Exhibit 10.24
                                  AMENDMENT TO
                              AMENDED AND RESTATED
                             GAS PURCHASE AGREEMENT

     This Amendment is made by and among Oryx Gas Marketing Limited Partnership,
Kerr-McGee Oil & Gas Corporation and Kerr-McGee Oil & Gas Onshore LP,  successor
in interest to Sun Operating Limited  Partnership  (collectively,  "Seller") and
Cinergy Marketing & Trading, LLC ("Buyer").

     WHEREAS,  Seller and Buyer  have  entered  into that  certain  Amended  and
Restated  Gas  Purchase  Agreement  dated July 1, 1998,  as amended,  whereunder
Seller sells certain gas to Buyer (the "Agreement").

     WHEREAS,  Seller and Buyer desire to amend the  Agreement in the manner set
forth hereinbelow.

     NOW,  THEREFORE,  in consideration of the mutual covenants contained herein
and other good and valuable consideration,  the receipt and sufficiency of which
are hereby acknowledged, the parties agree as follows:

     Section 1.4 of Article I,  DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety.


     Section 1.8 of Article I,  DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety and substituting therefor the following:

          1.8 "Contract Price" shall mean the Baseload Price or the Swing Price,
     as defined in Section 7.1.


     Section 1.20 of Article I, DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety and substituting therefor the following:

          1.20 "Index" for a  particular  source of supply in the area where the
     applicable  Delivery  Point(s)  is/are  located  shall  be  that  published
     index(es)  or  pricing  component  which  has  been  determined  by  mutual
     agreement  (or if there is no  published  index for the  relevant  Delivery
     Point(s), then such other index(es) or pricing component as may be selected
     by mutual  agreement),  to best  represent the market price for Gas of like
     quantities  and  quality  at  the  Delivery  Point(s),  after  Index  Price
     Adjustments and deduction for Costs of Delivery.  The Index(es)  applicable
     to each  Delivery  Point(s) are set forth on Exhibit A as the Monthly Index
     and the Daily Index.


                                       IV.

     Section 1.21 of Article I, DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety and substituting therefor the following:

          1.21 Unless  specified to the contrary in Exhibit "A," "Monthly Index"
     shall be the price per MMBtu determined from the entry in the Monthly Index
     column on Exhibit "A" for the respective Aggregation Area. Unless specified
     to the contrary in Exhibit "A," "Daily  Index" shall be the price per MMBtu
     determined  from the entry in the Daily Index column on Exhibit "A" for the
     respective Aggregation Area.

                                       V.

     Section 1.22 of Article I, DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety and substituting therefor the following:

          1.22 "Index Price  Adjustments" shall mean, with respect to a Baseload
     Price ("Monthly Index Price Adjustment") or Swing Price ("Daily Index Price
     Adjustment") for any Delivery Point(s),  differentials reasonably necessary
     to adjust the Monthly  Index or Daily Index for Gas to  accurately  reflect
     the market price for Gas (after  taking into account  Costs of Delivery) of
     like  quantities  and  quality at the  Delivery  Point(s).  The Index Price
     Adjustments applicable to each Delivery Point(s) are listed on Exhibit "A".

                                       VI.

     Section 1.23 of Article I, DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety.

                                      VII.

     Section 1.32 of Article I, DEFINITIONS,  of the Agreement is hereby amended
by deleting same in its entirety and substituting therefor the following:

          Section  1.32   "Seller's   Estimate"   means  with  respect  to  each
     Aggregation  Area,  Seller's good faith  estimate  under Section 3.5 of the
     quantity of  Committed  Gas that seller  expects to deliver at all Delivery
     Point(s) within an Aggregation  Area for the relevant Month and each Day of
     the Month.

          The term "Baseload  Designated  Percentage"  shall mean the percentage
     designated by Seller each quarter,  which will be utilized to establish the
     Baseload  Quantity for all of Seller's gas at all Delivery Points,  for all
     Aggregation  Areas. The term "Swing  Designated  Percentage" shall mean the
     percentage  designated  by  Seller  each  calendar  quarter  which  will be
     utilized to establish in part the Swing Quantity for all of Seller's gas at
     all Delivery  Points,  for all Aggregation  Areas.  The sum of the Baseload
     Designated Percentage and the Swing Designated Percentage for each calendar
     quarter shall equal 100%.

          The  initial  Baseload  Designated  Percentage  and  Swing  Designated
     Percentage for Gas delivered in May 2000 shall be:

                    Baseload Designated Percentage -- 90%; Swing
                    Designated, Percentage -- 10%.

          Seller  shall have the right to designate in writing by May 16, 2000 a
     different Baseload  Designated  Percentage and Swing Designated  Percentage
     for Gas  delivered  in June 2000.  Thereafter,  Seller will  designate  the
     Baseload  Designated  Percentage  and the Swing  Designated  Percentage  in
     writing  to Buyer at least  fifteen  (15) days  before the first day of the
     applicable calendar quarter. The Baseload Designated Percentage shall be no
     less than 50% and no greater than 90%, with a restriction that the Baseload
     Designated  Percentage will not vary from the previous  calendar  quarter's
     Baseload Designated Percentage by more than 20 percentage points.

          The term  "Baseload  Quantity"  shall  mean an amount of gas each Day,
     determined for each Aggregation  Area  separately,  equal to the product of
     the Baseload Designated  Percentage  multiplied by the daily quantities set
     forth in the initial Seller's Estimate provided by Seller under Section 3.5
     each  month for all  Delivery  Points in such  Aggregation  Area.  The term
     "Swing  Quantity"  shall mean all Gas delivered  each Day by Seller from an
     Aggregation  Area  that is in  excess  of the  Baseload  Quantity  for such
     Aggregation Area.

                                      VIII.

     Section  3.5(c) of ARTICLE  III,  COMMITMENT  OF GAS, is hereby  amended by
deleting the same in its entirety and substituting therefor the following:

          (c) Estimates of Additional  Quantities of Committed  Gas.  Seller and
     Buyer  are aware  that  additional  quantities  of  Committed  Gas from new
     sources of supply not included in Seller's  Estimate will become  available
     for delivery to Buyer at various times after the first Day of an applicable
     Month.  At least two  Business  Days before the Day that  Seller  wishes to
     begin  deliveries of such  additional  quantities of Committed Gas,  Seller
     shall  provide Buyer with a written  notice  setting forth (i) the Delivery
     Point(s) at which Seller shall make such deliveries, (ii) the quantities of
     Committed Gas that Seller estimates will be delivered to each such Delivery
     Point  during  the  Month in which  initial  deliveries  occur,  (iii)  the
     Index(es)  proposed to be applicable to such  Delivery  Point(s),  (iv) any
     Index Price  Adjustments  proposed to be applicable to the price determined
     in accordance  with such Index(es) and (v) any other  information set forth
     on Exhibit A. The Contract Price for such  additional  quantities  shall be
     determined in accordance  with the  foregoing  information,  subject to the
     provisions of Article VII, including without limitation the rights of Buyer
     to propose other  Index(es) or Index Price  Adjustments in accordance  with
     Section  7.4  and  identify  Costs  of  Delivery.  Buyer  shall  take  such
     additional  quantities of Committed Gas in accordance  with, and subject to
     the terms of, Section 4.1, however, all such additional  quantities will be
     deemed to be Swing  Quantity  to be priced at the Swing Price for the Month
     in which the initial delivery date for such new Gas occurs and, at Seller's
     option on a  month-by-month  basis,  the next three (3) succeeding  months.
     Thereafter, the new Gas will be divided between Baseload Quantity and Swing
     Quantity each Month in accordance with Section 1.32.

                                       IX.

     Section 4.2(a) of ARTICLE IV, QUANTITY;  SCHEDULING AND  TRANSPORTATION  OF
DAILY  VOLUMES,  is hereby  amended by  deleting  the same in its  entirety  and
substituting therefor the following:

          (a) Seller  Delivery  Event.  If, during any Day, (i) Seller fails for
     any reason  (other than Force  Majeure as defined in Article X or any other
     reason excusing performance of Seller's obligation to deliver Committed Gas
     hereunder)  to deliver 100% of the Baseload  Quantity for each  Aggregation
     Area (defined as a "Seller Delivery  Event"),  and (ii) Buyer,  acting in a
     commercially  reasonable  manner to mitigate any damages,  purchases Gas to
     replace  such  quantities,  whether on the Day in question or a  subsequent
     Day, in order to satisfy  Buyer's  Contractual  Obligations  (as defined in
     Section  9.2) to third  parties for the Day in question  existing  prior to
     Buyer's  knowledge  of any  shortfalls,  then  Seller  shall pay Buyer,  in
     accordance  with the  provisions  of Article  VIII,  an amount equal to the
     product  of (x) the  positive  difference  between  (A) the price per MMBtu
     actually paid by Buyer for the replacement  quantities and (B) the Baseload
     Price that Buyer would have paid Seller for the,  quantities  of  Committed
     Gas not delivered by Seller and (y) the quantities of such  replacement Gas
     purchased by Buyer.  Seller shall also pay Buyer,  in  accordance  with the
     provisions  of Article  VIII,  the amount of any  incidental  out-of-pocket
     costs  reasonably  incurred by Buyer  (including,  by way of example rather
     than enumeration,  brokers' fees and any incremental transportation costs),
     less any  expenses  saved by  Buyer,  as a result of such  Seller  Delivery
     Event.  In the event daily  deliveries  are  incapable of being  determined
     because the measuring party does not provide daily quantities, then it will
     be assumed that Seller delivered on each Day of a Month from an Aggregation
     Area a quantity  equal to the monthly  quantity  for the  Aggregation  Area
     divided  by the  number  of days in the  Month.  Nothing  herein  shall  be
     construed  as  relieving  Seller from  liability  for an  Imbalance  Charge
     arising under Section 11.3. Any amounts due Buyer  hereunder  shall be paid
     in accordance with Article VIII.

                                       X.

     Section 7.1 of ARTICLE VII,  PRICE,  is hereby amended by deleting the same
in its entirety and substituting therefor the following:

          7.1  Baseload  Price and Swing  Price.  Buyer  shall  pay  Seller  the
     applicable "Baseload Price" for the Baseload Quantity delivered on each Day
     of each Month from the applicable Aggregation Area and the applicable daily
     "Swing  Price" for the Swing  Quantity  delivered on each Day of each Month
     from the applicable  Aggregation  Area. Unless specified to the contrary in
     Exhibit "A,"  "Baseload  Price" shall mean the price per MMBtu equal to the
     Monthly  Index,  as  designated  for the Gas  from an  Aggregation  Area on
     Exhibit  "A," for the Month of  deliveries,  (i) plus or minus any  Monthly
     Index Price  Adjustments  specified  in Exhibit "A" for such Gas,  and (ii)
     minus  the Costs of  Delivery  for such  Gas.  In the  event  more than one
     published index is listed on Exhibit "A" for use in determining the Monthly
     Index for Gas at a Delivery  Point,  the Monthly  Index will be  calculated
     using an average of the published  indexes with  appropriate  Monthly Index
     Price  Adjustments  and  deductions  for  Costs  of  Delivery  (hereinafter
     referred  to as a "Basket  Price").  Unless  specified  to the  contrary in
     Exhibit  "A,"  "Swing  Price"  shall mean the price per MMBtu  equal to the
     Daily Index, as designated for the Gas from an Aggregation  Area on Exhibit
     "A," attributable to the Day on which the Gas is delivered (however, if the
     Gas is  delivered  at a Delivery  Point where a daily  quantity is not made
     available by the measuring  party,  then this  component of the Swing Price
     for the Swing Quantity of Gas delivered at such location on each Day of the
     Month of  deliveries  will be equal to the average of the Daily Indexes for
     all Days of the Month  attributable  to the Gas from an Aggregation  Area),
     (i) minus  $0.02 per  MMBtu,  (ii)  plus or minus  any  Daily  Index  Price
     Adjustments  specified  in Exhibit  "A" for such Gas,  and (iii)  minus the
     Costs of Delivery for such Gas.

