<PAGE>

                                                                     EXHIBIT 4.6

                                                                           FINAL

                  ASSIGNMENT, ASSUMPTION, AND CONSENT AGREEMENT

      This ASSIGNMENT, ASSUMPTION AND CONSENT AGREEMENT ("Assignment"), is dated
July 22, 2004, between QUEST CHEROKEE, LLC ("Assignor" or "Quest"), UBS AG
("Assignee"), BANK ONE, NA ("Bank One") and JPMORGAN CHASE BANK, for itself and
as successor to Bank One ("JPMorgan" and such party and each of Assignor,
Assignee and Bank One may individually be referred to as "Party" and
collectively as "Parties"). Certain capitalized terms used in this Assignment
shall have the meanings specified for such terms in Section 6(a) below.

      WHEREAS, Assignor and Bank One are parties in and to the Transaction(s)
identified in Schedule 1 attached hereto (whether one or more, the
"Transactions");

      WHEREAS, Assignor is willing to assign its rights and benefits, duties and
obligations with respect to the Transactions to the Assignee, and Assignee is
willing to accept such rights and benefits and assume such duties and
obligations of Assignor with respect to the Transactions;

      WHEREAS, Bank One has entered into an arrangement with JPMorgan wherein
Bank One would assign its rights and benefits, duties and obligations with
respect to the Transactions to JPMorgan, and JPMorgan would accept such rights
and benefits and assume such duties and obligations of Bank One with respect to
the Transaction; and

      WHEREAS, it is proposed that, following the Service Time (as defined in
Section 3 below), the Transactions be subject to that certain ISDA Master
Agreement between Assignee and JPMorgan dated as of May 21, 1995, as amended and
supplemented from time to time, governing the commodity to which the
Transactions relate;

      NOW, THEREFORE, in consideration of the premises and of the mutual
agreements herein contained and for good and valuable consideration, the receipt
and sufficiency of which is hereby acknowledged, the Parties agree as follows:

Section 1. ASSIGNMENT AND ASSUMPTION.

            (a)   Assignor hereby assigns, sells, transfers and conveys to the
Assignee all right, title, benefit, privileges, and interest of Assignor in, and
to the Transactions, between Assignor and Bank One (or Bank One's affiliates)
and other records relating to the Transactions (collectively, the "Assets"), and
Assignee hereby accepts assignment of such right, title, benefit, privileges,
and interest. Such assignment is "AS IS, WHERE IS" and "WITH ALL FAULTS," except
as otherwise specifically provided herein.

            (b)   Assignor hereby delegates to Assignee, and Assignee hereby
assumes and agrees to perform, the Liabilities of Assignor with respect to the
Transactions which are to be performed or accrue after the Service Time, except
to the extent such Liabilities arise from or relate to acts, omissions or events
occurring or conditions existing prior to the Service Time and the Liabilities
associated therewith (collectively, the "Assumed Liabilities"). All Liabilities
other than the Assumed Liabilities (the "Excluded Liabilities"), including but
not limited to those Liabilities relating to, resulting from, or arising out of
any breach of contract or any other actual

<PAGE>

or alleged failure of Assignor to perform any obligation, in each case arising
out of, or relating to, the Transactions or the performance thereof prior to the
Service Time including any payment obligations arising from calculation periods
prior to the Service Time shall be the obligation and responsibility of
Assignor, and Assignee does not assume and shall not discharge, perform or be
responsible in any way for any Excluded Liabilities.

Section 2. CONSENT TO ASSIGNMENT. Bank One and JPMorgan each hereby consent to
the foregoing assignment by Assignor to Assignee of all the right, title,
benefit, privileges, and interest of Assignor in, and to the Transactions
pursuant to this Assignment, and the assumption by Assignee of the Assumed
liabilities, and in connection therewith releases Assignor from the Assumed
Liabilities and all of the terms, conditions, and covenants contained in the
Transactions with respect to the Assumed Liabilities; provided that such release
shall not be construed as releasing Assignor in any way from any Excluded
Liabilities, which Bank One acknowledges and agrees are the sole obligation and
responsibility of Assignor.

