EXHIBIT 5.1


                             VInson & Elkins L.L.P.
                                Attorneys at Law

                             Vinson & Elkins L.L.P.
                             2300 First City Tower
                               1001 Fannin Street
                           Houston, Texas 77002-6760
                            Telephone (713) 758-2222
                               Fax (713) 758-2346


                                  May 14, 2002


Duke Energy Field Services, LLC
370 17th Street, Suite 900
Denver, Colorado 80202

Ladies and Gentlemen:

     We have acted as counsel for Duke Energy Field Services, LLC, a Delaware
limited liability company (the "Company"), with respect to certain legal matters
in connection with the registration by the Company and DEFS Capital Trust I, a
Delaware statutory business trust (the "Trust"), under the Securities Act of
1933, as amended (the "Securities Act"), of the offer and sale (a) by the
Company from time to time, pursuant to Rule 415 under the Securities Act, of (i)
unsecured debt securities, in one or more series, consisting of notes,
debentures or other evidences of indebtedness (the "Debt Securities"), (ii)
junior subordinated notes (the "Junior Subordinated Notes") to be purchased by
the Trust with the proceeds from the sale of preferred securities by the Trust
(the "Trust Preferred Securities") and (iii) a guarantee of the Trust Preferred
Securities (the "Trust Preferred Securities Guarantee"), and (b) by the Trust
from time to time pursuant to Rule 415 under the Securities Act of the Trust
Preferred Securities. The Company has advised us that the aggregate initial
offering prices of the Debt Securities, and Trust Preferred Securities
(excluding the aggregate initial offering price of the Junior Subordinated
Notes) offered by the Company and the Trust (collectively, including the Junior
Subordinated Notes, the "Securities") will not exceed $500,000,000 or, if
applicable, the equivalent thereof in any other currency or currency unit. The
Company has advised us that the Securities will be offered in amounts, at prices
and on terms to be determined in light of market conditions at the time of sale
and to be set forth in supplements to the Prospectus contained in the Company's
and the Trust's Registration Statement on Form S-3 to which this opinion is an
exhibit.

     We have examined originals or copies, certified or otherwise identified to
our satisfaction, of (i) the Amended and Restated Limited Liability Company
Agreement of the Company, as amended to the date hereof; (ii) the Indenture for
Senior Debt Securities dated as of August 16, 2000 between the Company and
JPMorgan Chase Bank (formerly known as The Chase Manhattan Bank), as
supplemented by the First Supplemental Indenture dated as of August 16, 2000,
the Second Supplemental Indenture dated as of February 2, 2001 and the Third
Supplemental Indenture dated as of November 9, 2001 (together, the "Senior
Indenture"); (iii) a form of the Indenture for Subordinated Debt Securities
(including Junior Subordinated Notes) to






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be entered into between the Company and JPMorgan Chase Bank (the "Subordinated
Indenture," and together with the Senior Indenture, the "Indentures," and each,
an "Indenture"), in the form included as an exhibit to the Registration
Statement; (iv) a form of Trust Preferred Securities Guarantee Agreement to be
entered into by the Company and JPMorgan Chase Bank (the "Guarantee Agreement"),
in the form included as an exhibit to the Registration Statement; and (v) such
other certificates, statutes and other instruments and documents as we
considered appropriate for purposes of the opinions hereafter expressed. In
addition, we reviewed such questions of law as we considered appropriate.

     As to any facts material to our opinion, we have made no independent
investigation of such facts and have relied, to the extent that we deem such
reliance proper, upon certificates of public officials and officers or other
representatives of the Company.

     In rendering the opinions set forth below, we have assumed that (i) all
information contained in all documents reviewed by us is true and correct; (ii)
all signatures on all documents examined by us are genuine; (iii) all documents
submitted to us as originals are authentic and all documents submitted to us as
copies conform to the originals of those documents; (iv) each natural person
signing any document reviewed by us had the legal capacity to do so; (v) each
person signing in a representative capacity (other than on behalf of the
Company) any document reviewed by us had authority to sign in such capacity;
(vi) the Registration Statement and any amendments thereto (including
post-effective amendments) will have become effective and comply with all
applicable laws; (vii) a prospectus supplement will have been prepared and filed
with the Securities and Exchange Commission describing the Securities offered
thereby; (viii) all Securities will be issued and sold in compliance with
applicable federal and state securities laws and in the manner stated in the
Registration Statement and the applicable prospectus supplement; (ix) the Senior
Indenture and the Subordinated Indenture, together with any supplemental
indenture or other instruments establishing a series of Debt Securities or
Junior Subordinated Notes, as the case may be, to be issued under any of the
Indentures, will each be duly authorized, executed and delivered by the parties
thereto in substantially the form reviewed by us or with changes that do not
affect the opinions given hereunder; and (x) a definitive purchase, underwriting
or similar agreement with respect to any Securities offered will have been duly
authorized and validly executed and delivered by the Company and the other
parties thereto.