                                       XI.

     Section 7.2 of ARTICLE VII,  PRICE,  of the Agreement is hereby  amended by
deleting same in its entirety.

                                      XII.

     Section 7.4 of ARTICLE  VII,  PRICE,  of is hereby  amended by deleting the
same in its entirety and substituting therefor the following:

7.4  Redetermination  of Index(es) and Index Price  Adjustments.  If, during the
     term of this  Agreement (a) an Index used to determine the Monthly Index or
     Daily Index for any Delivery Point ceases to be available, (b) either party
     believes  that  another  Index more  accurately  reflects  existing  market
     conditions  with respect to any Delivery  Point(s) than the Index currently
     being used with  respect to such  Delivery  Point(s),  or (c) either  party
     believes that the Index Price Adjustments with respect to any Monthly Index
     or Daily Index for any Delivery Point(s) no longer accurately  reflects all
     differentials  reasonable  necessary  to adjust the Monthly  Index or Daily
     Index  for Gas to  accurately  reflect  the  market  price  for Gas of like
     quantities  and quality at such  Delivery  Point(s),  then either party may
     request the other to  reconsider  the  currently-applicable  Index or Index
     Price Adjustment,  in accordance with Section 7.5. The parties shall review
     the  appropriateness  of all  Index(es)  and Index Price  Adjustments  used
     hereunder not less than annually.

                                      XIII.

     The current  form of Exhibit  "A,"  however  designated,  that is in effect
immediately  prior to May 1, 2000,  is hereby  amended by deleting  the same and
substituting therefor the attached Exhibit "A-0005," a copy of which is attached
hereto as  Attachment  "A."  Each  reference  in the  Agreement  to the  phrase,
"Exhibit  A,"  shall  be a  reference  to such  Exhibit  "A-0005."  The  parties
acknowledge that they will modify the current version of the Exhibit "A" between
the time that  this  Amendment  is  signed  and such  Exhibit  "A-0005"  becomes
effective,  and that  they may need to modify  the  Exhibit  "A-0005"  before it
becomes effective to add or delete miscellaneous wells where necessary.

                                      XIV.

     Schedule  3.6 of the  Agreement is hereby  amended by deleting  same in its
entirety and  substituting  therefor the Schedule  3.6-A attached  hereto.  Each
reference in the Agreement to the phrase,  "Schedule  3.6," shall be a reference
to such Schedule 3.6-A.

                                       XV.

     Except as specifically  amended hereby,  the remaining terms and conditions
of the Agreement shall remain in full force and effect.

<PAGE>
     IN WITNESS WHEREOF,  this Amendment is executed in multiple originals to be
effective on May 1, 2000.

                                           ORYX GAS MARKETING LIMITED
                                           PARTNERSHIP

                                           By:  Kerr-McGee Oil & Gas Onshore LLC
                                           Its Managing General Partner

                                           By:  /s/ Charles D. Johnson
                                                ----------------------
                                           Name:  Charles D. Johnson
                                           Title:  Vice President

                                           KERR-MCGEE OIL & GAS ONSHORE LP

                                           By:  Kerr-McGee Oil & Gas Onshore LLC
                                           Its Managing General Partner

                                           By:  /s/ D R Kimes
                                                -------------
                                           Name:  D R Kimes
                                           Title:  Vice President

                                           KERR-MCGEE OIL & GAS CORPORATION

                                           By:  /s/ James Kleckner
                                                ------------------
                                           Name:  James Kleckner
                                           Title:  Vice President

                                           CINERGY MARKETING & TRADING, LLC

                                           By:  /s/ Joseph W. Toussaint
                                                -----------------------
                                           Name:  Joseph W. Toussaint
                                           Title:  Vice President