Section 3. MASTER AGREEMENT. Bank One and JPMorgan acknowledge and agree that
(i) the Transactions shall be evidenced by the confirmations attached hereto as
Exhibit A (the "Trade Confirms") and shall be governed by and subject to that
certain ISDA Master Agreement between Assignee and JPMorgan dated as of May 21,
1995 (the "UBS Master"). Bank One and JPMorgan acknowledge and agree that their
execution and delivery of this Assignment shall constitute and be deemed as
execution of the Trade Confirms. Bank One and JPMorgan acknowledge that the
Trade Confirms specify as the "Trade Date" the trade date of the Transaction
between Assignor and Assignee, include the "deal number" assigned to the
Transaction by Assignor, and that such provisions are not substantive terms of
the transactions contemplated thereby.

Section 4. SERVICE TIME. This Assignment shall become effective as of 11:59 p.m.
(central daylight time) on July 22, 2004 (the "Service Time") provided that it
shall have been executed by each of Assignor, Assignee, Bank One and JP Morgan
and each Party shall have received from the other Parties a duly executed
counterpart hereof. Facsimiles shall be effective as originals.

Section 5. REPRESENTATIONS AND WARRANTIES.

            (a)   Power and Authority; Regulatory Approvals. Bank One, JPMorgan,
Assignor and Assignee each represents and warrants to each of the other Parties
hereto that as of the date hereof and as of the Service Time (i) it has all
requisite power and authority to execute, deliver and perform its obligations
under this Assignment and, in the case of Assignee (with respect to the Assumed
Liabilities) and JPMorgan, to perform its obligations under the Transactions and
(ii) no consent, license, approval or authorization of, or other action by, or
any notice, registration, declaration, or filing with, any court or
administrative or governmental body or any other person or entity, except for
the consent evidenced by this Assignment and such as have been obtained, is
necessary in connection with the execution, delivery and performance by such
Party of this Assignment or, in the case of Assignee (with respect to the
Assumed Liabilities) and JPMorgan, the performance of the Transactions.

            (b)   Transactions' Status. JPMorgan acknowledges as of the date
hereof, and as of the Service Time after giving effect to the provisions of this
Assignment, that (i) the

                                       2
<PAGE>

Transactions are in full force and effect and are legal, valid, and binding
agreements of JPMorgan, enforceable against it in accordance with its terms,
except in each case where enforceability may be limited or otherwise impacted by
bankruptcy, insolvency or other similar laws affecting creditors' rights
generally and except where enforceability is subject to the application of
equitable principles or remedies, (ii) no breach or default (or event or
condition that, with notice or lapse of time or both would reasonably be
expected to constitute a breach or default) by JPMorgan exists thereunder, and
(iii) to Bank One's knowledge, no breach or default by Assignor or other remedy
triggering event (or event or condition that, with notice or lapse of time or
both would reasonably be expected to constitute a breach, default, or other
remedy triggering event) exists thereunder. Bank One further acknowledges that
it has not entered into any written or oral amendments, supplements or other
modifications of the Transactions.

Section 6. MISCELLANEOUS.

            (a)   Definitions. As used in this Assignment, the following terms
shall have the following meanings:

      "Liabilities" means all indebtedness, obligations, duties and other
      liabilities, whether absolute, accrued, contingent, fixed or otherwise, or
      whether due or to become due with respect to the Transactions, including,
      but not limited to, any charges, fees, taxes (however denominated,
      including any interest, penalties or other additions to tax that may
      become payable in respect thereof), assessments, adders or surcharges
      imposed or authorized by any court or tribunal in any jurisdiction
      (domestic or foreign) or any federal, state, municipal or local government
      or other governmental body, agency, authority (including any state
      attorney's general office or office of consumer protection), department,
      commission, board, bureau, instrumentality, arbitrator or arbitral body
      (domestic or foreign).

            (b)   Governing Law. The Assignment shall be governed by and
construed in accordance with the laws of the State of New York.

            (c)   Headings. The headings used in this Assignment are for
convenience of reference only and are not to affect the construction of or to be
taken into consideration in interpreting this Assignment.

            (d)   Successors; Counterparts; Facsimile Signatures. This
Assignment shall be binding upon and shall inure to the benefit of Assignor,
Assignee, Bank One and JPMorgan and each of their respective successors and
assigns. This Assignment may be executed in counterparts, each of which shall be
deemed an original, and may be delivered by telecopier.

            (e)   Other Agreements. Bank One and JPMorgan each hereby agrees
that, as of the Service Time, Bank One and/or JPMorgan releases any liens on
Quest's property delivered to Bank One as collateral or performance assurance
under the ISDA Master Agreement dated December 22, 2003 between Bank One and
Quest.

