**Exhibit
      99.29**





**Joinder
      to Security Agreement**





The
      undersigned, SONTERRA OPERATING, INC., a Delaware corporation, hereby joins
      in
      the execution of that certain Security Agreement dated as of July 9, 2007 (as
      amended by the First Amendment to Security Agreement, dated as of August 3,
      2007, and as may be further amended, restated, supplemented or otherwise
      modified and in effect from time to time, the “ **Security
      Agreement** ”)
      by and
      between Sonterra Oil & Gas, Inc. (f/k/a Sonterra Resources, Inc.), a
      Delaware corporation, Buyer (as defined therein), and each other Person that
      becomes a Debtor thereunder after the date thereof and hereof and pursuant
      to
      the terms thereof, to and in favor of Viking Asset Management, LLC, in
      its
      capacity as Collateral Agent for Buyer .
      By
      executing this Joinder, the undersigned hereby agrees that it is a Debtor
      thereunder and agrees to be bound by all of the terms and provisions of the
      Security Agreement.








The
      undersigned represents and warrants to Secured Party that:





(a)  all
      of
      the Equipment, Inventory and Goods owned by such Debtor is located at the places
      as specified on Schedule
      I and such
      Debtor conducts business in the jurisdiction set forth on Schedule
      I ;





(b)  except
      as
      disclosed on Schedule
      I ,
      none of
      such Collateral is in the possession of any bailee, warehousemen, processor
      or
      consignee;





(c)  the
      chief
      place of business, chief executive office and the office where such Debtor
      keeps
      its books and records are located at the place specified on Schedule
      I ;





(d)  such
      Debtor (including any Person acquired by such Debtor) does not do business
      or
      has not done business during the past five years under any tradename or
      fictitious business name, except as disclosed on Schedule
      II ;





(e)  all
      Copyrights, Patents and Trademarks owned or licensed by the undersigned are
      listed in Schedules
      III , IV and V ,
      respectively;





(f)  all
      Deposit Accounts, securities accounts, brokerage accounts and other similar
      accounts maintained by such Debtor, and the financial institutions at which
      such
      accounts are maintained, are listed on Schedule
      VI ;





(g)  all
      Commercial Tort Claims of such Debtor are listed on Schedule
      VII ;





(h)  all
      interests in real property and mining rights held by such Debtor are listed
      on Schedule
      VIII ;





(i)  all
      Equipment (including Motor Vehicles) owned by such debtor are listed on Schedule
      IX ;
      and










(j)  all
      other
      representations and warranties made by the Debtors in the Security Agreement
      are
      true, complete and correct in all respects as of the date hereof.








[Signature
      Page Follows]




2




SONTERRA OPERATING, INC., a Delaware
              corporationBy:
              /s/ Wayne A. PsencikName:Wayne
              A. PsencikTitle:   
              PresidentFEIN:26-0888425





**[Signature
      Page to Joinder to Security Agreement - Sonterra Operating,
      Inc.]**