<PAGE>
                                                                   EXHIBIT 10.15
 
                                    "Pages where confidential treatment has been
                           requested are stamped Confidential Treatment Request.
                        The redacted material has been separately filed with the
                             Commission; the appropriate section has been marked
                    at the appropriate place and in the margin with a star (*)."

                                                                         El Paso
                                                                                
                                                                                
                          FEEDSTOCK SALE AND REFINERY
                          ---------------------------
                           PRODUCT PURCHASE AGREEMENT
                           --------------------------


          THIS FEEDSTOCK SALE AND REFINERY PRODUCT PURCHASE AGREEMENT (the
"Agreement") is made and entered into effective the 1st day of September, 1996,
by and between WARREN PETROLEUM COMPANY, LIMITED PARTNERSHIP, a Delaware limited
partnership with offices at 13430 Northwest Freeway, Suite 1200, Houston, TX
77040-6095 (hereinafter referred to as "WPC"), and CHEVRON PRODUCTS COMPANY, A
DIVISION OF CHEVRON U.S.A. INC., a Pennsylvania corporation with offices at 6501
Trowbridge, El Paso, Texas 79905 (hereinafter referred to as "CPC").

                                  WITNESSETH:

          WHEREAS, Chevron U.S.A. Inc. ("CUSA") and NGC Corporation ("NGC") have
entered into certain agreements (the "Merger Agreements") pursuant to which CUSA
would contribute certain gas gathering, processing, and other midstream assets
and related liabilities of CUSA's Warren Petroleum Company division ("Warren")
and natural gas business unit division to a corporation to be formed which NGC
would then be merged into (the "Merger");

          WHEREAS, immediately subsequent to the Merger, the gas gathering,
processing and other midstream assets and related liabilities of Warren will be
transferred to WPC;

          WHEREAS, Warren previously sold to CPC and CPC purchased from Warren
all of CPC's Feedstock needs and Warren previously purchased from CPC and CPC
sold to Warren all of the Refinery Products and certain Offspec Refinery
Products produced at CPC's Refinery and both CPC and WPC desire that such
relationship continue;

          WHEREAS, WPC desires to sell to CPC, and CPC desires to purchase from
WPC quantities of Feedstocks;

          WHEREAS, CPC has quantities of Refinery Products available for sale
from its Refinery (as defined in Article I, below) that it desires to sell to
WPC, and WPC desires to purchase such Refinery Products from CPC; and

          WHEREAS, CPC desires that WPC maintain the same level of service that
was previously provided to it by Warren and WPC desires to continue such level
of service.

                                       1
<PAGE>
 
          NOW, THEREFORE, in consideration of the premises and for the mutual
benefit of the parties as well as for other good and valuable consideration, WPC
and CPC agree as follows:

                                   ARTICLE I
                                  DEFINITIONS
                                  -----------

     1.1 As used in this Agreement, the following terms shall have the following
meanings:

     Accounting Period shall mean a period of one (1) Month commencing at 12:01
     a.m. local time on the first Day of a calendar Month and ending at 12:01
     a.m. local time on the first Day of the next succeeding Month.

     Affiliate shall mean any Person that directly or indirectly through one or
     more intermediaries, controls or is controlled by or is under common
     control with the Person specified.  The term "control" (including the terms
     "controlled by" or "under common control with") means the possession,
     directly or indirectly, of the power to direct or cause the direction of
     the management and policies of a Person, whether through ownership, by
     contract, or otherwise.  Any Person shall be deemed to be an Affiliate of
     any specified Person if such Person owns fifty percent (50%) or more of the
     voting securities of the specified Person, if the specified Person owns
     fifty percent (50%) or more of the voting securities of such Person, or if
     fifty percent (50%) or more of the voting securities of the specified
     Person and such Person are under common control.

     Alternate Index shall have the meaning specified in Section 5.3
     hereinafter.

     Arbitration Notice shall have the meaning specified in Section 13.1(d)
     hereinafter.

     Bankruptcy Event shall mean the occurrence of one or more of the following
     events with respect to a Party: (A) the entry of a decree or order for
     relief against a Party by a court of competent jurisdiction in any
     involuntary case brought against a Party under any bankruptcy insolvency or
     other similar law (collectively, "Debtor Relief Laws") generally affecting
     the rights of creditors and relief of debtors now or hereafter in effect,
     (B) the appointment of a receiver, liquidator, assignee, custodian,
     trustee, sequestrator, or other similar agent under applicable Debtor
     Relief Laws for a Party or for any substantial part of its assets or
     property, (C) the ordering of the winding up or liquidation of a Party's
     affairs, (D) the filing of a petition in any such involuntary bankruptcy
     case, which petition remains undismissed for a period of 180 Days or which
     is not dismissed or suspended pursuant to Section 305 of the Federal
     Bankruptcy Code (or any corresponding provision of any future United States
     bankruptcy law), (E) the commencement by a Party of a voluntary case under
     any applicable Debtor Relief Law now or hereafter in effect, (F) the
     consent by a Party to the entry of an order for relief in an involuntary
     case under any such law or to the appointment of or the taking of

                                       2
<PAGE>
 
     possession by a receiver, liquidator, assignee, trustee, custodian,
     sequestrator or other similar agent under any applicable Debtor Relief Laws
     for a Party or for any substantial part of its assets or property, or (G)
     the making by a Party of any general assignment for the benefit of its
     creditors.

     Barrel shall mean forty-two (42) U. S. Gallons.

     Base Rate shall mean the lesser of (i) two percent (2%) above the per annum
     rate of interest announced from time to time as the "prime rate" for
     commercial loans by First National Bank of Chicago, as such "prime rate"
     may change from time to time, or (ii) the maximum applicable non-usurious
     rate of interest.
 
     Business Day shall mean a Day on which Federal Reserve member banks in New
     York City are open for business.

     Contract Quantity means, for any Delivery Month, a quantity of Feedstocks
     nominated by CPC that (a) is not less than ninety-five percent (95%) of the
     Nominated Volumes nor (b) more than one hundred and five percent (105%) of
     the Nominated Volumes. By way of illustration, if the Nominated Volumes for
     a Delivery Month equal 100, then the Contract Quantity shall be not less
     than ninety-five (95) nor more than one hundred and five (105).

     CPC Deficiency Quantity shall have the meaning specified in Section 4.7
     hereinafter.

     Day or Daily shall mean a twenty-four (24) hour period commencing 12:01
     a.m. local time and extending until 12:01 a.m. local time on the following
     Day.

     Delivery Month shall mean the Month in which Feedstocks are to be delivered
     to CPC based on CPC's nominations.

     Delivery Point(s) shall have the meaning specified in Section 6.2
     hereinafter.

     Effective Date shall mean September 1, 1996.

     Emergency Supplies shall mean any Feedstocks or volumes of a particular
     Feedstock that CPC may need during a particular Month above the Nominated
     Volumes applicable during such Month.

     Feedstock shall mean Isobutane, Normal Butane, Mixed Butane, and any other
     Feedstocks mutually agreed to in writing by the Parties.  Feedstock shall
     also mean, where applicable (but excluding Articles IV and V hereunder),
     Offspec Feedstock, but such will in no way prevent, preclude, or otherwise
     affect the right of CPC to reject Offspec Feedstock in accordance with
     Section 7.3 hereinafter.

                                       3
<PAGE>
                                              "Confidential Treatment Requested.
                                                  The redacted material has been
                                          separately filed with the Commission."
 
     Force Majeure shall have the meaning specified in Section 12.2 hereinafter.

     Gallon shall mean the unit of volume used for the purpose of measurement of
     liquid.  One (1) U.S. liquid Gallon contains two hundred thirty-one (231)
     cubic inches when the liquid is at a temperature of sixty degrees
     Fahrenheit (60 degrees F) and at the vapor pressure of the liquid being
     measured.

     Isobutane shall mean a liquid hydrocarbon stream which meets the
     specifications set forth in Exhibit "A".

     Keep Whole Acquisition Price shall mean the price paid by WPC to acquire
     Feedstocks for resale to CPC plus all Transportation Costs incurred in
*    connection therewith plus REDACTED per Gallon.  If WPC uses Feedstock that
     is owned and stored by WPC to satisfy the Feedstock needs of the Refinery
     in the situation where a Keep Whole Acquisition Price is applicable, the
     "price paid by WPC to acquire Feedstock for resale to CPC" as used above
*    shall be REDACTED as quoted by OPIS for Mont Belvieu, Texas (Non-TET) on
     the Day the transportation of the Feedstock to CPC commences.  For the
     purpose of this Agreement, transportation of Feedstock shall be deemed to
     have commenced on the Day (i) the loading of the Feedstock onto trucks,
     rail cars, or barges initially commences or (ii) the delivery of such
     Feedstock into the transporting pipeline commences.  In obtaining Feedstock
     for CPC in the situation where a Keep Whole Acquisition Price is
     applicable, WPC will use every reasonable effort to purchase such Feedstock
     at the lowest possible spot price taking into consideration the location of
     the Refinery, the prior notice given by CPC to WPC and other factors beyond
     WPC's control.

     Keep Whole Disposition Amount shall have the meaning specified in Section
     4.7 hereinafter.

     Month or Monthly shall mean a period commencing at 12:01 a.m. local time on
     the first Day of a calendar Month and extending until 12:01 a.m. local time
     on the first Day of the next succeeding calendar Month.

     Mixed Butane shall mean a liquid hydrocarbon stream which meets the
     specifications set forth in Exhibit "A".

     Netback Price shall mean the price obtained by WPC in an arm's length sale
     of Refinery Products to a third Person who is not an Affiliate of WPC less
     Transportation Costs and/or T&F Costs that are reasonably incurred in
     connection therewith.

     WPC Deficiency Amount shall have the meaning specified in Section 14.1
     hereinafter.

                                       4
<PAGE>
 
     WPC Deficiency Quantity shall have the meaning specified in Section 14.1
     hereinafter.

     New Taxes shall mean any Taxes enacted and effective after the Effective
     Date, including that portion of any Taxes or New Taxes that constitutes an
     increase either in rate or breadth of coverage.

     Nominated Volumes shall have the meaning specified in Section 4.3
     hereinafter.

     Normal Butane shall mean a liquid hydrocarbon stream which meets the
     specifications set forth in Exhibit "A".

     Offspec Feedstocks shall have the meaning specified in Section 7.1
     hereinafter.

     Offspec Refinery Products shall have the meaning specified in Section 7.2
     hereinafter.

     Party shall mean individually either CPC or WPC (including their respective
     successors and permitted assigns); collectively, the "Parties."

     Person shall mean any individual, corporation, partnership, limited
     liability company, association, joint venture, trust, or other organization
     of any nature or kind.

     PP Mix shall mean a liquid hydrocarbon stream which meets the
     specifications set forth in Exhibit "B".

     Propane shall mean a liquid hydrocarbon stream which meets the
     specifications set forth in Exhibit "B".

     Refinery shall mean the refinery owned by CPC and situated in El Paso,
     Texas.

     Refinery Products shall mean Propane, PP Mix, Normal Butane, Mixed Butane,
     and those other light end streams identified on Exhibit "B" and produced
     from the Refinery.  Refinery Products shall also mean, where applicable
     (but excluding Articles IV and V hereunder), Type A Offspec Refinery
     Products, but such will in no way prevent, preclude, or otherwise affect
     the right of WPC to reject Type A Offspec Refinery Products in accordance
     with Section 7.4 hereinafter.

     Taxes shall mean any and all ad valorem, property, occupation, severance,
     production, extraction, first use, conservation, Btu or energy, gathering,
     transport, pipeline, utility, gross receipts, gas or oil revenue, gas or
     oil import, privilege, sales, use, consumption, excise, lease, transaction,
     environmental, and other taxes, governmental charges, duties, licenses,
     fees, permits, and assessments.

     T&F Costs shall mean all Transportation Costs and all costs and expenses
     reasonably incurred in connection with the receipt, fractionation and sale
     or resale of Refinery Products received by WPC from CPC.  It is understood
     and agreed that any fractionation costs that are incurred at a 

                                       5
<PAGE>
 
     facility owned and/or controlled by WPC or any of its Affiliates shall not
     exceed the lesser of (i) the fair market value for such fractionation
     services or (ii) the fees charged by WPC or its Affiliates to CUSA in
     connection with the fractionation of natural gas liquids (other than
     Refinery Products) owned by CUSA and purchased by WPC.

     Transportation Costs shall mean all costs and expenses reasonably incurred
     in connection with the transportation of Feedstock(s) and/or Refinery
     Product(s) hereunder, including, without limitation, rail car, barges, and
     truck costs, Feedstock and/or Refinery Product losses that occur during
     transportation for reasons other than the negligence or willful misconduct
     of WPC and all costs and expenses reasonably incurred in loading,
     unloading, transporting, terminaling, storing (if required), and handling
     such Feedstock(s) and/or Refinery Products.  It is understood and agreed
     that Transportation Costs shall not include any portion of WPC's general
     and administrative costs and expenses, but will include amounts paid by WPC
     to CPC in connection with the Propane rail cars owned or leased by CPC but
     operated by WPC in connection with the services rendered by WPC to CPC
     pursuant to the Feedstock and Refinery Products Master Services Agreement
     of even date herewith between CPC and WPC.  With respect to barges and
     trucks owned by WPC or its Affiliates, the applicable Transportation Costs
     shall not exceed the fair market value of the use of such barges and trucks
     in transporting Feedstocks and/or Refinery Products hereunder.  When WPC
     purchases Feedstocks for resale to the Refinery at a delivered price (i.e.,
     which includes the price for such Feedstock and Transportation Costs), the
     Transportation Costs charged to CPC shall not exceed the fair market value
     for such transportation services, which shall be determined with reference
     to transportation services rendered to non-affiliated third Persons that
     are comparable in time, quality, distance transported and type of Feedstock
     transported.

     Type A Offspec Refinery Product shall have the meaning specified in Section
     7.2 hereinafter.

     Type B Offspec Refinery Product shall have the meaning specified in Section
     7.2 hereinafter.

     Year shall mean a period of twelve (12) consecutive Months commencing from
     the Effective Date.

     1.2 Other Definitions. Other terms may be defined elsewhere in the text of
this Agreement and shall have the meanings indicated throughout this Agreement.

                                   ARTICLE II
                         REPRESENTATIONS AND WARRANTIES
                         ------------------------------

  2.1  CPC hereby represents and warrants to WPC that on and as of the date
hereof:

                                       6
<PAGE>
 
          (a)  It has all requisite power and authority to carry on the business
               in which it is engaged and to perform its respective obligations
               under this Agreement;

          (b)  The execution and delivery of this Agreement have been duly
               authorized and approved by all requisite corporate action;

          (c)  It has all requisite power and authority to enter into this
               Agreement and perform its obligations hereunder;

          (d)  The execution and delivery of this Agreement does not, and
               consummation of the transactions contemplated herein will not,
               violate any of the material provisions of its organizational
               documents, any material agreement pursuant to which CPC or its
               properties are bound or, to its knowledge, any material laws
               applicable to CPC; and

          (e)  This Agreement is valid, binding, and enforceable against it in
               accordance with its terms, subject to bankruptcy, moratorium,
               insolvency, and other laws generally affecting creditors' rights
               and general principles of equity (whether applied in a proceeding
               in a court of law or equity).

     2.2  WPC hereby represents and warrants to CPC that on and as of the date
hereof:

          (a)  It has all requisite power and authority to carry on the business
               in which it is engaged and to perform its respective obligations
               under this Agreement;

          (b)  The execution and delivery of this Agreement have been duly
               authorized and approved by all requisite partnership action;

          (c)  It has all requisite power and authority to enter into this
               Agreement and perform its obligations hereunder;

          (d)  The execution and delivery of this Agreement does not, and
               consummation of the transactions contemplated herein will not,
               violate any of the material provisions of its organizational
               documents, any material agreement pursuant to which WPC or its
               properties are bound or, to its knowledge, any material laws
               applicable to WPC;  and

          (e)  This Agreement is valid, binding, and enforceable against it in
               accordance with its terms, subject to bankruptcy, moratorium,
               insolvency, and other laws generally affecting creditors' rights
               and general principles of equity (whether applied in a proceeding
               in a court of law or equity).

                                       7
<PAGE>
                                              "Confidential Treatment Requested.
                                                  The redacted material has been
                                          separately filed with the Commission."

 
                                  ARTICLE III
                                      TERM
                                      ----

     3.1  Unless otherwise provided herein, this Agreement shall remain in
* full force and effect for a period of REDACTED Years from the Effective Date
  hereof and shall continue from Year to Year thereafter unless terminated by
* either Party hereto at the end of such REDACTED Year period or any Yearly
  anniversary thereafter by giving the other Party at least ninety (90) Days,
  but not more than one hundred eighty (180) Days, advance written notice of its
  intention to so terminate.

     3.2  Notwithstanding Section 3.1 above, this Agreement may be terminated as
follows:

          (a)  By the non-defaulting Party, upon thirty (30) Days written notice
               to the other Party, after it has been determined through the
               alternative dispute resolution procedures of Article XIII that a
               Material Default has occurred in the performance of a Party's
               obligations hereunder (it being understood that, for purposes of
               the foregoing, "Material Default" shall mean that the arbitrators
               have determined that (i) in consequence of such default, the
               objectives of this Agreement (as expressed in the Master Alliance
               Agreement of even date herewith by and among CUSA, CPC, WPC and
               others) are not being met and (ii) the defaulting Party failed to
               take the steps necessary to accomplish such objectives);

          (b)  By a Party, in the event the other Party is dissolved (unless the
               successor to such dissolved Party or its assets is an Affiliate
               of CPC or WPC);

          (c)  By a Party, if a Bankruptcy Event occurs with respect to the
               other Party; or

          (d)  By CPC, upon the occurrence of a Refinery Closure Event as
               provided in Section 3.3.

In the event the Refinery is sold to a third Person not affiliated with CPC, the
reference to the Master Alliance Agreement set forth in Section 3.2(a), above,
shall be inapplicable.

     3.3  A Refinery Closure Event (as hereinafter defined) shall be presumed to
be a Material Default, and the provisions of this Section 3.3 shall apply,
notwithstanding any other provisions of this Agreement to the contrary
(including but not limited to the provisions of Section 3.2 and the alternative
dispute resolution provisions of Article XIII).  Within fifteen (15) Days after
the receipt by WPC of written notice that a Refinery Closure Event has 

                                       8
<PAGE>
 
occurred, senior executives of both Parties shall meet in person and attempt in
good faith, through the process of discussion and negotiation, to resolve all
disputes and claims arising from the Refinery Closure Event. If, within fifteen
(15) Days after such meeting, such senior executives cannot so resolve all such
disputes and claims, either Party shall have the right to submit such disputes
and claims to arbitration. The Party exercising such right shall submit an
Arbitration Notice to the other Party in accordance with Section 13.1(d) within
sixty (60) Days after the date of the initial meeting of the Parties' senior
executives. Unless the Parties otherwise agree in writing, the failure of either
Party to make such submission within such sixty (60) Days period shall waive all
rights of both Parties in respect of such disputes and claims arising from such
Refinery Closure Event. It is understood and agreed that the provisions of
Sections 13.1(a) through 13.1(c) shall not apply to any dispute arising from a
Refinery Closure Event. If the arbitrators determine that a Refinery Closure
Event has occurred, CPC shall have the right to terminate this Agreement upon
thirty (30) Days written notice to WPC. "Refinery Closure Event" shall mean a
shutdown of the Refinery or any operating unit thereof for more than twenty-four
(24) consecutive hours that occurs more than one time during any twelve (12)
Month period as a result of WPC's unexcused failure to deliver Feedstock or
purchase Refinery Products in accordance with this Agreement.

     3.4  It is agreed and understood that CPC, in its sole discretion, may
permanently close the Refinery at any time during the term of this Agreement.
Upon such permanent closure, CPC and WPC shall be relieved of any further
obligations under this Agreement, if CPC has provided WPC with written notice of
such closure at least one hundred and eighty (180) Days prior to the date of
such closure.

     3.5  Upon the termination of this Agreement, any monies due and owing
either Party shall be paid to the other Party pursuant to the terms hereof and
any refunds due either Party shall be made at the earliest possible time, and in
any event no later than sixty (60) Days after the expiration or termination of
this Agreement.  All audit rights shall survive for the period prescribed by
Section 11.8.

     3.6  Termination of this Agreement hereunder shall be cumulative of any
other rights or remedies that the terminating Party may have in connection with
such termination, including, but not limited to, damages and injunctive relief.

                                   ARTICLE IV
                       QUANTITY AND FEEDSTOCK NOMINATIONS
                       ----------------------------------

     4.1  During the term of this Agreement, unless WPC is excused from
supplying Feedstock, or CPC is excused from purchasing Feedstock pursuant to the
terms and provisions hereof, WPC agrees to sell, or cause to be sold, to CPC,
and CPC agrees to purchase from WPC, the Nominated Volumes of each Feedstock
nominated by CPC.   All Feedstock sold by WPC and delivered to CPC shall be used
solely by CPC as feedstock or fuel in the Refinery.  Unless mutually agreed to
by the Parties, CPC's nominations, and WPC's obligation to sell, shall not
exceed (i) four thousand five hundred Barrels per Day (4,500 BPD) of Isobutane
and (ii) two thousand Barrels per Day (2,000 BPD) of Normal Butane or Mixed
Butane (the 

                                       9
<PAGE>
 
Required Volumes). Every six (6) Months after the Effective Date, CPC and WPC
shall meet to discuss the appropriate levels of Required Volumes, after which
CPC shall have the right to make reasonable adjustments to said Required Volumes
as necessary and appropriate after taking into consideration CPC's good faith
estimate of the volumes that will be needed during the subsequent six (6) Month
period. However, WPC shall have no obligation to sell volumes in excess of the
previously established Required Volumes until ninety (90) Days after its receipt
of written notice from CPC of any such adjustment. During any Delivery Month in
no event shall (i) WPC be obligated to sell more than the Nominated Volumes and
(ii) CPC be obligated to purchase more than ninety-five percent (95%) of the
Nominated Volumes. To the extent that Section 2.306 of the Texas Business and
Commerce Code, or any provision of any other law with similar provisions
(collectively, "Output Contract Laws") are held to apply to this Agreement and
the transactions hereby contemplated, the Parties agree that, so long as the
Contract Quantity does not exceed the Required Volumes, such Contract Quantity
shall not be deemed unreasonably disproportionate to any stated estimate or to
any normal or otherwise comparable prior requirements of CPC. Notwithstanding
the foregoing, if CPC needs Emergency Supplies of Feedstock(s), WPC will use
every reasonable effort to obtain such Feedstocks on behalf of CPC, but will
have no liability to CPC if, through WPC's exercise of every reasonable effort,
it is unable to supply such Emergency Supplies. In addition to any applicable
Transportation Costs reasonably incurred in connection therewith, all out of
pocket costs and expenses reasonably incurred by WPC in obtaining and delivering
Emergency Supplies of Feedstocks in excess of one hundred and five percent
(105%) of the Nominated Volumes shall be paid by CPC or, as applicable,
reimbursed to WPC by CPC through the billing and payment procedures of Article
XI.

     4.2  Subject to the terms and provisions hereof, including, without
limitation, the provisions respecting the Required Volumes set forth in Section
4.1, above, CPC agrees to purchase from WPC and WPC agrees to sell to CPC, one
hundred percent (100%) of CPC's Feedstock requirements.  However, in the event
WPC is unable to provide Feedstocks in excess of the Nominated Volumes or
Required Volumes, as applicable, CPC shall have the right to purchase from third
Persons volumes in excess of such Nominated Volumes or Required Volumes.  In
addition, WPC agrees to purchase from CPC and CPC agrees to sell to WPC all
Refinery Products. The foregoing, however, shall not be construed as limiting
CPC's right to transfer, from time to time, Feedstocks and Refinery Products (i)
from the Refinery to one or more other refineries owned by CPC as of the
Effective Date (such refineries being collectively called the "Refineries"), or
(ii) to the Refinery from one or more of the Refineries.