            (f)   Further Assurances. The Parties hereto agree, each at its own
expense, to perform all such further acts and execute and deliver all such
further agreements, instruments

                                       3
<PAGE>

and other documents as any other Party shall reasonably request to evidence more
effectively the assignments, assumptions and consents made by the Parties under
this Assignment.

      IN WITNESS WHEREOF, the parties have executed this Assignment as of the
date first above written.

                                                ASSIGNOR:
                                                QUEST CHEROKEE, LLC

                                                By: /s/ DAVID GROSE
                                                    ----------------------------
                                                Name: David Grose
                                                      --------------------------
                                                Title: Chief Financial Officer
                                                       -------------------------

                                                BANK ONE:
                                                BANK ONE, NA
ASSIGNOR:
UBS AG                                          By: /s/ ERIC W. BONATZ
By: UBS Energy LLC, As Agent                        ----------------------------
                                                Name: Eric W. Bonatz
                                                      --------------------------
                                                Title: Vice President
                                                       -------------------------

By: /s/ JEFFREY T. HODGE                        JPMORGAN:
    -------------------------------------       JPMORGAN CHASE BANK
Name: Jeffrey T. Hodge
      -----------------------------------
Title: Executive Director
       ----------------------------------

By: /s/ MARK TAYLOR                             By: /s/ WILLIAM SPOTA
    -------------------------------------           ----------------------------
Name: Mark Taylor                               Name: William Spota
      -----------------------------------             --------------------------
Title: Executive Director                       Title: Vice President
       ----------------------------------              -------------------------


                                       4
<PAGE>

                                   SCHEDULE I

<TABLE>
<CAPTION>
REFERENCE      PRODUCT             INDEX          TRADE DATE
---------      -------             -----          ----------
<S>            <C>             <C>                <C>
03NG23688       Swap           Williams -- TOK     12/23/03
03NG23697       Swap           Williams -- TOK     12/23/03
03NG23714      Collar          Williams -- TOK     12/23/03
03NG23422       Swap             NYMEX (1)         12/11/03
03NG23684      Collar          Williams -- TOK     12/23/03
03NG23680      Collar          Williams -- TOK     12/23/03
</TABLE>
                                       5
<PAGE>

                                    EXHIBIT A

                                 TRADE CONFIRMS

                                       6
<PAGE>

                                Deal No. AJQ450.1

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - SWAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.1

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Swap          TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas               COMMODITY UNIT: MMBtu (One Million
                                           British  Thermal Units)

      EFFECTIVE DATE: August 01, 2004      TERMINATION DATE: December 31, 2006

      NOTIONAL QUANTITY PER CALCULATION PERIOD: See Attachment

      CALCULATION PERIOD(S): Each calendar month beginning with August 01,
      2004 and ending on December 31, 2006.

      PAYMENT DATE(S): See Attachment

      PARTY B PAYS FIXED PRICE: See Attachment

      PARTY A PAYS FLOATING PRICE: The settlement price for the last scheduled
      Trading Day of the NYMEX Henry Hub Natural Gas Futures Contract for the
      applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1
<PAGE>

places and (iv) gigajoules shall be rounded to four places. If the number after
the final number is five (5) or greater then the final number shall be increased
by one (1), and if the number after the final number is less than five (5) then
the final number shall remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                     JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:     <<SignatureGoesHere>>
Name:   <<SignerName>>
Title:  <<SignerTitle>>                   By: _________________________________
By:     <<Signature2GoesHere>>            Name: _______________________________
Name:   <<Signer2Name>>                   Title: ______________________________
Title:  <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2
<PAGE>

