EXHIBIT 10.6
 
                                  [LETTERHEAD OF ENCAL ENERGY LTD. APPEARS HERE]


December 13, 1996

Pinnacle Oil International Inc.
380 - 1090 West Georgia St.
Vancouver, British Columbia
V6E 3V7

Attention: Mr. R. Dirk Stinson

Dear Sir:

Re:  JOINT VENTURE PROPOSAL
     EAST CENTRAL ALBERTA, CANADA
- --------------------------------------------------------------------------------

Further to our recent meeting on the captioned subject, please accept this 
letter of understanding as a term sheet from which Encal Energy Ltd. ("Encal") 
and Pinnacle Oil International Inc. ("Pinnacle Oil") may pursue a joint venture 
proposal.

The general terms of the joint venture are as follows:

1.   OBJECTIVES

     .    to provide a field test of the Stress Field Detector ("SFD")
          technology by Pinnacle for Encal which may be further tested through
          the drilling of oil and gas test wells by Encal.

     .    to utilize Pinnacle Oil's expertise and proprietary SFD technology
          within the Acme/Swalwell area, as set forth on the attached Schedule
          "A", for the purpose of identifying and further enhancing drilling
          opportunities for Encal and the joint venture as, herein described
          (such area shall be hereinafter called "the Area").

2.   PINNACLE'S WORK COMMITMENT AND TIMING

     .    Pinnacle will carry out and interpret SFD surveys within the Area and
          more specifically over Encal's undeveloped lands in the Area prior to
          January 30, 1997. Encal's undeveloped lands to be evaluated by
          Pinnacle will be lands in which Encal holds a working interest, or may
          be entitled to hold an interest, of not less than 50%. Specified

 
                                                 Pinnacle Oil International Inc.
                                                          Joint Venture Proposal
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          exclusions from the Schedule "A" Acme/Swalwell Lands will be any lands
          and rights not owned by Encal and in addition, shall exclude any well
          spacing units of Encal's Acme/Swalwell Lands which are shown as
          excluded portions through cross hatching on Schedule "A".

     .    Upon completion of the survey, Pinnacle will present an interpreted
          SFD survey to Encal which shall highlight prospects and anomalies that
          have been identified by Pinnacle in a ranked order from most
          prospective to least prospective. Undeveloped prospects identified by
          Pinnacle and presented for acceptance to Encal at this stage will be
          the prospects in which Pinnacle shall have the right to participate as
          hereafter referenced.

3.   ENCAL'S COMMITMENT

     Encal will provide seismic geophysical evaluation on a minimum of the three
     most prospective anomalies identified by Pinnacle as soon as possible.
     Pending incorporation of the seismic data, Encal will proceed to test
     through test well drilling, none, some or all of the identified anomalies.
     Upon Encal having drilled a test well to test a prospect, Pinnacle will
     receive a casing point election to participate in such well as to 5% of
     Encal's interest on each of the first three test wells. In the event
     Pinnacle elects to participate beyond casing point in a test well, Pinnacle
     shall thereafter be entitled to a working interest equal to 5% of Encal's
     interest in the test well and the test well spacing unit, with such
     interest earned by Pinnacle to be subject to all existing royalties and
     other burdens on Encal's interest ("Earned Interest"). Costs incurred after
     the casing election point would be paid at election to Encal by Pinnacle
     and Pinnacle would participate as to the Earned Interest share in costs
     (including casing costs) from that point on. Subject to the further terms
     of this agreement, Pinnacle will have the right to participate with Encal
     as to 5% of Encal's interest in subsequent option wells and development
     wells after the third test well on any prospects identified in Clause 2
     hereof, during the term of this agreement as set forth in Clause 5.

4.   INFORMATION TO BE KEPT CONFIDENTIAL

     .    All data, interpretation and future rights from the SFD survey will
          remain the sole property of Pinnacle. All data interpretation and
          future rights from any seismic geophysical data will remain the sole
          property of Encal. It is understood that Pinnacle may use SFD surveys
          conducted and subsequently tested through drilling under this


 
                                                 Pinnacle Oil International Inc.
                                                          Joint Venture Proposal
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          agreement as templates to encourage further applications of SFD
          technology. Notwithstanding the foregoing, it is understood by both
          parties that any dissemination of SFD survey, drilling or other
          confidential information for a period of one year from rig release of
          each well must be with mutual consent. Press releases regarding the
          status, progress and results of operations involving both Encal and
          Pinnacle must also be jointly agreed upon.

5.   TERM

     .    Subject to Clause 6 hereof, Pinnacle's right to participate in the
          drilling of either option or development wells on Encal's
          Acme/Swalwell Lands as referred to in Clause 3 hereof will terminate
          on the later of August 31, 1997, or 120 days after notice by Encal to
          Pinnacle that Encal has no further intent of drilling test wells, or
          option wells, or development wells under this agreement.

6.   PINNACLE RIGHT TO FARMIN

     .    Until July 8, 1997, the parties shall consult as to the potential to
          drill further wells on Encal's Acme/Swalwell Lands. In the event that
          Encal proposes not to drill any further wells on any portion of the
          Acme/Swalwell Lands prior to the expiration of the term referenced in
          Clause 5, Pinnacle shall have the right to commit to drill, on a
          farmin basis, any number of additional wells on the remaining unearned
          Acme/Swalwell Lands. It is agreed and understood that in the event
          that Pinnacle commits to drill any additional wells, the parties will
          negotiate in good faith towards the execution of a formal farmout
          agreement. Such agreement shall contain the terms and conditions
          normally untilized by Canadian oil and gas companies for such
          transactions. The basic terms would provide for Pinnacle to drill to a
          depth sufficient enough to evaluate the Nisku formation, complete, and
          equip or abandon each well at its sole cost, risk, and expense each
          well. Upon Pinnacle having fulfilled its obligations pursuant to the
          Farmout Agreement, Pinnacle shall have earned from Encal:

          a)   an undivided 100% of Encal's pre-farmout working interest in each
               additional well spacing unit in all zones that Encal holds an
               interest down to the base of the Nisku formation. Such interest
               earned by Pinnacle would be subject to a convertible sliding
               scale gross overriding royalty to Encal of 1/150 (5%-15%) of
               monthly oil production and 15% of natural gas and all other
               products based


 
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                                                          Joint Venture Proposal
                                                                        12/16/96
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               on Encal's original pre-farmout working interest. This royalty 
               would be convertible at payout to an undivided 50% interest; and

          b)   in each additional well spacing unit Pinnacle shall have earned
               an undivided 50% of Encal's pre-farmout working interest in all
               zones that Encal holds an interest down to the base of the Nisku
               formation in the balance of a pre-selected one (1) section block.

7.   RIGHT-OF-FIRST REFUSAL

     .    Pinnacle and Encal hereby acknowledge that the opportunity to
          participate in the enhancement of drilling opportunities utilizing SFD
          technology will be limited to three joint venture partners.

     .    Encal, as one of the prospective partners, hereby requests and 
          Pinnacle agrees to provide Encal with a shared right-of-first refusal
          (to be shared equally and independently between Encal and Pinnacle's
          other joint venture partners) to participate in further exploration
          projects utilizing SFD technology in British Columbia, Alberta and
          Saskatchewan. The term of this right-of-first refusal will commence on
          the date of this letter and terminate on August 31, 1997, but subject
          to extension with the mutual agreement of the parties.

8.   MISCELLANEOUS

     .    This Agreement shall not be construed as a partnership.

     .    Pinnacle warrants to Encal that Pinnacle has full right and authority 
          to utilize SFD technology.

     .    Pinnacle, by entering into this agreement, does not violate or
          conflict with any term or provision of or constitute a default under
          any agreement of whatever nature.

     .    Each of Pinnacle and Encal shall indemnify the other against all
          actions, suits, demands, claims, losses, expenses and damages which
          may be brought against, incurred by or suffered by the other or which
          may sustain, pay or incur by reason of or in any way attributable to
          the operations contemplated by this agreement carried out by the
          other, its agents, servants, employees or contractors.


 
                                                 Pinnacle Oil International Inc.
                                                          Joint Venture Proposal
                                                                        12/16/96
                                                                          Page 5

If this summarizes your understanding of our discussions and you are prepared to
move forward on this basis, please execute and return one copy to the
undersigned. We are prepared to sit down and layout the most effective traverses
and identify template locations as soon as possible.


Yours very truly

ENCAL ENERGY LTD.

/s/ Peter A. Carwardine
Peter A. Carwardine
V.P Land & Corporate Development

/cdi
Attachment

ACCEPTED AND AGREED TO THIS 14 day of December, 1996

[SIGNATURE ILLEGIBLE]
_______________________________
PINNACLE OIL INTERNATIONAL INC.



 
This is Schedule "A" attached to and forming part of an Joint Venture Proposal 
dated December 13, 1996 between Encal Energy Ltd. and Pinnacle Oil International
Inc.


                [GRAPH OF JOINT VENTURE PROPOSAL APPEARS HERE]