EXHIBT 10.4

                                                                     [Execution]

                                    GUARANTY
                                    --------

         THIS GUARANTY is made as of May 1, 2002, by St. Mary Operating Company,
a Colorado corporation, St. Mary Energy Company, a Delaware corporation, Nance
Petroleum Corporation, a Montana corporation, St. Mary Minerals, Inc. a Colorado
corporation, Parish Corporation, a Colorado corporation, Four Winds Marketing
LLC, a Colorado limited liability company and Roswell LLC, a Texas limited
liability company (collectively herein called "Guarantors" and each a
"Guarantor"), in favor of Bank of America, N.A., individually and as agent for
Lenders, as such term is defined in the Credit Agreement described below (in
such capacity "Agent").

                                    RECITALS:

         1. St. Mary Land & Exploration Company, a Delaware corporation
("Borrower"), has executed in favor of Agent and Lenders those certain
promissory notes dated June 24, 2000, payable to the order of Lenders in the
aggregate principal amount of $200,000,000 (such promissory notes, as from time
to time amended, and all promissory notes given in substitution, renewal or
extension therefor or thereof, in whole or in part, being herein collectively
called the "Note").

         2. The Note was executed pursuant to a Credit Agreement dated June 30,
1998 (herein, as from time to time amended, supplemented or restated, called the
"Credit Agreement"), by and between Borrower, Agent and Lenders, pursuant to
which Lenders have agreed to advance funds to Borrower under the Note.

         3. It is a condition precedent to Lenders' obligations to advance funds
pursuant to the Credit Agreement that Guarantors shall execute and deliver to
Agent a satisfactory guaranty of Borrower's obligations under the Note and the
Credit Agreement.

         4. Borrower owns directly one hundred percent (100 %) of the
outstanding equity interests of each Guarantor.

         5. Borrower, Guarantors, and the other direct and indirect subsidiaries
of Borrower are mutually dependent on each other in the conduct of their
respective businesses under a holding company structure, with the credit needed
from time to time by each often being provided by another or by means of
financing obtained by one such affiliate with the support of the others for
their mutual benefit and the ability of each to obtain such financing being
dependent on the successful operations of the others.

         6. The board of directors of each Guarantor has determined that such
Guarantor's execution, delivery and performance of this Guaranty may reasonably
be expected to benefit such Guarantor, directly or indirectly, and are in the
best interests of such Guarantor.

         NOW, THEREFORE, in consideration of the premises, of the benefits which
will inure to each Guarantor from Lenders' advances of funds to Borrower under
the Credit Agreement, and of Ten Dollars and other good and valuable
consideration, the receipt and sufficiency of all of which are hereby
acknowledged, and in order to induce Lenders to advance funds under the Credit
Agreement, each Guarantor hereby agrees with Agent, for the benefit of Agent and
Lenders as follows:

                                   AGREEMENTS:

         Section 1. Definitions. Reference is hereby made to the Credit
                    -----------
Agreement for all purposes. All terms used in this Guaranty which are defined in
the Credit Agreement and not otherwise defined herein shall have the same
meanings when used herein. All references herein to this Guaranty, any
Obligation Document, Loan Document, or other document or instrument refer to the
same as from time to time amended, supplemented or restated. As used herein the
following terms shall have the following meanings:

         "Agent" means the Person who, at the time in question, is the "Agent"
          -----
under the Credit Agreement. Whenever there is only one Lender under the Credit
Agreement, "Agent" shall also refer to such Lender in such capacity as the only
Lender.

         "Lenders" means Bank of America, N.A. and all other Persons who at any
          -------
time are "Lenders" under the Credit Agreement.


         "Obligations" means collectively all of the indebtedness, obligations,
          -----------
and undertakings which are guaranteed by Guarantor and described in subsections
(a) and (b) of Section 2.

         "Obligation Documents" means the Note, the Credit Agreement, the Loan
          --------------------
Documents (other than this Guaranty), all other documents and instruments under,
by reason of which, or pursuant to which any or all of the Obligations are
evidenced, governed, secured, or otherwise dealt with, and all other documents,
instruments, agreements, certificates, legal opinions and other writings
heretofore or hereafter delivered in connection herewith or therewith.

         "Obligors" means Borrower, each Guarantor and any other endorsers,
          --------
guarantors or obligors, primary or secondary, of any or all of the Obligations.

         "Security" means any rights, properties, or interests of Agent or
          --------
Lenders, under the Obligation Documents or otherwise, which provide recourse or
other benefits to Agent or Lenders in connection with the Obligations or the
non-payment or non-performance thereof, including collateral (whether real or
personal, tangible or intangible) in which Agent or Lenders have rights under or
pursuant to any Obligation Documents, guaranties of the payment or performance
of any Obligation, bonds, surety agreements, keep-well agreements, letters of
credit, rights of subrogation, rights of offset, and rights pursuant to which
other claims are subordinated to the Obligations.

         "Security Agreement" means that certain Security Agreement of even date
          ------------------
herewith from Borrower and Guarantors in favor of Agent for the benefit of
Lenders.

                                       2

         Section 2.  Guaranty.
                     --------

         (a) Each Guarantor hereby, jointly and severally, irrevocably,
absolutely, and unconditionally guarantees to Agent and each Lender the prompt,
complete, and full payment when due, and no matter how the same shall become
due, of:

                  (i) the Note, including all principal, all interest thereon
         and all other sums payable thereunder; and

                  (ii) All other sums payable under the other Obligation
         Documents, whether for principal, interest, fees or otherwise; and

                  (iii) Any and all other indebtedness or liabilities which
         Borrower may at any time owe to Agent or any Lender, whether incurred
         heretofore or hereafter or concurrently herewith, voluntarily or
         involuntarily, whether owed alone or with others, whether fixed,
         contingent, absolute, inchoate, liquidated or unliquidated, whether
         such indebtedness or liability arises by notes, discounts, overdrafts,
         open account indebtedness or in any other manner whatsoever, and
         including interest, attorneys' fees and collection costs as may be
         provided by law or in any instrument or agreement evidencing any such
         indebtedness or liability.

Without limiting the generality of the foregoing, each Guarantor's liability
hereunder shall extend to and include all post-petition interest, expenses, and
other duties and liabilities of Borrower described above in this subsection (a),
or below in the following subsection (b), which would be owed by Borrower but
for the fact that they are unenforceable or not allowable due to the existence
of a bankruptcy, reorganization, or similar proceeding involving Borrower.

         (b) Each Guarantor hereby, jointly and severally, irrevocably,
absolutely, and unconditionally guarantees to Agent and each Lender the prompt,
complete and full performance, when due, and no matter how the same shall become
due, of all obligations and undertakings of Borrower to Agent or such Lender
under, by reason of, or pursuant to any of the Obligation Documents.

         (c) If Borrower shall for any reason fail to pay any Obligation, as and
when such Obligation shall become due and payable, whether at its stated
maturity, as a result of the exercise of any power to accelerate, or otherwise,
each Guarantor will, upon demand by Agent, pay such Obligation in full to Agent
for the benefit of Agent or the Lender to whom such Obligation is owed. If
Borrower shall for any reason fail to perform promptly any Obligation,
Guarantors will, upon demand by Agent, cause such Obligation to be performed or,
if specified by Agent, provide sufficient funds, in such amount and manner as
Agent shall in good faith determine, for the prompt, full and faithful
performance of such Obligation by Agent or such other Person as Agent shall
designate.

         (d) If Borrower or Guarantors fail to pay or perform any Obligation as
described in the immediately preceding subsections (a), (b), or (c) Guarantors
will incur the additional obligation to pay to Agent, and Guarantors will
forthwith upon demand by Agent pay to Agent, the amount of any and all expenses,

                                       3

including fees and disbursements of Agent's counsel and of any experts or agents
retained by Agent, which Agent may incur as a result of such failure.

         (e) As between Guarantors and Agent or Lenders, this Guaranty shall be
considered a primary and liquidated liability of Guarantor.

         (f) The liability of each Guarantor hereunder shall be limited to the
maximum amount of liability that can be incurred without rendering this
Guaranty, as it relates to such Guarantor, voidable under applicable law
relating to fraudulent conveyance or fraudulent transfer, and not for any
greater amount.

         Section 3  Unconditional Guaranty; Joint and Several Liability.
                    ---------------------------------------------------

         (a) No action which Agent or any Lender may take or omit to take in
connection with any of the Obligation Documents, any of the Obligations (or any
other indebtedness owing by Borrower to Agent or any Lender), or any Security,
and no course of dealing of Agent or any Lender with any Obligor or any other
Person, shall release or diminish any Guarantor's obligations, liabilities,
agreements or duties hereunder, affect this Guaranty in any way, or afford any
Guarantor any recourse against Agent or any Lender, regardless of whether any
such action or inaction may increase any risks to or liabilities of Agent or any
Lender or any Obligor or increase any risk to or diminish any safeguard of any
Security. Without limiting the foregoing, each Guarantor hereby expressly agrees
that Agent and Lenders may, from time to time, without notice to or the consent
of such Guarantor, do any or all of the following:

                  (i) Amend, change or modify, in whole or in part, any one or
         more of the Obligation Documents and give or refuse to give any waivers
         or other indulgences with respect thereto.

                  (ii) Neglect, delay, fail, or refuse to take or prosecute any
         action for the collection or enforcement of any of the Obligations, to
         foreclose or take or prosecute any action in connection with any
         Security or Obligation Document, to bring suit against any Obligor or
         any other Person, or to take any other action concerning the
         Obligations or the Obligation Documents.

                  (iii) Accelerate, change, rearrange, extend, or renew the
         time, rate, terms, or manner for payment or performance of any one or
         more of the Obligations (whether for principal, interest, fees,
         expenses, indemnifications, affirmative or negative covenants, or
         otherwise).

                  (iv) Compromise or settle any unpaid or unperformed Obligation
         or any other obligation or amount due or owing, or claimed to be due or
         owing, under any one or more of the Obligation Documents.

                  (v) Take, exchange, amend, eliminate, surrender, release, or
         subordinate any or all Security for any or all of the Obligations,
         accept additional or substituted Security therefor, and perfect or fail
         to perfect Agent's or Lenders' rights in any or all Security.

                                       4

                  (vi) Discharge, release, substitute or add Obligors.

                  (vii) Apply all monies received from Obligors or others, or
         from any Security for any of the Obligations, as Agent or Lenders may
         determine to be in their best interest, without in any way being
         required to marshall Security or assets or to apply all or any part of
         such monies upon any particular Obligations.

         (b) No action or inaction of any Obligor or any other Person, and no
change of law or circumstances, shall release or diminish Guarantors'
obligations, liabilities, agreements, or duties hereunder, affect this Guaranty
in any way, or afford Guarantors any recourse against Agent or any Lender.
Without limiting the foregoing, the obligations, liabilities, agreements, and
duties of each Guarantor under this Guaranty shall not be released, diminished,
impaired, reduced, or affected by the occurrence of any or all of the following
from time to time, even if occurring without notice to or without the consent of
such Guarantor:

                  (i) Any voluntary or involuntary liquidation, dissolution,
         sale of all or substantially all assets, marshalling of assets or
         liabilities, receivership, conservatorship, assignment for the benefit
         of creditors, insolvency, bankruptcy, reorganization, arrangement, or
         composition of any Obligor or any other proceedings involving any
         Obligor or any of the assets of any Obligor under laws for the
         protection of debtors, or any discharge, impairment, modification,
         release, or limitation of the liability of, or stay of actions or lien
         enforcement proceedings against, any Obligor, any properties of any
         Obligor, or the estate in bankruptcy of any Obligor in the course of or
         resulting from any such proceedings.

                  (ii) The failure by Agent or any Lender to file or enforce a
         claim in any proceeding described in the immediately preceding
         subsection (i) or to take any other action in any proceeding to which
         any Obligor is a party.

                  (iii) The release by operation of law of any Obligor from any
         of the Obligations or any other obligations to Agent or any Lender.

                  (iv) The invalidity or unenforceability of any of the
         Obligation Documents, in whole or in part, or any defense or excuse for
         failure to perform on account of force majeure, act of God, casualty,
         impossibility, impracticability, or other defense or excuse whatsoever.

                  (v) The failure of any Obligor or any other Person to sign any
         guaranty or other instrument or agreement within the contemplation of
         any Obligor, Agent or any Lender.

                  (vi) The fact that any Guarantor may have incurred directly
         part of the Obligations or is otherwise primarily liable therefor.

                  (vii) Without limiting any of the foregoing, any fact or event
         (whether or not similar to any of the foregoing) which in the absence
         of this provision would or might constitute or afford a legal or
         equitable discharge or release of or defense to a guarantor or surety
         other than the actual payment and performance by Guarantors under this
         Guaranty.

                                       5

         (c) Agent and Lenders may invoke the benefits of this Guaranty before
pursuing any remedies against any Obligor or any other Person and before
proceeding against any Security now or hereafter existing for the payment or
performance of any of the Obligations. Agent and Lenders may maintain an action
against any one or more Guarantors on this Guaranty without joining any other
Obligor therein and without bringing a separate action against any other
Obligor.

         (d) If any payment to Agent or any Lender by any Obligor is held to
constitute a preference or a voidable transfer under applicable state or federal
laws, or if for any other reason Agent or any Lender is required to refund such
payment to the payor thereof or to pay the amount thereof to any other Person,
such payment to Agent or such Lender shall not constitute a release of any
Guarantor from any liability hereunder, and each Guarantor agrees to pay such
amount to Agent or such Lender on demand and agrees and acknowledges that this
Guaranty shall continue to be effective or shall be reinstated, as the case may
be, to the extent of any such payment or payments. Any transfer by subrogation
which is made as contemplated in Section 6 prior to any such payment or payments
shall (regardless of the terms of such transfer) be automatically voided upon
the making of any such payment or payments, and all rights so transferred shall
thereupon revert to and be vested in Agent and Lenders.

         (e) This is a continuing guaranty and shall apply to and cover all
Obligations and renewals and extensions thereof and substitutions therefor from
time to time.

         (f) The obligation of each Guarantor hereunder shall be several and
also joint with all other Guarantors, each Guarantor with all other Guarantors
and also each Guarantor with any one or more other Guarantors, and may be
enforced at the option of Agent and/or Lenders against each Guarantor severally,
any two or more Guarantors jointly, or some Guarantor's severally and some
Guarantor's jointly. Each Guarantor acknowledges that the effectiveness of this
Guaranty is not conditioned on any or all of the Obligations being guaranteed by
anyone else, including the other Guarantors.

         Section 4. Waiver. Each Guarantor hereby waives, with respect to the
                    ------
Obligations, this Guaranty, and the Obligation Documents:

         (a) notice of the incurrence of any Obligation by Borrower, and notice
of any kind concerning the assets, liabilities, financial condition,
creditworthiness, businesses, prospects, or other affairs of Borrower (it being
understood and agreed that: (i) each Guarantor shall take full responsibility
for informing itself of such matters, (ii) neither Agent nor any Lender shall
have any responsibility of any kind to inform any Guarantor of such matters, and
(iii) Agent and Lenders are hereby authorized to assume that Guarantors, by
virtue of their relationships with Borrower which are independent of this
Guaranty, has full and complete knowledge of such matters whenever Lenders
extend credit to Borrower or take any other action which may change or increase
Guarantors' liabilities or losses hereunder).

         (b) notice that Agent, any Lender, any Obligor, or any other Person has
taken or omitted to take any action under this Guaranty, any Obligation Document
or any other agreement or instrument relating thereto or relating to any
Obligation.

                                       6

         (c) notice of acceptance of this Guaranty and all rights of Guarantors
under any State law discharging Guarantors from liability hereunder for failure
to sue on this Guaranty.

         (d) default, demand, presentment for payment, and notice of default,
demand, dishonor, nonpayment, or nonperformance.

         (e) notice of intention to accelerate, notice of acceleration, protest,
notice of protest, notice of any exercise of remedies (as described in the
following Section 5 or otherwise), and all other notices of any kind whatsoever.

         Section 5. Exercise of Remedies. Agent and each Lender shall have the
                    --------------------
right to enforce, from time to time, in any order and at Agent's or such
Lender's sole discretion, any rights, powers and remedies which Agent or such
Lender may have under this Guaranty or the Obligation Documents or otherwise,
including judicial foreclosure, the exercise of rights of power of sale, the
taking of a deed or assignment in lieu of foreclosure, the appointment of a
receiver to collect rents, issues and profits, the exercise of remedies against
personal property, or the enforcement of any assignment of leases, rentals, oil
or gas production, or other properties or rights, whether real or personal,
tangible or intangible; and Guarantors shall be liable to Agent and each Lender
hereunder for any deficiency resulting from the exercise by Agent or any Lender
of any such right or remedy even though any rights which Guarantors may have
against Borrower or others may be destroyed or diminished by exercise of any
such right or remedy. No failure on the part of Agent or any Lender to exercise,
and no delay in exercising, any right hereunder or under any Obligation Document
shall operate as a waiver thereof; nor shall any single or partial exercise of
any right preclude any other or further exercise thereof or the exercise of any
other right. The rights, powers and remedies of Agent and each Lender provided
herein and in the Obligation Documents are cumulative and are in addition to,
and not exclusive of, any other rights, powers or remedies provided by law or in
equity. The rights of Agent and each Lender hereunder are not conditional or
contingent on any attempt by Agent or any Lender to exercise any of its rights
under any Obligation Document against any Obligor or any other Person.

         Section 6.  Limited Subrogation.
                     -------------------

         (a) Until all of the Obligations have been paid and performed in full
Guarantors shall have no right to exercise any right of subrogation,
reimbursement, indemnity, exoneration, contribution or any other claim which it
may now or hereafter have against or to any Obligor or any Security in
connection with this Guaranty (including any right of subrogation under any
state law), and Guarantors hereby waive any rights to enforce any remedy which
Guarantor may have against Borrower and any right to participate in any Security
until such time. If any amount shall be paid to Guarantors on account of any
such subrogation or other rights, any such other remedy, or any Security at any
time when all of the Obligations and all other expenses guaranteed pursuant
hereto shall not have been paid in full, such amount shall be held in trust for
the benefit of Agent, shall be segregated from the other funds of Guarantors and
shall forthwith be paid over to Agent to be held by Agent as collateral for, or
then or at any time thereafter applied in whole or in part by Agent against, all
or any portion of the Obligations, whether matured or unmatured, in such order
as Agent shall elect.

                                       7

         (b) If Guarantors shall make payment to Agent of all or any portion of
the Obligations and if all of the Obligations shall be finally paid in full,
Agent will, at Guarantors' request and expense, execute and deliver to
Guarantors (without recourse, representation or warranty) appropriate documents
necessary to evidence the transfer by subrogation to Guarantors of an interest
in the Obligations resulting from such payment by Guarantors; provided that such
transfer shall be subject to Section 3(d) above and that without the consent of
Agent (which Agent may withhold in its discretion) Guarantors shall not have the
right to be subrogated to any claim or right against any Obligor which has
become owned by Agent or any Lender, whose ownership has otherwise changed in
the course of enforcement of the Obligation Documents, or which Agent otherwise
has released or wishes to release from its Obligations.

         Section 7. Successors and Assigns. Guarantors' rights or obligations
                    ----------------------
hereunder may not be assigned or delegated, but this Guaranty and such
obligations shall pass to and be fully binding upon the successors of
Guarantors, as well as Guarantors. This Guaranty shall apply to and inure to the
benefit of Agent and Lenders and their successors or assigns. Without limiting
the generality of the immediately preceding sentence, Agent and each Lender may
assign, grant a participation in, or otherwise transfer any Obligation held by
it or any portion thereof, and Agent and each Lender may assign or otherwise
transfer its rights or any portion thereof under this Guaranty and any
Obligation Document, to any other Person, and such other Person shall thereupon
become entitled to all of the benefits in respect thereof granted to Agent or
such Lender hereunder unless otherwise expressly provided by Agent or such
Lender in connection with such assignment or transfer.

         Section 8. Subordination and Offset. Guarantors hereby subordinate and
                    ------------------------
make inferior to the Obligations any and all indebtedness now or at any time
hereafter owed by Borrower to Guarantors on the terms set forth in this Section.
Guarantors agree that after the occurrence of any Default or Event of Default
they will neither permit Borrower to repay such indebtedness or any part thereof
nor accept payment from Borrower of such indebtedness or any part thereof
without the prior written consent of Agent and Lenders. If any Guarantor
receives any such payment without the prior written consent of Agent and
Lenders, the amount so paid shall be held in trust for the benefit of Lenders,
shall be segregated from the other funds of such Guarantor, and shall forthwith
be paid over to Agent to be held by Agent as collateral for, or then or at any
time thereafter applied in whole or in part by Agent against, all or any
portions of the Obligations, whether matured or unmatured, in such order as
Agent shall elect. Each Guarantor hereby grants to Lenders a right of offset to
secure the payment of the Obligations and such Guarantor's obligations and
liabilities hereunder, which right of offset shall be upon any and all monies,
securities and other property (and the proceeds therefrom) of such Guarantor now
or hereafter held or received by or in transit to Agent or any Lender from or
for the account of such Guarantor, whether for safekeeping, custody, pledge,
transmission, collection or otherwise, and also upon any and all deposits
(general or special), credits and claims of such Guarantor at any time existing
against Agent or any Lender. Upon the occurrence of any Default or Event of
Default Agent and each Lender is hereby authorized at any time and from time to
time, without notice to Guarantors, to offset, appropriate and apply any and all
items hereinabove referred to against the Obligations and Guarantors'
obligations and liabilities hereunder irrespective of whether or not Agent or
such Lender shall have made any demand under this Guaranty and although such
obligations and liabilities may be contingent or unmatured. Agent and each
Lender agrees promptly to notify Guarantors after any such offset and
application made by Agent or such Lender, provided that the failure to give such

                                       8

notice shall not affect the validity of such offset and application. The rights
of Agent and each Lender under this section are in addition to, and shall not be
limited by, any other rights and remedies (including other rights of offset)
which Agent and Lenders may have.

         Section 9. Representations and Warranties. Each Guarantor hereby
                    ------------------------------
represents and warrants to Agent and each Lender as follows:

         (a) The Recitals at the beginning of this Guaranty are true and correct
in all respects.

         (b) Such Guarantor is a corporation or limited liability company, as
applicable, duly organized, validly existing and in good standing under the laws
of the state of its incorporation or organization, as set forth in the Recitals
to this Guaranty; and such Guarantor has all requisite power and authority to
execute, deliver and perform this Guaranty.

         (c) The execution, delivery and performance by such Guarantor of this
Guaranty have been duly authorized by all necessary corporate action and do not
and will not contravene its certificate or articles of incorporation or bylaws.

         (d) The execution, delivery and performance by such Guarantor of this
Guaranty do not and will not contravene any law or governmental regulation or
any contractual restriction binding on or affecting such Guarantor or any of its
Affiliates or properties, and do not and will not result in or require the
creation of any lien, security interest or other charge or encumbrance upon or
with respect to any of its properties.

         (e) No authorization or approval or other action by, and no notice to
or filing with, any governmental authority or other regulatory body or third
party is required for the due execution, delivery and performance by such
Guarantor of this Guaranty.

         (f) This Guaranty is a legal, valid and binding obligation of such
Guarantor, enforceable against such Guarantor in accordance with its terms
except as limited by bankruptcy, insolvency or similar laws of general
application relating to the enforcement of creditors' rights.

         (g) There is no action, suit or proceeding pending or, to the knowledge
of such Guarantor, threatened against or otherwise affecting such Guarantor
before any court, arbitrator or governmental department, commission, board,
bureau, agency or instrumentality which may materially and adversely affect such
Guarantor's financial condition or its ability to perform its obligations
hereunder.

         Section 10. No Oral Change. No amendment of any provision of this
                     --------------
Guaranty shall be effective unless it is in writing and signed by Guarantors and
Lenders, and no waiver of any provision of this Guaranty, and no consent to any
departure by Guarantors therefrom, shall be effective unless it is in writing
and signed by Lenders, and then such waiver or consent shall be effective only
in the specific instance and for the specific purpose for which given.