                                                               Deal No. AJQ450.1

                                   Attachment
                              Contract No. AJQ450.l

Quantity Measurement: MMBtu

<TABLE>
<CAPTION>
                              Quantity Per Day Per                   Fixed Price
 Calculation Period            Calculation Period                    (per MMBtu)                      Payment Date
 ------------------            ------------------                    -----------                      ------------
<S>                           <C>                                    <C>                              <C>
August, 2004                         13,004                            $5.31500                          9/30/04
September. 2004                      13,004                            $5.31500                          10/29/04
October. 2004                        13,004                            $5.31500                          11/30/04
November, 2004                       16,004                            $5.31500                          12/30/04
December, 2004                       16,004                            $5.31500                          1/31/05
January, 2005                        14,328                            $4.68500                          2/28/05
February, 2005                       14,328                            $4.68500                          3/31/05
March, 2005                          14,328                            $4.68500                          4/29/05
April, 2005                          14,328                            $4.68500                          5/31/05
May, 2005                            14,328                            $4.68500                          6/30/05
June, 2005                           14,328                            $4.68500                          7/29/05
July, 2005                           14,328                            $4.68500                          8/31/05
August, 2005                         14,328                            $4.68500                          9/30/05
September. 2005                      14,328                            $4.68500                          10/31/05
October, 2005                        14,328                            $4.68500                          11/30/05
November, 2005                       18,328                            $4.68500                          12/30/05
December, 2005                       18,328                            $4.68500                          1/31/05
January, 2006                        15,382                            $4.53000                          2/28/06
February. 2006                       15,382                            $4.53000                          3/31/06
March, 2006                          15,382                            $4.53000                          4/28/06
April, 2006                          15,382                            $4.53000                          5/31/06
May, 2006                            15,382                            $4.53000                          6/30/06
June, 2006                           15,382                            $4.53000                          7/31/06
July, 2006                           15,382                            $4.53000                          8/31/06
August, 2006                         15,382                            $4.53000                          9/29/06
September, 2006                      15,382                            $4.53000                          10/31/06
October, 2006                        15,382                            $4.53000                          11/30/06
November, 2006                       15,382                            $4.53000                          12/29/06
December, 2006                       15,382                            $4.53000                          1/31/06
</TABLE>

End Of Attachment

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH
                                                                               3

<PAGE>

                                Deal No. AJQ450.2

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - SWAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.2

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Swap         TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 1,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Each calendar month beginning with August 01, 2004
      and ending on October 31, 2004.

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      PARTY B PAYS FIXED PRICE: US Dollars $4.16900 per MMBtu

      PARTY A PAYS FLOATING PRICE: The Williams Natural Gas Co. - Texas,
      Oklahoma, Kansas Index price for delivery during the applicable
      Calculation Period in the "Prices of Spot Gas Delivered to Pipelines"
      section located in the first issue of Inside F.E.R.C.'s Gas Market Report
      published during the applicable Calculation Period

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1
<PAGE>

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                    JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                   By: __________________________________
By:    <<Signature2GoesHere>>            Name: ________________________________
Name:  <<Signer2Name>>                   Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2
<PAGE>

                                Deal No. AJQ450.3

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - SWAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.3

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Swap         TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 3,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Each calendar month beginning with August 01, 2004
      and ending on October 31, 2004.

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      PARTY B PAYS FIXED PRICE: US Dollars $4.20650 per MMBtu

      PARTY A PAYS FLOATING PRICE: The Williams Natural Gas Co. - Texas,
      Oklahoma, Kansas Index price for delivery during the applicable
      Calculation Period in the "Prices of Spot Gas Delivered to Pipelines"
      section located in the first issue of Inside F.E.R.C.'s Gas Market Report
      published during the applicable Calculation Period

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1
<PAGE>

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                     JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                    By: __________________________________
By:    <<Signature2GoesHere>>             Name: ________________________________
Name:  <<Signer2Name>>                    Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2
<PAGE>

                                Deal No. AJQ450.4

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - CAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.4

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Cap          TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: November 01, 2004   TERMINATION DATE: October 31, 2005

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 4,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on November 01, 2004 and the final Calculation Period ending on
      October 31, 2005

      PAYMENT DATE(S): See Attachment

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party B

            FIXED PRICE: US Dollars $0.00 due to Party A on or before July 26,
            2004

      FLOATING AMOUNT:

            FLOATING PRICE PAYER: Party A

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1
<PAGE>

      CAP PRICE (STRIKE PRICE): US Dollars $5.30000 per MMBtu

      FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma, Kansas
      Index price for delivery during the applicable Calculation Period in the
      "Prices of Spot Gas Delivered to Pipelines" section located in the first
      issue of Inside F.E.R.C.'s Gas Market Report published during the
      applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                    JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                   By: __________________________________
By:    <<Signature2GoesHere>>            Name: ________________________________
Name:  <<Signer2Name>>                   Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2

<PAGE>

                                                               Deal No. AJQ450.4

                                   Attachment
                              Contract No. AJQ450.4

<TABLE>
<CAPTION>
Calculation Period                     Payment Date
------------------                     ------------
<S>                                    <C>
November, 2004                         12/7/04
December, 2004                         1/7/05
January, 2005                          2/7/05
February, 2005                         3/7/05
March, 2005                            4/7/05
April, 2005                            5/9/05
May, 2005                              6/7/05
June, 2005                             7/7/05
July, 2005                             8/8/05
August, 2005                           9/7/05
September. 2005                        10/7/05
October, 2005                          12/7/05
</TABLE>

End of Attachment

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               3

<PAGE>

                                Deal No. AJQ450.5

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                              CONFIRMATION - FLOOR

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.5

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Floor        TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: November 01, 2004   TERMINATION DATE: October 31, 2005

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 4,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on November 01, 2004 and the final Calculation Period ending on
      October 31, 2005

      PAYMENT DATE(S): See Attachment

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party A

            FIXED PRICE: US Dollars $0.00 due to Party B on or before July 26,
            2004

      FLOATING AMOUNT:

            FLOATING PRICE PAYER: Party B

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1

<PAGE>

      FLOOR PRICE (STRIKE PRICE): US Dollars $4.25000 per MMBtu

      FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma, Kansas
      Index price for delivery during the applicable Calculation Period in the
      "Prices of Spot Gas Delivered to Pipelines" section located in the first
      issue of Inside F.E.R.C.'s Gas Market Report published during the
      applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                     JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                    By: __________________________________
By:    <<Signature2GoesHere>>             Name: ________________________________
Name:  <<Signer2Name>>                    Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2

<PAGE>

                                                               Deal No. AJQ450.5

                                   Attachment
                              Contract No. AJQ450.5

<TABLE>
<CAPTION>
Calculation Period                     Payment Date
------------------                     ------------
<S>                                    <C>
November, 2004                         12/7/04
December, 2004                         1/7/05
January, 2005                          2/7/05
February, 2005                         3/7/05
March, 2005                            4/7/05
April, 2005                            5/9/05
May, 2005                              6/7/05
June, 2005                             7/7/05
July, 2005                             8/8/05
August, 2005                           9/7/05
September. 2005                        10/7/05
October, 2005                          12/7/05
</TABLE>

End of Attachment

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               3

<PAGE>

                                Deal No. AJQ450.6

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - CAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.6

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Cap          TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 2,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on August 01, 2004 and the final Calculation Period ending on
      October 31, 2004

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party B

            FIXED PRICE: US Dollars $0.00 due to Party A on or before July 26,
            2004

      FLOATING AMOUNT:

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1

<PAGE>

            FLOATING PRICE PAYER: Party A

            CAP PRICE (STRIKE PRICE): US Dollars $5.50000 per MMBtu

            FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma,
            Kansas Index price for delivery during the applicable Calculation
            Period in the "Prices of Spot Gas Delivered to Pipelines" section
            located in the first issue of Inside F.E.R.C.'s Gas Market Report
            published during the applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                   JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                  By: __________________________________
By:    <<Signature2GoesHere>>           Name: ________________________________
Name:  <<Signer2Name>>                  Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2

<PAGE>

                                Deal No. AJQ450.7

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                              CONFIRMATION - FLOOR

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.7

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Floor        TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 2,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on August 01, 2004 and the final Calculation Period ending on
      October 31, 2004

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party A

            FIXED PRICE: US Dollars $0.00 due to Party B on or before July 26,
            2004

      FLOATING AMOUNT:

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1

<PAGE>

            FLOATING PRICE PAYER: Party B

            FLOOR PRICE (STRIKE PRICE):  US Dollars $4.15000 per MMBtu

            FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma,
            Kansas Index price for delivery during the applicable Calculation
            Period in the "Prices of Spot Gas Delivered to Pipelines" section
            located in the first issue of Inside F.E.R.C.'s Gas Market Report
            published during the applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                   JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                  By: __________________________________
By:    <<Signature2GoesHere>>           Name: ________________________________
Name:  <<Signer2Name>>                  Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2
<PAGE>

                                Deal No. AJQ450.8

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                               CONFIRMATION - CAP

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.8

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Cap          TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 1,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on August 01, 2004 and the final Calculation Period ending on
      October 31, 2004

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party B

            FIXED PRICE: US Dollars $0.00 due to Party A on or before July 26,
            2004

      FLOATING AMOUNT:

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1

<PAGE>

            FLOATING PRICE PAYER: Party A

            CAP PRICE (STRIKE PRICE): US Dollars $5.50000 per MMBtu

            FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma,
            Kansas Index price for delivery during the applicable Calculation
            Period in the "Prices of Spot Gas Delivered to Pipelines" section
            located in the first issue of Inside F.E.R.C.'s Gas Market Report
            published during the applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                  JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                 By: __________________________________
By:    <<Signature2GoesHere>>          Name: ________________________________
Name:  <<Signer2Name>>                 Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2
<PAGE>

                                Deal No. AJQ450.9

                                                                  UBS ENERGY LLC
                                       Acting as agent for UBS AG, London Branch
                                                 677 Washington Blvd, Floor 10-N
                                                              Stamford, CT 06901
                                                           Phone: (203) 719-3000
                                                             Fax: (203) 719-5091

                              CONFIRMATION - FLOOR

To:  JPMorgan Chase Bank ("Party B")     Date: July 22, 2004
Attention: Document Department           From: UBS AG, London Branch ("Party A")
Fax No.: (212) 623-2511                  Re: Swap AJQ450.9

The purpose of this facsimile is to confirm the terms and conditions of the
Transaction entered into between us on the Trade Date specified below (the
"Transaction"). This facsimile supplements, forms part of, is subject to and
constitutes a "Confirmation" under the ISDA Master Agreement dated as of May 21,
1997, as amended and supplemented from time to time (the "Agreement"). All
provisions contained in the Agreement govern this Confirmation except as
expressly modified below. The terms of the particular Transaction to which this
Confirmation relates are as follows:

      TRANSACTION: Commodity Floor        TRADE DATE: July 22, 2004

      COMMODITY: Natural Gas              COMMODITY UNIT: MMBtu (One Million
                                          British Thermal Units)

      EFFECTIVE DATE: August 01, 2004     TERMINATION DATE: October 31, 2004

      NOTIONAL QUANTITY PER CALCULATION PERIOD: 1,000 MMBtu multiplied by the
      number of days in the relevant Calculation Period

      CALCULATION PERIOD(S): Monthly periods, with the first Calculation Period
      commencing on August 01, 2004 and the final Calculation Period ending on
      October 31, 2004

      PAYMENT DATE(S): The fifth (5th) Business Day succeeding the last Pricing
      Date for the applicable Calculation Period

      FIXED AMOUNT:

            FIXED PRICE PAYER: Party A

            FIXED PRICE: US Dollars $0.00 due to Party B on or before July 26,
            2004

      FLOATING AMOUNT:

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               1

<PAGE>

            FLOATING PRICE PAYER: Party B

            FLOOR PRICE (STRIKE PRICE): US Dollars $4.15000 per MMBtu

            FLOATING PRICE: The Williams Natural Gas Co. - Texas, Oklahoma,
            Kansas Index price for delivery during the applicable Calculation
            Period in the "Prices of Spot Gas Delivered to Pipelines" section
            located in the first issue of Inside F.E.R.C.'s Gas Market Report
            published during the applicable Calculation Period

      For the purposes of the calculations of the Floating Price(s), all numbers
shall be rounded as follows: Floating Price(s) relating to commodities quoted in
(i) gallons shall be rounded to five places, (ii) MMBtu's shall be rounded to
four places, (iii) barrels shall be rounded to three places and (iv) gigajoules
shall be rounded to four places. If the number after the final number is five
(5) or greater then the final number shall be increased by one (1), and if the
number after the final number is less than five (5) then the final number shall
remain unchanged.

      If this Confirmation correctly sets forth the terms of the Transaction
that we have entered into, please promptly confirm in a reply to us by signing
below and sending this Confirmation (or a copy hereof) to us (or notifying us of
any bona fide error that would require revision in order to accurately reflect
our agreement on the Transaction) by facsimile transmission within two Business
Days after your receipt of this Confirmation. If you fail to so reply within
such time period, the terms hereof will constitute binding and conclusive
evidence of the Transaction. We look forward to receiving your prompt reply.

Sincerely,

UBS AG, London Branch                    JPMorgan Chase Bank

By: UBS Energy LLC, as agent
By:    <<SignatureGoesHere>>
Name:  <<SignerName>>
Title: <<SignerTitle>>                   By: __________________________________
By:    <<Signature2GoesHere>>            Name: ________________________________
Name:  <<Signer2Name>>                   Title: _______________________________
Title: <<Signer2Title>>

            UBS ENERGY LLC ACTING AS AGENT FOR UBS AG, LONDON BRANCH

                                                                               2