DEPOSIT
      ACCOUNT CONTROL AGREEMENT

     

    
      	
              Dated
                as of:

              November
                13, 2008

               

            	
              Company:

              Sonterra
                Operating, Inc., a Delaware corporation

            
	
              The
                Bank:

              Sterling
                Bank, a Texas banking corporation

               

            	 
	
              Address
                of Bank:

              4040
                Broadway, Suite 110

              San
                Antonio, Texas 78209

            	
              Secured
                Party/Pledgee:

              Summerline
                Asset Management, LLC,
                a
                Delaware limited liability company, in its capacity as Collateral
                Agent
                for the benefit of itself and Buyers referred to
                below

            


    

     

    This
      DEPOSIT
      ACCOUNT CONTROL AGREEMENT (as
      amended, restated, supplemented or otherwise modified from time to time, this
      “Agreement”),
      by
      and among the Bank identified above, the Company identified above, and the
      Secured Party/Pledgee identified above (the “Collateral
      Agent”)
      is
      dated as of the date written above. 

     

    WHEREAS:

     

    A. Sonterra
      Resources, Inc., a Delaware corporation (“Sonterra”),
      and
      the Buyers (as defined in the Purchase Agreement described below) have entered
      into that certain Securities Purchase Agreement dated as of November 13, 2008
      (as amended, restated, supplemented or otherwise modified and in effect from
      time to time, the “Purchase
      Agreement”)
      pursuant to which Buyers have purchased certain senior secured notes dated
      as of
      November 13, 2008 in the aggregate original principal amount of $8,800,000
      (such
      note, together with any promissory notes or other securities issued in exchange
      or substitution therefor or replacement thereof, and as any of the same may
      be
      amended, supplemented, restated or modified and in effect from time to time,
      the
“Notes”)
      and
      made certain financial accommodations to the Sonterra .

     

    B. Pursuant
      to a Security Agreement dated as of November 13, 2008 (as the same may be
      amended, restated, modified or supplemented and in effect from time to time,
      the
“Security
      Agreement”),
      entered into among the Company and Collateral Agent, the Company has granted
      the
      Collateral Agent, for its benefit and the benefit of Buyers, a first priority
      security interest in, lien upon and pledge of all of its right, title and
      interest in and to the Account(s) (as defined below) and the Account Collateral
      (as defined below), including, without limitation, all free credit balances,
      cash and cash balances contained or on deposit in the Accounts and all proceeds
      thereof, whether now existing or hereafter arising.

     

    C. This
      Agreement is intended to perfect Collateral Agent’s and Buyers’ security
      interest in the Account(s) and the Account Collateral pursuant to Sections
      9.104, 9.312 and 9.314 of the Uniform Commercial Code and shall also serve
      as
      instructions regarding the operation of and procedures for all deposit accounts
      now or hereafter maintained at Bank by, or for the deposit, credit or custody
      of
      property of, the Company. 

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    


    NOW
      THEREFORE,
      the
      Bank, the Company and Collateral Agent hereby agree as follows:

     

    1. Account
      Identification.
      This
      Agreement applies to the accounts identified below that have been established
      at
      the Bank on behalf of and in the name of the Company and to each other deposit
      account hereafter established at the Bank on behalf of the Company
      (collectively, the “Accounts”).
      The
      Bank represents and warrants to the Company and the Collateral Agent, on its
      behalf and on behalf of Buyers, that (a) the Bank is a “Bank”
(within
      the meaning of Article 9 of the Uniform Commercial Code) with which the Accounts
      are maintained, (b) each of the Accounts is a “Deposit
      Account”
(within
      the meaning of Article 9 of the Uniform Commercial Code) and (c) the Company
      is
      the only “Customer”
(within
      the meaning of Article 4 of the Uniform Commercial Code) of the Bank with
      respect to the Accounts.

     

    
      	
              Account
                Holder

            	 	
              Name
                of Account

            	 	
              Account
                Number

            
	 	 	 	 	 
	
              Sonterra
                Operating, Inc.

            	 	
              Company
                Checking Account

            	 	 


    

    


    2. Security
      Interest; Agency.
      

     

    (a) Each
      of
      Bank, the Company and Collateral Agent acknowledges that, in order to secure
      the
      prompt and complete payment, performance and observance of all “Liabilities”
(as
      defined in the Security Agreement), the Company has granted, and for avoidance
      of doubt and without limiting any prior grant, does hereby grant, to Collateral
      Agent, for the benefit of itself and Buyers, a continuing lien upon, and
      security interest in, the Accounts and all funds, checks, cash, items,
      instruments, investments, securities and other things of value at any time
      paid,
      deposited, credited or held in, payable or withdrawable from or in transit
      to
      any Account (whether for collection, provisionally or otherwise), and all other
      property of the Company from time to time in the possession or under the control
      of, or in transit to, the Bank or any agent, bailee or custodian therefor,
      and
      all proceeds of all of the foregoing (collectively, the “Account
      Collateral”).

     

    (b) The
      Bank
      agrees to comply with instructions originated by Collateral Agent directing
      disposition of the funds in the Accounts or any other Account Collateral or
      to
      take such other action as shall from time to time be specified in writing from
      Collateral Agent, in all cases without notice to or the consent of the Company.
      The Bank shall follow the instructions of Collateral Agent as to the holding,
      investment and transfer of all Account Collateral. The Company hereby
      irrevocably authorizes and directs the Bank to comply with any such instructions
      by Collateral Agent without further action or consent by the Company and
      notwithstanding any subsequent objection or contrary direction the Bank may
      receive from the Company. In addition, the Company agrees that the Bank may
      act
      as the agent of Collateral Agent in exercising any rights of set-off provided
      by
      applicable law or by any Transaction Document (as defined in the Purchase
      Agreement) as to any Account Collateral. The Company agrees that the Bank shall
      be entitled to rely, without independent investigation, on any written notice
      in
      the form of Exhibit
      A
      from
      Collateral Agent to the effect that an Event of Default (each as defined in
      the
      Notes) has occurred and is continuing or any other statement of Collateral
      Agent
      to the effect that any exercise of set-off requested by Collateral Agent is
      permitted under applicable law, the Security Agreement or any applicable
      Transaction Document.

     

    (c) Without
      limiting or qualifying the provisions of clause (b) above, Collateral Agent,
      on
      its behalf and on behalf of Buyers, hereby appoints the Bank as Collateral
      Agent’s and Buyers’ agent and pledgee-in-possession for the Accounts and all
      Account Collateral, for the purpose of perfecting Collateral Agent’s and Buyers’
security interest therein; and the Bank by its execution and delivery of this
      Agreement hereby accepts such appointment and agrees to be bound by the terms
      of
      this Agreement. The Company hereby agrees to such appointment of the Bank and
      further agrees that the Bank, on behalf of Collateral Agent and Buyers, shall
      be
      entitled to exercise, upon the instructions of Collateral Agent, any and all
      rights that the Collateral Agent and Buyers may have under the Purchase
      Agreement, the Security Agreement and all other agreements, documents and
      instruments executed pursuant thereto, or under applicable law, with respect
      to
      the Accounts and the Account Collateral. 

     

    
      
         

      

      
        2

        
          

        

      

      
         

      

    

     

    3. Debtor’s
      Access to Accounts.
      Collateral Agent agrees that, until such time as Bank receives written notice
      in
      the form of Exhibit
      A
      from
      Collateral Agent of the occurrence of any Event of Default, the Company shall
      be
      allowed full use of, and access to, the Accounts and the Account Collateral
      without Collateral Agent’s further consent (including, without limitation,
      presenting items drawn on the Accounts or giving Bank instructions as to the
      withdrawal or other disposition of any funds from time to time credited to
      the
      Accounts); provided, that the Company shall not be permitted to close any of
      the
      Accounts. Upon receipt by Bank of notice by Collateral Agent of the occurrence
      of an Event of Default, and at all times thereafter, the Company shall not
      be
      entitled use of, or access to, the Accounts or the Account Collateral and the
      Bank shall not comply with any instructions or directions originated by the
      Company or otherwise permit the Company access to or control over the Accounts
      or the Account Collateral, including without limitation giving stop payment
      orders, presenting items for payment or making withdrawals therefrom.


     

    4. Irrevocable
      Agreement.
      The
      Company hereby agrees and acknowledges that the agreements made by it and the
      authorizations granted by it herein are irrevocable and that the authorizations
      granted herein are powers coupled with an interest.

     

    5. Set-off.
      The
      Bank hereby waives all existing and future rights of recoupment or set-off
      and
      banker’s liens against the Accounts and the Account Collateral, except those
      rights of set-off and banker’s liens arising in connection with (a) items
      deposited in the Accounts that are subsequently returned to the Bank unpaid
      and
      (b) any compensation and expenses owing and payable to Bank with respect to
      the
      Accounts which are assessed in accordance with the Bank’s standard account
      documentation. 

     

    6. Account
      Information.
      The
      Bank shall provide Collateral Agent, at the address indicated in Section 11
      below, with such information with respect to the Accounts and Account Collateral
      as Collateral Agent may from time to time reasonably request, including, without
      limitation and duplicate copies of all bank statements which are sent to the
      Company. The Company hereby consents to such information being provided to
      Collateral Agent. 

     

    7. Exculpation.
      The
Company
      and the Collateral Agent agree that Bank shall have no liability to either
      of
      them for any loss or damage that one or both may claim to have suffered or
      incurred, either directly or indirectly, by reason of this Agreement or any
      transaction or service contemplated by the provisions hereof, other than any
      loss or damage incurred as a result of the gross negligence or willful
      misconduct of, or breach of this Agreement by, the Bank or its officers, agents
      or employees. Without limitation of the preceding sentence, the Company agrees
      that Bank shall have no liability to Company for any wrongful dishonor in
      connection with the execution by Bank of any Collateral Agent instructions,
      as
      authorized by and in accordance with Paragraph 2, and the Banks subsequent
      dishonor of any items presented for payment.
      In no
      event shall Bank
      be
      liable
      for
      losses or delays resulting from computer malfunction, interruption of
      communication facilities, labor difficulties or other causes beyond Bank’s
      reasonable control or
      for
      indirect, special or consequential damages.

     

    8. Indemnity.
      The
      Company agrees to indemnify the Bank and hold it harmless against any loss,
      damage, or expense (including reasonable attorneys’ fees and other litigation
      expenses) that it may suffer as a direct result of the Bank’s entering into this
      Agreement and performing its obligation hereunder, including, honoring any
      instructions or direction it receives from Collateral Agent with respect to
      the
      Accounts during the term of this Agreement, other than any loss, damage or
      expense incurred as a result of the gross negligence or willful misconduct
      of,
      or breach of this Agreement by, the Bank or its officers, agents or
      employees.

     

    
      
         

      

      
        3

        
          

        

      

      
         

      

    

     

    9. No
      Other Assignments.
      Bank
      represents and warrants to Collateral Agent, on its behalf and on behalf of
      Buyers, that no other notices of assignment of, lien upon or security interest
      in the Accounts or the Account Collateral are reflected in Bank’s records
      concerning the Accounts, and Bank has no knowledge of any such assignment or
      lien. The Company hereby instructs Bank and Bank hereby agrees to record in
      Bank’s records concerning the Accounts any such notice of assignment of the
      Accounts that it receives, including the notice conferred by this Agreement.
      Bank agrees with and covenants to Collateral Agent, on its behalf and on behalf
      of Buyers, that it shall not enter into any other agreement with any Person
      which would obligate Bank to follow such Person’s instructions with respect to
      the Account or the Account Collateral, or which would otherwise confer control
      of the Accounts or the Account Collateral upon such Person.

