PURCHASE AND SALE AGREEMENT


         THIS AGREEMENT, dated as of November 12, 1998, is between ST. MARY LAND
& EXPLORATION COMPANY ("St. Mary"), a Delaware corporation, 1776 Lincoln Street,
Suite 1100,  Denver,  Colorado 80203,  ST. MARY OPERATING  COMPANY  ("SMOC"),  a
Colorado corporation,  1776 Lincoln Street, Suite 1100, Denver,  Colorado 80203,
KENT J.  HARRELL,  d/b/a  Harrell  Energy Co.,  15 West 6th Street,  Suite 2510,
Tulsa, Oklahoma 74119-5433, RALPH H. SMITH, individually and as Trustees for the
Ralph H. Smith  Restated  Revocable  Trust dated  August 14,  1997,  15 West 6th
Street, Suite 1702, Tulsa,  Oklahoma  74119-5411,  RONALD D. BOONE, 3585 E. Long
Road,  Littleton,  Colorado 80121, RONALD E. HORNIG, 8201 South Park Lane, Suite
100,  Littleton,  Colorado 80120, and ENGLAND RESOURCES  CORPORATION,  a Wyoming
corporation,  8201  South  Park  Lane,  Suite  100,  Littleton,  Colorado  80120
(hereinafter  collectively  referred  to as the  "Seller")  and ONEOK  RESOURCES
COMPANY, a Delaware  corporation,  whose address is 100 West Fifth Street, Suite
1100, Tulsa, Oklahoma 74103-4298 ("Buyer").
         WHEREAS,  Seller desires to sell,  and Buyer desires to purchase,  upon
and subject to the terms and conditions hereinafter set forth, Seller's interest
in and to the following:
                  (i) All rights,  titles and  interests of Seller,  of whatever
kind or character, whether legal or equitable, and whether vested or contingent,
in and to the oil,  gas and other  minerals in and under or that may be produced
from the lands described in (or described by reference to another instrument in)
Exhibit A hereto  (herein  called the "Lands")  including,  without  limitation,
interests in oil, gas and/or mineral leases (the "Leases")  covering such Lands,
overriding  royalties (other than any overriding royalty interests owned by Kent
J. Harrell,  d/b/a  Harrell  Energy Co. or Ralph H. Smith,  individually,  or as
Trustee of the Ralph H. Smith  Restated  Revocable  Trust dated August 14, 1997,
which  overriding  royalty  interests are set forth on the attached  Exhibit A-1
which  overriding   royalty  interests  are  specifically   excluded  from  this
transaction),  production  payments  and net profits  interests in such Lands or
such  Leases,  and fee  mineral  interests,  fee  royalty  interests  and  other
interests in such oil, gas and other minerals,  whether such Lands are described
in a  description  set  forth in  Exhibit  A or are  described  in  Exhibit A by
reference to another instrument;
                  (ii) All rights,  titles and interests of Seller in and to, or
otherwise derived from, all presently existing and valid oil, gas and/or mineral
unitization,  pooling,  and/or communitization  agreements,  declarations and/or
orders  and in and to the  properties  covered  and the units  created  thereby,
including,   without   limitation,   all  units  formed  under  orders,   rules,
regulations,  or other official acts of any federal,  state,  or other authority
having  jurisdiction,  voluntary  unitization  agreements,  designations  and/or
declarations, relating to the Lands;
                   (iii) all of Seller's right,  title and interest in all wells
identified on Exhibit B (the "Wells") and the equipment, materials, fixtures and
facilities  and other  personal  property used or useful in connection  with the
production,  gathering, storing, measuring,  treating,  operating,  maintaining,
marketing  or  transportation  of  production  from the Lands or Leases or lands
pooled or unitized therewith (the "Equipment"),


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                  (iv)  all  of  Seller's  right,  title  and  interest  in  all
contracts and contractual  rights insofar and only insofar as they relate to the
Lands,  Leases,   Wells,  and  Equipment  including  without  limitation,   unit
agreements, surface leases, oil and gas leases and/or subleases and assignments,
mineral deeds, royalty deeds,  operating agreements,  easements,  right of ways,
farmout and farmin agreements, and all similar rights leased or owned by Seller,
and  oil  and  gas  sales,  purchase,  exchange  and  processing  contracts  and
agreements, whether of record or not (the "Contracts"). All of Seller's interest
as set forth above in the Lands,  Leases,  Wells,  Equipment and Contracts shall
hereinafter together be called the "Interests".
         THEREFORE,  in consideration of the above recitals and of the covenants
and agreements herein contained, Seller and Buyer agree as follows:

         1.   Sale  and  Purchase.  Subject  to and upon  all of the  terms  and
conditions  hereinafter set forth, Seller shall sell, transfer,  assign,  convey
and deliver the Interests to Buyer, and Buyer shall purchase,  receive,  pay for
and accept the Interests  from Seller,  effective  September 1, 1998, at 7 a.m.,
local time,  said time to be determined for each locality in which the Interests
are located in accordance with the time generally observed in said locality (the
"Effective Time").

         2.   Purchase Price.
                  (a)  The   Purchase   Price   for  the   Interests   shall  be
$25,500,000.00   ("Purchase  Price"),  subject  only  to  any  applicable  price
adjustment as provided for hereinbelow.
                  (b) Upon  execution  of this  Agreement,  Buyer  shall make an
earnest money deposit  ("Earnest  Money") in the amount of  $2,550,000.00.  This
deposit  together  with the interest  earned  thereon in an interest  bearing or
dividend  account  at  Norwest  Bank  Colorado,  National  Association  shall be
referred  to herein as the  "Earnest  Money".  In the event that the Closing (as
hereinafter  defined) does not occur as a result of Seller's  material breach of
this  Agreement,  then the Earnest  Money  shall be promptly  returned to Buyer.
Otherwise,  the Earnest  Money shall be credited  against the Purchase  Price at
Closing.
                  (c) The Purchase  Price  including the deposit  referred to in
Section  2(b) hereof shall be paid to St. Mary in  accordance  with its specific
instructions  given to Buyer. If these monies are paid to St. Mary in accordance
with  its  instructions,   St.  Mary  shall  assume  full   responsibility   for
distributing  these monies to the parties that constitute  Seller,  and St. Mary
will  indemnify and hold Buyer  harmless from any claims,  costs  (including any
reasonable  attorneys' fees and court costs) and liabilities  resulting from any
improper payment of these monies to the parties constituting Seller.

         3.  Allocated Values. Buyer and Seller hereby agree upon the allocation
(the  "Allocated  Value(s)")  of the Purchase  Price among the  Interests.  Such
Allocated  Values are made a part of this  Agreement  and are shown on Exhibit C
which is attached hereto.

         4.   Seller's Representations.  Seller represents and warrants to Buyer
that as of the  Closing  Date:  
                  (a) St. Mary is a duly organized corporation  validly existing
and in good  standing  under the laws of the State of  Delaware.  SMOC is a duly


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organized  corporation  validly  existing and in good standing under the laws of
the  State  of  Colorado.  England  Resources  Corporation  is a duly  organized
corporation validly existing and in good standing under the laws of the State of
Wyoming.  Ralph H. Smith  acting as the Trustee for the Ralph H. Smith  Restated
Revocable  Trust dated August 14, 1997, has all requisite  power to own and sell
this Trust's  interest in the Interests  and he has taken all  requisite  action
necessary to authorize sale of the Trust's interest in the Interests. Each party
constituting  Seller is duly  qualified to carry on its business in the state in
which the Interests are located,  has full power and authority to enter into and
perform under this Agreement according to its terms, and this Agreement has been
duly  executed  and  delivered by Seller and  constitutes  a legal,  valid,  and
binding obligation on it, enforceable against it in accordance with its terms;

                  (b) Seller,  St.  Mary's and SMOC's,  execution,  delivery and
performance  of  this  Agreement  has  been  duly  authorized  by any  necessary
corporate action and will not violate or conflict with any agreement, law, rule,
regulation,   charter,   or  other   instruments   governing   either   Seller's
organization,  management,  business  affairs or instrument to which Seller is a
party or is bound;
                  (c)  There  are  no  known  third  party   claims  or  demands
("Claims")  with  regard to the  Interests;  (d) Seller  shall have  "Marketable
Title," as defined in paragraph 7 below, with respect to the Interests;
                  (e) The Leases are in full force and effect in accordance with
their terms and Seller has not been advised directly or indirectly by any lessor
under any lease of a default under any lease;
                  (f) All  royalties,  rentals and other  payments due under the
Leases have been properly and timely paid, and all conditions  necessary to keep
the Leases in force have been fully performed;
                  (g)  Seller  is  not  obligated,  by  virtue  of a  prepayment
arrangement  under any contract for the sale of hydrocarbons  containing a "take
or pay" or similar provision,  or by virtue of a production payment or any other
arrangement to deliver  hydrocarbons  produced from the Interests at some future
time without then or thereafter receiving full payment therefor;
                  (h)  All  ad  valorem,  property,  production,  severance  and
similar taxes and assessments  based on or measured by the ownership of property
or the production of  hydrocarbons  or the receipt of proceeds  therefrom on the
Interests  for all years prior to the year in which this  Agreement  is executed
have been properly paid, and all such taxes and assessments which become due and
payable prior to the Closing shall be properly paid by Seller;
                  (i) All valid laws, regulations and orders of all governmental
agencies having  jurisdiction over the Interests have been and shall continue to
be complied  with until the Closing and Seller has not  received any notice from
any governmental agency that it is in violation of any law, regulation or order;
and
                  (j) To the best of Seller's  knowledge,  the material terms of
all leases, operating agreements, production sales contracts, farmout agreements
and other  contracts or agreements  respecting the Interests can be found either
of record in the counties in which the Interests are located or are reflected or
referenced in Seller's files.


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                  (k)  Seller has not executed any authority for expenditure  in
excess of $10,000.00 for operations  affecting the Interests since the Effective
Time except as disclosed to Buyer on the attached Schedule 4(k), and Seller will
not do so prior to Closing  without  Buyer's express written consent except when
required by  emergency  or as required  to  preserve  any rights  created by any
agreement, lease, contract, or instrument pertaining to the Interests.
                  (l)  To  the  best  of Seller's  knowledge,  but  without  any
warranty  whatsoever,  the  Equipment  is  suitable  for its  intended  purposes
regarding the Interests taking into consideration all circumstances  surrounding
the Interests and customary  industry  standards  regarding  properties  such as
these.
                  (m)  There  are  no   judicial  or   administrative   actions,
proceedings  or  investigations  pending or, to the best of Seller's  knowledge,
threatened  that (i)  challenge  the  validity of this  Agreement;  (ii) seek to
restrain or prevent any action taken or to be taken by Seller in connection with
this Agreement; or, (iii) if adversely determined, would have a material adverse
effect upon Seller's ability to perform its obligations under this Agreement.

         5.   Buyer's  Representations.  Buyer represents and warrants to Seller
that as of the Closing  Date:  
                  (a)  Buyer is a currently effective corporation and is or will
be by Closing duly  qualified to carry on its business in the state in which the
Interests  are located,  has full power and  authority to enter into and perform
under this  Agreement  according to its terms,  and this Agreement has been duly
executed and  delivered by Buyer and  constitutes  a legal,  valid,  and binding
obligation on it, enforceable against it in accordance with its terms.
                  (b)  Buyer's  execution,  delivery  and  performance  of  this
Agreement have been duly authorized by all necessary corporation action and will
not conflict with or violate any agreement,  law, rule,  regulation,  ordinance,
charter or other instruments governing either Buyer's organization,  management,
business  affairs or  instrument  to which Buyer is a party or by which Buyer is
bound.
                  (c)  Buyer  represents  that by reason  of its  knowledge  and
experience  in  the  evaluation,  acquisition,  and  operation  of oil  and  gas
properties, Buyer has evaluated the merits and risks of purchasing the Interests
from Seller, and if Closing occurs,  Buyer will have performed sufficient review
and due diligence  with respect to the Interests to enable it to consummate  the
transaction contemplated hereby based solely on Buyer's knowledge and experience
and not on any representations or warranties of Seller.

         6.   Access to Records. After execution of this Agreement, Seller shall
give Buyer and its authorized representatives, during regular business hours, at
Buyer's sole risk, cost and expense,  access,  with copying  privileges,  to all
geological,  geophysical,  production,  engineering and other technical data and


                                       4


records, and to all contract,  land, title and lease records, to the extent such
data and records are in Seller's possession and relate to the Interests and such
other  information  relating to the Interests as Buyer may  reasonably  request;
provided,  however, Seller shall have no obligation to provide Buyer such access
to any data or  information  which access  Seller cannot  legally  provide Buyer
because of third-party restrictions on Seller, but Seller agrees to use its best
efforts  to  obtain  the  consent  of  any  such  third-party  to  furnish  such
information  to  Buyer.  Buyer  shall  keep  all  materials  and  data  obtained
confidential  and shall return any and all materials and data including  Buyer's
notes and work papers as to any properties not purchased at Closing.

         7.   Marketable Title.  As  used  herein, the  term  "Marketable Title"
shall mean, as to the Interests set forth on Exhibit C, that title which:
                  (a)  Entitles  Seller to receive not less than the  percentage
set  forth  in  Exhibit  C as the "Net  Revenue  Interest"  of all  hydrocarbons
produced,  saved and  marketed  from the portion of the  Interests  specified in
Exhibit C throughout the productive life thereof;
                  (b)  Obligates  Seller to bear a  percentage  of the costs and
expenses  relating to the  maintenance  and  development of and operation of the
portion of the  Interests  specified in Exhibit C, not greater than the "Working
Interest" set forth in Exhibit C throughout the productive life thereof; and
         The Working Interest and Net Revenue Interest as set forth in Exhibit C
are intended to represent only Seller's ownership within the currently producing
horizons   in  the  Wells  and  the   proved   undeveloped,   proved   developed
non-producing,   probable,  and  possible  locations  and  attendant  formations
specifically  identified in Exhibit C. Seller's  ownership in all  non-producing
horizons  affected by the  Interests  which are not  specifically  identified in
Exhibit C may vary from the Working Interest and Net Revenue  Interest  depicted
in Exhibit C for any individual well based on individual wellbore interests, and
no representation or warranty whatsoever is made by virtue of this instrument as
to Seller's  Working  Interest or Net Revenue Interest outside the wellbores for
the  Wells  and  the  non-producing   locations  and  attendant  formations  not
specifically listed on Exhibit C.
                  (c) Is free and clear of liens, claims, encumbrances, charges,
contracts or other  burdens or defects,  except for Permitted  Encumbrances  (as
hereinafter defined). As used herein the term "Permitted Encumbrances" means:
                             (i)  preferential  rights to purchase  and required
         third party  consents to  assignment  with respect to which  waivers or
         consents are obtained from appropriate  parties prior to Closing or the
         applicable  response  period after notice has passed  without the party
         holding  the  preferential  right  having  exercised  such right or are
         otherwise deemed waived;
                           (ii) Unit or unitization agreements,  communitization
         agreements or pooling agreements,  and polling or unitization orders of
         any federal or state governmental agency having jurisdiction;
                           (iii)  Operating   agreements,   farmout  agreements,
         assignments, agreement for the sale or purchase of oil, gas, casinghead