     4.3  Solely for planning purposes, CPC shall provide WPC with a three (3)
Month rolling estimate of Feedstock volume needs and expected Refinery Product
availability on the first Business Day of each Month during the term of this
Agreement.  In addition, CPC shall nominate to WPC by the first Business Day of
the prior Month all volumes of each Feedstock to be purchased by CPC each Day
during the next succeeding Month (the "Nominated Volumes").  No later than the
tenth Day of the Month immediately preceding the Delivery Month, CPC shall have
the right to increase the Nominated Volumes for each Feedstock to be purchased
in the immediately succeeding Delivery Month.  If CPC increases the Nominated

                                       10
<PAGE>
 
Volumes after the tenth (10th) Day of the Month prior to the Delivery Month so
as to exceed the Contract Quantity, such excess shall be deemed Emergency
Supplies.

     4.4  To minimize the costs and expenses associated with Emergency Supplies
and variances between Nominated Volumes and the volumes of Feedstock actually
taken, CPC and WPC agree to establish a scheduling committee (the "Scheduling
Committee") to perform the duties as outlined below. The Scheduling Committee
shall be comprised of members from both CPC and WPC and where appropriate, shall
include a representative of CPC's Transportation Planning & Services Group (also
referred to as "TP&S").  CPC and WPC each shall bear their own costs and
expenses associated with the Scheduling Committee and its activities.  The
duties of the Scheduling Committee will include, but will not be limited to, the
following:

          (a)  administering and coordinating the routine business of the
               Scheduling Committee including forecasting, planning, and
               scheduling of Feedstock and Refinery Product deliveries and
               movements;

          (b)  determining and developing strategies with respect to Scheduling
               Committee activities;

          (c)  developing, monitoring, and communicating mutually agreed to
               standards of performance;

          (d)  monitoring the nomination procedures, deliveries of Feedstocks
               and Refinery Products, and adjustments to Required Volumes;

          (e)  reviewing all significant equipment, design, process, and
               operating changes affecting the volumes of Feedstocks needed by
               the Refinery and/or the volumes of Refinery Products produced at
               the Refinery;

          (f)  conducting regularly scheduled planning, problem solving, and
               expense review meetings;

          (g)  participating in the alternative dispute resolution procedures
               and set forth in Article XIII hereinafter;

          (h)  developing procedures for handling Offspec Feedstock and Offspec
               Refinery Products; and

          (i)  developing procedures for making the Parties' performance
               hereunder more efficient and cost-effective.

     4.5  The Parties shall use every reasonable effort to nominate, deliver,
and receive, as applicable, Feedstock and Refinery Products on a ratable Daily
basis; however, variations between the volumes nominated, taken, or delivered
may occur.  The Scheduling Committee shall meet periodically to allocate between
the Parties, on a fair and equitable basis, any costs 

                                       11
<PAGE>
 
and expenses resulting from Monthly variations in excess of those permitted in
determining the Contract Quantity, including, but not limited to, storage costs
for Feedstocks and Refinery Products, rail, tank car, or barge rental costs,
demurrage charges, and any other costs and expenses incurred in connection with
such Monthly variations. If the Scheduling Committee cannot agree on a fair and
equitable allocation of expenses within forty-five (45) Days after the
Submission Date (as defined in Section 13.1(b)), the dispute resolution
provisions of Article XIII shall apply. In addition to the foregoing, CPC shall
pay to WPC the Keep Whole Acquisition Price for Emergency Supplies, but only to
the extent such Emergency Supplies exceed one hundred and five percent (105%) of
the Nominated Volumes.

     4.6  With respect to any CPC Deficiency Quantity (as defined in Section
4.7) which exceeds five percent (5%) of the Nominated Volumes, CPC agrees to pay
to WPC the arithmetic product of (i) such CPC Deficiency Quantity in excess of
five percent (5%) of the Nominated Volumes and (ii) one (1) cent per Gallon.
CPC shall pay such amount in accordance with Article XI.  In addition, any Keep
Whole Disposition Amount (as defined in Section 4.7) payable in connection with
such CPC Deficiency Quantity in excess of five percent (5%) of the Nominated
Volumes shall be determined in accordance with Section 4.7 and shall be paid by
CPC or WPC, as applicable, in accordance with Article XI.

     4.7  (a)  Keep Whole Disposition Amount shall mean the following:
               -----------------------------  

                         KWDA=[(A-B) x (C-D)] + E

               where

               KWDA =    the Keep Whole Disposition Amount;

               A-B =     the CPC Deficiency Quantity;

               C-D =     the Price Differential; and

               E =       either the Third Party Costs or the Storage Costs,
                         as applicable.

               For purposes of the foregoing, the variables and terms set forth
               below have the following meanings:

               A =       the total Nominated Volumes for each Feedstock
                         nominated by CPC for delivery during the applicable
                         Delivery Month that are available by WPC for delivery
                         to CPC, minus the total quantities of each Feedstock
                         that CPC is excused from purchasing hereunder during
                         the applicable Delivery Month;

                                       12
<PAGE>
 
               B =       the quantities of each Feedstock actually accepted by
                         CPC during the applicable Delivery Month;

               C =       the price per Gallon of each Feedstock payable by CPC
                         to WPC for the applicable Delivery Month in accordance
                         with Section 5.1 (the "Contract Price");

               D =       either (i) if WPC sells the CPC Deficiency Quantity,
                         the price per Gallon obtained by WPC for such CPC
                         Deficiency Quantity in an arm's length sale made during
                         such Delivery Month to a third Person who is not an
                         Affiliate of WPC, or (ii) if WPC stores the CPC
                         Deficiency Quantity, a price per Gallon equal to the
                         Monthly average, during the applicable Delivery Month,
                         of the Daily high and low prices per Gallon quoted by
                         OPIS for Mont Belvieu, Texas (Non-TET) for each
                         Feedstock for which there is a CPC Deficiency Quantity
                         during such Delivery Month ((i) or (ii), as applicable,
                         being herein called the "Alternate Price").

                    "Third Party Costs" shall mean, if WPC sells the CPC
                    Deficiency Quantity, all Transportation Costs and
                    fractionation costs, if applicable, reasonably incurred by
                    WPC in connection with the sale of the CPC Deficiency
                    Quantity (without duplication of any Transportation Costs or
                    fractionation costs previously paid by CPC under Section
                    4.5).

                    "Storage Costs" shall mean, if WPC stores the CPC Deficiency
                    Quantity, Transportation Costs and fractionation costs, if
                    applicable, reasonably incurred by WPC to and at the storage
                    facility of the CPC Deficiency Quantity (without duplication
                    of any Transportation Costs or fractionation costs
                    previously paid by CPC under Section 4.5), which
                    Transportation Costs and fractionation costs shall not
                    exceed the Transportation Costs and fractionation costs, if
                    applicable, reasonably incurred in connection with such CPC
                    Deficiency Quantity if it were transported to and at Mont
                    Belvieu, Texas.

          (b)  If the Alternate Price exceeds the Contract Price by more than
               one (1) cent ($0.01) per Gallon, the amount computed in
               accordance with the first grammatical sentence of Section 4.6
               shall not be paid, and instead WPC shall pay CPC, in accordance
               with Article XI, an amount calculated as follows:

                         [[(D-C) - $0.01/Gallon] x (A-B)] - E]

                                       13
<PAGE>
                                              "Confidential Treatment Requested.
                                                  The redacted material has been
                                          separately filed with the Commission."

 
          (c)  It is understood and agreed that the CPC Deficiency Quantity
               shall always be equal to or greater than zero (0) and shall never
               exceed the Nominated Volumes for the applicable Delivery Month.

          (d)  In disposing of Feedstock in a situation where a Keep Whole
               Disposition Amount is applicable, WPC shall use every reasonable
               effort to dispose of same at the highest possible spot purchase
               price, taking into consideration the location of the Refinery,
               the prior notice given by CPC to WPC, and other factors beyond
               WPC's control.

                                   ARTICLE V
                                     PRICE
                                     -----
                                        
    5.1   Except as otherwise provided herein, CPC shall pay WPC for the
* Feedstock(s) purchased hereunder a price equal to REDACTED as quoted by the
  Oil Price Information Service ("OPIS") for Mont Belvieu, Texas (Non-TET) on
  the last five (5) Business Days of the Month prior to the Delivery Month plus
* Transportation Costs plus REDACTED per Gallon.

     5.2  Except as otherwise provided herein, WPC shall pay CPC for the
* Refinery Products purchased hereunder REDACTED (the "Netback Percentage") of
  (i) the Netback Price, if such Refinery Products are immediately sold by WPC,
  or (ii) a price equal to the Monthly average of the Daily high and low prices
  of each Refinery Product delivered during the Delivery Month as quoted by OPIS
  for Mont Belvieu, Texas (Non-TET), less Transportation Costs or T&F Costs to
  and at Mont Belvieu, Texas, if such Refinery Products are stored by WPC for
  its own account during the applicable Delivery Month. WPC shall use every
  reasonable effort to obtain the highest Netback Price for Refinery Products.
  Notwithstanding the foregoing, it is understood and agreed that WPC's share of
* the Netback Price received from the disposition of Refinery Products (i.e.,
* REDACTED), shall never be less than REDACTED per Gallon of the Refinery
  Products delivered to WPC at the Delivery Point. WPC agrees to use
  commercially reasonable efforts to maximize the value to CPC in connection
  with the disposition of Refinery Products.

     5.3  With respect to any Mixed Butanes or other mixed Feedstocks or
Refinery Products delivered hereunder, the price paid shall be based on the
primary components of each Feedstock or Refinery Product which meet the
specifications set forth in Exhibits A or B, as applicable, contained in such
Mixed Butanes or other mixed Feedstocks or Refinery Products.

     5.4  If for any reason the OPIS index for a particular Feedstock or
Refinery Product should cease to be published, the Parties agree promptly and in
good faith to negotiate a mutually satisfactory Alternate Index or substitute
methodology for calculating the price for 

                                       14
<PAGE>
 
such Feedstock or Refinery Product (the "Alternate Index"). If, on or before
thirty (30) Days after the index used to determine the price ceases to be
published, the Parties are unable to agree on an Alternate Index upon which to
base the calculation of the price, the Parties shall submit such determination
to the alternative dispute resolution procedures in accordance with the
provisions of Article XIII hereinafter, which alternative dispute resolution
procedures will determine the Alternate Index. From the date on which the index
price used to determine the price for a particular Feedstock or Refinery Product
ceases to be available until the Alternate Index is determined, the price for
such Feedstock or Refinery Product shall be the average of the prices in effect
(or that would have been in effect) during the twelve (12) Months preceding the
Month in which the index upon which the price was based ceased to be available,
which price shall be effective until the effective date of the Alternate Index
determined as set forth in this Section 5.4. Upon the determination of an
Alternate Index, the price will be adjusted retroactively to the date on which
the index upon which the price previously was based ceased to be available, plus
interest thereon at the Base Rate.

     5.5  Every five (5) Years after the Effective Date of this Agreement,
either Party shall have the option to open this Agreement solely for the purpose
of renegotiating the pricing provisions hereof.  To exercise such option, a
Party at least ninety (90) Days before the expiration of such five (5) Year
period must provide to the other Party written notification (the "Renegotiation
Notice") of its desire to renegotiate the price for the Feedstocks or Refinery
Products sold and purchased hereunder.  In any such renegotiations, the Parties
shall continue to recognize that the price for Feedstocks and/or Refinery
Products must reflect market prices for Feedstocks and/or Refinery Products in
El Paso, Texas.  If, after negotiating in good faith for a period of ninety (90)
Days following the date of the Renegotiation Notice, the Parties are unable to
agree upon a mutually acceptable price for such Feedstock(s) or Refinery
Product(s), the matter shall be submitted to the alternative dispute resolution
procedures as provided in Article XIII hereof.  During the period while
negotiations are ongoing until (i) a new price is agreed to or (ii) a new price
is established as provided herein, the price for the Feedstock or the Refinery
Product sold and purchased hereunder shall be determined in accordance with the
pricing formula that was applicable immediately prior to the date of the
Renegotiation Notice.  If a new price is established under this Section 5.5,
whether by renegotiation, arbitration, or otherwise, such new price shall be
effective as of, and shall, if necessary, be made retroactive to, the first Day
of the applicable five (5) Year period immediately following the Renegotiation
Notice, plus interest thereon at the Base Rate.