     Based on the foregoing, and subject to the assumptions, qualifications,
limitations and exceptions set forth herein, we are of the opinion that:

               1. With respect to Debt Securities to be issued under the Senior
          Indenture, when (i) the Senior Indenture has been duly qualified under
          the Trust Indenture Act of 1939, as amended (the "TIA"), (ii) the
          Board of Directors of the Company (or a committee thereof) has taken
          all necessary limited liability company action to approve the issuance
          and terms of such Debt Securities, the terms of the offering thereof
          and related matters, (iii) the terms of such Debt Securities and of
          their issuance and sale have been established so as not to violate any
          applicable law or result in a default under or breach of any agreement
          or instrument binding upon the Company and so as to comply with any
          requirement or restriction imposed by any court or governmental body
          having





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     jurisdiction over the Company and (iv) such Debt Securities have been duly
     executed, authenticated, issued and delivered in accordance with the
     provisions of the Senior Indenture and in accordance with the applicable
     definitive purchase, underwriting or similar agreement approved by the
     Board of Directors of the Company (or a committee thereof), then upon
     payment of the consideration provided for therein, such Debt Securities
     will be legally issued and will constitute valid and binding obligations of
     the Company, enforceable against the Company in accordance with their terms
     and will be entitled to the benefits of the Senior Indenture.

          2. With respect to Debt Securities, including the Junior Subordinated
     Notes, to be issued under the Subordinated Indenture ("Subordinated Debt
     Securities"), when (i) the Subordinated Indenture has been duly authorized,
     executed and delivered by the Company to the subordinated trustee, (ii) the
     Subordinated Indenture has been duly qualified under the TIA, (iii) the
     Board of Directors of the Company (or a committee thereof) has taken all
     necessary limited liability company action to approve the issuance and
     terms of such Subordinated Debt Securities, the terms of the offering
     thereof and related matters, (iv) the terms of such Subordinated Debt
     Securities and their issuance and sale and the terms of the Subordinated
     Indenture have been established so as not to violate any applicable law or
     result in a default under or breach of any agreement or instrument binding
     upon the Company and so as to comply with any requirement or restriction
     imposed by any court or governmental body having jurisdiction over the
     Company and (v) such Subordinated Debt Securities have been duly executed,
     authenticated, issued and delivered in accordance with the provisions of
     the Subordinated Indenture and in accordance with the applicable definitive
     purchase, underwriting or similar agreement approved by the Board of
     Directors of the Company (or a committee thereof), then upon payment of the
     consideration provided for therein, such Subordinated Debt Securities will
     be legally issued and will constitute valid and binding obligations of the
     Company, enforceable against the Company in accordance with their terms and
     will be entitled to the benefits of the Subordinated Indenture.

          3. With respect to the Trust Preferred Securities Guarantee, when (i)
     the Guarantee Agreement has been duly authorized, executed, issued and
     delivered by the Company to the guarantee trustee in accordance with the
     provisions of the Guarantee Agreement approved by the Board of Directors of
     the Company (or a committee thereof), (ii) the Guarantee Agreement has been
     duly qualified under the TIA and (iii) the Board of Directors of the
     Company (or a committee thereof) has taken all necessary limited liability
     company action to approve and establish the terms of the Guarantee
     Agreement and the Trust Preferred Securities Guarantee and to authorize and
     approve the issuance thereof, the terms of the offering and related
     matters, then upon payment for and delivery of the Trust Preferred
     Securities in accordance with the applicable purchase agreement, the Trust
     Preferred Securities Guarantee will constitute a valid and binding
     obligation of the Company, enforceable against the Company in accordance
     with its terms.

     The foregoing opinions are qualified to the extent that the enforceability
of any document, instrument or Security may be limited by or subject to (i)
bankruptcy, insolvency,






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fraudulent transfer or conveyance, reorganization, moratorium or other laws
relating to or affecting creditors' rights generally, and to general equitable
or public policy principles, and (ii) with respect to any Debt Securities
denominated in a currency other than United States dollars, the requirement that
a claim (or a foreign currency judgment in respect of such a claim) with respect
to such Securities be converted to United States dollars at a rate of exchange
prevailing on a date determined pursuant to applicable law or governmental
authority.

     We express no opinions concerning (i) the validity or enforceability of any
provisions contained in Indentures that purport to waive or not give effect to
rights to notices, defenses, subrogation or other rights or benefits that cannot
be effectively waived under applicable law or (ii) the enforceability of
indemnification provisions to the extent they purport to relate to liabilities
resulting from or based upon negligence or any violation of federal or state
securities or blue sky laws.

     The foregoing opinions are limited in all respects to the laws of the
Delaware General Corporation Law (including the applicable provisions of the
Delaware Constitution and the reported judicial decisions interpreting these
laws), the laws of the State of New York and the federal law of the United
States of America.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to our name under the caption
"Validity of the Securities" in the prospectus forming a part of the
Registration Statement. By giving such consent, we do not admit that we are
within the category of persons whose consent is required under Section 7 of the
Securities Act or the rules and regulations of the Securities and Exchange
Commission issued thereunder.

                                          Very truly yours,

                                          /s/ Vinson & Elkins L.L.P.

                                          Vinson & Elkins L.L.P.