*Execution Copy***EXHIBIT 4.A** **SIXTH SUPPLEMENTAL INDENTURE****among****EL PASO EXPLORATION & PRODUCTION COMPANY,****as Issuer,****MBOW FOUR STAR CORPORATION,****EL PASO EXPLORATION & PRODUCTION MANAGEMENT, INC.,****EL PASO E&P HOLDINGS, INC.,****EL PASO E&P COMPANY, L.P.,****EL PASO PRODUCTION RESALE COMPANY,****EL PASO ENERGY OIL TRANSMISSION, L.L.C.,****EL PASO PRODUCTION OIL & GAS GATHERING, L.P.,****EL PASO E&P INTERNATIONAL HOLDING COMPANY,****EL PASO PREFERRED HOLDINGS COMPANY,****and****EL PASO E&P FINANCE COMPANY, L.L.C.,****as Subsidiary Guarantors,****and****WILMINGTON TRUST COMPANY****as Trustee** **October 1, 2006** **73/4% Senior Notes due 2013** 
 

 
**SIXTH SUPPLEMENTAL INDENTURE**     This Sixth Supplemental Indenture, dated as of October 1, 2006 (this “Sixth SupplementalIndenture”), is entered into by and among (i) El Paso Exploration & Production Company (the“Company”), formerly known as El Paso Production Holding Company, (ii) MBOW Four StarCorporation (“MBOW Four Star”), El Paso Exploration & Production Management, Inc. (“ElPaso Management”), El Paso E&P Holdings, Inc. (“El Paso Holdings”), El Paso E&PCompany, L.P. (“El Paso E&P”), El Paso Production Resale Company (“El PasoResale”), El Paso Energy Oil Transmission, L.L.C. (“El Paso Transmission”), El PasoProduction Oil & Gas Gathering, L.P. (“El Paso Gathering”), El Paso E&P InternationalHolding Company (“El Paso International”), El Paso Preferred Holdings Company (“El PasoPreferred Holdings”), and El Paso E&P Finance Company, L.L.C. (“El Paso Finance”),(collectively, the “Subsidiary Guarantors”), and (iii) Wilmington Trust Company, as trustee(the “Trustee”). Capitalized terms used but not defined herein have the meanings ascribedto them in the Indenture (as defined below).**W I T N E S S E T H:**     WHEREAS, the Company, El Paso Production Company (“El Paso Production”), El PasoProduction GOM Inc. (“GOM”), Vermejo Minerals Corporation (“Vermejo”) and El PasoEnergy Raton, L.L.C. (“Raton”) heretofore executed and delivered to the Trustee thatcertain Indenture, dated as of May 23, 2003 (the “Original Indenture”), providing for theissuance of $1,200,000,000 aggregate principal amount of the Company’s 73/4% Senior Notes due 2013(the “Notes”);     WHEREAS, as set forth in the First Supplemental Indenture (as defined below), Raton andVermejo entered into an Agreement of Merger dated January 31, 2003, pursuant to which (i) Raton wasmerged with and into Vermejo, (ii) Vermejo was the surviving corporation of the merger contemplatedby such agreement, and (iii) Vermejo’s name was changed to “El Paso Energy Raton Corporation”(“Raton Corporation”);     WHEREAS, the Company, El Paso Production, GOM, Vermejo and the Trustee entered into thatcertain First Supplemental Indenture, dated as of January 31, 2004 (the “First SupplementalIndenture”), pursuant to which the Original Indenture was amended and Vermejo expressly assumedthe obligations of Raton under its Subsidiary Guarantee;     WHEREAS, the Company, El Paso Production, GOM, Raton Corporation and the Trustee entered intothat certain Second Supplemental Indenture, dated as of July 26, 2004 (the “Second SupplementalIndenture”), pursuant to which the Original Indenture was further amended and certain covenantswere added for the benefit of the Holders pursuant to Section 9.01(6) of the Original Indenture;     WHEREAS, the Company, El Paso Production, GOM, Raton Corporation, Medicine Bow EnergyCorporation (“Medicine Bow”), Medicine Bow Operating Company (“MBOW Operating”) andMBOW Four Star entered into that certain Third Supplemental Indenture, dated as of August 31, 2005(the “Third Supplemental Indenture”), pursuant to which the Original
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Indenture was further amended and Medicine Bow, MBOW Operating and MBOW Four Star eachexpressly assumed the obligations of a Subsidiary Guarantor under the Original Indenture;     WHEREAS, the Company, El Paso Production, Medicine Bow, MBOW Operating, MBOW Four Star, ElPaso Management, El Paso Holdings, El Paso E&P, El Paso Resale, El Paso Transmission and El PasoGathering entered into that certain Fourth Supplemental Indenture, dated as of December 31, 2005(the “Fourth Supplemental Indenture”), pursuant to which the Original Indenture was furtheramended and (i) El Paso Management, El Paso Holdings, El Paso E&P, El Paso Resale, El PasoTransmission and El Paso Gathering each expressly assumed the obligations of a Subsidiary Guarantorunder the Original Indenture and (ii) El Paso E&P, in connection with the merger of GOM and RatonCorporation with and into El Paso E&P, expressly assumed the obligations of GOM and RatonCorporation under their respective Subsidiary Guarantees;     WHEREAS, the Company, MBOW Four Star, El Paso Management, El Paso Holdings, El Paso E&P, ElPaso Resale, El Paso Transmission and El Paso Gathering entered into that certain FifthSupplemental Indenture, dated as of June 30, 2006 (the “Fifth Supplemental Indenture”),pursuant to which the Original Indenture was further amended and (i) El Paso E&P, in connectionwith the merger of El Paso Production and MBOW Operating with and into El Paso E&P, expresslyassumed the obligations of El Paso Production and MBOW Operating under their respective SubsidiaryGuarantees and (ii) the Company, in connection with the merger of Medicine Bow with and into theCompany, expressly assumed the obligations of Medicine Bow under its Subsidiary Guarantee;     WHEREAS, as of the date hereof, pursuant to a reorganization of certain subsidiaries of ElPaso Corporation, El Paso International, El Paso Preferred Holdings, and El Paso Finance becamedirect or indirect wholly owned subsidiaries of the Company;     WHEREAS, the Company and the Subsidiary Guarantors now desire to further amend the OriginalIndenture (as supplemented by the First Supplemental Indenture, the Second Supplemental Indenture,the Third Supplemental Indenture, the Fourth Supplemental Indenture and the Fifth SupplementalIndenture, the “Indenture”) to include El Paso International, El Paso Preferred Holdings,El Paso Brazil, and El Paso Finance as parties to the Indenture as guarantors of the Company’sobligations under the Notes, subject to the terms and conditions of the Indenture and the Notes;and     WHEREAS, the Trustee, upon satisfaction of all actions and conditions on the part of theCompany and the Subsidiary Guarantors necessary for the execution, delivery and performance of thisSixth Supplemental Indenture (including, without limitation, the receipt of an Officers’Certificate and an Opinion of Counsel) is willing to amend the Indenture as hereinafter set forth;     NOW, THEREFORE, the Company, the Subsidiary Guarantors and the Trustee mutually covenant andagree for the equal and proportionate benefit of all Holders of the Notes as follows:
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**ARTICLE 1**     Section 1.01 This Sixth Supplemental Indenture is supplemental to the Indenture, anddoes and shall be deemed to form a part of, and shall be construed in connection with and as a partof, the Indenture, for any and all purposes.     Section 1.02 This Sixth Supplemental Indenture shall become effective immediately uponits execution and delivery by each of the Company, the Subsidiary Guarantors and the Trustee.**ARTICLE 2**     Section 2.01 The Company, the Subsidiary Guarantors and the Trustee hereby acknowledgeand agree that each of El Paso International, El Paso Preferred Holdings, El Paso Brazil, and ElPaso Finance (collectively, the “New Subsidiary Guarantors”) hereby becomes a party to theIndenture, as a Subsidiary Guarantor, and as such will have all of the rights and be subject to allof the obligations and agreements of a Subsidiary Guarantor under the Indenture. The NewSubsidiary Guarantors agree to be bound by all of the provisions of the Indenture applicable to aSubsidiary Guarantor and to perform all of the obligations and agreements of a Subsidiary Guarantorunder the Indenture. Each New Subsidiary Guarantor hereby provides a full, unconditional andirrevocable Guarantee, as primary obligor and not merely as surety, jointly and severally with eachother Subsidiary Guarantor, to each Holder and to the Trustee and their successors and assigns, onthe terms and subject to the conditions set forth in the Indenture, including but not limited toArticle 10 thereof.**ARTICLE 3**     Section 3.01 Except as specifically modified herein, the Notes and the Indenture arein all respects ratified and confirmed and shall remain in full force and effect in accordance withtheir terms. This Sixth Supplemental Indenture shall form a part of the Indenture for allpurposes, and every Holder of Notes heretofore or hereafter authenticated and delivered shall bebound hereby. The Trustee shall not be responsible in any manner whatsoever for or in respect ofthe validity or sufficiency of this Sixth Supplemental Indenture or for or in respect of therecitals contained herein, all of which are made solely by the Company and the SubsidiaryGuarantors.     Section 3.02 Except as otherwise expressly provided herein, no duties,responsibilities or liabilities are assumed, or shall be construed to be assumed, by the Trustee byreason of this Sixth Supplemental Indenture. This Sixth Supplemental Indenture is executed andaccepted by the Trustee subject to all the terms and conditions set forth in the Indenture with thesame force and effect as if those terms and conditions were repeated at length herein and madeapplicable to the Trustee with respect hereto. In entering into this Sixth Supplemental Indenture,the Trustee shall be entitled to the benefit of every provision of the Indenture relating to theconduct or affecting the liability or affording protection to the Trustee, regardless of whetherelsewhere herein so provided, including indemnification pursuant to Section 7.07 of the OriginalIndenture, and the Company acknowledges that the Trustee shall be entitled to indemnificationpursuant to
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Section 7.07 of the Original Indenture against any and all loss, liability or expense(including attorney’s fees) in connection with the Trustee’s signing this Sixth SupplementalIndenture.     Section 3.03**THIS SIXTH SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND CONSTRUED INACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.**     Section 3.04 This Sixth Supplemental Indenture may be executed in any number ofcounterparts, each of which when so executed and delivered shall be deemed an original, but allsuch counterparts together shall constitute but one and the same instrument.     Section 3.05 All notices and other communications to the New Subsidiary Guarantorsshall be given as provided in Section 11.02 of the Original Indenture for notices to SubsidiaryGuarantors.[Signature page follows.]
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     IN WITNESS WHEREOF, the parties hereto have caused this Sixth Supplemental Indenture to beduly executed as of the date first written above.      Issuer: