[PETROGEN LOGO APPEARS HERE] PETROGEN

                                                                  April 15, 2005


Mr. Robert W. Kent
Nortex Corporation
1415 Louisiana, Suite 3100
Houston, TX  77002
Fax: 713.658.0739

RE:      PARTICIPATION AGREEMENT - EMILY HAWES FIELD
         CALHOUN COUNTY, TEXAS

Dear Mr. Kent

         This letter follows our recent discussions concerning the participation
by Nortex Corporation (96% of the Nortex interest),  Astra Exploration  Company,
Inc. (2% of the Nortex interest) and D. L. Stephens  Petroleum  Interests (2% of
the Nortex interest), collectively referred to herein as "Nortex," with Petrogen
Corp.  ("PETROGEN")  in  development  and  production of Petrogen's  interest in
certain leases ("LEASES") within the Emily Hawes Field of Calhoun County, Texas,
and shall evidence our agreement in that regard. The Leases are described on the
list  attached to this letter and marked  Exhibit  "A." The area  covered by the
Leases ("LEASE AREA") is shown on a plat attached to Exhibit "A."

         When  signed  by  Nortex,  this  letter  will  be a  binding  agreement
("AGREEMENT")  between Nortex and Petrogen  setting out the terms and conditions
under which Nortex will  participate with Petrogen in development and production
of the Leases.

         The terms and conditions of the Agreement are:

     1.   ASSIGNMENT.   Within  five  (5)  days  of  Nortex's  signing  of  this
          Agreement,  Petrogen  will offer an assignment  ("ASSIGNMENT")  of the
          Leases to Nortex.  The Assignment will be offered unsigned by Petrogen
          to allow Nortex to undertake its due diligence, as provided in Section
          5 below.

     2.   WORKING  INTEREST.  The  Assignment  will  be  of a  thirty-seven  and
          one-half percent of  eight-eighths  (37.5% of 8/8) working interest in
          the Leases,  if the Leases  cover  one-hundred  percent  (100%) of the
          minerals within the Lease Area If the Leases do not cover  one-hundred
          (100%) of the  minerals  within the Lease Area , then  Petrogen  shall
          assign and convey to Nortex so much of its  interest  in the Leases as
          will deliver to Nortex a determinable  fee interest in the minerals in
          the Lease Area (a working interest  therein) equal to thirty-seven and
          one-half  percent  of  eight-eighths  (37.5% of 8/8) of the  minerals,
          subject to the terms and provisions of this Agreement.

     3.   NET REVENUE INTEREST.  In the Assignment,  the Leases will burdened by
          royalties equal to twenty-two and one-half percent (22.5%),  such that
          Nortex  will  own a net  revenue  interest  in all of the  oil and gas
          produced  from the  Lease  Area  equal to  thirty-seven  and  one-half
          percent of  seventy-seven  percent  (37.5% of 77.5%) of all of the oil
          and gas produced from such lands.

     4.   CASH  PAYMENT.  In exchange for delivery of the signed  Assignment  by
          Petrogen,  Nortex will pay Petrogen $66,112.25 ("CASH CONSIDERATION").
          The fully executed and  acknowledged  Assignment shall be delivered to
          Nortex   contemporaneously   with   Nortex's   payment   of  the  Cash
          Consideration to Petrogen.

     5.   DUE DILIGENCE. The Assignment will be without warranty of title except
          by, through and under Petrogen. For a period of ten (10) business days
          following  delivery of  Petrogen's  unexecuted  Assignment  to Nortex,
          Nortex may conduct due diligence, including, without limitation, title
          due diligence.  During the due diligence period, Nortex shall have the
          right  to  review  all  of  Petrogen's  contract,  lease,  title,  and
          correspondence files and Petrogen's well files relating to the Leases.


<PAGE>


          Should Nortex be unsatisfied with the outcome of its due diligence, it
          may reject  Petrogen's  offer of the Assignment,  declining to pay the
          Cash  Consideration.  If Nortex rejects the Assignment and declines to
          pay the Cash  Consideration,  then the  parties  will have no  further
          obligations to each other. If the Assignment is executed and delivered
          to Nortex and Nortex has paid Petrogen the Cash Consideration,  Nortex
          shall be entitled to copy any or all of the  contract,  lease,  title,
          correspondence and well files of Petrogen that relate to the Leases.

     6.   INITIAL  WELL.  Following  Petrogen's  signing  and  delivery  of  the
          Assignment and Nortex's  payment of the Cash  Consideration,  Petrogen
          and Nortex  will  agree upon a location  on the Leases and a spud date
          for the  drilling  of a well  ("INITIAL  WELL")  to test  the  Miocene
          formation.   Such  agreement  shall  be  memorialized  in  a  detailed
          Authority for  Expenditure  ("AFE").  Nortex will pay fifty percent of
          eight-eighths  (50% of 8/8) of the costs for the Initial Well until it
          is  either  plugged  and  abandoned  as a dry  hole or  completed  and
          producing  into the tanks or a sales  pipeline at or above the Miocene
          formation.  To the  extent  that  costs for the  Initial  Well  exceed
          one-hundred  ten percent  (110%) of the AFE'd  costs,  Nortex will pay
          only  thirty-seven  and  one-half  percent  (37.5%)  of the costs that
          exceed  one-hundred  ten  percent  (110%)  of the  costs  incurred  in
          drilling and  completing  the Initial  Well.  After the Initial  Well,
          Nortex will pay its thirty-seven and one-half percent of eight-eighths
          (37.5% of 8/8) share of all operations on the Leases.

     7.   ESCROWED  COSTS.  Thirty (30) days in advance of the  mutually  agreed
          upon spud date for the Initial  Well,  Nortex will pay into a mutually
          acceptable  independent  escrow account  one-half of its fifty percent
          (50%) share of  estimated  costs,  as shown in the  approved  AFE. The
          remaining  one-half of Nortex's fifty percent (50%) share of estimated
          costs will be paid into the escrow  account  upon the spud date of the
          Initial Well.  Funds escrowed will only be escrowed under the terms of
          a mutually acceptable escrow agreement.

     8.   OPTION TO PARTICIPATE IN FRIO TEST. Nortex will have a one time option
          to  participate  for up to fifty  percent (50%) of the costs to Casing
          Point (and retain a proportionate working interest as set forth below)
          in a well with Petrogen  (including a deepening of the Initial Well if
          it has  been  determined  to be a dry  hole at or  above  the  Miocene
          formation)  on the Leases to test the Frio  formation  at depths below
          7,000  feet TVD  Should a Frio test well be  proposed  on the  Leases,
          Nortex shall have thirty (30) days in which to elect to participate in
          the Frio test well or opt out of the  drilling  and forfeit its rights
          below 7,000 feet.

          If Nortex elects to participate in the Frio test, Nortex will have the
          election to bear up to fifty percent (50%) of the cost to Casing Point
          in the test well (or any amount less than that that  Nortex  elects to
          bear)  on a  one-third  (1/3) of cost for  one-fourth  (1/4)  interest
          basis,  such that Nortex would have a working  interest  (determinable
          fee  interest  in the  minerals  carved  out of the  Leases)  equal to
          seventy-five percent (75%) of the cost percentage to Casing Point that
          is borne by Nortex in the Frio  test,  as to depths  below  7,000 feet
          below the surface of the earth. For example,  if Nortex elects to bear
          the full fifty  percent  (50%) of the cost to Casing Point in the Frio
          test  well it will  have a  working  interest  in that  well  equal to
          seventy-five percent (75%) of fifty percent (50%), or thirty-seven and
          one-half percent (37.5%).

          Should Nortex elect to participate in the Frio test well for less than
          its full  thirty-seven and one-half percent (37.5%) working  interest,
          it will re-assign to Petrogen a percentage of its rights in the Leases
          below 7,000 feet,  which  percentage will be equal to a fraction where
          the numerator is  thirty-seven  and one-half  percent (37.5%) less the
          working  interest  percentage that Nortex would own as a result of its
          participation election (calculated in the manner stated above) and the
          denominator is thirty-seven and one-half percent (37.5%). For example,
          if Nortex  elects to  participate  in a Frio test well for a three and
          three-quarters  percent  (3.75%)  working  interest  (meaning  that it
          elected to bear 5% of the costs),  the fraction  would  be(37.5%  less
          3.75%)/37.5%=90%,,  meaning that Nortex would re-assign ninety percent
          (90%)  of  its  thirty-seven  and  one-half  percent  (37.5%)  working
          interest in the Leases below 7,000 feet to Petrogen.  If Nortex elects
          not to participate in the Frio test well for any percentage,  then the
          fraction  would be (37.5% less  0.0%)/37.5%=100%,  meaning that Nortex
          would re-assign  one-hundred  percent (100%) of its  thirty-seven  and
          one-half  percent (37.5%)  working  interest in the Leases below 7,000
          feet. In addition to Nortex's interest in the Leases below 7,000 feet,
          this  re-assignment  shall  include  a like  percentage  of any  other
          interests  below 7,000 feet that  Nortex may have  acquired in the AMI
          (as  subsequently  defined) below 7,000 feet.  Any such  re-assignment
          shall be made within five (5) days of the time that the Frio test well
          is spud; provided, however, if the Frio test well has not been spudded
          within sixty (60) days  following  the date on which it was  proposed,
          the proposal shall be null and void and deemed as if it had never been


<PAGE>


          made, such that if Petrogen desires to initiate the drilling of a Frio
          test at a later date,  it must again propose that test to Nortex under
          the terms  and  provisions  of this  agreement  and as if the  earlier
          proposal had not been made.

     8.   OPERATING AGREEMENT.  Within thirty (30) days of Nortex's execution of
          this letter, Petrogen and Nortex will enter into a mutually acceptable
          joint  operating  agreement  ("JOA") on the AAPL Form  610-1989  Model
          Form, which shall name Petrogen as operator and include provisions for
          "Average"  fixed rate  administrative  overhead  for similar  wells in
          accordance  with the latest survey of such rates  published by Ernst &
          Young,  LLP. In the event Nortex elects not to  participate  in a Frio
          test for any  percentage,  the Operating  Agreement will be amended to
          only include depths above 7,000 feet.

          If  Nortex  elects  not  to  participate  in the  Frio  test  for  any
          percentage, if proposed, Nortex agrees to maintain information that it
          has  received  from   Petrogen,   with  respect  to  that   formation,
          confidential  and agrees that it will not compete with Petrogen in any
          manner as to depths  below  7,000 feet below the  surface of the earth
          during the term of this Agreement.

     9.   KNOWLEDGEABLE  INVESTOR.  Nortex is an experienced  and  knowledgeable
          investor  and  operator  in the oil and gas  business.  In making  its
          decision to participate in the Leases, Nortex has relied solely on its
          own independent investigation, analysis and evaluation.

     10.  SECURITIES REPRESENTATION.  Nortex is acquiring the Leases for its own
          account  and not with a view to, or for offer of resale in  connection
          with, a distribution thereof, within the meaning of the Securities Act
          of 1933 and any other  applicable laws pertaining to the  distribution
          of securities.

     11.  ASSIGNABILITY.  The rights and obligations  under this Agreement shall
          not be  assignable  or  delegable  without  the consent of Petrogen or
          Nortex.

