SECOND AMENDMENT TO REGISTRATION RIGHTS AGREEMENT

THIS SECOND AMENDMENT TO REGISTRATION RIGHTS AGREEMENT (the “Amendment”) is made
and entered into as of this 19th day of May, 2008, by and among Sonterra
Resources, Inc., a Delaware corporation, (the “Company”), and The Longview Fund,
L.P., a California limited partnership (“Buyer”).

In consideration of the mutual covenants and agreements set forth herein and for
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties agree to amend that certain Registration Rights
Agreement, dated as of February 14, 2008, as amended by that certain First
Amendment to Registration Rights Agreement, dated as of March 12 2008 (as
amended, the “Agreement”), between the Company and Buyer.

Section 1. All capitalized terms used but not defined in this Amendment shall
have the respective meanings ascribed to such terms in the Agreement.

Section 2. The definition of “Initial Filing Deadline” contained in Section 1(i)
of the Agreement is hereby amended and restated to read in its entirety as
follows:

“i. “Initial Filing Deadline” means July 30, 2008; provided, however that, if on
the Exchange Closing Date the Warrant Registrable Securities are not then
eligible for sale on a delayed or continuous basis by the Investors pursuant to
Rule 415, the Initial Filing Deadline shall be the later of (i) July 30, 2008
and (ii) the earlier of (A) the date that is the tenth (10th) Business Day
following the date on which the Investors shall have delivered to the Company
the information required by Item 508 of Regulation S-K under the Securities Act
with respect to a plan of distribution for the Warrant Registrable Shares other
than in accordance with Rule 415 and (B) the first date on which the Warrant
Registrable Securities are eligible for sale on a delayed or continuous basis by
the Investors pursuant to Rule 415.”

Section 3. As amended by this Amendment, the parties hereto agree the Agreement
remains in full force and effect and nothing herein shall affect, or be deemed
to be a waiver of, the other terms and provisions of the Agreement.

Section 4. This Amendment 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. In the event that any signature to this Amendment or any amendment
hereto is delivered by facsimile transmission or by e-mail delivery of a “.pdf”
format data file, such signature shall create a valid and binding obligation of
the party executing (or on whose behalf such signature is executed) with the
same force and effect as if such facsimile or “.pdf” signature page were an
original thereof. No party hereto shall raise the use of a facsimile machine or
e-mail delivery of a “.pdf” format data file to deliver a signature to this
Amendment or any amendment hereto or the fact that such signature was
transmitted or communicated through the use of a facsimile machine or e-mail
delivery of a “.pdf” format data file as a defense to the formation or
enforceability of a contract, and each party hereto forever waives any such
defense.

Section 5. This Amendment and the Agreement (as amended hereby) represent the
final agreement of the parties hereto with respect to the matters contained
herein and may not be contradicted by evidence of prior or contemporaneous
agreements, or prior or subsequent oral agreements, between the parties hereto.
 

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IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of the
date first above written.
 

        COMPANY:       SONTERRA RESOURCES, INC.  
   
   
    By:     Name: Michael J. Pawelek   Title:  President

: 

        BUYER:       THE LONGVIEW FUND, L.P.  
   
   
    By:
Viking Asset Management, Ltd.
Its General Partner
        By:
Viking Asset Management, LLC
Its Investment Advisor
        By:     Name:     Title:  

: