 
subparagraph (e), the intent of the parties to establish the quantities to be 
delivered by Seller from January 1, 1998 through October 31, 1998 as follows:

     "(e) Notwithstanding the preceding subparagraphs, the quantities of gas to 
          be delivered shall be all of the requirements of Buyer from January 1,
          1998 through October 31, 1998".

     3.   Article VI, TERM, shall be modified by deleting paragraph (a) and 
replacing it with the following new paragraph (a):

     "(a) The parties agree that this Agreement, and the obligations to sell and
          purchase gas, shall terminate as of October 31, 1998.  This 
          termination date my be extended upon mutual consent of the parties.

     4.   Article XI, PRICE AND BILLING, shall be amended by deleting the 
first sentence of paragraph (a) in its entirety and replacing it with the 
following:

     "(a) The price of gas sold hereunder for the period from January 1, 
          1998 through March 31, 1998 shall be Two Dollars and Seventy Two 
          Cents ($2.72) per MMBTU. The price of the gas sold hereunder for 
          the period from April 1, 1998 through October 31, 1998 (and any 
          extension mutually consented to) shall be the price per MMBTU as 
          reported in the Denver Julesburg Basin Index as published by the 
          Gas Daily, plus $.07 per MMBTU gross heating value at the Receipt 
          Point. Notwithstanding the preceding, the price of gas sold 
          hereunder shall in no event be less than $1.35 per MMBTU (lower 
          collar) nor greater than $1.85 MMBTU (upper collar) gross heating 
          value at the Receipt Point.

     5.  On February 2, 1998, Prima shall be paid in good funds the amount of 
Three Million Eight Hundred Fifty Thousand Dollars ($3,850,000) in 
consideration of the elimination of its obligation to provide gas to the 
Buyer for the original Agreement term.

     6. On or before October 31, 1998, Prima and Buyer shall execute a mutual 
release releasing each other and Prima Oil & Gas Company from any and all 
liability arising out of the Agreement.
                                          
     7. Prima and Buyer agree to negotiate in good faith a replacement gas 
supply agreement on or before October 31, 1998, but are not obligated to 
enter into such an agreement.

                                       2
<PAGE>

Except for the foregoing, all of the terms and provisions of the Gas Sales 
Agreement dated May 24, 1989, as previously amended, shall remain in full 
force and effect.
                                          
   In witness whereof, the parties have executed this Amendment the date and 
year first written above.
                                          

COLORADO POWER PARTNERS
                                          
                                          
By: /s/  Rodney E. Bellendir  
    -------------------------------------
Name:  Rodney E. Bellendir  
       ----------------------------------
Title: Management Committee Member
       ----------------------------------


PRIMA OIL & GAS COMPANY

<TABLE>
<S>                                               <C>
By: /s/  Richard H. Lewis                         Attest:  /s/  Sandra J. Irlando
    -------------------------------------                  -----------------------------
Name:  Richard H. Lewis                           Name:  Sandra J. Irlando
       ----------------------------------                -------------------------------
Title: President                                  Title: Secretary
       ----------------------------------                -------------------------------
</TABLE>


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