     12.  AREA OF MUTUAL INTEREST.  Petrogen and Nortex hereby establish an Area
          of  Mutual  interest  within  the  area  ("AMI")  outlined  on the map
          attached hereto as Exhibit "B." During the term of this Agreement,  if
          either Petrogen or Nortex acquire an interest in the rights to explore
          for and produce oil and gas from the AMI (the term  "interest" as used
          herein  shall  include  any  interest  whatsoever  in the oil and gas,
          including but not limited to royalties,  overriding royalties, leases,
          renewals of existing  leases,  farm-ins,  etc.),  the acquiring  party
          shall notify the non-acquiring  party, giving complete  information as
          to the  interest  acquired,  along with  copies of the  instrument  or
          instruments by which the interest was acquired,  and the consideration
          to be given or paid. For a period of thirty (30) days after receipt of
          notice of acquisition, the non-acquiring party shall have the right to
          acquire an interest in the interest  acquired by the acquiring  party,
          by  notifying  the  acquiring  party  of its  desire  to  share in the
          acquisition, and paying the acquiring party its proportionate share of
          the  consideration  given or assuming its  proportionate  share of the
          obligations assumed.  Thereupon, the acquiring party shall immediately
          execute and deliver the  appropriate  assignment to the  non-acquiring
          party, without covenants of warranty,  except by, through or under the
          acquiring party. If Petrogen is the non-acquiring party, it shall have
          a right to acquire a sixty-two and one-half  percent (62.5%)  interest
          and if Nortex is the  non-acquiring  party it shall  have the right to
          acquire a thirty-seven  and one-half  percent (37.5%)  interest,  such
          percentages  subject  to  adjustment  for rights  below  7,000 feet if
          Nortex elects not to participate in a Frio test well for  thirty-seven
          and one-half percent (37.5%).  Thus, for example,  if Nortex elects to
          participate  in a Frio  test well for five  percent  (5%) its right to
          acquire a portion of Petrogen acquisitions in the AMI below 7,000 feet
          shall be five percent (5%) and  Petrogen's  right to acquire a portion
          of  Nortex   acquisitions  in  the  AMI  below  7,000  feet  shall  be
          ninety-five  percent (95%).  Should Nortex decline to participate  for
          any  percentage  of a Frio test well,  the AMI would still apply,  but
          Nortex's  right to acquire a portion of Petrogen  acquisitions  in the
          AMI below  7,000  feet  shall be zero  (-0-) and  Petrogen's  right to
          acquire a portion of Nortex  acquisitions  in the AMI below 7,000 feet
          shall be one-hundred percent (100%).

          Notwithstanding  its  participation or  non-participation  in any Frio
          test well,  Nortex agrees that it will  continue to keep  confidential
          all information and data related to the Leases and the AMI.


<PAGE>


     14.  LEASING  UNLEASED  MINERALS.  Petrogen agrees that it will endeavor to
          lease all  un-leased  mineral  interests in the AMI and the renewal of
          any of the Leases that are likely to expire  during the next  ________
          (____) months.

     15.  TERM. The term of this Agreement shall be for the longer of so long as
          any of the Leases  (including  any  extensions or renewals)  remain in
          force and effect or the JOA remains in force and effect  according  to
          its terms.

         If this Agreement  meets with your  approval,  please sign the enclosed
duplicate  in  the  space  provided  and  return  it to  the  attention  of  the
undersigned.   Upon  receipt  of  the  signed  Agreement,  Petrogen  will  begin
preparation of the Assignment.

         Unless this  Agreement is returned to Petrogen  signed by Nortex before
5:00 PM on May __,  2004,  it  shall be  deemed  withdrawn  and of no force  and
effect.

Very truly yours,

PETROGEN CORP.



Sacha H. Spindler
CEO

                                  AGREED & ACCEPTED, THIS ___ DAY OF
                                  _______ 2004



                                  NORTEX CORPORATION


                                  ________________________________________
                                  Robert W. Kent, Executive Vice-President



                                  ASTRA EXPLORATION COMPANY, INC.



                                  ________________________________________
                                  Robert W. Kent, President



                                  D. L. STEPHENS PETROLEUM INTERESTS



                                  ________________________________________
                                  D. L. Stephens, Owner



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                          Email: info@petrogencorp.com
                          Website: www.petrogencorp.com