     5.6  In the event conditions change such that this Agreement causes, or
could reasonably be expected to cause, a material long term economic or
operational hardship to either Party, upon the written request of either Party,
CPC and WPC shall meet to renegotiate in good faith such burdensome terms and
provisions so as to make them fair and equitable.  Such renegotiations shall
occur within thirty (30) Days of the date of the non-requesting Party's receipt
of such written request for such renegotiations.  If the parties are unable to
agree on new provisions to replace such burdensome terms and provisions within
ninety (90) Days of the non-requesting Party's receipt of such written request,
the matter shall be submitted to the alternative dispute resolution procedures
set forth in Article XIII hereof.  It is understood and agreed that the rights
granted in this Section 5.6 can only be used by a Party to 

                                       15
<PAGE>
 
commence good faith renegotiations once during each Year during the term hereof.
If new provisions are agreed upon under this Section 5.6, whether by
renegotiation, arbitration, or otherwise, such new provisions shall be effective
as of, and shall, if necessary, be made retroactive to, the date on which the
notice commencing renegotiations under this Section 5.6 was given, plus interest
thereon at the Base Rate.

                                   ARTICLE VI
                                   DELIVERIES
                                   ----------

     6.1  The Feedstock to be sold by WPC hereunder shall be delivered by WPC
(or at WPC's direction) to CPC or to CPC's designated representative for the
account of CPC, at the Delivery Points (as defined in Section 6.2).  The
Refinery Products to be sold hereunder by CPC to WPC shall be delivered by CPC
at the Delivery Points in Section 6.2.

     6.2  The point(s) of delivery for Feedstock and Refinery Product sold and
delivered hereunder (hereinafter the "Delivery Point(s)") shall be determined as
follows:

     (a)  In the event delivery is to be to or from a pipeline, the Delivery
          Point shall be located, and delivery of Feedstock or Refinery Product
          shall be deemed to occur, at the point at which Feedstock or Refinery
          Product passes the pipeline meter.  If pipeline delivery is by in-line
          inventory transfer, delivery shall be deemed to occur on the date and
          time that the relevant pipeline carrier advises CPC and WPC, by
          product transfer order, book transfer, or letter of transfer, that
          Feedstock or Refinery Product shall be transferred to CPC's account,
          and the Delivery Point shall be the location of the Feedstock or
          Refinery Product in the pipeline of the pipeline carrier on the Day
          and time that such in-line transfer of  Feedstock or Refinery Product
          is deemed to occur.  The Parties hereto understand and agree that WPC
          has no control over the operations of the pipeline carrier and
          therefore cannot control when Feedstock transfer to CPC's account or
          Refinery Product transfer to WPC's account by the pipeline carrier
          will, in fact, occur.

     (b)  In the event delivery is to be by a rail car, truck, or barge whether
          owned, operated, leased, or hired by WPC or CPC, the Delivery Point
          shall be located, and delivery of Feedstock or Refinery Product shall
          be deemed to occur, (i) at the point at which the Feedstock or
          Refinery Product passes through the flange connecting the WPC's or
          CPC's owned, operated, leased, or hired rail car, truck, or barge that
          is used to deliver the Feedstock to the Refinery, to the receiving
          facility equipment of CPC or WPC, whether said rail car, truck, or
          barge is unloaded by CPC or WPC directly or on behalf of CPC or WPC
          through CPC's or WPC's agent or (ii) at the point at which the rail
          car, truck, or barge which is used to deliver the Feedstock is
          constructively placed and/or spotted on arrival at or near the
          Refinery and available for delivery, whichever is earlier.

                                       16
<PAGE>
 
     (c)  In the event delivery is to be by a rail car, truck, or barge whether
          owned, operated, leased, or hired by WPC or CPC, the Delivery Point
          shall be located, and delivery of Refinery Product shall be deemed to
          occur, (i) at the point at which the Refinery Product passes through
          the flange connecting the rail car, truck, or barge which is used to
          receive the Refinery Product, as long as such rail car, truck, or
          barge is immediately released by the Refinery to WPC for transport, or
          (ii) if the rail car, truck, or barge is not immediately released to
          WPC for transport, at the point at which such rail car, truck, or
          barge is released to WPC for transport, whichever is later.

     (d)  In the event delivery is into or from a storage facility, except as
          provided below in this Section 6.1, the Delivery Point shall be
          located, and delivery of Feedstock shall be deemed to occur, at the
          point at which the Feedstock passes the flange between the delivering
          or receiving line of the storage facility and the receiving or
          delivering equipment, as applicable.  If delivery is by in-storage
          transfer, delivery of Feedstock shall be deemed to occur on the date
          and time that the operator of the storage facility advises WPC and CPC
          by product transfer order, book transfer, or letter of transfer, that
          Feedstock shall be transferred to CPC's account, and the Delivery
          Point shall be the storage facility in which the Feedstock is then
          located; provided, however, that in the case of an in-storage transfer
          of Feedstock located in a storage facility wholly owned by WPC or
          leased by WPC and in which CPC owns no interest (leased or otherwise),
          for purposes of determining when possession and control of the
          Feedstock in storage and the risk of loss, damage, and liability
          associated therewith passes from WPC to CPC the Delivery Point shall
          be the point at which the Feedstock passes the discharge flange of
          WPC's owned or leased storage facility connecting the delivering line
          to the receiving line.  To the extent that WPC does not operate the
          storage facility, the parties hereto understand and agree that WPC
          cannot control when the Feedstock transfer to CPC's account by the
          storage facility will, in fact, occur.

     6.3  Title to and risk of loss associated with the Feedstocks delivered
hereunder shall pass from WPC to CPC upon the commencement of the delivery of
such Feedstocks at the Delivery Point unless such Feedstock is rejected in
accordance with Article VII.  CPC shall be responsible for all risk of loss,
damage, or liability to the extent that any such loss, liability, or damage
arises from acts or omissions occurring after the commencement of physical
delivery of the Feedstock at and downstream of the Delivery Point(s), unless
such Feedstock is rejected in accordance with Article VII.  In the event
delivery of the Feedstock sold hereunder is by in-storage transfer of Feedstock,
title to the Feedstock shall pass from WPC to CPC at the point in time when such
in-storage transfer shall be deemed to have occurred as provided in Section 6.2,
above.

     6.4  Except as hereinafter provided, title to and risk of loss associated
with the Refinery Products delivered hereunder shall pass from CPC to WPC upon
the commencement of the delivery of such Refinery Products at the Delivery
Points, unless such Refinery Products 

                                       17
<PAGE>
 
are rejected in accordance with Article VII. WPC shall be responsible for all
risk of loss, damage, or liability to the extent that any such loss, liability,
or damage arises from acts or omissions occurring after the commencement of
physical delivery of the Refinery Product at and downstream of the Delivery
Point(s), unless such Refinery Products are rejected in accordance with Article
VII. Except for Type A Offspec Refinery Products knowingly accepted, title to
and risk of loss associated with Offspec Refinery Products delivered hereunder
shall remain with CPC until such Offspec Refinery Products meet the
specifications set forth in Section 7.2 hereinafter. Notwithstanding the
foregoing, CPC shall be responsible for all risk of loss, damage, or liability
to the extent such loss, liability, or damage arises from or is in any way
related to the existence of carbonyl sulfide ("COS") in the Propane delivered
hereunder equal to or in excess of two parts per million (2 ppm) and WPC shall
be responsible for any such risk of loss to the extent such loss, liability, or
damage arises from or is in any way related to the existence of COS in such
Propane in an amount less than two parts per million (2 ppm).

     6.5  The following rules shall be applicable to the transportation,
loading, and unloading of Feedstocks or Refinery Products at the Delivery Point:

          (a)  If rail cars subject to payment of demurrage or any other similar
               charges to a third Person not affiliated with either Party are
               used to deliver Feedstock to the Delivery Point or to transport
               Refinery Products from the Delivery Point, CPC agrees to unload
               or load, as the case may be, and start the relevant cars on the
               return trip in accordance with the detention policy of the owner
               or operator of such rail car equipment and CPC further agrees to
               pay any and all such charges that may be due thereunder.
               
          (b)  CPC shall be liable for the payment of invoices from the
               railroad for demurrage and hazardous materials storage charges
               incurred by WPC as the prepaid shipper due to CPC's inability to
               receive a rail car and/or have a rail car placed on CPC's siding;
               and

          (c)  Rail cars shall not be diverted while in transit except upon
               prior written authorization of WPC.  Any charge incurred by WPC
               for the diversion of rail cars by CPC shall be for the account of
               CPC.

          (d)  If WPC's owned or leased trucks are used to deliver Feedstock to
               the Delivery Point or to transport Refinery Products from the
               Delivery Point, CPC agrees to unload or load, as the case may be,
               immediately upon arrival at the Delivery Point, and CPC's failure
               to do so shall render CPC liable to WPC for damages incurred as a
               result of such delay.

          (e)  For Feedstock sold hereunder, WPC will be liable for all rail car
               shortages claimed by CPC in excess of one percent (1%) of the net
               Gallons reflected on the bill of lading and acknowledged by the
               railroad agent's signature prior to unloading; provided, however,
               that such shortages, if any, are reported in writing to WPC
               within twenty-four 

                                       18
<PAGE>
 
               (24) hours after delivery by the carrier and prior to the
               unloading of the shipment in which the relevant shortage occurs.
               CPC shall ask WPC for permission to unload, and WPC, at its
               expense, shall have the right to inspect each car at its
               destination within forty-eight (48) hours after receipt of
               written notice of such shortage. All demurrage charges arising
               from the failure of WPC to release the car for unloading within
               such forty-eight (48) hour period shall be paid by WPC.
               Similarly, WPC shall be liable for all truck shortages claimed by
               CPC in excess of three percent (3%) of the net Gallons reflected
               on the bill of lading; provided, however, that such shortages, if
               any, are noted on the delivery ticket and acknowledged by the
               truck driver's signature prior to unloading. The failure of CPC
               to observe this provision or any action by CPC which impedes
               identification of an alleged defect shall operate as a waiver of
               CPC's rights to make any such claim.

          (f)  For Refinery Products purchased hereunder, CPC will be liable for
               all rail car shortages claimed by WPC in excess of one percent
               (1%) of the net Gallons reflected on the bill of lading and
               acknowledged by the railroad agent's signature prior to
               unloading; provided, however, that such shortages, if any, are
               reported in writing to CPC within twenty-four (24) hours after
               delivery by the carrier and prior to the unloading of the
               shipment in which the relevant shortage occurs.  WPC shall ask
               CPC for permission to unload, and CPC, at its expense, shall have
               the right to inspect each car at its destination within forty-
               eight (48) hours after receipt of written notice of such
               shortage.  All demurrage charges arising from the failure of CPC
               to release the car for unloading within such forty-eight (48)
               hour period shall be paid by CPC.  Similarly, CPC shall be liable
               for all truck shortages claimed by WPC in excess of three percent
               (3%) of the net Gallons reflected on the bill of lading;
               provided, however, that such shortages, if any, are noted on the
               delivery ticket and acknowledged by the truck driver's signature
               prior to unloading.  The failure of WPC to observe this provision
               or any action by WPC which impedes identification of an alleged
               defect shall operate as a waiver of WPC's rights to make any such
               claim.

Notwithstanding the foregoing, if the detention and/or demurrage charges set
forth above are insufficient to cover any such charges paid by WPC to such third
Person not affiliated with WPC, CPC shall reimburse WPC for such amounts.

     6.6  If, CPC uses a rail car, truck, or barge leased by WPC for purposes
other than those contemplated by WPC's lease, CPC shall be responsible for, and
agrees to indemnify and hold WPC harmless from and against, all costs,
liabilities, and expenses arising out of, or in any way associated with, CPC's
use of such equipment, including, but not limited to, cleaning and inspection
costs and additional rental fees for such equipment and/or for other equipment
required to be leased as a result of CPC's use.

                                       19
<PAGE>
 
                                  ARTICLE VII
                                    QUALITY
                                    -------

     7.1  All Feedstocks sold by WPC and purchased by CPC hereunder shall meet
the specifications set forth in Exhibit A, attached hereto and made a part
hereof.  CPC shall have the right to reject Feedstock which fails to meet such
quality specifications ("Offspec Feedstock").  All costs associated with the
return of Offspec Feedstock shall be borne by WPC.

     7.2  All Refinery Products sold by CPC and purchased by WPC hereunder shall
meet the specifications set forth in Exhibit B, attached hereto and made a part
hereof.  WPC shall have the right to reject any Refinery Product which fails to
meet such quality specifications ("Offspec Refinery Product").  All Offspec
Refinery Products shall be deemed to be either Type A Offspec Refinery Products
or Type B Offspec Refinery Products.  "Type A Offspec Refinery Products" are
Offspec Refinery Products of sufficient quality to permit them to be sold to a
third Person not Affiliated with CPC or WPC at a discount off the price provided
for Refinery Products in Article V.  "Type B Offspec Refinery Products" are
Offspec Refinery Products that are not of sufficient quality to permit them to
be sold to a third Person not Affiliated with CPC or WPC at a discount off the
price provided for Refinery Products in Article V.  All costs associated with
the return and/or disposal of Offspec Refinery Products shall be borne by CPC.

     7.3  Should the Feedstock delivered hereunder to CPC, or to CPC's
designated representative for the account of CPC, fail at any time to conform to
the specifications set forth in Exhibit A, either Party shall notify the other
Party of any such failure, and WPC immediately shall undertake and diligently
pursue such acts as may be necessary to correct such failure, including
treatment to the extent such treatment is economical in WPC's opinion, so as to
deliver Feedstock conforming to the specifications set forth above; but nothing
contained in this Article VII or any other part of this Agreement shall be
construed to affect CPC's right, at any time and from time to time, to reject
any Feedstock not conforming to said specifications and to refuse or suspend
receipt until it is established to CPC's reasonable satisfaction that subsequent
deliveries of Feedstock will conform to said specifications.  The term of this
Agreement shall not be extended by the length of time of any period or periods
when deliveries have been rejected, refused, or suspended as provided for
herein.  Notwithstanding the foregoing, the knowing acceptance by CPC of any
Offspec Feedstock shall constitute a waiver by CPC of any and all other rights
and remedies available to CPC under this Agreement or otherwise with respect to
WPC's tender of such Offspec Feedstock and all risk of loss, damage, or
liability arising out of CPC's ownership, control, possession, or use of such
Offspec Feedstock shall pass to and be borne by CPC.  If it is subsequently
determined that CPC unknowingly accepted Offspec Feedstock, the Parties will
mutually agree upon a discounted price for such Offspec Feedstock to reflect its
diminution in value from Feedstock meeting the specifications hereof.  If the
Parties are unable to agree on a mutually acceptable discount price for such
Offspec Feedstock, the matter shall be subjected to the alternative dispute
resolution procedures set forth in Article XIII hereinafter.

                                       20
<PAGE>
 
     7.4  Should the Refinery Products delivered hereunder to WPC, or to WPC's
designated representative for the account of WPC, fail at any time to conform to
the specifications set forth in Exhibit B, either Party shall notify the other
Party of any such failure, and CPC immediately shall undertake and diligently
pursue such acts as may be necessary to correct such failure, including
treatment to the extent such treatment is economical in CPC's opinion, so as to
deliver Refinery Product conforming to the specifications set forth above; but
nothing contained in this Article VII or any other part of this Agreement shall
be construed to affect WPC's right, at any time and from time to time, to reject
any Refinery Product not conforming to said specifications and to refuse or
suspend receipt until it is established to WPC's reasonable satisfaction that
subsequent deliveries of Refinery Product will conform to said specifications.
The term of this Agreement shall not be extended by the length of time of any
period or periods when deliveries have been rejected, refused, or suspended as
provided for herein.  Notwithstanding the foregoing, the knowing acceptance by
WPC of any Type A Offspec Refinery Product  shall constitute a waiver by WPC of
any and all other rights and remedies available to WPC under this Agreement or
otherwise with respect to CPC's tender of such Type A Offspec Refinery Product,
and all risk of loss, damage or liability arising out of WPC's ownership,
control , possession, or use of such Type A Offspec Refinery Product shall pass
to and be borne by WPC.  If it is subsequently determined that WPC unknowingly
accepted Type A Offspec Refinery Products, the Parties will mutually agree upon
a discounted price for such Type A Offspec Refinery Products to reflect their
diminution in value from Refinery Products meeting the specifications hereof.
If the Parties are unable to agree on a mutually acceptable discount price for
such Offspec Refinery Products, the matter shall be subjected to the alternative
dispute resolution procedures set forth in Article XIII hereunder.  CPC agrees
to INDEMNIFY and HOLD HARMLESS WPC, its Affiliates, and their respective
officers, directors, employees, agents, and contractors, from all actual losses,
costs, expenses, claims (including, without limitation, personal injury or
property damage claims), damages, and causes of action, including, without
limitation, reasonable attorneys' fees and costs of court (collectively, the
"Losses") incurred by WPC, such Persons, or such Affiliates arising out of, or
in any way associated with, the delivery to WPC of Propane that fails to meet
the specifications set forth in Exhibit B and is unknowingly accepted by WPC.

                                  ARTICLE VIII
                               WARRANTY OF TITLE
                               -----------------

     8.1  WPC warrants title to all Feedstocks sold and delivered by it to CPC,
and further warrants that WPC has the right to sell such Feedstocks and that
such Feedstocks meet the quality specifications as set forth herein and are free
from all liens, claims, or other charges.  THERE ARE, HOWEVER, NO OTHER
WARRANTIES OF ANY KIND WHATSOEVER, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT
LIMITATION, ANY WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY,
CONFORMITY TO MODELS OR SAMPLES, OR AGAINST INFRINGEMENT OF ANY PATENT,
TRADEMARK, COPYRIGHT, OR OTHERWISE, 

                                       21
<PAGE>
 
AND ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED BY WPC AND EXCLUDED FROM
THIS AGREEMENT.

     8.2  CPC warrants title to all Refinery Products sold and delivered by it
to WPC, and further warrants that CPC has the right to sell such Refinery
Products and that such Refinery Products meet the quality specifications as set
forth herein and are free from all liens, claims or other charges.  THERE ARE,
HOWEVER, NO OTHER WARRANTIES OF ANY KIND WHATSOEVER, EITHER EXPRESS OR IMPLIED,
INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE,
MERCHANTABILITY, CONFORMITY TO MODELS OR SAMPLES, OR AGAINST INFRINGEMENT OF ANY
PATENT, TRADEMARK, COPYRIGHT, OR OTHERWISE, AND ALL SUCH WARRANTIES ARE HEREBY
EXPRESSLY DISCLAIMED BY CPC AND EXCLUDED FROM THIS AGREEMENT.

                                   ARTICLE IX
                                     TAXES
                                     -----

     9.1  WPC shall be liable for and shall pay, or cause to be paid, or
reimburse CPC, if CPC has paid, all Taxes (other than environmental Taxes, which
environmental Taxes include, without limitation, Taxes imposed under Sections
4611, 4612, 4661, 4662, 4771, and 4772 and successor sections of the Internal
Revenue Code) applicable to the Feedstock sold hereunder upstream of the
Delivery Point(s).  If CPC is required to remit such Tax, the amount thereof
shall be deducted from any sums becoming due to WPC hereunder.  CPC shall be
liable for and shall pay, cause to be paid, or reimburse WPC, if WPC has paid,
all environmental Taxes and all Taxes applicable to the sale and/or delivery of
Feedstock hereunder at and downstream of the Delivery Point(s) including any
Taxes imposed or collected by a taxing authority with jurisdiction over CPC,
provided, however, when laws, ordinances or regulations permit or impose upon
WPC the obligation to collect or pay Taxes applicable to the sale and/or
delivery of Feedstock hereunder at the Delivery Point, WPC shall collect all
such Taxes from CPC, which shall be in addition to the applicable Price, and
remit the same to the appropriate governmental authority, unless CPC furnishes a
certificate of exemption.  WPC SHALL INDEMNIFY, DEFEND, AND HOLD CPC HARMLESS
FROM AND AGAINST ANY LIABILITY WITH RESPECT TO THE TAXES FOR WHICH WPC IS
LIABLE.

     9.2  CPC shall be liable for and shall pay, or cause to be paid, or
reimburse WPC, if WPC has paid, all Taxes (other than environmental Taxes, which
environmental Taxes include, without limitation, Taxes imposed under Sections
4611, 4612, 4661, 4662, 4771, and 4772 and successor sections of the Internal
Revenue Code) applicable to the Refinery Product sold hereunder upstream of the
Delivery Point(s).  If WPC is required to remit such Tax, the amount thereof
shall be deducted from any sums becoming due to CPC hereunder.  WPC shall be
liable for and shall pay, cause to be paid, or reimburse CPC, if CPC has paid,
all environmental Taxes and all Taxes applicable to the sale and/or delivery of
Refinery Product hereunder at and downstream of the Delivery Point(s) including
any Taxes imposed or collected by a taxing authority with jurisdiction over WPC,
provided, however, when laws, 

                                       22
<PAGE>
 
ordinances or regulations permit or impose upon CPC the obligation to collect or
pay Taxes applicable to the sale and/or delivery of Refinery Product hereunder
at the Delivery Point, CPC shall collect all such Taxes from WPC, which shall be
in addition to the applicable Price, and remit the same to the appropriate
governmental authority, unless WPC furnishes a certificate of exemption. CPC
SHALL INDEMNIFY, DEFEND, AND HOLD WPC HARMLESS FROM AND AGAINST ANY LIABILITY
WITH RESPECT TO THE TAXES FOR WHICH CPC IS LIABLE.

     9.3  While this Agreement remains in effect, CPC shall pay to WPC on
demand, from time to time, all amounts necessary to compensate WPC for any New
Taxes incurred by WPC after the Effective Date of this Agreement applicable to
the sale and/or delivery of Feedstock at and downstream of the Delivery
Point(s), and CPC SHALL INDEMNIFY, DEFEND, AND HOLD WPC FREE AND HARMLESS FROM
AND AGAINST ANY LIABILITY WITH RESPECT TO ALL SUCH NEW TAXES.  WPC will notify
CPC of the enactment of any New Taxes as promptly as practical after it obtains
knowledge thereof.  WPC will furnish CPC with a statement setting forth the
basis and amount of each request by WPC for compensation under this Section 9.3.
It is understood and agreed that the enactment of any material New Taxes shall
constitute a hardship under the provisions of Section 5.6, above.

     9.4  To claim an exemption from payment of a Tax, a Party shall provide a
certificate of exemption or other reasonably satisfactory evidence of exemption
from any Tax, and each Party agrees to cooperate with the other Party in
obtaining any such exemption.  In addition, WPC has provided CPC with, and CPC
acknowledges receipt of, the disclosure statement from WPC (as set forth in
Section 4101 of the Internal Revenue Code of 1986).

                                   ARTICLE X
                            MEASUREMENT AND ANALYSES
                            ------------------------

     10.1 On all deliveries into or out of rail cars, the quantity shall be
determined by official tank car capacity tables or slip tube gauges in
accordance with Gas Processors Association ("GPA") Publication 8162, latest
revision.  On all deliveries into or out of truck equipment, quantities shall be
determined by meter, rotary gauge or weighing, in accordance with GPA
Publications 8162 and 8186, latest revision.  On all deliveries into or out of
pipelines, quantities shall be determined by pipeline meter in accordance with
the America Petroleum Institute ("API") Manual of Petroleum Measurement
Standards.  For raw make mixtures, volumes of the component products shall be
determined (where practical) on a mass (pound) measurement basis in accordance
with the latest edition of GPA Publications 8173 and 8182.  On all deliveries
into or out of shore tanks, quantities shall be determined either meter or gauge
from a static tank in accordance with the API Manual of Petroleum Measurement
Standards and based upon the practice of the relevant terminal.  All quantities
shall be corrected to standard conditions of sixty degrees Fahrenheit (60
degrees F) and equilibrium vapor pressure in accordance with the API Manual of
Petroleum Measurement Standards, Chapter 14, Section B. The quantity and quality
of Feedstock and Refinery Product covered by this Agreement shall be measured
according to the current versions of the applicable standards of

                                       23
<PAGE>
 
API and the American Society for Testing Materials, if available. Each Party
shall be entitled to have its representatives present during all loadings,
unloadings, tests, and measurements involving Feedstock or Refinery Product
delivered hereunder. If the Parties cannot agree on measurement or quality tests
results, the measurements and quality tests required to determine the volume of
receipts or shipments or the conformity of the Feedstock or Refinery Product
delivered to the specifications set forth herein shall be made by an independent
inspector selected jointly by the Parties, the cost of which shall be shared
equally by the Parties.

                                   ARTICLE XI
                              BILLING AND PAYMENT
                              -------------------

     11.1 After delivery of Feedstock(s) hereunder, WPC shall submit an invoice
to CPC by facsimile transmission setting forth the quantity of each Feedstock
delivered, the price for such Feedstock, the amount due hereunder for such
quantities, and such other information and detail as may be mutually agreeable
to the Parties.  CPC shall remit by wire transfer of funds, into an account
designated by WPC, any amounts due no later than ten (10) Days after CPC's
receipt of WPC's invoice.  If the Day on which any payment is due is not a
Business Day, then the relevant payment shall be due upon the immediately
preceding Business Day, except if such payment due date is a Sunday or Monday,
then the relevant payment shall be due upon the immediately succeeding Business
Day.

     11.2 After delivery of Refinery Products  hereunder, CPC shall submit a
statement to WPC by facsimile transmission setting forth the quantity of each
Refinery Product delivered to WPC.  By not later than thirty (30) Days after the
receipt of CPC's statement, WPC shall provide CPC with a statement setting forth
the price or Netback Price, as applicable, of such Refinery Products, the amount
due CPC for such Refinery Products, and such other information and detail as may
be mutually agreeable to the Parties, along with payment for such Refinery
Products, which shall be remitted by wire transfer of funds into an account
designated by CPC.  If the Day on which any payment is due is not a Business
Day, then the relevant payment shall be due upon the immediately  preceding
Business Day, except if such payment due date is a Sunday or Monday, then the
relevant payment shall be due upon the immediately succeeding Business Day.

     11.3 If CPC or WPC should fail to remit any amounts in full when due as
required hereunder, or if any adjustments are made under this Agreement,
including, without limitation, adjustments as the result of the conclusion of
any audits or as a result of the resolution of a billing dispute, interest on
the unpaid portion shall accrue from the date upon which such payment should
have been made hereunder until paid in full at the Base Rate.    All such
accrued interest shall be added to the amount reflected as being owed hereunder
by either CPC or WPC, as the case may be, on the next invoice or by separate
invoice.

     11.4 If a good faith dispute arises as to the amount payable in any
statement, the amount not in dispute shall be paid.  If either Party elects to
withhold any payment otherwise due as a consequence of such good faith dispute,
the withholding Party shall provide the other Party with written notice of  its
reasons for withholding payment, and shall simultaneously place the 

                                       24
<PAGE>
 
disputed amount into an escrow account at a mutually acceptable commercial bank,
pending resolution of the dispute. Any such dispute shall be resolved in
accordance with the alternative dispute resolution procedures of Article XIII.
The performance of both Parties under this Agreement shall continue pending the
outcome of such procedures. If it is subsequently determined, whether by mutual
agreement of the Parties or otherwise, that the withholding Party is required to
pay all or any portion of the disputed amounts to the other Party, the
withholding Party, in addition to paying over such amounts, shall also pay
interest accrued on such amounts from the original due date until paid, at the
Base Rate.

     11.5 No retroactive adjustments may be made for any overcharge or
undercharge after a period ending twenty-four (24) Months from the end of the
Month in which the Feedstock or Refinery Product invoice or statement forming
the basis of the overcharge or undercharge was delivered or not delivered, as
the case may be, unless a claim for such adjustment shall have been presented
prior to the end of such period.  Any payment with respect to a retroactive
adjustment shall include an amount equal to interest on all amounts past due
from the date of the initial payment at the Base Rate, except in instances where
neither Party knew or could have known that the overcharge or undercharge
occurred, in which case interest shall run from the date of demand for payment.

     11.6 Either Party, upon notice in writing to the other, shall have the
right at reasonable hours to audit the accounts and records relating to the
accounting or billing under the provisions of any article hereof; provided,
however, that the auditing Party must take written exception to and make claim
upon the other Party for all discrepancies disclosed by said audit within
twenty-four (24) Months of the rendition of any statement or invoice forming the
basis of such claim.  Such audit shall be conducted by the auditing Party's
representative or auditor at the auditing Party's expense.

     11.7 All payments will be made without setoff or counterclaim; provided,
however, that upon a Party's (the defaulting Party) failure to make payment of
undisputed amounts on the due date, the other Party (the non-defaulting Party)
may, at its option and in its discretion, setoff against any amounts owed to the
defaulting Party any amounts owed by the defaulting Party under this Agreement
or otherwise.  The obligations of the non-defaulting Party and the defaulting
Party under this Agreement in respect of such amounts shall be deemed satisfied
and discharged to the extent of any such setoff.  The non-defaulting Party will
give the defaulting Party notice of any setoff made under this Section 11.7 as
soon as practicable after the setoff is made provided that failure to give such
notice shall not offset the validity of the setoff.

     11.8 ALL DISPUTES ARISING UNDER THIS ARTICLE XI THAT ARE NOT OTHERWISE
RESOLVED AS PROVIDED HEREIN SHALL BE SUBMITTED TO THE ALTERNATIVE DISPUTE
RESOLUTION PROCEDURES AS SET FORTH IN ARTICLE XIII HEREOF.  TO THE EXTENT THAT
ANY SUCH UNRESOLVED DISPUTE HAS NOT BEEN SUBMITTED TO SUCH ALTERNATIVE DISPUTE
RESOLUTION PROCEDURES WITHIN TWENTY-FIVE (25) MONTHS AFTER THE EVENT CAUSING THE
DISPUTE IS DISCOVERED OR REASONABLY SHOULD HAVE BEEN DISCOVERED, THE PARTY
ASSERTING THE CLAIM IN DISPUTE SHALL BE 

                                       25
<PAGE>
 
DEEMED TO HAVE WAIVED ANY SUCH CLAIM AND ALL RIGHTS HEREUNDER WITH RESPECT
THERETO.

                                  ARTICLE XII
                                 FORCE MAJEURE
                                 -------------

     12.1 In the event either Party is rendered unable, wholly or in part, by
Force Majeure to carry out its obligations under this Agreement, it is agreed
that upon such Party's giving notice and reasonably full particulars of such
Force Majeure in writing to the other Party after the occurrence of the cause
relied on, then the obligations of the Party giving such notice, so far as and
to the extent that they are affected by such Force Majeure, shall be suspended
during the continuance of any inability so caused, but for no longer period, and
such cause shall so far as possible be remedied with all reasonable dispatch.
This Agreement shall not be terminated by reason of any such cause, but shall
remain in full force and effect, and this Agreement shall not be extended
regardless of such curtailment or cessation.

     12.2 The term "Force Majeure" as used herein shall mean acts of God,
strikes, lockouts, or other industrial disturbances, acts of the public enemy,
wars, blockades, insurrections, riots, epidemics, landslides, lightning,
earthquakes, fires, tornadoes, hurricanes, or storms, tornado, hurricane, or
storm warnings which in any Parties' judgment require the precautionary shutdown
of the Refinery or any operating units thereof, or modes of transportation used
by WPC to supply Feedstocks to the Refinery, or transport Refinery Products from
the Refinery, floods, washouts, arrests or restraints of the government, either
federal or state, civil or military, civil disturbances, explosions, sabotage,
breakage or accident to equipment, machinery or lines of pipe, freezing of
machinery, equipment or lines of pipe, electric power shortages, inability of
any Party to obtain necessary permits and/or permissions due to existing or
future rules, orders, laws or governmental authorities (both federal, state and
local), shutdowns of the Refinery or any operating units thereof or modes of
transportation used by WPC to supply Feedstocks to the Refinery, or transport
Refinery Products from the Refinery, due to explosion or other extraordinary
incident, or any other causes, whether of the kind herein enumerated or
otherwise, which were not reasonably foreseeable on the Effective Date, and
which are not within the control of the Party claiming suspension and which such
Party is unable to overcome by the exercise of due diligence.  It is understood
and agreed that the settlement of strikes or lockouts shall be entirely within
the discretion of the Party having the difficulty, and that the above
requirement that any Force Majeure shall be remedied with all reasonable
dispatch shall not require the settlement of strikes or lockouts by acceding to
the demands of opposing parties when such course is inadvisable in the
discretion of the Party having difficulty.  The term "Force Majeure" shall also
include any event of Force Majeure occurring with respect to the facilities or
services of either CPC's or WPC's third Party suppliers or customers delivering
or receiving any product, fuel, feedstock, or other substance necessary to the
performance of such Party's obligations, and shall also include curtailment or
interruption of deliveries or service by such third Party suppliers or customers
as a result of an event of Force Majeure.  It is expressly agreed by the Parties
that neither (i) CPC's inability economically to use Feedstock purchased under
this Agreement nor (ii) WPC's ability to sell Feedstock to a market at a more
advantageous price shall constitute an event of Force Majeure.

                                       26
<PAGE>
 
                                  ARTICLE XIII
                   ALTERNATIVE DISPUTE RESOLUTION PROCEDURES
                   -----------------------------------------

     13.1 Any dispute, controversy or claim arising out of or relating to this
Agreement, or the breach or performance hereof, including, but not limited to,
any disputes concerning the interpretation of the terms and provisions hereof,
shall be resolved through the use of the following procedures:

          (a)  The Parties will initially attempt in good faith to resolve any
               disputes, controversy or claim arising out of or relating to this
               Agreement.

          (b)  Should the Parties directly involved in any dispute, controversy
               or claim be unable to resolve same within a reasonable period of
               time, such dispute, controversy or claim shall be submitted to
               the Scheduling Committee with such explanation or documentation
               as the Parties deem appropriate to aid the Scheduling Committee
               in their consideration of the issues presented.  The date the
               matter is first submitted to the Scheduling Committee shall be
               referred to as the "Submission Date."  The Scheduling Committee
               representatives shall attempt in good faith, through the process
               of discussion and negotiation, to resolve any dispute,
               controversy, or claim presented to it within forty-five (45) Days
               after the Submission Date.

          (c)  If the Scheduling Committee representatives cannot so resolve any
               dispute, controversy, or claim submitted to it within forty-five
               (45) Days after the Submission Date, the Parties shall attempt in
               good faith to settle the matter by submitting the dispute,
               controversy or claim to mediation within sixty (60) Days after
               the Submission Date using any mediator upon which they mutually
               agree.  If the Parties are unable to mutually agree upon a
               mediator within seventy-five (75) Days after the Submission Date,
               the case shall be referred for mediation to the office of
               Judicial Arbitration and Mediation Services, Inc. ("JAMS") in
               Houston, Texas. The cost of the mediator will be split equally
               between the Parties unless they agree otherwise in writing.

          (d)  If the matter has not been resolved pursuant to the aforesaid
               mediation procedure within thirty (30) Days of the initiation of
               such procedure, or if either Party will not participate in such
               mediation, either Party may request that the matter be resolved
               through arbitration by submitting a written notice (the
               "Arbitration Notice") to the other.  Any arbitration that is
               conducted hereunder shall be governed by the Federal Arbitration
               Act, 9 U.S.C. (S) 1 et seq., and will not be governed by the
               arbitration acts, statutes, or rules of any other jurisdiction.

                                       27
<PAGE>
 
          (e)  The Arbitration Notice shall name the noticing Party's arbitrator
               and shall contain a statement of the issue(s) presented for
               arbitration.  Within fifteen (15) Days of receipt of an
               Arbitration Notice, the other Party shall name its arbitrator by
               written notice to the other and may designate any additional
               issue(s) for arbitration.  The two named arbitrators shall select
               the third arbitrator within fifteen (15) Days after the date on
               which the second arbitrator was named.  Should the two
               arbitrators fail to agree on the selection of the third
               arbitrator, either Party shall be entitled to request the Senior
               Judge of the United States District Court for the Southern
               District of Texas to select the third arbitrator.  All
               arbitrators shall be qualified by education or experience within
               the liquefied petroleum gas, natural gas liquids, or petroleum
               refining industry to decide the issues presented for arbitration.
               No arbitrator shall be:  a current or former director, officer,
               or employee of either Party or its Affiliates; an attorney (or
               member of a law firm) who has rendered legal services to either
               Party or its Affiliates within the preceding three Years; or an
               owner of any of the common stock of either Party, or its
               Affiliates.

          (f)  The three arbitrators shall commence the arbitration proceedings
               within twenty-five (25) Days following the appointment of the
               third arbitrator.  The arbitration proceedings shall be held at a
               mutually acceptable site and if the Parties are unable to agree
               on a site, the arbitrators shall select the site.  The
               arbitrators shall have the authority to establish rules and
               procedures governing the arbitration proceedings.  Each Party
               shall have the opportunity to present its evidence at the
               hearing.  The arbitrators may call for the submission of pre-
               hearing statements of position and legal authority, but no post-
               hearing briefs shall be submitted. The arbitration panel shall
               not have the authority to award (i) punitive or exemplary damages
               or (ii) consequential damages, except as expressly provided
               herein.  The arbitrators' decision must be rendered within thirty
               (30) Days following the conclusion of the hearing or submission
               of evidence, but no later than ninety (90) Days after appointment
               of the third arbitrator.  With respect to disputes regarding
               price or any redeterminations thereof under Article V or the
               selection of an Alternate Index under Section 5.3, each Party
               shall submit to the arbitration panel a final offer of its
               proposed resolution of the dispute.  A majority of the
               arbitrators shall approve the final offer of one Party without
               modification, and reject the offer of the other Party.

          (g)  The decision of the arbitrators or a majority of them, shall be
               in writing and shall be final and binding upon the Parties as to
               the issue(s) submitted.  The cost of the hearing shall be shared
               equally by the Parties, and each Party shall be responsible for
               its own expenses and those of its counsel or other
               representatives.  Each Party hereby irrevocably waives, to the
               fullest extent permitted by law, any objection 

                                       28
<PAGE>
 
               it may have to the arbitrability of any such disputes,
               controversies or claims and further agrees that a final
               determination in any such arbitration proceeding shall be
               conclusive and binding upon each Party. Judgment on the award
               rendered by the arbitrator may be entered in any court having
               jurisdiction thereof. The prevailing Party shall be entitled to
               recover reasonable attorneys' fees and court costs in any court
               proceeding relating to the enforcement or collection of any award
               or judgment rendered by the arbitration panel under this
               Agreement.

          (h)  All deadlines specified herein may be extended by mutual written
               agreement of the Parties.  The procedures specified herein shall
               be the sole and exclusive procedures for the resolution of
               disputes between the parties arising out of or relating to this
               Agreement; provided, however, that a Party may seek a preliminary
               injunction or other preliminary judicial relief if in its
               judgment such action is necessary to avoid irreparable damage.
               Despite such action, the Parties will continue to participate in
               good faith in the procedures specified herein.  All applicable
               statutes of limitation, including, without limitation,
               contractual limitation periods provided for in this Agreement,
               shall be tolled while the procedures specified in this Section
               are pending.  The Parties will take all actions, if any,
               necessary to effectuate the tolling of any applicable statutes of
               limitation.
 
                                  ARTICLE XIV
                             LIMITATION OF DAMAGES
                             ---------------------

     14.1 Unless performance is excused by another provision of this Agreement,
if WPC fails to deliver the Nominated Volumes of Feedstock during a Delivery
Month during the term of this Agreement, WPC shall pay CPC the WPC Deficiency
Amount.  "WPC Deficiency Amount" shall mean the following:

                    [(F-G) x (H-I)] + J + K

          where

          F-G =   the WPC Deficiency Quantity  which shall always be equal to or
                    greater than zero (0);

          H-I =     the CPC Alternate Price which shall never be less than zero
                    (0);

          J =       the costs reasonably incurred by CPC in replacing the WPC
                    Deficiency Quantity pursuant to an arm's length purchase of
                    such WPC Deficiency Quantity from a third Person, including,
                    but not limited to, CPC's transportation and storage costs;
                    and

                                       29
<PAGE>
 
          K =       CPC's administrative and operational costs associated with
                    the WPC Deficiency Quantity, which shall equal
                    [$0.0025/Gallon X (F-G)], and which shall constitute
                    liquidated damages hereunder.

          For purposes of the foregoing, the variables and terms set forth below
          have the following meanings:

          F =       the total Nominated Volumes for each Feedstock nominated by
                    CPC for delivery during the applicable Delivery Month, minus
                    the total quantities of each Feedstock that WPC is excused
                    from delivering hereunder during the applicable Delivery
                    Month;

          G =       the quantities of each Feedstock actually delivered by WPC
                    during the applicable Delivery Month;

          H =       the price obtained by CPC for the WPC Deficiency Quantity in
                    an arm's length purchase of such WPC Deficiency Quantity
                    from a third Person; and

          I =       the price of each Feedstock payable by CPC to WPC for the
                    applicable Delivery Month in accordance with Section 5.1.

     14.2 FOR BREACH OF ANY PROVISION FOR WHICH AN EXPRESS REMEDY OR MEASURE OF
DAMAGES IS PROVIDED IN THIS AGREEMENT, SUCH EXPRESS REMEDY OR MEASURE OF DAMAGES
SHALL BE THE SOLE AND EXCLUSIVE REMEDY HEREUNDER, AND THE OBLIGOR'S LIABILITY
SHALL BE LIMITED AS SET FORTH IN SUCH PROVISION, AND ALL OTHER REMEDIES OR
DAMAGES ARE WAIVED.  IF NO REMEDY OR MEASURE OF DAMAGES IS EXPRESSLY PROVIDED
HEREIN, THE OBLIGOR'S LIABILITY SHALL BE LIMITED TO DIRECT ACTUAL DAMAGES ONLY,
EXCLUDING LOST PROFITS, AND SUCH DIRECT ACTUAL DAMAGES SHALL BE THE SOLE AND
EXCLUSIVE REMEDY HEREUNDER, AND ALL OTHER REMEDIES OR DAMAGES ARE WAIVED.  IN NO
EVENT SHALL EITHER PARTY BE LIABLE TO THE OTHER PARTY UNDER ANY PROVISION OF
THIS AGREEMENT (INCLUDING, WITHOUT LIMITATION, ANY INDEMNITY PROVISION HEREOF)
FOR PUNITIVE OR EXEMPLARY DAMAGES IN TORT OR CONTRACT.   EXCEPT AS EXPRESSLY
PROVIDED HEREIN, NEITHER PARTY SHALL BE LIABLE TO THE OTHER PARTY UNDER ANY
PROVISION OF THIS AGREEMENT FOR CONSEQUENTIAL, INCIDENTAL, OR INDIRECT DAMAGES.
THE PRECEDING SENTENCE SHALL NOT BE CONSTRUED AS LIMITING THE OBLIGATION OF
EITHER PARTY HEREUNDER TO INDEMNIFY THE OTHER PARTY AGAINST CLAIMS ASSERTED BY
THIRD PARTIES, INCLUDING, BUT NOT LIMITED TO, THIRD PARTY CLAIMS FOR
CONSEQUENTIAL, INCIDENTAL, OR INDIRECT DAMAGES, BUT EXCLUDING CLAIMS FOR SUCH
DAMAGES UNDER ARTICLE IX.  TO THE EXTENT ANY PAYMENT REQUIRED TO BE MADE
PURSUANT TO 

                                       30
<PAGE>
 
ANY PROVISION OF THIS AGREEMENT IS AGREED BY THE PARTIES TO CONSTITUTE
LIQUIDATED DAMAGES, THE PARTIES ACKNOWLEDGE THAT THE DAMAGES ARE DIFFICULT OR
IMPOSSIBLE TO DETERMINE, AND THAT SUCH PAYMENT CONSTITUTES A REASONABLE
APPROXIMATION OF THE AMOUNT OF SUCH DAMAGES.

                                   ARTICLE XV
                                 MISCELLANEOUS
                                 -------------

     15.1 This Agreement and the operations hereunder shall be subject to the
valid and applicable federal and state laws and the valid and applicable orders,
laws, local ordinances, rules, and regulations of any local, state or federal
authority having jurisdiction, but nothing contained herein shall be construed
as a waiver of any right to question or contest any such order, laws, rules, or
regulations in any forum having jurisdiction in the premises.  If any provision
of this Agreement is held to be illegal, invalid, or unenforceable under the
present or future laws effective during the term of this Agreement, (i) such
provision will be fully severable, (ii) this Agreement will be construed and
enforced as if such illegal, invalid, or unenforceable provision had never
comprised a part of this Agreement, and (iii) the remaining provisions of this
Agreement will remain in full force and effect and will not be affected by the
illegal, invalid, or unenforceable provision or by its severance from this
Agreement.  Furthermore, in lieu of such illegal, invalid, or unenforceable
provision, there will be added automatically as a part of this Agreement a
provision similar in terms to such illegal,  invalid, or unenforceable provision
as may be possible and as may be legal, valid, and enforceable.  If a provision
of this Agreement is or becomes illegal, invalid, or unenforceable in any
jurisdiction, the foregoing event shall not affect the validity or
enforceability in that jurisdiction of any other provision of this Agreement nor
the validity or enforceability in other jurisdictions of that or any other
provision of this Agreement.

     15.2 THIS AGREEMENT AND THE RIGHTS AND DUTIES OF THE PARTIES ARISING OUT OF
THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED,  ENFORCED, AND PERFORMED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS, AS THE SAME MAY BE AMENDED FROM
TIME TO TIME, WITHOUT GIVING EFFECT TO ANY CHOICE OR CONFLICT OF LAW PROVISION
OR RULE THAT WOULD CAUSE THE APPLICATION OF THE LAWS OF ANY JURISDICTION OTHER
THAN THE STATE OF TEXAS.

     15.3 This Agreement, including, without limitation, all exhibits hereto,
integrates the entire understanding between the Parties with respect to the
subject matter covered and supersedes all prior understandings, drafts,
discussions, or statements, whether oral or in writing, expressed or implied,
dealing with the same subject matter.  This Agreement may not be amended or
modified in any manner except by a written document signed by both Parties that
expressly amends this Agreement. No waiver by CPC or WPC of any of the
provisions of this Agreement shall be deemed or shall constitute a waiver of any
other provision hereof (whether or not similar) nor shall such waiver constitute
a continuing waiver unless expressly 

                                       31
<PAGE>
 
provided. No waiver shall be effective unless made in writing and signed by the
Party to be charged with such wavier.

     15.4 (a)  Subject in all respects to Section 15.4(b), the terms, covenants,
               and conditions of this Agreement shall inure to and be binding
               upon the Parties and their respective successors and permitted
               assigns, including, but not limited to, any and all subsequent
               owners of the Refinery, but (i) neither Party may assign all or
               any part of its rights under this Agreement without the prior
               written consent of the other Party, such consent not to be
               unreasonably withheld, (ii) either Party may assign its rights
               hereunder to any Affiliate of such Party without the approval of
               the other Party (but such assignment shall in no way relieve or
               release the assigning Party from any obligations hereunder,
               whether accrued or unaccrued, unless agreed to in writing by the
               non assigning Party and (iii) either Party may, for collateral
               purposes, mortgage, pledge, encumber, or grant a security
               interest in or a lien on its interest in this Agreement and/or
               its rights hereunder to any commercial bank, trustee, or other
               Person acting on behalf of any such commercial bank, but only
               with the prior written consent of the other Party, such consent
               not to be unreasonably withheld. Any transfer or assignment in
               violation of this Section 15.4 shall be void.

          (b)  It is understood and agreed that CPC may assign all (but not less
               than all) its rights under this Agreement in connection with the
               assignment, sale, transfer, or other disposition (collectively, a
               "Disposition") of the Refinery to a third Person who is not an
               Affiliate of either Party (such third Person being herein called
               the "Transferee"), but only with the prior written consent of
               WPC, such consent not to be unreasonably withheld.  CPC shall
               provide WPC with written notice of the Disposition prior to its
               consummation, including in such notice the name of the proposed
               Transferee.  Within thirty (30) Days after WPC's receipt of such
               notice, WPC shall deliver to CPC a written notice (the
               "Assignment Notice") that (i) WPC consents to the assignment of
               this Agreement to the proposed Transferee or (ii) WPC does not
               consent to such assignment, together with a statement of WPC's
               reasons for withholding its consent  If WPC fails to deliver such
               Assignment Notice within such thirty (30) Day period, WPC shall
               be deemed to have consented to such assignment.  If WPC consents
               to such assignment, the Transferee shall assume all obligations
               of CPC under this Agreement upon consummation of the Disposition,
               and CPC shall have no further liability hereunder.

               If WPC withholds its consent hereunder, then, within thirty (30)
               Days after CPC's receipt of WPC's Assignment Notice, either Party
               may 

                                       32
<PAGE>
 
               terminate this Agreement, effective upon consummation of the
               Disposition.

     15.5 With the other documents required hereunder, WPC shall provide to CPC
a Material Safety Data Sheet for each Feedstock delivered hereunder.  CPC
acknowledges that there may be hazards associated with the loading, unloading,
transporting, handling or use of the Feedstock sold hereunder, which may require
that warning be communicated to or other precautionary action taken with all
Persons handling, coming into contact with, or in any way concerned with the
Feedstock sold hereunder.  CPC assumes as to its employees, independent
contractors, and subsequent purchasers of the Feedstock sold hereunder all
responsibility for all such necessary warnings or other precautionary measures
relating to hazards to person and property associated with the Feedstock sold
hereunder and, furthermore, CPC shall defend at its own expense, indemnify fully
and hold harmless WPC and its parents, subsidiaries and Affiliates and its and
their agents, officers, directors, employees, representatives, successors and
assigns from and against any and all liabilities; losses; damages; demands;
claims; penalties; fines; actions; suits; legal, administrative or arbitration
or alternative dispute resolution proceedings; judgments, orders, directives,
injunctions, decrees or awards of any jurisdiction; costs, and expenses
(including, but not limited to, attorneys' fees and related costs) arising out
of or in any manner related to CPC's failure to provide necessary warnings or
other precautionary measures in connection with the Feedstock sold hereunder.

     15.6 With the other documents required hereunder, CPC shall provide to WPC
a Material Safety Data Sheet for each Refinery Product and Type A Offspec
Refinery Product delivered hereunder.  WPC acknowledges that there may be
hazards associated with the loading, unloading, transporting, handling, or use
of the Refinery Product and Type A Offspec Refinery Product sold hereunder,
which may require that warning be communicated to or other precautionary action
taken with all Persons handling, coming into contact with, or in any way
concerned with the Refinery Product and Type A Offspec Refinery Product sold
hereunder.  WPC assumes as to its employees, independent contractors, and
subsequent purchasers of the Refinery Product and Type A Offspec Refinery
Product sold hereunder all responsibility for all such necessary warnings or
other precautionary measures relating to hazards to Person and property
associated with the Refinery Product and Type A Offspec Refinery Product sold
hereunder and, furthermore, WPC shall defend at its own expense, indemnify fully
and hold harmless CPC and its parents, subsidiaries and Affiliates and its and
their agents, officers, directors, employees, representatives, successors and
assigns from and against any and all liabilities; losses; damages; demands;
claims; penalties; fines; actions; suits; legal, administrative or arbitration
or alternative dispute resolution proceedings; judgments, orders, directives,
injunctions, decrees or awards of any jurisdiction; costs and expenses
(including, but not limited to, attorneys' fees and related costs) arising out
of or in any manner related to WPC's failure to provide necessary warnings or
other precautionary measures in connection with the Refinery Product and Type A
Offspec Refinery Product sold hereunder.

     15.7 Except as otherwise provided herein, each Party reserves to itself all
rights, set-offs, counterclaims, and other remedies and/or defenses which such
Party is or may be entitled to arising from or out of this Agreement or as
otherwise provided by law.

                                       33
<PAGE>
 
     15.8 (a)  Each Party agrees that it will maintain this Agreement, all terms
               and conditions of this Agreement, and all other Confidential
               Information (as hereinafter defined) in strictest confidence, and
               that it will not cause or permit disclosure of Confidential
               Information to any third Person without the express written
               consent of the other Party hereto.  Disclosures of Confidential
               Information otherwise prohibited by this Section 15.8 may be made
               by either Party:  (i) to the extent necessary for such Party to
               enforce its rights hereunder against the other Party; (ii) to the
               extent a Party is contractually or legally bound to disclose
               information to a third Person (such as a shareholder or
               commercial lender);  (iii) only to the extent to which a Party
               hereto is required to disclose all or part of this Agreement by a
               statute or by the order of a court, agency, or other governmental
               body exercising jurisdiction over the subject matter hereof, by
               order, by regulations, or by other compulsory process (including,
               but not limited to, deposition, subpoena, interrogatory, or
               request for production of documents); (iv) to the extent required
               by the applicable regulations of a securities or commodities
               exchange; or (v) to an Affiliate (but only if such Affiliate
               agrees to be bound by the provisions of this Section).  In
               addition to the foregoing, CPC may disclose the terms of this
               Agreement to any prospective purchaser of the Refinery.
               "Confidential Information" shall mean any information,
               proprietary to either Party and maintained by it in confidence or
               as a trade secret, including, without limitation, business plans
               and strategies, proprietary software, financial statements,
               customer or client lists, personnel records, analysis of general
               energy market conditions, sales, transportation, and service
               contracts and the commercial terms thereof, relationships with
               current and potential business partners, suppliers, customers,
               service providers and financial sources, data base contents and
               valuable information of a like nature relating to the business of
               such Party.  It is understood and agreed that Confidential
               Information shall not include information of a Party that (w)
               becomes generally available to the public at the time of
               disclosure to the other Party, or (x) after the time of
               disclosure to the other Party, was generally made available to
               the public without breach of this Agreement, or (y) the Person
               receiving the information can show was rightfully in its
               possession at the time of disclosure, or (z) was rightfully
               acquired by the recipient from third Persons who did not
               themselves obtain such information under a confidentiality or
               other similar agreement with the Party whose information was
               disclosed.

          (b)  If either Party is or becomes aware of a fact, obligation, or
               circumstance that has resulted or may result in a disclosure of
               Confidential Information authorized by this Section 15.8, it
               shall so notify the other Party promptly and shall provide
               documentation or an explanation of 

                                       34
<PAGE>
 
               such disclosure as soon as it is available. Each Party further
               agrees to cooperate to the fullest extent in seeking confidential
               status to protect any Confidential Information so disclosed.

          (c)  The Parties hereto acknowledge that independent legal counsel,
               certified public accountants, or other consultants or independent
               contractors of a Party (collectively, "Outside Consultants") may,
               from time to time, be provided with a copy of this Agreement if,
               in the judgment of the disclosing Party, the information
               contained in this Agreement is necessary to the performance of
               such Outside Consultants' duties.  Accordingly, the Parties agree
               that such disclosure does not require consent by the other Party,
               provided that any such Outside Consultants agree to be bound by
               the provisions of this Section 15.8.

          (d)  Each Party will be deemed solely responsible and liable for the
               actions of its employees, Outside Consultants, officers, and
               agents for maintaining the confidentiality commitments of this
               Section 15.8, but will be required in that regard only to
               exercise such care in maintaining the confidentiality of the
               Confidential Information as such Party normally exercises in
               preserving the confidentiality of its other commercially
               sensitive information.

     15.9 Nothing contained in this Agreement shall be construed to create an
association, trust, partnership, or joint venture or impose a trust or
partnership duty, obligation, or liability on or with regard to either Party.

     15.10  In construing this Agreement, the following principles shall be
followed:

          (a)  no consideration shall be given to the fact or presumption that
               one Party had a greater or lesser hand in drafting this
               Agreement;

          (b)  examples shall not be construed to limit, expressly or by
               implication, the matter they illustrate;

          (c)  the word "includes" and its syntactical variants mean "includes,
               but is not limited to" and corresponding syntactical variant
               expressions; and

          (d)  the plural shall be deemed to include the singular and vice
               versa, as applicable.

     15.11  EACH PARTY EXECUTING THIS AGREEMENT HEREBY WAIVES ITS RESPECTIVE
RIGHTS, IF ANY, UNDER THE DECEPTIVE TRADE PRACTICES-CONSUMER PROTECTION ACT,
SECTION 17.41 ET SEQ., TEXAS BUSINESS & COMMERCE CODE, A LAW THAT GIVES
CONSUMERS SPECIAL RIGHTS AND PROTECTIONS.  AFTER CONSULTATION WITH AN ATTORNEY

                                       35
<PAGE>
 
OF ITS OWN SELECTION, EACH PARTY EXECUTING THIS AGREEMENT VOLUNTARILY CONSENTS
TO THIS WAIVER.  IN ADDITION, EACH PARTY EXECUTING THIS AGREEMENT HEREBY
REPRESENTS AND WARRANTS TO THE OTHER PARTY THAT (I) SUCH PARTY'S LEGAL COUNSEL
WAS NOT DIRECTLY OR INDIRECTLY IDENTIFIED, SUGGESTED, OR SELECTED BY THE OTHER
PARTY OR BY AN AGENT OF SUCH OTHER PARTY, AND (II) NEITHER PARTY EXECUTING THIS
AGREEMENT IS IN A SIGNIFICANTLY DISPARATE BARGAINING POSITION.

     15.12  Any notice or other communication provided for in this Agreement or
any notice which either Party may desire to give to the other shall be in
writing and shall be deemed to have been properly given if and when sent by
facsimile transmission, delivered by hand; or, if sent by mail, upon deposit in
the United States mail, either U.S. Express Mail, registered mail, or certified
mail, with all postage fully prepaid; or, if sent by courier, by delivery to a
bonded courier with charges paid in accordance with the customary arrangements
established by such courier, in each case addressed to the parties at the
following addresses:

     If to WPC:          WARREN PETROLEUM COMPANY,
                         LIMITED PARTNERSHIP
                         13430 Northwest Freeway, Suite 1200
                         Houston, Texas  77040-6095
                         Attention:  Vice President and General Manager -
                         NGL Marketing
                         Telephone: (713) 507-6408
                         Telecopy: (713) 507-3715

                    with a copy to:

                         Vice President & General Counsel
                         WARREN PETROLEUM COMPANY,
                         LIMITED PARTNERSHIP
                         13430 Northwest Freeway
                         Suite 1200
                         Houston, Texas  77040-6095
                         Telephone: (713) 507-3725
                         Telecopy: (713) 507-6834

          If to CPC:     CHEVRON PRODUCTS COMPANY
                         6501 Trowbridge
                         El Paso, Texas 79905
                         Attention:  Refinery Manager
                         Phone:  (915) 775-3411
                         Telecopy: (713) 775-5568

                                       36
<PAGE>
 
                    with a copy to:

                         Vice President & General Counsel
                         CHEVRON PRODUCTS COMPANY
                         575 Market Street - Suite 2182
                         San Francisco, California 94105-2854
                         Telephone: (415) 894-3232
                         Telecopy: (415) 894-5489

or at such other address as either Party shall designate by written notice to
the other.  A notice sent by facsimile shall be deemed to have been received by
the close of the Business Day following the Day on which it was transmitted and
confirmed by transmission report or such earlier time as confirmed orally or in
writing by the receiving Party.  Notice by U. S. Mail, whether by U. S. Express
Mail, registered mail or certified mail, or by overnight courier shall be deemed
to have been received by the close of the second Business Day after the Day upon
which it was sent, or such earlier time as is confirmed orally or in writing by
the receiving Party.  Any Party may change its address or facsimile number by
giving notice of such change in accordance with herewith.

     15.13  No director, employee, or agent of either Party shall give or
receive any commission, fee, rebate, gift, or entertainment of significant cost
or value in connection with this Agreement.

     15.14  Each Party shall provide the other Party with such reports as may be
mutually agreeable to both Parties.  Each Party shall maintain such records and
accounts as may be necessary to the performance of its respective duties and
obligations hereunder, in accordance with good business practices.

     15.15  This Agreement is for the sole benefit of the Parties and their
respective successors and permitted assigns, and shall not inure to the benefit
of any other Person whomsoever, it being the intention of the Parties that no
third Person shall be deemed a third Party beneficiary of this Agreement.

     15.16  Each Party shall take such acts and execute and deliver such
documents in form and substance reasonably satisfactory to each of them, in
order to effectuate the purposes of this Agreement.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement the Day
and Year first above written.

                                       37
<PAGE>
 
                              WARREN PETROLEUM COMPANY,
                              LIMITED PARTNERSHIP
                              BY: WARREN PETROLEUM G. P., INC.



                              By:  ______________________________
                              Name: _____________________________
                              Title:  ___________________________

 


                              CHEVRON PRODUCTS COMPANY,
                              a division of CHEVRON U.S.A. INC.



                              By:  ______________________________
                              Name: _____________________________
                              Title:  ___________________________

                                       38