SECOND AMENDMENT TO AMENDED AND RESTATED LIMITED LIABILITY COMPANY AGREEMENT OF DUKE ENERGY FIELD SERVICES, LLC

Exhibit 10.4

SECOND AMENDMENT

TO

AMENDED AND RESTATED LIMITED

LIABILITY COMPANY AGREEMENT

OF DUKE ENERGY FIELD SERVICES, LLC

This Second Amendment to Amended and Restated Limited Liability Company Agreement of Duke Energy Field Services, LLC (this “Amendment”), dated as of July 29, 2004, is entered into by and between Phillips Gas Company, a Delaware corporation (“PGC”) and Duke Energy Field Services Corporation, a Delaware Corporation (“DEFS Holding”).

WHEREAS, reference is made to that certain Amended and Restated Limited Liability Company Agreement of Duke Energy Field Services, LLC by and between PGC and DEFS Holding dated as of March 31, 2000, as amended by that certain First Amendment to Amended and Restated Limited Liability Company Agreement of Duke Energy Field Services, LLC, by and among PGC, DEFS Holding, Phillips Gas Investment Company and Duke Energy Field Services Investment Corp. (the “LLC Agreement”) (capitalized terms used but not defined herein shall have the meaning given thereto in the LLC Agreement); and

WHEREAS, the parties desire to amend the LLC 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:

“For the period from the date hereof until the consummation of the IPO, (a) DEFS Holding shall own and hold all of Duke’s Company Interests and (b) PGC shall own and hold all of Phillips’ Company Interests and shall have no other assets or liabilities.”

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.

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