         Section 11. Invalidity of Particular Provisions. If any term or
                     -----------------------------------
provision of this Guaranty shall be determined to be illegal or unenforceable
all other terms and provisions hereof shall nevertheless remain effective and

                                       9

shall be enforced to the fullest extent permitted by applicable law.

         Section 12. Headings and References. The headings used herein are for
                     -----------------------
purposes of convenience only and shall not be used in construing the provisions
hereof. The words "this Guaranty," "this instrument," "herein," "hereof,"
"hereby" and words of similar import refer to this Guaranty as a whole and not
to any particular subdivision unless expressly so limited. The phrases "this
section" and "this subsection" and similar phrases refer only to the
subdivisions hereof in which such phrases occur. The word "or" is not exclusive,
and the word "including" (in its various forms) means "including without
limitation". Pronouns in masculine, feminine and neuter genders shall be
construed to include any other gender, and words in the singular form shall be
construed to include the plural and vice versa, unless the context otherwise
requires.

         Section 13. Term. This Guaranty shall be irrevocable until all of the
                     ----
Obligations have been completely and finally paid and performed, no Lender has
any obligation to make any loans or other advances to Borrower, and all
obligations and undertakings of Borrower under, by reason of, or pursuant to
this Guaranty and the Obligation Documents have been completely performed, and
this Guaranty is thereafter subject to reinstatement as provided in Section
3(d). All extensions of credit and financial accommodations heretofore or
hereafter made by Agent or Lenders to Borrower shall be conclusively presumed to
have been made in acceptance hereof and in reliance hereon.

         Section 14. Excess Payment. To the extent that after payment in full of
                     --------------
the Obligations and termination of Lenders' commitments to advance funds to
Borrower, a court of competent jurisdiction enters a final judgment determining
that the aggregate amount of the Obligations received by the Lenders is in
excess of the amount which they were entitled to receive, each Guarantor shall
be entitled to recover its allocable portion of such excess.

         Section 15. Notices. Any notice or communication required or permitted
                     -------
hereunder shall be given as provided in the Security Agreement.

         Section 16. Limitation on Interest. Agent, Lenders and Guarantor intend
                     ----------------------
to contract in strict compliance with applicable usury law from time to time in
effect, and the provisions of the Credit Agreement limiting the interest for
which Guarantors are obligated are expressly incorporated herein by reference.

         Section 17. Loan Document. This Guaranty is a Loan Document, as defined
                     -------------
in the Credit Agreement, and is subject to the provisions of the Credit
Agreement governing Loan Documents. Guarantors hereby ratify, confirm and
approve the Credit Agreement and the other Loan Documents and, in particular,
any provisions thereof which relate to Guarantor.

         Section 18. Counterparts; Fax. This Guaranty may be executed in any
                     -----------------
number of counterparts, each of which when so executed shall be deemed to
constitute one and the same Guaranty. This Agreement may be validly executed and
delivered by facsimile or other electronic transmission.

                                       10

         SECTION 19. GOVERNING LAW. THIS GUARANTY IS TO BE PERFORMED IN THE
                     -------------
STATE OF COLORADO AND SHALL BE GOVERNED BY AND CONSTRUED AND ENFORCED IN
ACCORDANCE WITH THE LAWS OF SUCH STATE WITHOUT REGARD TO PRINCIPLES OF CONFLICTS
OF LAW. GUARANTOR HEREBY IRREVOCABLY SUBMITS ITSELF TO THE NON-EXCLUSIVE
JURISDICTION OF THE STATE AND FEDERAL COURTS OF SUCH STATE. EACH GUARANTOR
HEREBY IRREVOCABLY DESIGNATES AND APPOINTS CT CORPORATION SYSTEM, AS AGENT OF
SUCH GUARANTOR TO RECEIVE SERVICE OF ALL PROCESS BROUGHT AGAINST SUCH GUARANTOR
WITH RESPECT TO ANY SUCH PROCEEDING IN ANY SUCH COURT IN COLORADO, SUCH SERVICE
BEING HEREBY ACKNOWLEDGED BY SUCH GUARANTOR TO BE EFFECTIVE AND BINDING SERVICE
IN EVERY RESPECT. COPIES OF ANY SUCH PROCESS SO SERVED SHALL ALSO, IF PERMITTED
BY LAW, BE SENT BY REGISTERED MAIL TO SUCH GUARANTOR AT ITS ADDRESS SET FORTH
BELOW, BUT THE FAILURE OF SUCH GUARANTOR TO RECEIVE SUCH COPIES SHALL NOT AFFECT
IN ANY WAY THE SERVICE OF SUCH PROCESS AS AFORESAID. EACH GUARANTOR SHALL
FURNISH TO AGENT A CONSENT OF CT CORPORATION SYSTEM AGREEING TO ACT HEREUNDER
PRIOR TO THE EFFECTIVE DATE OF THIS AGREEMENT. NOTHING HEREIN SHALL AFFECT THE
RIGHT OF AGENT TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR SHALL
LIMIT THE RIGHT OF AGENT TO BRING PROCEEDINGS AGAINST ANY GUARANTOR IN THE
COURTS OF ANY OTHER JURISDICTION. IF FOR ANY REASON CT CORPORATION SYSTEM SHALL
RESIGN OR OTHERWISE CEASE TO ACT AS ANY GUARANTOR'S AGENT, SUCH GUARANTOR HEREBY
IRREVOCABLY AGREES TO IMMEDIATELY DESIGNATE AND APPOINT A NEW AGENT ACCEPTABLE
TO AGENT TO SERVE IN SUCH CAPACITY AND, IN SUCH EVENT, SUCH NEW AGENT SHALL BE
DEEMED TO BE SUBSTITUTED FOR CT CORPORATION SYSTEM FOR ALL PURPOSES HEREOF AND
(A) PROMPTLY DELIVER TO AGENT THE WRITTEN CONSENT (IN FORM AND SUBSTANCE
SATISFACTORY TO AGENT) OF SUCH NEW AGENT AGREEING TO SERVE IN SUCH CAPACITY.

         SECTION 20. FINAL AGREEMENT. THIS WRITTEN AGREEMENT AND THE OTHER LOAN
                     ---------------
DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES HERETO AND MAY NOT
BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES HERETO. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN
THE PARTIES HERETO.
            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

                                       11



         IN WITNESS WHEREOF, Guarantors have executed and delivered this
Guaranty as of the date first written above.


                                         ST. MARY OPERATING COMPANY


                                         By: /s/ MILAM RANDOLPH PHARO
                                            -----------------------------------
                                            Milam Randolph Pharo
                                            Vice President - Land and Legal


                                         ST. MARY ENERGY COMPANY


                                         By: /s/ MILAM RANDOLPH PHARO
                                            -----------------------------------
                                            Milam Randolph Pharo
                                            Vice President - Land and Legal


                                         NANCE PETROLEUM CORPORATION


                                         By: /s/ RONALD B. SANTI
                                            -----------------------------------
                                            Ronald B. Santi
                                            Vice President - Land


                                         ST. MARY MINERALS, INC.


                                         By: /s/ RICHARD C. NORRIS
                                            -----------------------------------
                                            Richard C. Norris
                                            Vice President - Finance


                                         PARISH CORPORATION


                                         By: /s/ RICHARD C. NORRIS
                                            -----------------------------------
                                            Richard C. Norris
                                            Vice President - Finance





                                         FOUR WINDS MARKETING, LLC


                                         By:    ST. MARY LAND & EXPLORATION
                                                COMPANY, as Manager


                                         By: /s/ MILAM RANDOLPH PHARO
                                            -----------------------------------
                                            Milam Randolph Pharo
                                            Vice President - Land and Legal


                                         ROSWELL, L.L.C.


                                         By:    ST. MARY LAND & EXPLORATION
                                                COMPANY, as a Member


                                         By: /s/ MILAM RANDOLPH PHARO
                                            -----------------------------------
                                            Milam Randolph Pharo
                                            Vice President - Land and Legal