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                                                                    EXHIBIT 10.1


                           PURCHASE AND SALE AGREEMENT

         THIS AGREEMENT is dated this 14TH day of June, 2001, by and between
BENSON MINERAL GROUP, INC. ("Benson"), an Oklahoma corporation, also known as
Benson Mineral Group, of 1560 Broadway, Suite 1900, Denver, Colorado 80202
(hereinafter called "Seller"), and DEVON SFS OPERATING, INC., a Delaware
corporation, of 20 North Broadway, Suite 1500, Oklahoma City, Oklahoma
73102-8260 (hereinafter called "Buyer"). Buyer is the Assignee of Legacy
International, Inc., of said assignor's rights and duties under that certain
"Offer to Purchase" agreement dated May 8, 2001, between Legacy International,
Inc. and Benson Mineral Group, Inc.

         For and in consideration of Ten Dollars ($10.00) and other good and
valuable consideration, Buyer and Seller agree to the purchase and sale of the
Subject Property described below, under the following terms:

         1. Property Being Sold. Subject to the terms and conditions of this
Agreement, Seller agrees to sell and convey and Buyer agrees to purchase and
accept the Subject Property for the Purchase Price as defined hereinafter. The
"Subject Property" shall include the following:

            a. Leaseholds. All of Seller's right, title and interest, with no
depth limitations created by Seller, 'in all oil and gas leaseholds, oil, gas
and other minerals, including working interests, rights of assignment and
reassignment, corresponding net revenue interests, operating rights, record
title interests, and all other interests under, in or useful in connection with
oil, gas or mineral leases, and interests in rights to explore for and produce
oil, gas or other minerals ("Leases"), which are (i) described in Exhibit "A" or
(ii) associated with the land ("Land") described in Exhibit "A";

            b. Rights in Production. All of Seller's night, title and interest
in all reversionary interests, back-in interests, and in production of oil, gas
or other minerals relating to the Leases and/or Land;

            c. Contract Rights. All of Seller's right, title and interest in or
derived from all orders and decisions of state and federal regulatory
authorities, joint operating agreements, gas purchase agreements, gathering
agreements, transportation agreements, processing agreements, farmout agreements
and farmin agreements and any other agreements, which (1) are described in
Exhibit "A" or (ii) relate to any of the interests or the Land described in
Exhibit "A". All contracts benefitting the Subject Property are described in
Exhibit "C" ("Contracts");

            d. Easements. All of Seller's right, title and interest in all
rights-of-way, easements, licenses, servitudes and franchises (i) described in
Exhibit "A" or (ii) appurtenant to


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or used in connection with the Land or other property described in Exhibit "A"
(hereinafter "Easements"),

            e. Permits. All of Seller's right, title and interest in all permits
and licenses of any nature owned, held or operated in connection with operations
for the exploration and production of oil, gas or other minerals to the extent
the same are used or obtained in connection with any of the Land or other
property described in Exhibit "A" ("Permits");

            f. Wells. All of Seller's right, title and interest in all
producing, non- producing and shut-in oil and/or gas wells, saltwater disposal
wells, water wells, production spacing units and undeveloped locations (i)
described in Exhibit "D" or (ii) described in or used or obtained in connection
with the Land or other property described in Exhibit "A" (hereinafter "Wells").
Exhibit "D" shall reflect the location of and interest in Wells being conveyed
to Buyer from Seller;

            g. Equipment. All of Seller's right, title and interest in all
personal property, surface equipment from the wellhead to the initial wellhead
meter house, down-hole equipment (1) described in Exhibit "A" or (ii) used or
obtained in connection with the Leases, Easements, Wells, Permits or Land;

            h. Remaining Interests. All of Seller's night, title and interest in
all other rights and interests 'in, to or under or derived from the Subject
Property, even though improperly described in or omitted from the Exhibits.

         i. Net Revenue Delivered. All leases and other interests in the Subject
Property will be delivered by Seller in favor of Buyer on the basis of
eighty-three and six/tenths percent (83.6%) net revenue interest, subject only
to proportionate reduction to the extent a particular lease or interest covers
less than one hundred percent of the mineral ownership.

         2. Purchase Price. Subject to the other provisions hereof, Buyer agrees
to pay to Seller for the Subject Property the sum of Six Million Three Hundred
Thirty-Six Thousand Dollars ($6,336,000.00), as adjusted herein (the "Final
Purchase Price") in the following manner: (i) a nonrefundable One Million
Dollars ($1,000,000.00) (the "Deposit"), except as provided in Paragraph 8(d)(4)
or if Closing does not occur through no fault of Buyer, payable upon execution
of this Agreement in immediately available funds, and (ii) Four Million Seven
Hundred Two Thousand Four Hundred Dollars ($4,702,400.00) (the "Closing
Payment") payable at Closing to Seller in immediately available funds, and (iii)
Six Hundred Thirty-Three Thousand Six Hundred Dollars ($633,600.00) (the
"Post-Closing Reserve") to be adjusted and payable to Buyer in immediately
available funds pursuant to Section 4 below. Also at Closing, Buyer shall
reimburse Seller, in immediately available funds, for all Seller's reasonable
actual direct out-of- pocket costs of surveying, permitting, building locations,
paying related surface use fees or damages, drilling, completing, recompleting
or converting, equipping, testing, production testing, water hauling and
disposal, and operating the Wells described on Exhibit "D", as to all such costs
incurred through


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Closing. Buyer shall also have the option at Closing to purchase from Seller the
currently existing yard inventory for the Subject Property at Seller's actual
cost, subject to Buyer's inspection and approval. Seller designates that all
payments hereunder are to be made by wire transfer to the credit of United
States Exploration, Account #814102189, at Bank of Oklahoma, N.A.,
ABA#103-900-036.

         3. Closing. The conveyance of the Subject Property to Buyer shall be
effective as of 12:01 a.m. on May 1, 2001, and shall be delivered at the
Closing, which shall take place on or before the close of business on June 20,
2001 (the "Closing Date") unless postponed by agreement of the parties. Unless
otherwise agreed, the Closing shall be held at Seller's offices. At the Closing,
the following shall occur:

            a. Seller shall execute, acknowledge and deliver: (i) an Assignment,
Conveyance and Bill of Sale in the form attached hereto as Exhibit "B" (the
"Assignment"); and (ii) letters-in-lieu of transfer orders (if applicable), and
other instruments conveying title to the Subject Property and the production
therefrom to Buyer.

            b. Buyer shall deliver the Closing Payment to Seller by wire
transfer and reimbursements mentioned in Paragraph 2 and cost of inventory if
Buyer wishes to purchase same.

            c. Any ad valorem, property, production, severance and similar taxes
and assessments based on or measured by the ownership of property or the
production of oil or gas or the receipt of proceeds therefrom on the Subject
Property shall be prorated between Seller and Buyer as of the Closing Date to
the extent Seller has received any production proceeds on which such taxes or
assessments are based; otherwise, if Seller has not received any such proceeds,
then all such taxes or assessments shall be allocated to Buyer, except for such
taxes or assessments attributable to the overriding royalty retained by Seller's
assigns on future oil and/or gas production.

            d. The Final Purchase Price provided for under this Agreement
excludes any sales taxes or other taxes in connection with the sale of property
pursuant to this Agreement because the parties believe that this sale is exempt
from sales tax. If a determination is ever made that a sales tax or other
transfer tax applies, Buyer shall be liable for payment of such tax. Buyer shall
also be liable for any applicable conveyance, transfer and recording fees, and
real estate transfer stamps or taxes imposed on any transfer of property
pursuant to this Agreement.

         4. Post-Closing Adjustments. Not more than fifteen (15) days after the
Closing, Seller shall prepare and deliver to Buyer a statement (the "Final
Settlement Statement") setting forth each adjustment to the Post Closing Reserve
as provided 'in Section 8 of this Agreement, reflecting the calculation of each
adjustment (the "Post Closing Adjustments") provided therein. Not more than
fifteen (15) days after receipt of the Final Settlement Statement, Buyer shall
deliver to Seller a written report containing any changes which Buyer proposes
be made to the


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Final Settlement Statement. No later than thirty (30) days after the Closing,
the parties shall agree with respect to the amounts due pursuant to such
Post-Closing Adjustments. The date upon which such agreement is reached or upon
which the Final Purchase Price is established shall be called the "Final
Settlement Date." In the event that the Final Purchase Price is less than Six
Million Three Hundred Thirty-Six Thousand Dollars ($6,336,000.00) cumulative,
Buyer shall deduct such difference from the PostClosing Reserve and pay to
Seller in immediately available funds the remainder of such Post-Closing
Reserve. Payment by Buyer shall be made within three (3) business days of the
Final Settlement Date.

         5. Representations and Warranties of Seller. Seller represents and
warrants to Buyer as of the date hereof and will represent and warrant at the
Closing, as follows:

            a. Corporate or Other Relevant Authority. Seller is duly organized
and in good standing under the laws of the State of Oklahoma, is duly qualified
to carry on its business in the State of Kansas, and has all the requisite power
and authority to enter into and perform this Agreement and carry out the
transactions contemplated under this Agreement.

            b. Valid Agreement. This Agreement constitutes the legal, valid and
binding Agreement of Seller. At the Closing, all instruments required hereunder
to be executed and delivered by Seller shall be duly executed and delivered to
Buyer and shall constitute legal, valid and binding obligations of Seller.
Subject to obtaining the necessary consents to assignment as required herein in
subparagraph (j) under this Section 5, the execution and delivery by Seller of
this Agreement, the consummation of the transactions set forth herein and the
performance by Seller of Seller's obligations hereunder have been duly and
validly authorized by the Seller and to the best of Seller's knowledge after
diligent inquiry will not conflict with or result in any violation of any
provision of (i) any agreement, contract, mortgage, lease, license or other
instrument to which Seller is a party or by which Seller is bound; (ii) any
governmental franchise, license, permit or authorization or any judgment or
order of judicial or governmental body applicable to Seller, or (iii) any law,
statute, decree, rule or regulation of any jurisdiction in the United States to
which Seller is subject.

            By Agreement dated effective September 1, 2000, by and between
Seller and E. Wayne Willhite, James R. Perkins, and William M. Stout,
collectively referred to as the "Willhite Group", the Willhite Group was
entitled to certain overriding royalties and working interests in, to, and under
the Subject Property as defined herein. Attached hereto as Exhibit "F" are
Special Powers of Attorney whereby Seller has been appointed as their attorney
in fact to deal on their behalf in this Agreement and the Assignment to be made
pursuant hereto. Any reference herein to Seller's interest in the Subject
Property shall include the beneficial working interests owned in the Subject
Property by the Willhite Group. Seller represents that it currently owns the
legal title under the Subject Property. All conveyances made pursuant hereto
shall include the beneficial working interests of the Willhite Group. The
necessary assignments of overriding royalties into the Willhite Group will be
made and delivered prior to delivering the


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Assignment to Buyer at Closing. The assignments of overriding royalty will not
reduce the net revenue interest Seller has agreed to deliver hereunder.

            c. Authorization. This Agreement has been duly authorized, executed
and delivered by Seller. All instruments required to be delivered by Seller at
the Closing shall be duly authorized, executed and delivered by Seller. This
Agreement and all documents executed by Seller in connection with this Agreement
shall constitute legal, valid and binding obligations of Seller, enforceable
against Seller in accordance with their terms, subject only to the effects of
bankruptcy, insolvency, reorganization, moratorium and similar laws from time to
time in effect, as well as general principles of equity.

            d. Leases. To the best of Seller's knowledge, after diligent
inquiry, except as provided on Exhibit "E," the Leases are in full force and
effect and are valid and subsisting documents covering the entire estates which
they purport to cover; all royalties, rentals and other payments due under the
Leases have been fully, properly and timely paid; no party to any Lease is in
breach of any provision thereof and no such breach has been alleged by any
lessor; and all conditions necessary to keep the Leases in force have been
performed. Except as to be set forth on Exhibit "E", Seller has received no
currently pending demand for release regarding any portion of the Leases. Seller
will use its best efforts to take all prudent action necessary to keep the
Leases in force and effect until the Closing.

            Seller shall provide to Buyer a schedule of all special provisions
on a lease-by- lease basis as soon as practicable after execution of this
Agreement.

            Buyer shall assume, at its sole option and at Seller's actual cost
and expense, any and all interests in the nature of the Subject Properties
acquired, and any and all outstanding offers and commitments made by Seller
which become due after the date of this Agreement, and as to offers for new
leases, which are beyond the first 66,000 net acres covered by the Leases.
Seller shall not compete for or acquire any interest in lands within the Kansas
counties of Neosho or in the easternmost ten miles of Wilson for a period of two
(2) years from or after the date of this Agreement. Any such subsequent interest
so acquired by Seller, at Buyer's option, shall be promptly assigned to Buyer
without reservation of any interest and within fifteen (15) days thereafter, and
Buyer shall reimburse Seller the actual cost incurred in the payment of bonus
therefor. The Willhite Group shall not be prohibited from normal well consulting
or participation in wells 'in the area, but they shall not acquire new acreage
blocks (more than 640 acres cumulative) which might conflict with the activities
and interests of Buyer.

            e. Taxes. All due and payable ad valorem, property, production,
severance and similar taxes and assessments based on or measured by the
ownership of property or the production of oil and/or gas or the receipt of
proceeds therefrom on the Subject Property, which became due prior to the
Closing Date, have been properly paid.


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            f. Maintenance of Interests. Seller will continue to use all
reasonable efforts from the date of execution of this Agreement until the
Closing, to maintain and operate the Subject Property in a reasonable and
prudent manner, in full compliance with applicable law and orders of any
governmental authority, to maintain insurance and bonds now in force with
respect to the Subject Property, to pay when due all costs and expenses coming
due and payable in connection with the Subject Property, and to perform all of
the covenants and conditions contained in the Leases and all related agreements.
Without the prior written consent of the Buyer, Seller will not: (i) develop,
maintain and operate the Subject Property in a manner substantially inconsistent
with prior operations or introduce any new method of operation or accounting
with respect to the Subject Property; (ii) enter into any new agreements or
commitments with respect to the Subject Property (except for additional leases
or properties acquired and subject hereto); (iii) incur any liabilities other
than in the ordinary course for normal operating expenses on the Subject
Property; (lv) abandon, or consent to abandonment of, any producing or shut-in
Well or any injection well located on the Subject Property, nor release or
abandon all or any portion of the Leases; (v) modify or terminate any of the
Leases or related agreements or waive any right thereunder; or (vi) encumber,
sell or otherwise dispose of any of the Subject Property other than personal
property which is replaced with equivalent property or consumed in the ordinary
course of operation of the Subject Property and other than the oil and/or gas
sold in the ordinary course of business.

            g. Default. To the best of Seller's knowledge after diligent
inquiry, Seller is not in default under or in violation of (i) any law, order,
writ, injunction, rule, regulation or decree of any governmental body, or court,
or of any commission or other administrative agency relating to the Subject
Property, or (ii) any material related agreement or obligation to which it is a
party or by which it is bound relating to the Subject Property.

            h. Suits and Claims. Except as to be set forth on Exhibit "E", no
suit, action, claim, audit, investigation or other proceeding is now pending or,
to Seller's knowledge, after diligent inquiry, threatened before any court or
governmental agency which might result in material impairment of the value or
operation of any Subject Property, and Seller shall promptly notify Buyer of any
such proceeding which arises or is threatened prior to the Closing.

            i. Access. Buyer and the employees and agents of Buyer shall have
access to the Subject Property at Buyer's sole risk, cost and expense at
reasonable times, and shall have the right to conduct production tests,
equipment inspection, environmental audits, and any other investigation of the
Subject Property on prior notice to Seller and upon agreement with Seller as to
the time and place of such actions.

            j. Consents. Seller will use its reasonable efforts to obtain all
necessary consents and waivers of preferential rights of third parties to
purchase any part of the Subject Property. There are no preferential purchase
rights applicable to the Subject Property except those to be set forth on
Exhibit "E".


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            k. Contracts. With respect to the Contracts, to the best of Seller's
knowledge after diligent inquiry: (i) all are identified on Exhibit "C" and all
are in full force and effect; (ii) all payments due thereunder have been made by
Seller; (iii) Seller is not in breach or default thereunder; and (iv) neither
Seller nor any other party thereto has given or threatened to give notice of any
action to terminate, cancel, rescind or procure a judicial reformation of any
Contract.

            l. Environmental Claims. To Seller's best knowledge after diligent
inquiry, there are no adverse environmental claims or conditions affecting the
Subject Property.

            m. No Production. None of the Wells have produced any oil or gas
which have been sold to third parties, and there exists no gas balancing
obligations among any owners in such wells.

            n. Obligation to Close. Seller shall take or cause to be taken all
actions necessary or advisable to consummate the transactions contemplated by
this Agreement and to assure that as of the Closing it will not be under any
material company, legal, governmental or contractual restriction that would
prohibit or delay the timely consummation of such transactions.

         6. Representations and Warranties of Buyer. Buyer represents and
warrants to Seller as of the date hereof and will represent and warrant at the
Closing, as follows:

            a. Corporate Authority. Buyer is duly organized and in good standing
under the laws of the State of Delaware, is duly qualified to carry on its
business in the State of Kansas, and has all the requisite power and authority
to enter into and perform this Agreement and carry out the transactions
contemplated under this Agreement.

            b. Valid Agreement. This Agreement constitutes the legal, valid and
binding Agreement of Buyer. At the Closing, all payments required hereunder to
be made by Buyer shall be made and delivered to Seller and shall constitute
legal, valid and binding obligations of Buyer. The execution and delivery by
Buyer of this Agreement, the consummation of the transactions set forth herein
and the performance by Buyer of Buyer's obligations hereunder have been duly and
validly authorized by the Buyer and will not conflict with or result in any
violation of any provision of (1) any agreement, contract, mortgage, lease,
license or other 'instrument to which Buyer is a party or by which Buyer is
bound; (ii) any governmental franchise, license, permit or authorization or any
judgment or order of judicial or governmental body applicable to Buyer, or (iii)
any law, statute, decree, rule or regulation of any jurisdiction in the United
States to which Buyer is subject.

            c. Governmental Approvals. Buyer has or shall obtain all required
local, federal or state governmental and/or agency permissions, approvals,
permits, bonds and consents, as may be required to assume Seller's obligations
and responsibilities attributable to the Subject Property.


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            d. Further Distribution. Buyer is not acquiring the Subject Property
with a view to, or for offer of resale in connection with, a non-exempt
distribution thereof within the meaning of the Securities Act of 1933, as
amended, and the rules and regulations pertaining to it or a distribution
thereof in violation of any applicable Securities laws. Buyer agrees that if in
the future it should decide to dispose of any of its interest in the Subject
Property, Buyer will do so only in compliance with any applicable Federal and
State Securities laws.

            e. Obligation to Close. Buyer shall take or cause to be taken all
actions necessary or advisable to consummate the transactions contemplated by
this Agreement and to assure that as of the Closing it will not be under any
material company, legal, governmental or contractual restriction that would
prohibit or delay the timely consummation of such transactions.

         7. Files and Records. Seller will make available to Buyer all title
opinions and other information available in Seller's files relating to the
Subject Party (collectively "Data"). All Data shall be made available at
Seller's office during normal working hours. Seller shall furnish to Buyer all
original land and well files and all other related information and Data
affecting the Subject Properties at the Closing.

         8. Title Examination/Other Defects.

            a. Title Standards and Defects. Seller represents and warrants that
Seller's ownership interests in the Leases result in Seller owning approximately
66,000 net acres of Leases, covering at least all gas and coalbed methane gas
rights. Seller represents and warrants that its working interest in each Well is
no more than, and its net revenue interests 'in each Well is no less than those
set forth on Exhibit "D." Buyer has Seller's permission to contact Hambright &
Assoc. to discuss all issues of title and will authorize Hambright & Assoc. to
allow Buyer to review all title in their files affecting the Subject Property
and to make copies of title information in their files.

            Upon execution of and pursuant to the ten-ns of this Agreement,
Buyer shall have the right to conduct its investigation into the status of the
title of the Subject Property. If, in the course of such investigation, Buyer
discovers title defects which renders title less than defensible, Buyer may,
immediately upon discovery but no later than the Closing Date, notify Seller in
writing specifying such defect, the Subject Property affected thereby, and
Buyer's estimate of the net reduction in value of the Subject Property, as set
forth in Section 8(d) below. A Title Defect shall be deemed to exist when (1)
there is a defect in title to a lease or property which would render Seller's
title thereto less than defensible, (2) a lease or property is subject to
reversionary interest obligations which are not eliminated, (3) Seller is unable
to obtain a consent or waiver of a preferential right to purchase from a third
party which is required in order to convey the lease or property to the Buyer,
or any required consent to assign is not obtained, (4) Seller does not hold
title to the working interests and/or net revenue interests in a Lease or
property as represented in Exhibit "D", or (5) there exists the uncured material
breach of the Seller's representations and warranties set forth in Section 5
above.


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            b. Environmental Defects. Except as described on Exhibit "E," Seller
represents and warrants that no environmental damage has occurred to any of the
Subject Properties which has been caused by or through Seller.

         Buyer agrees and acknowledges that (a) it will have access to and the
opportunity to inspect the Subject Property for all purposes, including without
limitation, for the purposes of detecting the presence of hazardous or toxic
substances, pollutants or other contaminants, environmental hazards, naturally
occurring radioactive materials (NORM) produced water contamination of the
surface and/or subsurface and any other environmental condition, and, (b) it
will have satisfied itself as to the physical and environmental surface and
subsurface condition of the Subject Property and their method of operation; and
except as set forth in Seller's representations, warranties, or indemnities, to
accept an assignment of the Subject Property at Closing on an "AS IS, WHERE IS"
basis, "WITH ALL FAULTS".

            If, however, Buyer determines reasonably and in good faith that any
portion of the Subject Property is materially and adversely affected by an
Environmental Condition which is in violation of or not in compliance with
Environmental Laws as defined below as of the Closing Date (except as described
on Exhibit "E," which shall not be considered a Defect hereunder), Buyer may
claim a Defect with respect to that portion of the Subject Property, exclude
same from purchase hereunder, and calculates the net reduction in value of the
Subject Property by Ninety-Six Dollars ($96.00) per net acre.

            As used herein, the term "Environmental Laws" shall mean any and all
federal, state and local statutes, regulations, rules, orders, ordinances or
permits of any governmental authority pertaining to health, the environment,
wildlife and natural resources in effect in any and all jurisdictions in which
the Subject Property is located, including without limitation, the Clean Air
Act, as amended, and the Federal Water Pollution Control Act, as amended, the
Rivers and Harbors Act of 1899, as amended, the Safe Drinking Water Act, as
amended, the Comprehensive Environmental Response, Compensation and Liability
Act ("CERCLA"), as amended, the Superfund Amendments and Reauthorization Act of
1986 ("SARA"), as amended, the Resource Conservation and Recovery Act ("RCRA"),
as amended, the Hazardous and Solid Water Amendments Act of 984, as amended, the
Toxic Substances Control Act, as amended, the Occupational Safety and Health Act
("OSHA"), as amended, and the Hazardous Materials Transportation Act, as
amended. Upon Closing, Buyer hereby assumes and shall be responsible for and
agrees to indemnify, defend and hold harmless Seller, its employees, officers,
directors, consultants, or agents (the "Seller Indemnified Parties") from and
against any and all losses attributable to damage to property, injury to or
death of persons or other living things, natural resource damages, CERCLA
response costs, environmental remediation and restoration costs, violations of
Environmental Laws, or fines or penalties (collectively, "Environmental
Liabilities") arising out of or attributable to, in whole or in part, either
directly or indirectly, the ownership or operation of the Subject Property at
any time after the Closing Date. Similarly, as to and only as to acts caused by
or through Seller itself, with Buyer accepting the Subject Property otherwise on
an "AS IS" basis, Seller shall be responsible for and agrees to indemnify,


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<PAGE>   10

defend and hold harmless Buyer, its employees, officers, directors, consultants
or agents (the "Buyer Indemnified Parties") from and against any and all losses
attributable to Environmental Liabilities arising out of or attributable to, IN
whole or in part either directly or indirectly, the ownership, condition or
operation of the Subject Property before the Closing Date.

            c. Defect Exclusions. In addition to other limitations on claims for
defects as contained elsewhere herein, the following items are not to be
considered Title Defects or Defects: (i) the ability to secure Clean Air
Permits, (ii) surface access to a location on a Lease, (iii) subordination of a
Lessor's mortgage when not in default, or (iv) any other imperfection in title
which does not render the same less than defensible.

            d. Procedure Regarding Defects Claimed by Buyer.

               i. Notices. Buyer may, by delivery of written notice to Seller of
the existence of a title or environmental Defect (collectively "Defects"),
request reduction of the Purchase Price ("Defect Adjustment") in an amount equal
to the aggregate Defects based on net defective acreage (and exclusion of the
Defect acreage or property from the Closing). Any notice shall include
appropriate evidence to substantiate the Buyer's position, including: a
description of the Defect; the basis for the Defect that Buyer believes causes
such Subject Property to be treated as a Defect; the portion of a Lease or other
part of the Subject Property affected by the Defect; and, to the extent then
determinable, the amount by which Buyer believes the value of the Subject
Property has been reduced because of the Defect and the computations and
information upon which Buyer's belief is based. Assessment of the deduction for
a Defect cannot exceed the price per net acre paid for the Subject Property
compared to the net acreage affected by the Defect.

               It is understood and agreed that the Purchase Price of Six
Million Three Hundred Thirty-Six Thousand Dollars ($6,336,000.00) is based on
Buyer acquiring from Seller at least Sixty-Six Thousand (66,000) net acres
covered by the Leases covering at least gas and coalbed methane rights, i.e.
Buyer is paying Seller no more than Ninety-Six Dollars ($96.00) per net acre for
the Subject Property. For the purposes of adjusting the Purchase Price for title
or environmental Defects, Buyer and Seller agree that for all Defect Adjustments
which reduce the actual net acres covered in the Subject Property to less than
66,000 net acres, the claim for a Defect shall be Ninety-Six Dollars ($96.00)
per net acre as to those portions of the Subject Property affected by the
claimed Defect.

               Any Defect notice shall be delivered by Buyer to Seller no later
than the Closing Date. If a Defect Notice is not timely delivered, the Buyer
shall waive and shall have no right to claim a Defect Adjustment; provided that
with respect to an asserted title Defect, such waiver shall not apply to any
claim by Buyer for breach of the special warranty of title contained in the
assignment delivered by the Seller at the Closing (as to and only as to acts by
and through the Seller) or to any claims by Buyer pursuant to the
indemnification provisions set forth in this Agreement.


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               ii. Mandatory Negotiations. Upon timely delivery of a Defect
notice, Buyer and Seller shall promptly meet and IN good faith use reasonable
efforts to agree on the validity of the claim and the Defect Adjustment, if any,
by which the Purchase Price should be adjusted. If the existence of a Defect, or
the appropriate Defect Adjustment cannot be mutually agreed after Seller has
completed any curative measures it deems appropriate, Buyer has the option to
adjust the Purchase Price to account for the claimed Defect Adjustment(s) of any
Subject Property pursuant to Subsection (d)(1) above,

               iii. Seller's Right to Cure Defects. If Seller receives a timely
Defect notice, Seller shall have until thirty (30) days after the Closing to
cure the underlying Defect at its sole cost. If by such date Seller can
demonstrate to Buyer's reasonable satisfaction that such Defect has been cured,
then no purchase price adjustment shall occur. If such Defect cannot be cured to
Buyer's satisfaction, Buyer has the option to reduce the Post Closing Reserve by
such amount and Buyer shall reassign such portion of defective Leases to Seller.

               iv. Termination. Either party may elect to terminate this
Agreement in the event Defects equal or exceed thirty percent (30%) of the
Purchase Price, in which event Seller shall immediately repay to Buyer the
Deposit and the Closing payment.

         9. Costs and Revenues Before and After Closing. Subject to the
reimbursements provided herein, Seller shall be responsible for the payment of
all costs, liabilities and expenses incurred in the ownership and operation of
the Subject Property prior to the Closing. Subject to the other provisions
hereof, Buyer shall be responsible for all costs, liabilities and expenses
incurred in the ownership and operation of the Subject Property from and after
the Closing. The proceeds from the sale of hydrocarbons produced from the
Subject Property prior to the Closing, if any, shall be the property of Seller.
The proceeds from the sale of hydrocarbons produced after the Closing shall be
the property of Buyer. Adjustments shall be made to the Purchase Price to
account for such costs and revenues in the Preliminary Settlement Closing
Statement and the Final Settlement Statement.

         10. Casualty Loss/Extraordinary Loss. If, prior to the Closing Date,
any portion of the Subject Property shall be destroyed by fire or other
casualty, or if Seller should incur any liability relating to any portion of the
Subject Property other than routine operating costs and expenses for which Buyer
is to be responsible for hereunder, Buyer shall have the right to treat such
affected property as a Defect under Section 8 above. Should the portion of
Subject Property affected be in excess of Three Hundred Thousand Dollars
($300,000.00), Buyer shall have the right to exclude the affected portion of the
Subject Property by giving notice thereof to Seller or terminate this Agreement,
in which event both parties shall be released from all obligations hereunder,
any documents or payments exchanged shall be returned to the party who provided
same and Seller shall immediately repay to Buyer the Deposit.

         11. Conditions to Closing. The obligations of a party to close shall be
subject to the satisfaction by the other party or parties of all material
agreements herein to be performed at or


                                     - 11 -
<PAGE>   12

prior to Closing and to all representations and warranties of such party being
true and correct. In the event Buyer's Conditions of Closing are not satisfied
by Seller, Seller shall immediately repay to Buyer the Deposit and this
Agreement shall terminate.

         12. Assumption of Obligations. From and after the Closing, Buyer
assumes and agrees to perform all express or implied covenants and obligations
of Seller relating to the Subject Property. Buyer also assumes Seller's
proportionate part of the expenses and costs of plugging and abandoning wells
and restoration of wells or operation sites, all in accordance with the
applicable laws, regulations, and contractual provisions.

         From and after the Closing, Buyer assumes, will be bound by, and agrees
to perform all express and implied covenants and obligations relating to the
Subject Property, whether arising under (i) the Leases, the Contracts, the
Easements, the Permits or any other contractually-binding arrangements to which
the Subject Property (or any component thereof) may be subject and which will be
binding on Buyer and/or the Subject Property (or any component thereof) after
the Closing (collectively, the "Basic Documents"), or (ii) any applicable laws,
ordinances, rules and regulations of any federal, state or local governmental or
quasi-governmental authority having jurisdiction over the Subject Property.

         The Subject Property is understood to be subject to all existing
Contracts relating to the Subject Property that are of record, have been
furnished to Buyer, and are described in Exhibit "C". Buyer shall assume and be
responsible for all obligations of Seller under such contracts as of the
Closing.

         From and after the Closing, Buyer shall assume all rights and duties of
the operator of any properties which are presently operated by Seller or
Seller's contractors, including but not limited to all necessary filings with
state agencies to properly effectuate such transfer. Seller agrees that it will
not enter into any new contracts, or modify any existing contracts, without the
written consent of Buyer which, however, shall not unreasonably be withheld.

         13. Independent Investigation and Disclaimer. The express
representations of Seller set forth in this Agreement are exclusive and in lieu
of any and all other representations. Seller disclaims all liability and
responsibility for any other representation, warranty, statement or information
made or communicated (orally or in writing) to Buyer, including any statements,
representations, opinions, information or advice which may have been provided as
an accommodation to the Buyer by any officer, shareholder, director, employee,
agent, consultant or representative of Seller, or any engineer or engineering
fin-n, or any other agent, consultant or representative. Without limiting the
generality of the foregoing, except as expressly set forth in the Assignment,
Seller makes absolutely no representation or warranty, express, implied or
statutory, as to (i) title to any of the Subject Property; (ii) the ability of
any component of the Subject Property to produce gas, coalbed methane, or oil,
(iii) the amounts, quality or deliverability of reserves of gas, coalbed
methane, or oil attributable to the Subject Property, or any part thereof, (lv)
geological or other interpretation of any economic evaluation, (v) present or


                                     - 12 -
<PAGE>   13

future sales prices, operating costs, or other economic factors, or (vi) the
condition or state of repair of any well or equipment relating to the Subject
Property. Buyer acknowledges and affirms that it has exercised its night to
inspect the Subject Property, and each component thereof; has satisfied itself
as to its physical and environmental condition, both surface and subsurface; and
further that Buyer has made its own independent investigation, analysis and
evaluation of the Subject Property, and each component thereof (including
Buyer's own estimate and appraisal of the extent and value of the petroleum,
natural gas and other hydrocarbon reserves, if any, respecting each component of
the Subject Property). The items of well equipment (surface and subsurface)
conveyed as part of the Subject Property are sold hereunder "WHERE IS, AS IS,
WITH ALL FAULTS," and without any warranties or representations of any kind or
character, express or implied or statutory, regarding the condition or state of
repair of any of the equipment comprising part of the Subject Property.

         14. Indemnity.

             a. By Seller. To the extent permissable under applicable law,
Seller agrees to indemnify and hold harmless Buyer, its employees and agents,
from all loss, cost, liability and expense arising out of, in connection with,
or resulting from Seller's ownership or operation of the Subject Property prior
to the Closing Date (except applicable plugging obligations, if any, under
Kansas law). Seller further covenants and agrees to defend any suits brought
against Buyer on account of any such claims and to pay any judgments, costs and
expenses incident to the foregoing indemnity; provided, Buyer shall have the
right, if it so elects, to participate in the defense of any such suit or suits
in which it may be a party, at its own expense, without relieving Seller of the
obligation to defend the same.

             b. By Buyer. To the extent permissable under applicable law, Buyer
agrees to indemnify and hold harmless Seller, its employees and agents, from all
loss, cost, liability and expense arising out of, in connection with, or
resulting from Buyer's ownership or operation of the Subject Property after the
Closing Date. Buyer further covenants and agrees to defend any suits brought
against Seller on account of any such claims and to pay any judgments, costs and
expenses incident to the foregoing indemnity; provided, Seller shall have the
right, if it so elects, to participate in the defense of any such suit or suits
in which it may be a party, at its own expense, without relieving Buyer of the
obligation to defend the same.

         15. Warranties. Notwithstanding any provision of this Agreement to the
contrary, it is understood that the Assignment, Conveyance and Bill of Sale in
the form of Exhibit "B" to be delivered at Closing shall be made with a special
warranty of title (warranting title only as to acts by or through Seller). It is
specifically understood that the personal property and fixtures are being sold
hereunder AS IS, WHERE IS, WITH ALL FAULTS.


                                     - 13 -
<PAGE>   14

         16. Miscellaneous.

             a. Brokers. Each party agrees that it will hold the other party
harmless from any claim by any broker or finder asserting it was employed by
such party in connection with the transactions contemplated hereby.

             b. Further Assurances. Seller agrees to execute any documents which
it has the authority to execute, whether before or after the Closing, to aid
Buyer in clearing or perfecting title and ownership to the Subject Property, and
to facilitate the receipt of the proceeds of the sale of the production
therefrom and attributable thereto. Buyer shall make any request for execution
of such document in writing and shall provide Seller with a copy of the document
and an appropriate explanation of its significance and purpose.

             c. Entire Agreement. This Agreement, together with the Exhibits
attached hereto and Data delivered hereunder, shall constitute the complete
agreement between the parties hereto and shall supercede all prior agreements,
whether written or oral, and any representations or conversations with respect
to the Subject Property.

             d. Press Releases. After entering into this Agreement, either party
shall be entitled to issue a press release concerning this transaction, provided
such press release shall not make reference to the consideration paid to Seller
by Buyer nor shall a press release disclose the other parties name without its
written approval, unless required by law, the Securities and Exchange Commission
or the rules, regulations or guidelines of the stock exchange under which a
party is listed.

             e. Notices. All communications required or permitted under this
Agreement shall be in writing and shall be deemed made when actually received,
or if mailed by registered or certified mail or Federal Express, postage or fees
prepaid, addressed as set forth below, shall be deemed made three (3) days after
such mailing. Either party may, by written notice to the other, change the
address for mailing such notices. Faxes may be sent for convenience but must be
followed up with mailing on any important notice issues.

             Notices to Seller:

                           ATTN: Bruce Benson
                           BENSON MINERAL GROUP, INC.
                           1560 Broadway, Suite 1900
                           Denver, Colorado 80202
                           FAX (303) 863-1932


                                     - 14 -
<PAGE>   15



                  Notices to Buyer:

                           ATTN: Jack Richards
                           DEVON SFS OPERATING, INC.
                           20 North Broadway, Suite 1500
                           Oklahoma City, Oklahoma 73102-8260
                           FAX (405) 228-4461

             f. Binding Effect. Except as specifically provided herein, this
Agreement shall be binding upon and shall inure to the benefit of the parties
hereto, and their successors and assigns; provided, no assignment by either
party shall be made without the express consent of the other party, which
consent shall not be unreasonably withheld, and if such consent is granted, no
assignment shall relieve such party of any of its obligations hereunder.

             g. Counterparts. This Agreement may be executed in any number of
counterparts, which taken together shall constitute one instrument and each of
which shall be considered an original.

             h. Law Applicable. This Agreement shall be governed by and
construed in accordance with the laws of the State of Kansas applicable to
contracts made and performed entirely therein. The prevailing party in any
dispute hereunder shall be entitled to recover its attorneys' fees and costs.

             i. Waivers. No parties' rights hereunder will be deemed waived
except by a writing signed by such party.

             j. Incorporation of Exhibits. All exhibits and schedules referred
to herein are attached hereto and are made a part hereof by this reference.

             k. Survival. Except for the special warranty of title which is
incorporated in the assignment documents and except as otherwise provided
herein, all other representations, warranties and provisions of this Agreement
shall not survive the Final Settlement Date and shall not merge into the
assignment documents to be delivered hereunder.


                                     - 15 -
<PAGE>   16



SELLER:


BENSON MINERAL GROUP, INC., on its
own behalf and as Attorney-in-Fact for E. Wayne
Willhite, Perkins, and William M. Stout



By:      /s/ Bruce D, Benson
     ---------------------------------------
     Bruce D. Benson, President



BUYER:


DEVON SFS OPERATING, INC.


By:      /s/ R. D. Clark
     ---------------------------------------
    R. D. Clark, Vice President


                                     - 16 -
<PAGE>   17

                                EXHIBITS OMITTED


                                     - 17 -