     

    10. Termination.
      This
      Agreement shall remain in full force and effect until such time as Collateral
      Agent shall deliver written notice to the Bank that all of the Liabilities
      have
      been indefeasibly paid in full in cash and the Security Agreement has been
      terminated, whereupon this Agreement shall terminate. All rights of the Bank
      under Sections 7 and 8 for the period prior to any such termination shall
      survive such termination.

     

    11. Notices.
      Any
      notices, consents, waivers or other communications required or permitted to
      be
      given under the terms of this Agreement must be in writing and will be deemed
      to
      have been delivered: (i) upon receipt, when delivered personally; (ii) upon
      receipt, when sent by facsimile (provided confirmation of transmission is
      mechanically or electronically generated and kept on file by the sending party);
      or (iii) one (1) business day after deposit with a nationally recognized
      overnight delivery service, in each case properly addressed to the party to
      receive the same. The addresses and facsimile numbers for such communications
      shall be:

     

    
      	
              Collateral
                Agent:

               

            	
              Summerline
                Asset Management, LLC

              70
                West Red Oak Lane, 4th Floor

              White
                Plains, New York 10604

              Attention:
                Robert Brantman

              Telecopy:
                (914) 697-4767

               

            
	
              Bank:

               

            	
              Sterling
                Bank

              4040
                Broadway, Suite 110

              San
                Antonio, Texas 78209

              Attention: Steve
                York

              Telephone: (210)
                277-3301

              Facsimile: (210)
                826-6641

               

              With
                a copy to:

               

              Sterling
                Bank

              2550
                North Loop West, Suite 600 

              Houston,
                Texas 77092

              Attention: Chris
                M. Shamaly

              Telephone: (713)
                507-7952

              Facsimile: (713)
                507-2900

            


    

     

    
      
         

      

      
        4

        
          

        

      

      
         

      

    

     

    
      	
              Company:

               

            	
              Sonterra
                Operating , Inc.

              c/o
                Sonterra Resources, Inc.

              523
                North Sam Houston Pkwy East

              Suite
                175

              Houston,
                Texas 77060

              Attention: D.
                E. Vandenberg 

              Telephone: (281)
                _______

              Facsimile: (281)
                741-0895

               

            


    

    If
      to any
      party named above, at such other address and/or facsimile number and/or to
      the
      attention of such other person as the recipient party has specified by written
      notice given to each other party five (5) days prior to the effectiveness of
      such change. Written confirmation of receipt (A) given by the recipient of
      such
      notice, consent, waiver or other communication, (B) mechanically or
      electronically generated by the sender’s facsimile machine containing the time,
      date, recipient facsimile number and an image of the first page of such
      transmission or (C) provided by a nationally recognized overnight delivery
      service shall be rebuttable evidence of personal service, receipt by facsimile
      or deposit with a nationally recognized overnight delivery service in accordance
      with clause (i), (ii) or (iii) above, respectively.

    


    12. Applicable
      Law.
      TEXAS
      LAW
      WITHOUT
      REGARD TO ITS CONFLICT OF LAW
      PRINCIPLES GOVERNS THIS AGREEMENT. BEXAR COUNTY, TEXAS IS THE PLACE OF
      PERFORMANCE OF THIS AGREEMENT AND IS THE PROPER VENUE FOR ANY ACTION OR
      PROCEEDING RELATING TO THIS AGREEMENT, WHETHER SUCH ACTION IS IN CONTRACT,
      TORT,
      OR OTHERWISE.

     

    13. Miscellaneous
      Provisions.
      This
      Agreement shall supersede any other agreement (to the extent conflicting
      herewith) relating to the matters referred to herein, including any conflicting
      provision of the Bank’s customary account documentation or any other account
      agreement between the Company and the Bank. This Agreement is binding upon
      the
      parties hereto and their respective successors and assigns (including any
      trustee of the Company appointed or elected in any action under the Bankruptcy
      Reform Act of 1978, as amended) and shall inure to their benefit. This Agreement
      may not be changed, amended, modified or waived, except by a writing signed
      by
      the parties hereto, provided that any such writing need be signed only by the
      Bank and Collateral Agent if it does not change any rights or obligations of,
      or
      authorizations granted by, the Company hereunder and notice thereof is provided
      to the Company by Collateral Agent. Any provision of this Agreement that may
      prove unenforceable under any law or regulation shall not affect the validity
      of
      any other provision hereof. This Agreement may be executed in two or more
      identical counterparts, all of which shall be considered one and the same
      agreement and shall become effective when counterparts have been signed by
      each
      party and delivered to each other party; provided that a facsimile signature
      shall be considered due execution and shall be binding upon the signatory
      thereto with the same force and effect as if the signature were an original,
      not
      a facsimile signature.

     

    -
      Remainder of Page Intentionally Left Blank; Signature Page Follows
      -

     

    
      
         

      

      
        5

        
          

        

      

      
         

      

    

    


    IN
      WITNESS WHEREOF, the undersigned have executed this Deposit Account Control
      Agreement by their respective duly authorized officers as of the date first
      forth above.

    


    Company:

    


    
      	
              SONTERRA
                OPERATING, INC.,
                a
                Delaware corporation

            
	 	 
	
              By:

            	 

	
              Name:

            	 
	
              Title:

            	 


    

     

    
      Account
        Control Agreement

       

    

    
      
         

      

      
         

        
          

        

      

      
         

      

    


    Secured
      Party/Pledgee:

    


    SUMMERLINE
      ASSET MANAGEMENT, LLC,
      a


    Delaware
      limited liability company, in its 

    capacity
      as Collateral Agent

    


    
      	
              By:

            	    

	
              Name:

            	
              Robert
                J. Brantman

            
	
              Title:

            	
              Co-Managing
                Member

            


    

     

    
      Account
        Control Agreement

    

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    


    Bank:

    


    STERLING
      BANK,
      a Texas
      banking corporation

    


    
      	
              By:

            	   

	
              Name:

            	  

	
              Title:

            	  



    

     

    
      Account
        Control Agreement

    

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    

    


    EXHIBIT
      A

    


    Form
      of Notification of Event of Default

    


    Sterling
      Bank

    4040
      Broadway, Suite 110

    San
      Antonio, Texas 78209

    Attention:
      Steve York

    


    Ladies
      and Gentlemen:

    


    Reference
      is made to the Deposit Account Control Agreement, dated as of November __,
      2008
      (the “Account
      Control Agreement”)
      among
      Sterling Bank, a Texas banking corporation, Sonterra Operating, Inc., a Delaware
      corporation, and Summerline Asset Management, LLC, in its capacity as Collateral
      Agent. Capitalized terms used and not otherwise defined in this notification
      letter are used with the meanings set forth in the Account Control Agreement.
      

    


    You
      are
      hereby notified, in accordance with Section 3 of the Account Control Agreement,
      that an Event of Default has occurred. In light of the foregoing, you are hereby
      instructed not to allow Company to access the Accounts or the Account Collateral
      and not to comply with any instructions or directions originated by Company
      or
      otherwise permit Company access to or control over the Accounts or the Account
      Collateral, including without limitation giving stop payment orders, presenting
      items for payment or making withdrawals therefrom. 

    


    


    
      	
              Date:
                [                  
                ], 200__

            	 	
              SUMMERLINE
                ASSET MANAGEMENT, LLC,
                in
                its capacity as Collateral Agent

            
	 	 	 	 
	 	 	
              By:

            	   

	 	 	
              Name:
                

            	   

	 	 	
              Title: