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                                                                    EXHIBIT 10.1

                                 THIRD AMENDMENT
                                       TO
                            PARENT COMPANY AGREEMENT

            This Third Amendment to Parent Company Agreement (this "Amendment"),
dated as of July 29, 2004, is entered into by and among Duke Energy Field
Services Corporation, a Delaware corporation ("DEFS Holding"), Duke Energy Field
Services, LLC, a Delaware limited liability company (the "Company"),
ConocoPhillips Company, a Delaware corporation ("COP") and Duke Energy
Corporation, a North Carolina corporation ("Duke").

            WHEREAS, reference is made to that certain Parent Company Agreement
by and among the Company, DEFS Holding, COP and Duke dated as of March 31, 2000,
as amended by the First Amendment to Parent Company Agreement dated as of May
25, 2000 and as further amended by the Second Amendment to Parent Company
Agreement dated as of August 4, 2000 (as so amended the "Parent Company
Agreement") (capitalized terms used but not defined herein shall have the
meaning given thereto in the Parent Company Agreement); and

            WHEREAS, the parties desire to amend the Parent Company Agreement as
set forth herein.

            NOW, THEREFORE, for and in consideration of the mutual benefits to
be derived from this Amendment, and intending to be legally bound hereby, the
parties hereto hereby agree as follows:

      1.    PARENT COMPANY AGREEMENT AMENDMENT. The Parent Company Agreement is
            hereby amended as follows:

                  (a) Section 5.1 of the Parent Company Agreement is hereby
            amended by deleting Section 5.1 thereof and replacing it with the
            following in its place and stead:

                        "Section 5.1 Structure; Transfers. For the period from
                        the date of this Agreement until the consummation of the
                        IPO, (i) Duke shall cause DEFS Holding to own and hold
                        all of Duke's Company Interest, and (ii) Phillips shall
                        cause (A) PGC to own and hold all of Phillips' Company
                        Interest and no other assets or liabilities and (B)
                        PGCSI to own and hold all of the capital stock of PGC
                        and no other assets or liabilities."

                  (b) Article V of the Parent Company Agreement is hereby
            amended by adding at the end of such Article the following new
            Section:

                        "Section 5.4 Indemnity. Duke shall indemnify and hold
                        harmless COP and its Affiliates and the Company and its
                        Affiliates (excluding Duke and Duke's Subsidiaries other
                        than the Company and the Company's Subsidiaries) from
                        and against the present value tax cost incurred by COP
                        and its Affiliates and the Company and its Affiliates
                        (excluding Duke and Duke's Subsidiaries other than the
                        Company and the Company's Subsidiaries) in connection
                        with any tax depreciation restart liability that

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                        COP and its Affiliates may incur as a result of the
                        restructuring or reorganization of the Company by Duke
                        if an IPO is consummated in the structure originally
                        contemplated by Duke and COP on the Closing Date."

      2.    ACKNOWLEDGEMENT. Except as amended hereby, the Parent Company
            Agreement shall remain in full force and effect as previously
            executed, and the parties hereby ratify the Parent Company Agreement
            as amended hereby.

      3.    COUNTERPARTS. This Amendment may be executed in one or more
            counterparts, all of which shall be considered one and the same
            agreement, and shall become effective when one or more counterparts
            have been signed by each of the parties hereto and delivered
            (including by facsimile) to the other parties.

      4.    INCORPORATION. The provisions of Sections 8.2 through 8.12 of the
            Parent Company Agreement are hereby incorporated herein and shall be
            deemed to include and/or apply to this Agreement, as appropriate.

            IN WITNESS WHEREOF, each of the undersigned, intending to be legally
bound, has caused this Amendment to be duly executed and delivered on the date
first set forth above.

                                         DUKE ENERGY FIELD SERVICES CORPORATION
                                         By:    /s/ W. H. Easter III
                                                -------------------------------
                                         Name:  W. H. Easter III
                                         Title: Chairman of the Board, President
                                                and CEO

                                         DUKE ENRGY FIELD SERVICES, LLC
                                         By:    /s/ W. H. Easter III
                                                --------------------------------
                                         Name:  W. H. Easter III
                                         Title: Chairman of the Board, President
                                                and CEO

                                         DUKE ENERGY CORPORATION
                                         By:    /s/ Fred J. Fowler
                                                -------------------------------
                                         Name:  Fred J. Fowler
                                         Title: President and COO Duke Energy

                                         CONOCOPHILLIPS
                                         By:    /s/ John E. Lowe
                                                --------------------------------
                                         Name:  John E. Lowe
                                         Title: Executive VP, Planning, Strategy
                                                & Corporate Affairs

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