

                   [Letterhead of Davis, Graham & Stubbs LLP]





                               September 22, 1997


Basin Exploration, Inc.
370 Seventeenth Street, Suite 3400
Denver, Colorado  80202


         Re:      Shelf Registration Statement on Form S-3 Relating
                  to $200,000,000 Aggregate Principal Amount
                  of Equity Securities and Debt Securities

Ladies and Gentlemen:

     We have acted as counsel for Basin Exploration, Inc., a Delaware
corporation (the "Company") in connection with the preparation of a Registration
Statement on Form S-3 (the "Registration Statement") filed by the Company with
the Securities and Exchange Commission. The Registration Statement relates to
the registration under the Securities Act of 1933, as amended (the "1933 Act"),
of $200,000,000 principal amount of equity securities (the "Equity Securities")
and debt securities (the "Debt Securities" and together with the Equity
Securities, the "Securities") that may be issued by the Company.

     This opinion is delivered pursuant to the requirements of Item 601(b)(5) of
Regulation S-K under the 1933 Act.

     We have examined the form of the Indenture filed by the Company as an
exhibit to the Registration Statement (the "Indenture"). In addition, we have
examined and relied on originals or copies, certified or otherwise identified to
our satisfaction, of such documents, corporate records and other instruments,
have made such inquiries as to questions of fact of officers and representatives
of the Company and have made such examinations of law as we have deemed
necessary or appropriate for purposes of giving the opinion expressed below. In
such examination, we have assumed the genuineness of all signatures, the
authenticity of all documents submitted to us as originals and the conformity
with the originals of all documents submitted to us as copies.


<PAGE>


Basin Exploration, Inc.
Page 2


     We have assumed for purposes of this opinion (i) the corporate power,
authority and legal right of the trustee or trustees (the "trustees") under the
Indenture to execute, deliver and perform their obligations under the Indenture,
that the performance of such obligations by the trustees will not violate their
charters or by-laws and that the trustees have the legal ability to exercise
their trust powers and (ii) that the Indenture will have been duly
authenticated, authorized, executed and delivered by the applicable trustee at
the time of issuance of any Debt Securities.

     The following opinions are limited solely to the applicable federal law of
the United States of America, the law of the State of Colorado and the General
Corporation Law of the State of Delaware. While we are not licensed to practice
in the State of Delaware, we have reviewed applicable provisions of the General
Corporation Law of Delaware as we have deemed appropriate in connection with the
provisions expressed herein. Except as described, we have neither examined nor
do we express any opinion with respect to Delaware law.

     Based upon and subject to the foregoing, we are of the opinion that:

     1. The issuance and sale by the Company of up to $200,000,000 of
Securities, as provided in the Registration Statement, have been duly and
validly authorized by all necessary corporate action of the Company.

     2. The Company's common stock, $0.01 par value per share (the "Common
Stock"), when issued and sold in conformity with the resolutions of the board of
directors of the Company and as contemplated in the Registration Statement, the
prospectus contained therein (the "Prospectus") and in the applicable supplement
to the Prospectus, will be validly issued, fully paid and non-assessable.

     3. The Company's Equity Securities (other than the Common Stock), when
issued and sold in conformity with the resolutions of the board of directors of
the Company and as contemplated in the Registration Statement, the Prospectus
and in the applicable supplement to the Prospectus, will be validly issued.

     4. When (i) the Registration Statement has become effective under the 1933
Act, (ii) the applicable Indenture has been qualified under the Trust Indenture
Act of 1939, as amended, and has been duly executed and delivered by the parties
thereto, (iii) the definitive terms of any Debt Securities and of their issue
and sale have been duly established in conformity with the resolutions

<PAGE>

of the board of directors of the Company and the applicable Indenture so as not
to violate any applicable law or agreement or instrument then binding on the
Company, (iv) such Debt Securities have been duly executed and authenticated in
accordance with the Indenture and (v) such Debt Securities have been issued and
sold as contemplated in the Registration Statement, the Prospectus and in the
applicable supplement to the Prospectus, such Debt Securities will constitute
valid and legally binding obligations of the Company, entitled to the benefits
provided by the applicable Indenture, except (A) the enforceability thereof may
be limited by bankruptcy, insolvency, reorganization, fraudulent transfer,
moratorium or other similar laws now or hereafter in effect relating to
creditors' rights generally and (B) the remedy of specific performance and
injunctive and other forms of equitable relief may be subject to certain
equitable defenses and to the discretion of the court before which any
proceeding therefor may be brought.

     We hereby consent to the filing of this opinion with the Commission as
Exhibit 5.1 to the Registration Statement. We also consent to the reference to
this firm under the heading "Legal Matters" in the Prospectus included in the
Registration Statement as the counsel who will pass upon the validity of the
securities. In giving this consent, we do not thereby admit that we are in the
category of persons whose consent is required under Section 7 of the Securities
Act or the rules of the Securities and Exchange Commission thereunder.

                              Very truly yours,

                              /s/ Davis, Graham & Stubbs LLP

                              DAVIS, GRAHAM & STUBBS LLP