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         gas or other hydrocarbon substances,  processing agreements, salt water
         or  other  disposal  agreements,  seismic  or  geophysical  permits  or
         agreements,  and other  contracts or agreements  which are customary in
         the oil and gas industry.
                           (iv)     division orders;
                           (v)      such  other  defects  or  irregularities  of
         title or  liens,  charges or encumbrances as  Buyer may have  waived in
         writing;
                           (vi) notwithstanding anything to the contrary in this
         Section 7, all rights to consent by, required  notices to, filings with
         or other actions by  governmental  entities in connection with the sale
         or conveyance of federal,  state,  Indian or other governmental oil and
         gas leases or interest  therein or related  thereto  where the same are
         customarily  obtained  subsequent  to  assignment  of such  Leases  and
         Interests; and
                           (vii)   lessors'  royalties,   overriding  royalties,
         production payments, net profits interest,  reversionary interests, and
         similar burdens which do not operate to reduce any Net Revenue Interest
         set forth on Exhibit C to less than such amount.
                           (viii)   All  other  liens,  charges,  encumbrances, 
         defects   and   irregularities  which  do  not  materially  impair  the
         operation, or use of the Interests.

         8.   Preferential  Rights.   If  any of  the Interests are  subject  to
preferential  purchase  rights,  rights of first  refusal,  consents  to assign,
lessor's approvals,  or similar rights  (collectively,  "preferential  rights"),
Seller shall promptly upon the execution of this Agreement by the parties hereto
notify all holders of preferential rights of its intention to sell the Interests
affected thereby,  and of the  corresponding  Allocated  Value(s).  Seller shall
promptly  notify  Buyer if the  preferential  rights  are  exercised,  or if the
requisite period has elapsed without said rights having been exercised.

         9.   Title Examination and Physical Inspection.
                  (a)  After  the  execution  of this  Agreement,  Buyer and its
authorized  representatives  shall  have  physical  access to the  Interests  at
Buyer's sole cost, risk and expense for the purpose of inspecting the Interests,
conducting  such tests,  examination,  investigations  and assessments as may be
reasonable  and  necessary  or  appropriate  to evaluate the  environmental  and
physical conditions of the Interests. For those Interests which are not operated
by Seller,  Buyer or Seller shall obtain  permission from the operator for Buyer
to conduct such  inspections.  Buyer shall defend and indemnify  Seller from any
and all liability, claims, causes of action, injury to Buyer's employees, agents
or  contractors  or to Buyer's  property,  and/or  injury to Seller's  property,
employees,  agents or contractors which may arise out of Buyer's inspections. In
the event this  Agreement  fails to close,  Buyer shall keep any and all data or
information  acquired  by  all  such  examinations   including  the  Independent
Environmental Review described in Section 10 and results of all analysis of such
data and information  strictly  confidential and not disclose same to any person
or agency without the prior written approval of Seller, unless required to do so
by court order or applicable  law.  Upon Closing,  Seller shall keep all matters
pertaining to the Interests confidential unless disclosure is required by law.


                                       6


                  (b) Buyer will  conclude  its title  review and give notice to
Seller of asserted title defects  ("Title  Defects")  which would cause title to
any Interest not to be Marketable  Title as defined in paragraph 7, on or before
December 9, 1998.  All  Environmental  Defects shall be dealt with in accordance
with Section 10. To be effective,  Buyer's written notice of a Title Defect must
include (i) a brief  description of the matter  constituting  the asserted Title
Defect and (ii) supporting  documents or briefs thereof reasonably necessary for
Seller (or a title attorney or examiner hired by Seller) to verify the existence
of such asserted  Title  Defect,  and (iii) the value for any  individual  Title
Defect must exceed  $10,000.00  and the value of all Title  Defects  must exceed
$250,000.00 in the aggregate.  No individual Title Defect having a value of less
than $10,000.00  shall be considered a Title Defect even if the aggregate amount
is otherwise  reached.  This $250,000.00  aggregate number shall be considered a
threshold  and not a  deductible.  The term  "Title  Defect"  will  not  include
reductions  in any Net Revenue  Interest  or  increase  in any Working  Interest
without a  corresponding  increase in the  attendant  Net Revenue  Interest from
those set forth in  Exhibit C caused by any  computational  error  committed  by
Seller or as a result of the failure of Seller to properly  calculate the effect
of any overriding royalty interest or other non-cost bearing interest created by
Seller. Any item described in the preceding sentence shall be referred to herein
as a "Computational Error".
                  (c)  After  Buyer  delivers  to Seller  written  notice of any
matters which  constitute a Title Defect to the Interests,  Seller,  at Seller's
sole cost and expense,  may attempt to cure such matters. In the event Seller is
unable to cure such matters within 60 days after receipt of notice in accordance
with  this  Section  9,  Buyer,  at  Buyer's  option,  may  elect  either of the
following:
                           (i) the  Interest(s) or portion  thereof  affected by
         such Title  Defect may be excluded  from the  Interests to be purchased
         and sold hereunder,  and the Purchase Price shall be adjusted  downward
         by the Allocated  Value(s)  attributable to such Interest(s) or portion
         thereof; or
                           (ii) the  Interest(s)  affected by such Title  Defect
         may be  included  at a reduced  value and the  Purchase  Price shall be
         adjusted downward by a value mutually agreed to by Buyer and Seller.
If Closing  has  occurred  prior to the  running  of this cure  period and Buyer
chooses  to elect  remedy (i) or (ii)  above,  Seller  will  refund to Buyer the
corresponding  portion  of  the  Purchase  Price  to  accommodate  the  downward
adjustment.

         10.  Environmental Matters.   After the  execution of  this  Agreement,
Buyer and its  authorized  representatives  shall  have  physical  access to the
Interests at Buyer's sole cost,  risk and expense for the purpose of  inspecting
the  Interests,   conducting  such  tests,   examination,   investigations   and
assessments  as may be reasonable  and necessary or  appropriate to evaluate the


                                       7


environmental  and physical  conditions of the  Interests.  For those  Interests
which are not  operated  by  Seller,  Buyer  shall  obtain  permission  from the
operator to conduct  such  inspections.  Seller  shall  provide  all  reasonable
assistance  in  obtaining  this  permission  for Buyer.  Buyer shall  defend and
indemnify Seller from any and all liability, claims, causes of action, injury to
Buyer's employees,  agents or contractors or to Buyer's property,  and/or injury
to Seller's  property,  employees,  agents or contractors which may arise out of
Buyer's inspections,  but only to the extent of Buyer's negligence. Buyer agrees
to provide to Seller,  upon request,  a copy of any  environmental  assessments,
including any reports, data, and conclusions.  Likewise, Seller shall furnish to
Buyer a copy of any environmental assessments,  including any reports, data, and
conclusions  pertaining to the Interests in the possession of Seller.  Buyer and
Seller  shall  keep  any  and all  data  or  information  acquired  by all  such
examinations  and results of all analysis of such data and information  strictly
confidential  and not  disclose  same to any person or agency  without the prior
written  approval  of both Buyer and Seller,  unless  required to do so by court
order or applicable  law. The  foregoing  obligation  of  confidentiality  shall
survive Closing or termination of this Agreement  without  Closing.  Buyer shall
have until  December 9, 1998,  to complete  this  environmental  inspection  and
analysis of the Interests.
          If, on or before December 9, 1998,  Buyer discovers a material adverse
environmental  condition which would adversely affect the value of the Interests
by $25,000 per occurrence and the value of all Environmental Defects must exceed
$250,000 in the aggregate net to Seller's interest in the affected property, and
Seller is not in compliance with  Environmental  Laws (as  hereinafter  defined)
with respect to such property ("Environmental  Defect"), Buyer shall give Seller
written notice thereof not later than December 9, 1998,  together with the basis
for such  assertion and data in support  thereof,  and shall furnish Seller with
any proposed  reduction in the Purchase Price  attributable to each such matter.
For purposes of this Agreement, Environmental Laws shall mean any statute, rule,
order,  or regulation of any federal,  state,  or local  governmental  authority
relating to pollution or protection of the  environment  to the extent in effect
before the Effective  Time. No  individual  Environmental  Defect having a value
less than  $25,000  shall be  considered  an  Environmental  Defect  even if the
aggregate amount is otherwise  reached.  This $250,000 aggregate number shall be
considered a threshold and not a deductible.
         Upon timely delivery of a notice by Buyer of an  Environmental  Defect,
Seller, at Seller's option,  shall either (i) remove the defective property from
the sale and reduce the Purchase Price by the Allocated  Value  attributable  to
the  defective  property,  (ii) attempt to cure the defect at Seller's sole cost
and  expense  within 120 days after the  notice,  or (iii) agree with Buyer to a
mutually  acceptable  Purchase Price  reduction with regard to an  Environmental
Defect which shall be equal to the cost  reasonably  associated with curing such
defect. If Seller attempts to cure the  Environmental  Defect and is not able to
do so in accordance with item (ii) above, the property  affected by such uncured
Environmental  Defect shall be withdrawn unless a mutually  acceptable  Purchase
Price reduction is agreed to by Buyer and Seller.  If withdrawn,  the portion of
the Purchase Price  attributable to such property shall be promptly  refunded to
Buyer.

         11.  Purchase Price Adjustments. The Buyer and Seller have agreed to an
Allocated  Value for each  Interest  (and the Lands,  Leases and other  property


                                       8


related  thereto) as set forth on Exhibit C hereto.  The Purchase Price is based
upon Seller having the Net Revenue  Interests  specified on Exhibit C. If Seller
is unable to deliver, at Closing, the Net Revenue Interest shown on Exhibit C as
a result of a Computational  Error and the Buyer has not previously excluded the
affected portion of the Interests pursuant to paragraph 9(c), the Purchase Price
shall be reduced by an amount equal to a  proportionate  amount of the Allocated
Value for such  Well.  Likewise,  if Seller  shall  have a greater  Net  Revenue
Interest  in an  interest  set forth in Exhibit C, the  Purchase  Price shall be
increased  proportionately.  In the event that the  aggregate  reduction  in the
Purchase Price on account of any adjustments contemplated by paragraphs 9 or 10,
equals or exceeds twenty percent (20%) of the Purchase  Price,  either Seller or
Buyer shall have the right to terminate  this Agreement by written notice to the
other party,  in which event all rights,  duties and obligations of either party
hereunder  shall cease and the Earnest  Money shall  immediately  be returned to
Buyer. The parties  acknowledge that Closing may occur prior to the finalization
of the  Purchase  Price  adjustments  contemplated  by this  Section 11. If this
occurs,  Seller  and Buyer  shall  nevertheless  adjust  the  Purchase  Price in
accordance with this Section 11 at an intermediate post-Closing adjustment to be
held on January 15, 1999, if necessary.

         12.  Assignment and Warranty of Title.  The conveyance of the Interests
shall be on the form of  assignment  attached  hereto  as  Exhibit  D and  shall
contain a warranty of title by, through and under Seller, as to their respective
percentage ownership only, but not otherwise.

         13.  Conditions of Closing by Buyer.   The obligation of Buyer to close
is subject to the satisfaction of the following conditions:
                  (a) Buyer  shall  have had  reasonable  access  during  normal
business  hours  to all data  and  records  obligated  to be  provided  Buyer as
provided herein;
                  (b) Buyer  shall  have had  reasonable  access  to the  Lands,
Leases,  Wells, and Equipment included in the Interests to conduct an inspection
for all purposes, including environmental condition;
                  (c) All  representations and warranties of Seller contained in
this  Agreement  shall be true,  correct,  and not  misleading  in any  material
respects,  and Seller shall have  performed  and satisfied  all  agreements  and
covenants in all material  respects  required by this  Agreement to be performed
and satisfied by Seller;
                  (d) Seller shall have  obtained and delivered to Buyer (i) all
prerequisite  waivers  of  preferential  rights of  purchase  or the  expiration
thereof shall have occurred, and (ii) all necessary consents for transfer of the
Interests,  except those which by their  nature  cannot be requested or obtained
until after Closing,  or Buyer and Seller shall have adjusted the Purchase Price
in accordance with the provisions of this Agreement;
                  (e) No suit or other proceeding shall be pending or threatened
before any court or  governmental  agency  seeking  to  restrain,  prohibit,  or
declare  illegal,   or  seeking  substantial  damages  in  connection  with  the
transaction contemplated hereby;


                                       9


         14.  Conditions of Closing by Seller. The obligation of Seller to close
is subject to the satisfaction of the following conditions:
                  (a) All  representations  and warranties of Buyer contained in
this  Agreement  shall be true,  correct,  and not  misleading  in any  material
respect,  and Buyer  shall have  performed  and  satisfied  all  agreements  and
covenants in all material  respects  required by this  Agreement to be performed
and satisfied by Buyer.
                  (b) No suit or other proceeding shall be pending or threatened
before any court or  governmental  agency  seeking  to  restrain,  prohibit,  or
declare  illegal,   or  seeking  substantial  damages  in  connection  with  the
transaction contemplated hereby.

         15.  Preliminary Closing Statement. Seller shall prepare and furnish to
Buyer at least five (5) days prior to Closing a  preliminary  closing  statement
setting  forth  the  adjustments  to the  Purchase  Price to be paid by Buyer at
Closing.  Such statement shall reflect each adjustment and the calculation  used
to determine such amount. The preliminary adjusted Purchase Price shall mean the
Purchase Price adjusted as provided herein, including but not limited to Earnest
Money,  Title  Defects,  interest  variances,  gas  imbalances,  proration of ad
valorem and other  applicable  taxes and  allocation  of operating  expenses and
revenues  attributable to the Interests.  Insofar as concerns operating expenses
and revenues  attributable  to the  Interests  subject to Closing for the period
from the Effective Time through Closing, for purposes of the preliminary closing
statement, Buyer shall receive a net adjustment for estimated operating expenses
and revenues for those periods which the actual  amounts cannot be determined at
Closing.  Final  adjustments to the actual gas balancing,  expenses incurred and
revenues received shall be taken into account on the Final Settlement Statement.

         16.  Closing.   The Closing shall occur on or before December 15, 1998,
at 10:00 a.m., at the offices of St. Mary Land &  Exploration  Company in Tulsa,
Oklahoma, or at such other time and place as Seller and Buyer may mutually agree
in writing. In the event the transaction contemplated under this Agreement fails
to close on or before  December 31, 1998, and Seller is otherwise  ready,  able,
and willing to consummate the transaction contemplated hereby, the Earnest Money
shall be forfeited to Seller as liquidated damages,  and this Agreement shall be
terminated  and of no  further  force or  effect.  If  however,  Buyer is ready,
willing, and able to close the transaction  contemplated by this Agreement,  and
Closing has not occurred on or before  December  31,  1998,  through no fault of
Buyer,  Buyer shall be entitled either to declare this Agreement  terminated and
the immediate  return of the Earnest Money,  or to seek specific  performance of
this transaction. At Closing the following will occur:
                  (a) Seller shall execute,  acknowledge and deliver to Buyer an
Assignment and Bill of Sale substantially in the form and substance of Exhibit D
attached hereto, covering all of the Interests to be sold pursuant hereto;


                                       10


                  (b) Buyer shall in accordance with Section 2(c) hereof deliver
to St. Mary by wire  transfer the total  Purchase  Price as adjusted  hereunder,
subject to further adjustment after Closing as provided for herein;
                  (c) On or before  Closing,  Seller and Buyer shall execute all
necessary  forms  to  be  filed  with  the  appropriate  regulatory  authorities
concerning the change of ownership of the Interests, and Buyer shall submit same
for approval to such regulatory  authorities at Buyer's expense, and Buyer shall
deliver to Seller evidence of the appropriate  state and federal  plugging bond,
surety  letter,  or letter of credit  acceptable to such  authority to authorize
Buyer's right to conduct operations, if applicable;
                  (d)  Seller  shall,  subject  to the  terms of any  applicable
operating  agreements,  deliver to Buyer exclusive  possession of the Interests,
effective as of the Effective Time;
                  (e) Seller  shall  execute  and deliver  appropriate  transfer
orders or letters in lieu of transfer orders with respect to each of the Wells;
                  (f) Seller shall transfer all suspense accounts  maintained by
it  that  relate  to  the  Interests  to  Buyer,  and  Buyer  shall  assume  all
responsibility   for  the  administration  and  distribution  of  such  accounts
thereafter;
                  (g) Seller shall  promptly  after  Closing  provide  Buyer any
maps, reports,  and other written material relating to the Interests,  including
without limitation,  lease files,  division order and revenue files,  accounting
files,  property  records,   contract  files,   operations  files,  well  files,
geological maps and geophysical data (provided such is not prohibited from being
transferred  by  operation  of any third party  agreement),  core  analyses  and
hydrocarbon  analyses,  well  logs,  mud  logs,  core  data  and  field  studies
("Records");  however, Seller shall have no obligation to furnish Buyer any data
or  information  which  Seller  cannot  provide  Buyer  because  of third  party
restrictions.  Seller  agrees to request that any such third party  furnish such
information to Buyer.  Buyer agrees to maintain the Records and allow Seller, at
its sole cost and  expense,  reasonable  access  thereto for a period of six (6)
years after Closing; and
                  (h) Seller shall,  as  appropriate,  resign as operator of the
Interests and Seller agrees not to support any third party as successor operator
to Seller with regard to the Interests.

         17.  Reservations and Exceptions. Sale and purchase of the Interests is
made subject to all reservations,  exceptions,  limitations, contracts and other
burdens or instruments  which are of record or are listed on Exhibits A, A-1, or
B hereto.

         18.  Indemnification.
                  (a) Buyer agrees to indemnify,  defend, and hold Seller, their
successors,  and assigns, harmless from and against any and all claims, demands,
liabilities,  judgments,  penalties, causes of action, lawsuits, damages, costs,
and expenses, including reasonable attorney's fees, expert fees, and court costs
of every kind and character  arising out of or attributable to Buyer's ownership
or  operation  of the  Interests,  including,  but not limited to  environmental
matters,  arising from  matters  occurring  on or after the  Effective  Time and


                                       11


further this indemnity shall extend to any  environmental  matter which has been
dealt with in accordance with Section 10 hereof.
                  (b) Seller agrees to indemnify,  defend,  and hold Buyer,  its
successors,  and assigns, harmless from and against any and all claims, demands,
liabilities,  judgments,  penalties, causes of action, lawsuits, damages, costs,
and expenses, including reasonable attorney's fees, expert fees, and court costs
of every kind and character arising out of or attributable to Seller's ownership
or  operation  of the  Interests,  including,  but not limited to  environmental
matters (except as to those dealt with under Sections 10 and 28 hereof), arising
from matters occurring prior to the Effective Time.
                  (c)   Notwithstanding   the  foregoing,   the  indemnification
obligation  of Seller as set forth in Section 18 (b) hereof shall  terminate one
year after Closing  regarding all matters except liability for personal injuries
that are covered by Section  18(b) hereof which  indemnification  obligation  of
Seller shall  terminate two years after Closing,  and  respectively  thereafter,
Buyer  shall  defend  and  indemnify   Seller   against  all  claims,   demands,
liabilities,  judgments,  penalties, causes of action, lawsuits, damages, costs,
and expenses  (including  reasonable  attorney's  fees,  expert fees,  and court
costs)  of  every  kind  or  character  arising  out of or  attributable  to the
ownership  or  operation of the  Interests  and  asserted  after the one-year or
two-year  anniversary  of  Closing,  even though  caused by,  arising out of, or
attributable to, in whole or in part, the sole or concurrent negligence,  fault,
or strict liability of Seller.

         19.  Casualty  Loss.   Notwithstanding  anything  that may be contained
herein to the contrary,  if, prior to the Closing, a Casualty Loss occurs, Buyer
may elect (i) to delete the property  that is subject to the Casualty  Loss from
the Interests and the Purchase Price shall be reduced by the value  allocated to
the deleted  interest based on the value reflected on Exhibit C, (ii) to proceed
with the purchase of the  Interests  without  reduction  of the Purchase  Price,
notwithstanding any such destruction or taking, in which case at Closing, Seller
shall pay to Buyer all sums  paid to  Seller by third  parties  by reason of the
destruction  or taking of that portion of the  Interests  that is subject to the
Casualty  Loss and shall  assign,  transfer  and set over unto  Buyer all of the
right,  title and  interest  of Seller in and to any  claims,  causes of action,
unpaid  proceeds  or other  payments,  from third  parties  arising  out of such
destruction or taking. Seller shall not voluntarily compromise, settle or adjust
any amounts  payable by reason of a Casualty  Loss without  first  obtaining the
written consent of Buyer. For the purposes hereof the term "Casualty Loss" means
the destruction of all or any portion of the Interests by fire or other casualty
or taking thereof by condemnation or under the right of eminent domain.

         20.  Taxes.   All Ad valorem taxes,  real property  taxes,  and similar
obligations  with respect to the tax period in which the  Effective  Time occurs
(the "current tax period") shall be  apportioned  between Seller and Buyer as of
the Effective Time.

         21.  Accounting.
                  (a) All  proceeds  (including  proceeds  held in  suspense  or
escrow) from the sale of production  actually sold and delivered by Seller prior
to the Effective Time  attributable  to the Interests shall belong to Seller and


                                       12


all proceeds from the sale of production  actually sold and delivered  after the
Effective Time attributable to the Interests shall belong to Buyer.
                  (b)  All  oil,  condensate  or  liquid  hydrocarbons  and  any
products (liquid, gas or solid) separated or processed therefrom (hereinafter in
this paragraph  called "oil") in storage shall be measured or gauged and all gas
meter charts shall be replaced at the Effective Time. Buyer shall pay Seller for
such oil at the actual  price  received  for the sale of such oil. If not known,
this  Purchase  Price shall be  estimated at Closing and paid to Seller with the
actual final settlement of this matter to occur at the post-Closing  accounting,
provided  that Buyer shall not pay Seller for oil in storage  below the level of
the tank cut off valve (tank bottoms).
                  (c) Any gas imbalance shall be accounted for between Buyer and
Seller as follows:  Buyer and Seller  agree for the  purposes of this  Agreement
that the net gas  imbalance  attributable  to the  Interests as of the Effective
Time is as set forth on Exhibit E (the "Agreed Imbalance"), notwithstanding that
the actual  imbalance  may be lesser or greater.  The Agreed  Imbalance has been
used by Buyer and Seller in negotiating the Purchase Price under this Agreement.
Buyer and Seller shall verify the actual net gas  imbalance in the  post-Closing
accounting  and any imbalance  shall be accounted for between the parties at the
price of $1.00  per MCF but only as to those  volumes  which  exceed or are less
than the Agreed  Imbalance;  provided  that if an  applicable  operating  or gas
balancing  agreement  requires cash balancing upon  conveyance of the Interests,
the  adjustment  price  shall  equal the  greater  of $1.00 per MCF or the price
received with respect to such cash balancing. Such settlement shall be final and
neither  party  thereafter  shall make claim upon the other  concerning  the gas
balances of the Interests.  Buyer assumes all rights and liabilities relating to
gas  imbalances  discovered  after the  post-Closing  settlement  including  any
revenue adjustment caused by such subsequently discovered imbalance.
                  (d)  Except  as  otherwise   specifically   provided  in  this
Agreement,  all normal and routine costs,  expenses and contractual  obligations
and benefits,  including  accounts  receivable,  relating to the Interests which
accrue prior to the Effective  Time shall be paid and  discharged or received by
Seller regardless of when invoices for such costs,  expenses and obligations are
received and all normal and routine costs, expenses and contractual  obligations
and benefits  relating to the Interests  which accrue after the  Effective  Time
shall be paid and discharged or received by Buyer.
                  (e) The  foregoing  adjustments  shall be made by  debits  and
credits between the parties at Closing or post-Closing as provided for herein.
                  (f) To the extent necessary to comply with requirements of the
Securities and Exchange  Commission  (the "SEC"),  Buyer shall have the right to
audit Seller's  business and financial  records,  including  without  limitation
property detail,  standardized  measure data and independently  prepared reserve
information,  maintained in connection with the Interests (except for income tax
records) for all periods for which audited financials are required by the SEC to
be prepared and filed by Buyer.


                                       13


         22.  Sales Tax. The Purchase Price provided for hereunder  excludes any
sales taxes or other taxes in connection  with the sale of property  pursuant to
this  Agreement.  If a  determination  is ever  made  that a sales  tax or other
transfer  tax  applies,  Buyer  shall  be  liable  for  such  tax as well as any
applicable  conveyance,  transfer and recording  fees, and real estate  transfer
stamps or taxes imposed on any transfer of property  pursuant to this Agreement.
Buyer shall defend and hold Seller  harmless  with respect to the payment of all
such taxes, if any, including any interest or penalties assessed thereon.

         23.  Post-Closing  Adjustments.   As soon as practicable after Closing,
but in any event within one hundred twenty (120) days  thereafter,  Seller shall
prepare,  in accordance with this Agreement and (where applicable) in accordance
with generally  accepted  accounting  principles  consistently  applied, a final
settlement  statement (herein called the "Final  Statement")  setting forth each
adjustment or payment  which was not finally  determined as of the Closing Date,
and showing the  calculation of the final  settlement  price based on such Final
Statement  (the  "final  settlement  price").  Seller  shall  submit  the  Final
Statement to Buyer and shall afford Buyer access to Seller's records  pertaining
to the  computations  contained in the Final  Statement.  As soon as practicable
after receipt of the  statement,  Buyer shall deliver to Seller a written report
containing any changes which Buyer proposes be made to the Final Statement.  The
parties   shall  agree  with  respect  to  the  amounts  due  pursuant  to  such
post-Closing  adjustment not later than sixty (60) days after Buyer's receipt of
Seller's Final Statement. The date upon which such agreement is reached shall be
herein called the "Settlement  Date". In the event that (i) the final settlement
price is more than the  amount  previously  paid to Seller,  Buyer  shall pay to
Seller in immediately available funds the amount of such difference; or (ii) the
final settlement price is less than the amount previously paid to Seller, Seller
shall pay to Buyer in immediately available funds the amount of such difference.

         24.  Brokers' Fee.  Each of Seller and Buyer represents and warrants to
the other that it has not  incurred  liability,  contingent  or  otherwise,  for
brokers'  or  finders'  fees in respect of this  Agreement  or the  transactions
contemplated hereby.

         25.  Notices.   All  communications  required or  permitted  under this
Agreement shall be in writing and any communication or delivery  hereunder shall
be deemed to have been duly given and received  when  actually  delivered to the
addressee or received  via  facsimile  at the  number(s)  set forth below of the
party to be notified.
                           SELLER:
                           St. Mary Operating Company
                           7060 South Yale, Suite 800
                           Tulsa, Oklahoma  74136-5741
                           Attention:       Julian C. Pope
                                            Vice President
                           Telephone:       (918) 488-7600
                           Fax:             (918) 488-0105



                                       14


                           WITH A COPY TO:
                           St. Mary Land & Exploration Company
                           1776 Lincoln Street, Suite 1100
                           Denver, Colorado  80203
                           Attention:       Milam Randolph Pharo
                          Vice President - Land & Legal
                            Telephone: (303) 861-8140
                               Fax: (303) 863-1040


                           BUYER:
                           ONEOK Resources Company
                           100 West Fifth Street, Suite 1100
                           Tulsa, Oklahoma   74103-4298
                           Attention:       J.D. Holbird, Vice President
                           Telephone:       918-588-7934
                           Fax:             918-588-7773

                           WITH A COPY TO:
                           Donald A. Kihle
                           Gable and Gotwals
                           100 West Fifth Street, Suite 1000
                           Tulsa, Oklahoma  74103-4219
                           Telephone:       918-585-8141
                           Fax:             918-588-7873

         26.  Interim Operations.  Seller covenants that from the date hereof to
the Closing Date, except (A) as provided herein,  or (B) as otherwise  consented
to in writing by Buyer, Seller will:
         (a) Not (A) operate or in any manner deal with, incur  obligations with
respect to, or undertake any transactions  relating to, the Interests other than
transactions (i) in the normal, usual and customary manner, (ii) of a nature and
in an amount  consistent with prior practice,  (iii) in the ordinary and regular
course of business of owning and  operating the  Interests,  and (iv) subject to
the  terms and  conditions  of this  Agreement;  (B)  dispose  of,  encumber  or
relinquish any of the Interests (other than  relinquishments  resulting from the
expiration of leases that Seller has no right or option to renew); or (C) waive,
compromise  or settle any right or claim  that  would  have a  material  adverse


                                       15


effect on the  ownership,  operation or value of any of the Interests  after the
Effective Time.
         (b) Use all reasonable efforts to preserve in full force and effect all
oil and gas leases,  operating  agreements,  easements,  rights of way, permits,
licenses,  and  agreements  which relate to the  Interests and shall perform all
obligations of Seller in or under all such agreements relating to the Interests.
Seller shall,  except for emergency  action taken in the face of serious risk to
life,  property,  or the environment,  consult with, inform and advise Buyer, to
the extent Seller has such knowledge,  regarding all material matters concerning
the operating,  management, and administration of the Interests, and not approve
or elect to go  non-consent as to any proposed well or plug and abandon or agree
to plug and abandon any well without  Buyer's  prior  written  approval.  On any
matter  requiring  Buyer's  approval  under this Section 26, Buyer shall respond
within  five (5) days to  Seller's  request  for  approval;  failure of Buyer to
respond to Seller's  request for approval  within such time shall release Seller
from the obligation to obtain Buyer's approval before proceeding on such matter.
         (c) Promptly notify Buyer of any suit,  lessor demand action,  or other
proceeding before any court, arbitrator, or governmental agency and any cause of
action which  relates to the  Interests or which might result in  impairment  or
loss of any  portion  of the  Interests  or which  might  hinder or  impede  the
operation of the Interests.
         (d) Make or give all notifications, filings, consents or approval from,
to or with all  governmental  authorities,  and  will  cooperate  with  Buyer in
obtaining the issuance, assignment or transfer, as the case may be, by each such
authority of such  permits as may be necessary  for Buyer to own and operate the
Interests  following the consummation of the  transactions  contemplated in this
Agreement;  provided that Seller shall not be required to incur any unreasonable
expense in connection therewith.
         (e) Through Closing,  maintain in effect  insurance  providing the same
type  coverage,  in the same amounts with the same  deductibles as the insurance
maintained in effect by Seller or its affiliates on the Effective Time.
         (f) To the extent  Seller is not the operator of any of the  Interests,
the  obligations  of Seller in this  Section  26,  which have  reference  to the
operations or activities  which  normally or pursuant to existing  contracts are
carried out or  performed  by the  operator,  shall be construed to require that
Seller use all  reasonable  efforts to cause the  operator of such  Interests to
take such  actions or render  such  performance  within the  constraints  of the
applicable operating agreements and other applicable agreements.

         27.  Further  Assurance.   After  Closing  each  of the  parties  shall
execute, acknowledge and deliver to the other such further instruments, and take
such other actions as may be reasonably necessary to carry out the provisions of
this Agreement. However, Buyer shall assume all responsibility for notifying the
purchasers  of oil and  gas  production  from  the  Interests,  and  such  other
designated  persons  who may be  responsible  for  disbursing  payments  for the
purchase of such production, of the change of ownership of the Interests.  Buyer
shall take all actions  necessary  to effect the  transfer  of such  payments to
Buyer. After the final post-Closing settlement,  additional proceeds received by


                                       16


or  expenses  paid by either  Buyer or  Seller  on behalf of the other  shall be
settled by invoicing the other party for expenses paid or remitting to the other
party any proceeds received.

         28.  DISCLAIMER OF  WARRANTIES.   EXCEPT AS OTHERWISE  PROVIDED IN THIS
AGREEMENT  (INCLUDING ANY EXHIBITS  HERETO) OR DOCUMENTS  EXECUTED AND DELIVERED
HEREUNDER,  THIS  AGREEMENT  AND ANY  INSTRUMENT  OF CONVEYANCE OR SALE EXECUTED
PURSUANT HERETO SHALL BE EXECUTED WITHOUT ANY WARRANTY OF TITLE, EITHER EXPRESS,
IMPLIED,  STATUTORY,  OR OTHERWISE,  WITHOUT ANY EXPRESS OR IMPLIED  WARRANTY OR
REPRESENTATION  AS TO THE  MERCHANTABILITY  OF ANY OF  THE  EQUIPMENT  OR  OTHER
PERSONAL  PROPERTY  INCLUDED IN THE INTERESTS OR ITS FITNESS FOR ANY  PARTICULAR
PURPOSE,  AND WITHOUT ANY OTHER  EXPRESS OR IMPLIED  WARRANTY OR  REPRESENTATION
WHATSOEVER.  IT IS  UNDERSTOOD  AND AGREED THAT BUYER SHALL HAVE  INSPECTED  THE
INTERESTS  FOR ALL PURPOSES,  INCLUDING  WITHOUT  LIMITATION  FOR THE PURPOSE OF
DETECTING THE PRESENCE OF NATURALLY OCCURRING  RADIOACTIVE MATERIAL (HEREINAFTER
REFERRED TO AS "NORM") AND MAN MADE MATERIAL FIBERS (HEREINAFTER  REFERRED TO AS
"MMMF") AND SATISFIED ITSELF AS TO THEIR PHYSICAL AND  ENVIRONMENTAL  CONDITION,
BOTH SURFACE AND SUBSURFACE,  INCLUDING BUT NOT LIMITED TO CONDITIONS RELATED TO
THE PRESENCE,  RELEASE, OR DISPOSAL OF HAZARDOUS  SUBSTANCES,  AND THAT BUYER IS
RELYING  SOLELY UPON THE RESULTS OF SUCH  INSPECTION  OF THE INTERESTS AND SHALL
ACCEPT  ALL OF THE SAME IN THEIR "AS IS,  WHERE  IS"  CONDITION.  AFTER  CLOSING
SELLER  DISCLAIMS ALL LIABILITY  ARISING IN CONNECTION WITH THE PRESENCE OF NORM
ON THE INTERESTS AND IF TESTS HAVE BEEN  CONDUCTED BY SELLER FOR THE PRESENCE OF
NORM,  SELLER  DISCLAIMS ANY WARRANTY  RESPECTING  THE ACCURACY OF SUCH TESTS OR
RESULTS.  IN ADDITION,  EXCEPT FOR  REPRESENTATIONS  SET FORTH IN THIS AGREEMENT
(INCLUDING ANY EXHIBITS HERETO) OR DOCUMENTS  EXECUTED AND DELIVERED  HEREUNDER,
SELLER SHALL MAKE NO WARRANTY OR REPRESENTATION,  EXPRESS OR IMPLIED,  AS TO THE
ACCURACY OR  COMPLETENESS  OF ANY DATA,  INFORMATION OR MATERIALS  HERETOFORE OR
HEREAFTER FURNISHED BUYER IN CONNECTION WITH THE INTERESTS, OR AS TO THE QUALITY
OR QUANTITY OF HYDROCARBON  RESERVES (IF ANY)  ATTRIBUTABLE  TO THE INTERESTS OR
THE ABILITY OF THE  INTERESTS  TO PRODUCE  HYDROCARBONS.  ANY AND ALL SUCH DATA,
INFORMATION  AND OTHER  MATERIALS  FURNISHED BY SELLER IS PROVIDED TO BUYER AS A
CONVENIENCE  AND ANY  RELIANCE  ON OR USE OF THE SAME SHALL BE AT  BUYER'S  SOLE
RISK.

         29.  Securities  Laws.  The  solicitation of offers and the sale of the
Interests by Seller have not been registered  under any securities  laws.  Buyer
represents that at no time has it been presented with or solicited by or through
any  public  promotion  or any  form of  advertising  in  connection  with  this


                                       17


transaction.  Buyer  represents that it intends to acquire the Interests for its
own  benefit and account and that it is not  acquiring  the  Interests  with the
intent of distributing fractional,  undivided interests that would be subject to
regulation by federal or state securities laws, and that if it sells, transfers,
or otherwise disposes of the Interests or fractional,  undivided  interests,  it
will do so in compliance with applicable federal and state securities laws.

         30.  Due Diligence.  Buyer  represents  that it has performed,  or will
perform on or before December 9, 1998,  sufficient review and due diligence with
respect to the Interests,  which includes  reviewing well data, title, and other
files,  and  performing  necessary  evaluations,  assessments,  and other  tasks
involved in evaluating the Interests, to satisfy its requirements completely and
to enable it to make an informed  decision to acquire  the  Interests  under the
terms of this Agreement.

         31.  Press Release.  Prior to Closing,  there shall be no press release
or public  communication  concerning  this  purchase  and sale by either  party,
except  as  required  by law or  with  the  written  consent  of the  party  not
originating said release or  communication.  Prior to Closing,  the parties will
endeavor to consult each other in a timely manner on all press releases required
by law.

         32.  Entire  Agreement.   This instrument  states the entire  agreement
between the  parties  and may be  supplemented,  altered,  amended,  modified or
revoked by writing only,  signed by all parties.  This Agreement  supersedes any
prior agreements  between the parties  concerning sale of the Interests,  except
that any confidentiality  agreement shall terminate at Closing. The headings are
for guidance only and shall have no significance in the  interpretations of this
Agreement.

         33.  Tax Reporting.  Seller and Buyer agree that if this transaction is
subject to the  reporting  requirement  of Section 1060 of the Internal  Revenue
Code of 1986, as amended,  and, IRS Form 8594, Asset Acquisition  Statement,  is
required to be filed for this transaction, the parties will confer and cooperate
in the preparation and filing of their  respective forms to reflect a consistent
reporting of the agreed upon allocation.

         34.  Assignability. Prior to Closing, this Agreement and the rights and
obligations  hereunder  shall not be assignable or delegable by any party hereto
without the prior written  consent of the other parties  unless such  assignment
occurs by merger,  reorganization or sale of all of a party's assets. Subsequent
to Closing, Buyer may assign its rights or obligations hereunder.

         35.  Survival.    Except  as  expressly  provided  herein, all  of  the
representations  and  warranties  of or  by  the  parties  hereto  except  those
contained in Sections  4.a. and 4.b.  hereof shall not survive the execution and
delivery of the Assignment and Bill of Sale.

         36.  Tax Deferred Exchange Election.  In the event Seller has not found
a suitable Exchange  Property prior to the Closing,  Seller may elect, by notice
to Buyer  delivered on or before the Closing  Date,  to have all or a portion of
the  Purchase  Price paid to a  qualified  intermediary.  If Seller  makes a tax
deferred exchange  election,  Buyer shall not be obligated to pay any additional
costs or incur any additional obligations in the acquisition of the Interests.

         37.  Governing Laws.   THIS AGREEMENT SHALL  BE GOVERNED BY THE LAWS OF
THE STATE OF OKLAHOMA.


                                       18


         38.  Counterpart  Execution.     This  Agreement  may  be  executed  in
counterparts and each counterpart shall constitute a binding agreement as if the
parties had executed a single document.  The parties agree that such counterpart
execution  may be evidenced by a facsimile  transmission  of the  execution  and
acknowledgment  page for each such party,  and such  facsimile  execution  shall
constitute a binding execution and acknowledgment by such party. At Closing, the
parties agree that a sufficient  number of original  counterpart  executions and
acknowledgments  will be  obtained  and affixed to this  Agreement  so that each
party will have an originally executed and acknowledged Agreement.

         EXECUTED  by each  party  hereto  as of the  date of  their  respective
acknowledgment, effective as of the Effective Time.

                          SELLER:

                          ST. MARY LAND & EXPLORATION COMPANY


                          By:  /S/ MILAM RANDOLPH PHARO
                               -----------------------------------
                               Milam Randolph Pharo
                               Vice President - Land & Legal


                          ST. MARY OPERATING COMPANY


                          By:  /S/ MILAM RANDOLPH PHARO
                               -----------------------------------
                               Milam Randolph Pharo
                               Vice President - Land & Legal


                          /S/ KENT J. HARRELL
                          -----------------------------------
                          Kent J. Harrell, d/b/a Harrell Energy Co.


                          RALPH H. SMITH RESTATED REVOCABLE TRUST
                          DATED AUGUST 14, 1997


                          By:  /S/ RALPH H. SMITH
                               -----------------------------------
                               Ralph H. Smith, individually and as Trustee


                          /S/ RONALD D. BOONE
                          -----------------------------------
                          Ronald D. Boone


                          /S/ RONALD D. BOONE
                          -----------------------------------
                          Ronald D. Boone, Attorney-in-Fact for Ronald E. Hornig



                                       19


                          ENGLAND RESOURCES CORPORATION


                          By:  /S/ RONALD D. BOONE
                               -----------------------------------
                               Ronald D. Boone, Attorney-in-Fact


                          BUYER:

                          ONEOK RESOURCES COMPANY


                          By:      /S/ J.D. HOLBIRD
                                   ------------------------------
                          Name:    J.D. Holbird
                          Title:   Vice President




STATE OF COLORADO                   )
                                    ) ss.
CITY AND COUNTY OF DENVER           )

         This  instrument  was  acknowledged  before me on November 11, 1998, by
Milam Randolph Pharo, Vice President Land & Legal of ST. MARY LAND & EXPLORATION
COMPANY, a Delaware corporation, on behalf of said corporation.

     Witness my hand and official seal.
(SEAL)

                                                  /S/ PATRTICIA FLANIGAN
                                                  --------------------------
                                                  Notary Public

My commission expires:  May 15, 1999


STATE OF COLORADO                   )
                                    ) ss.
CITY AND COUNTY OF DENVER           )

         This  instrument  was  acknowledged  before me on November 11, 1998, by
Milam Randolph Pharo, Vice President Land & Legal of ST. MARY OPERATING COMPANY,
a Colorado corporation, on behalf of said corporation.

     Witness my hand and official seal.
(SEAL)

                                                  /S/ PATRTICIA FLANIGAN
                                                  --------------------------
                                                  Notary Public

My commission expires:  May 15, 1999


                                       20


STATE OF OKLAHOMA                   )
                                    ) ss.
CITY AND COUNTY OF TULSA            )

     This instrument was acknowledged before me on November 12, 1998, by KENT J.
HARRELL, d/b/a Harrell Energy Co.

     Witness my hand and official seal.
(SEAL)



                                                  /S/ Sherry L. Askew
                                                  --------------------------
                                                  Notary Public
My commission expires:  December 11, 2001



STATE OF OKLAHOMA                   )
                                    ) ss.
CITY AND COUNTY OF TULSA            )

     This instrument was  acknowledged  before me on November 12, 1998, by RALPH
H. SMITH,  individually and as Trustee of the Ralph H. Smith Restated  Revocable
Trust dated August 14, 1997. 

     Witness my hand and official seal. 
(SEAL)



                                                  /S/ KAREN A. CHISM
                                                  --------------------------
                                                  Notary Public
My commission expires:  1-6-99



STATE OF COLORADO                   )
                                    ) ss.
CITY AND COUNTY OF DENVER           )

     This instrument was acknowledged  before me on November 11, 1998, by RONALD
D. BOONE.

Witness my hand and official seal. 
(SEAL)



                                                  /S/ PATRTICIA FLANIGAN
                                                  --------------------------
                                                  Notary Public
My commission expires:  May 15, 1999



                                       21



STATE OF COLORADO                   )
                                    ) ss.
CITY AND COUNTY OF DENVER           )

     This instrument was acknowledged  before me on November 11, 1998, by Ronald
D. Boone, Attorney-in-Fact for RONALD E. HORNIG.  

     Witness my hand and official seal. 
(SEAL)



                                                  /S/ PATRTICIA FLANIGAN
                                                  --------------------------
                                                  Notary Public
My commission expires:  May 15, 1999


STATE OF COLORADO                   )
                                    ) ss.
CITY AND COUNTY OF DENVER           )

         This  instrument  was  acknowledged  before me on November 11, 1998, by
Ronald D. Boone,  Attorney-in-Fact for ENGLAND RESOURCES CORPORATION,  a Wyoming
corporation, on behalf of said corporation.

     Witness my hand and official seal.
(SEAL)



                                                  /S/ PATRTICIA FLANIGAN
                                                  --------------------------
                                                  Notary Public
My commission expires:  May 15, 1999

STATE OF OKLAHOMA                   )
                                    ) ss.
CITY AND COUNTY OF TULSA            )

     This  instrument  was  acknowledged  before me on Nov.  12,  1998,  by J.D.
Holbird, as Vice President of ONEOK RESOURCES COMPANY a Delaware corporation, on
behalf of said corporation. 

     Witness my hand and official seal. 
(SEAL)



                                                  /S/ PAM BUSTAMANTE
                                                  --------------------------
                                                  Notary Public
My commission expires:  11/24/2001




                                       22





Exhibit A       -   Leases and Lands

Exhibit A-1     -   Harrell and Smith Retained Overriding Royalty Interests

Exhibit B       -   Wells and Net Revenue Interests

Exhibit C       -   Allocated Values

Exhibit D       -   Assignment

Exhibit E       -   Agreed Imbalance

Schedule 4(k)



                                       23