SENIOR SECURED NOTE

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS. THE SECURITIES MAY NOT BE OFFERED FOR SALE, SOLD, TRANSFERRED OR ASSIGNED (I) IN THE ABSENCE OF (A) AN EFFECTIVE REGISTRATION STATEMENT FOR THE SECURITIES UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS OR (B) AN OPINION OF COUNSEL, IN A GENERALLY ACCEPTABLE FORM, THAT REGISTRATION IS NOT REQUIRED UNDER SAID ACT OR APPLICABLE STATE SECURITIES LAWS OR (II) UNLESS SOLD PURSUANT TO RULE 144 UNDER SAID ACT. NOTWITHSTANDING THE FOREGOING, THE SECURITIES MAY BE PLEDGED IN CONNECTION WITH A BONA FIDE MARGIN ACCOUNT OR OTHER LOAN OR FINANCING ARRANGEMENT SECURED BY THE SECURITIES. ANY TRANSFEREE OF THIS NOTE SHOULD CAREFULLY REVIEW THE TERMS OF THIS NOTE, INCLUDING SECTION 5 HEREOF. THE PRINCIPAL AMOUNT REPRESENTED BY THIS NOTE MAY BE LESS THAN THE AMOUNTS SET FORTH ON THE FACE HEREOF PURSUANT TO SECTION 5 HEREOF.

FOR VALUE RECEIVED, SONTERRA RESOURCES, INC. (f/k/a River Capital Group, Inc.),   a Delaware corporation (the “ Company ”), hereby promises to pay to the order of Longview Marquis Master Fund, L.P., a British Virgin Islands limited partnership, or its registered assigns (the “ Holder ”) the principal amount of Eight Million Eight Hundred Seventy-Five Thousand Dollars ($8,875,000) when due, whether upon maturity, acceleration, redemption or otherwise, and to pay interest (“ Interest ”) on the unpaid principal balance hereof on each Interest Payment Date (as defined in Section 2) and upon maturity, or earlier upon acceleration or prepayment pursuant to the terms hereof, at the Applicable Interest Rate (as defined in Section 2). Interest on this Note payable on each Interest Payment Date and upon maturity, or earlier upon acceleration or prepayment pursuant to the terms hereof, shall accrue from the Issuance Date (as defined in Section 2) and shall be computed on the basis of a 365-day year and actual days elapsed.

(1)   Payments of Principal and Interest . All payments under this Note shall be made in lawful money of the U.S. (as defined in Section 2) by wire transfer of immediately available funds to such account as the Holder may from time to time designate by written notice in accordance with the provisions of this Note. Interest on the Principal shall be paid in arrears on each Interest Payment Date and upon Maturity. The Company has no right, but under certain circumstances has an obligation, to make payments of Principal of this Note prior to the Maturity Date (as defined in Section 2), except as set forth in Section 3 hereof. Whenever any amount expressed to be due by the terms of this Note is due on any day that is not a Business Day (as defined in Section 2), the same shall instead be due on the next succeeding day that is a Business Day. This Note and all Other Notes (as defined in Section 2) issued by the Company pursuant to the Securities Purchase Agreement (as defined in Section 2) on the Closing Date (as defined in the Securities Purchase Agreement), and all notes issued in exchange or substitution therefor or replacement thereof are collectively referred to in this Note as the “ Notes .”

(2)   Certain Defined Terms . Each capitalized term used in this Note, and not otherwise defined, shall have the meaning ascribed thereto in the Securities Purchase Agreement, dated as of November 13, 2008, pursuant to which this Note was originally issued (as such agreement may be amended, restated, supplemented or otherwise modified from time to time as provided therein, the “ Securities Purchase Agreement ”). For purposes of this Note, the following terms shall have the following meanings:

(a)   “ Applicable Interest Rate ” means the Interest Rate, or, for so long as an Event of Default shall have occurred and be continuing, the Default Rate.

(b)   “ Bankruptcy Law ” means Title 11, U.S. Code, or any similar U.S. federal or state law or law of any applicable foreign government or political subdivision thereof for the relief of debtors.

(c)   “ Business Day ” means any day other than Saturday, Sunday or other day on which commercial banks in the city of New York are authorized or required by law to remain closed.

(d)   “ Cash and Cash Equivalents ” means (I) cash, (II) certificates of deposit or time deposits, having in each case a tenor of not more than six (6) months, issued by any U.S. commercial bank or any branch or agency of a non-U.S. bank licensed to conduct business in the U.S. having combined capital and surplus of not less than $250,000,000, and (III) money market funds, provided that substantially all of the assets of such funds consist of securities of the type described in clauses (I) or (II) immediately above, all as determined in accordance with GAAP applied on a consistent basis.

(e)   “ Change of Control ” means (i) the consolidation, merger or other business combination of the Company with or into another Person (other than (A) a consolidation, merger or other business combination in which holders of the Company’s voting power immediately prior to the transaction continue after the transaction to hold, directly or indirectly, a majority of the combined voting power of the surviving entity or entities entitled to vote generally for the election of a majority of the members of the board of directors (or their equivalent if other than a corporation) of such entity or entities, or (B) pursuant to a migratory merger effected solely for the purpose of changing the jurisdiction of incorporation of the Company), (ii) the sale or transfer of all or substantially all of the Company’s assets (including, for the avoidance of doubt, the sale of all or substantially all of the assets of the Subsidiaries in the aggregate); (iii) the consummation of a purchase, tender or exchange offer made to and accepted by the holders of more than the fifty percent (50%) of the outstanding shares of Common Stock; (iv) the acquisition by any Person or group (within the meaning of Section 13(d)(3) or 14(d)(2) of the 1934 Act) of the beneficial ownership (within the meaning of Rule 13d-3 promulgated under the 1934 Act) of fifty percent (50%) or more of the outstanding shares of Common Stock or of the combined voting power of the then outstanding voting securities of the Company entitled to vote generally in the election of directors; or (v) any change in the composition of the Board of Directors of the Company (the “ Board ”) such that the individuals who, as of the date of the Securities Purchase Agreement, constituted the Board of the Company (such Board of the Company being hereinafter referred to as the “ Incumbent Board ”) cease for any reason to constitute at least a majority of the Board; provided, however, that any individual who becomes a member of the Board whose election, or nomination for election by the Company's stockholders, was approved by a vote of at least a majority of those individuals who are members of the Board and who were also members of the Incumbent Board (or deemed to be such pursuant to this proviso) shall be considered as though such individual were a member of the Incumbent Board; but, provided, further, that any such individual whose initial assumption of office occurs as a result of either an actual or threatened election contest (as such terms are used in Rule 14a-11 of Regulation 14A promulgated under the 1934 Act) or other actual or threatened solicitation of proxies or consents by or on behalf of a Person or group other than the Board shall not be so considered as a member of the Incumbent Board.

(f)   “ Collateral Agent ” shall have the meaning ascribed to such term in the Security Agreement.

(g)   “ Custodian ” means any receiver, trustee, assignee, liquidator or similar official under any Bankruptcy Law.

(h)   “ Daily Production Average ” means, for any calendar quarter, the arithmetic average of the aggregate number of thousands of cubic feet equivalents (“ Mcfe ”) of natural gas produced by all of the Real Property of the Company and the FC Subsidiaries, net to the Working Interests (as defined in the Conveyances of Limited Overriding Royalty Interests) owned by the Company and such Subsidiaries in such Real Property, on each of the days in such calendar quarter.

(i)   “Daily Production Test Failure ” means that, as of any date of determination, the Daily Production Average for the calendar quarter ending on such date is less than the Required Daily Production Average for such calendar quarter.

(j)   “ Daily Production Test Failure Percentage ” means, in the event that there is a Daily Production Test Failure as of any date of determination, an amount equal to the result of (A) one (1) minus (B) the quotient of the Daily Production Average for the calendar quarter ended on such date, divided by the Required Daily Production Average for such calendar quarter.

(k)   “ Default Rate ” means the per annum interest rate equal to the sum of (i) the Interest Rate plus (ii) two percent (2.0%) (i.e., 200 basis points).

(l)   “ Dollars ” or “ $ ” means United States Dollars.

(m)   “ Excluded Taxes ” means, with respect to the Holder, or any other recipient of payment to be made by or on account of any obligations of the Company or any of the Subsidiaries under the Notes, the Securities Purchase Agreement or under any other Transaction Document, income or franchise taxes imposed on (or measured by) such recipient’s net income or gross receipts by the U.S. or such other jurisdiction under the laws of which such recipient is organized or its principal offices are located.

(n)   “ FC Subsidiaries ” means the domestic Included Subsidiaries that (i) are directly or indirectly wholly-owned by the Company, (ii) are party to the Guaranty and the Security Agreement, and (iii) in all of the assets of which the holders of the Notes have a valid, first priority, perfected security interest as of the applicable date of determination.

(o)   “Financial Covenant Test Failure” means that, as of any date of determination, (A) there is a Daily Production Test Failure or (B) the PRV Ratio as of such date is less than the Required PRV Ratio as of such date.

(p)   “ Financial Covenant Test Failure Amount ” means, in the event that there is a Financial Covenant Test Failure as of any date of determination, an amount equal to the sum of:

(i)   the product of (A) the result of (I) one (1) minus (II) the quotient of the Daily Production Average for the calendar quarter ended on such date, divided by the Required Daily Production Average for such calendar quarter (provided, however, that such result shall not be less than zero (0)), multiplied by (B) the aggregate outstanding principal amount of all Notes then outstanding; plus

(ii)   the product of (A) the result of (I) one (1) minus (II) the quotient of the PRV Ratio as of such date, divided by the Required PRV Ratio as of such date (provided, however, that such result shall not be less than zero (0)), multiplied by (B) the aggregate outstanding principal amount of all Notes then outstanding.

(q)   “ GAAP ” means U.S. generally accepted accounting principles, as in effect at the relevant time.

(r)   “ Governmental Authority ” means the government of the U.S. or any other nation, or any political subdivision thereof, whether state, provincial or local, or any agency, authority, instrumentality, regulatory body, court, central bank or other entity exercising executive, legislative, judicial, taxing, regulatory or administration powers or functions of or pertaining to government over the Company, or any of their respective properties, assets or undertakings.

(s)   “ Indemnified Taxes ” means all taxes other than Excluded Taxes.

(t)   “ Interest Amount ” means, as of any date, with respect to any Principal, all accrued and unpaid Interest (including any Interest at the Default Rate) on such Principal through and including such date.

(u)   “ Interest Payment Date ” means the last Business Day of each of December 2008, March 2009 and June 2009, and thereafter on the first Business Day of each calendar month, beginning with August 2009, until this Note has been repaid in full.

(v)   “ Interest Rate ” means thirteen percent (13.0%) per annum, subject to adjustment as provided in Section 3(c)(iii).

(w)   “ Issuance Date ” means the original date of issuance of this Note pursuant to the Securities Purchase Agreement, regardless of any exchange or replacement hereof.

(x)   “ Maturity Date ” means November 13, 2011, unless such date is not a Business Day, in which case “Maturity Date” shall mean the first Business Day following November 13, 2011.

(y)   “ Other Notes ” means all of the senior secured notes, other than this Note, that have been issued by the Company pursuant to the Securities Purchase Agreement and all notes issued in exchange or substitution therefor, addition thereto or replacement thereof.

(z)   “ PDNP ” as of any date of determination, means the total proved developed non-producing   reserves (in Mcfe) of the Company and the FC Subsidiaries, determined as of such date of determination in accordance with SEC guidelines from an independent reserve report prepared in good faith by the Petroleum Engineer in accordance with industry standards and best practices (an “ Independent Reserve Report ”); provided, however, that PDNP shall mean zero (0) unless (A) it is based upon an Independent Reserve Report (or an update thereof prepared (but not certified) by the Petroleum Engineer, which update includes all material adjustments to the amounts set forth in the most recent Independent Reserve Report to reflect the Company’s and the Subsidiaries’ oil and gas drilling, exploration, development and production since the date of such Independent Reserve Report (a “ Reserve Update ”)) that was current as of a date within 92 days of such date of determination, (B) the Company has publicly disclosed the PDNP in a Periodic Report as of a date within 274 days of such date of determination (based on an Independent Reserve Report that was current as of such date of determination), (C) the PDNP is based upon the same Independent Reserve Report or Reserve Update on which the PDP, PUD and Probable are based as of such date of determination, and (D) if the PDNP is not based upon an Independent Reserve Report (or a Reserve Update) that was current as of such date of determination, the Company reasonably believes, based upon its own analysis conducted in good faith and reflecting the Company’s and the FC Subsidiaries’ oil and gas drilling, exploration, development and production since the date of the Independent Reserve Report (or Reserve Update) on which the PDNP is based (the “ Recent Production ”) (and has certified to the Holder in the applicable Officer’s Certificate to the Holder that it so reasonably believes), that the PDNP is not less than that disclosed in the Independent Reserve Report (or Reserve Update) on which the PDNP is based.

(aa)   “ PDP ” means the total proved developed producing reserves (in Mcfe) of the Company and the FC Subsidiaries, determined in accordance with SEC guidelines from an Independent Reserve Report; provided, however, that PDP shall mean zero (0) unless (A) it is based upon an Independent Reserve Report (or a Reserve Update) that was current as of a date within 92 days of such date of determination, (B) the Company has publicly disclosed the PDP in a Periodic Report as of a date within 274 days of such date of determination (based on an Independent Reserve Report that was current as of such date of determination), (C) the PDP is based upon the same Independent Reserve Report or Reserve Update on which the PDNP, PUD and Probable are based as of such date of determination, and (D) if the PDP is not based upon an Independent Reserve Report (or a Reserve Update) that was current as of such date of determination, the Company reasonably believes, based upon its own analysis conducted in good faith and reflecting the Recent Production (and has certified to the Holder in the applicable Officer’s Certificate that it so reasonably believes), that the PDP is not less than that disclosed in the Independent Reserve Report (or Reserve Update) on which the PDP is based.

(bb)   “ Periodic Report ” means a quarterly report on Form 10-Q (or successor thereto) or an annual report on Form 10-K (or successor thereto), in the form required to be filed with the SEC.

(cc)   “ Person ” means an individual, a limited liability company, a partnership, a joint venture, a corporation, a trust, an unincorporated organization or a government or any department or agency thereof or any other legal entity.

(dd)   “ Petroleum Engineer ” means an independent petroleum engineer that is an SPE (Society of Petroleum Engineers) Certified Petroleum Professional and is selected and engaged by the Company and approved by the holders of Notes representing at least two thirds (2/3) of the aggregate principal amount of the Notes then outstanding, which approval shall not be unreasonably withheld, conditioned or delayed.

(ee)   “ Prepayment Notice ” means a written notice from the Company to Holder indicating the Company’s commitment to prepay a specified amount of Principal, together with the applicable Interest Amount and Prepayment Premium with respect thereto on the applicable prepayment date.

(ff)   “ Prepayment Premium ” means an amount equal to twenty-five percent (25%) of the amount of Principal so prepaid or required to be prepaid.

(gg)   “ Principal ” means the outstanding principal amount of this Note as of any date.

(hh)   “ Probable ” means the total probable undeveloped reserves (in Mcfe) of the Company and the FC Subsidiaries, determined in accordance with SEC guidelines based on an Independent Reserve Report; provided, however, that Probable shall mean zero (0) unless (A) it is based upon an Independent Reserve Report (or a Reserve Update) that was current as of a date within 92 days of such date of determination, (B) the Company has publicly disclosed the Probable in a Periodic Report as of a date within 274 days of such date of determination (based on an Independent Reserve Report that was current as of such date of determination), (C) the Probable is based upon the same Independent Reserve Report or Reserve Update on which the PDNP, PDP and PUD are based as of such date of determination, and (D) if the Probable is not based upon an Independent Reserve Report (or a Reserve Update) that was current as of such date of determination, the Company reasonably believes, based upon its own analysis conducted in good faith and reflecting the Recent Production (and has certified in the applicable Officer’s Certificate that it so reasonably believes), that the Probable is not less than that disclosed in the Independent Reserve Report (or Reserve Update) on which the Probable is based.

(ii)   “ Pro Rata Financial Covenant Test Failure Amount ” means, as of the date of any determination, an amount equal to the sum of (i) the product of (A) a fraction, of which the numerator is the outstanding Principal as of such date, and of which the denominator is the aggregate outstanding principal amount of all Notes as of such date, multiplied by (B) the Financial Covenant Test Failure Amount, and (ii) the Interest Amount with respect to such Principal as of the date such amount is paid to the Holder.

(jj)   “ PRV Ratio ” means, as of any date of determination, the quotient of:

(I) the result of:

(i) (A) the product of the aggregate actual PDP and PDNP of the Company’s and the FC Subsidiaries’ oil and gas properties and interests in which the holders of the Notes have a valid, first priority, perfected security interest as of such date of determination (the “PRV Properties ”), multiplied by (B) the relevant hub spot price as of such date of determination, and multiplied by (C) 40%; plus

(ii) the product of (A) the actual PUD of the PRV Properties, multiplied by (B) the relevant hub spot price as of such date of determination, and multiplied by (C) 15%; plus

(iii) the product of (A) the actual Probable of the PRV Properties, multiplied by (B) the relevant hub spot price as of such date of determination and multiplied by (C) 5%; plus

(iv) the aggregate Cash and Cash Equivalents of the Company and the FC Subsidiaries, the aggregate hydrocarbon receivables of the Company and the FC Subsidiaries (net of any provision for uncollectibility thereof and excluding any such receivables that are impaired or have been outstanding (and uncollected) for more than 60 days since the initial booking thereof), and the market value of hedges of the Company and the FC Subsidiaries, each as of such date of determination, as set forth in the financial statements included in the Periodic Report for the fiscal quarter or year ended on such date of determination; plus

(v) $4,400,000 (representing the deemed liquidation value as of the Issuance Date of the drilling rigs, trucks and equipment of North Texas, which was acquired and became a Subsidiary as of the Issuance Date), adjusted as agreed upon by the Company and the holders of Notes representing at least two-thirds (2/3) of the aggregate principal amount outstanding under the Notes as of such date of determination, to reflect any sales, transfers or other dispositions of, or any failure of the holders of the Notes to have a valid, first priority, perfected security interest in, any of such drilling rigs, trucks and equipment (other than due to the FNBW Security Interest); minus

(vi) the aggregate hedge margin collateral of the Company and the Subsidiaries, the aggregate hydrocarbon payables (including with respect to royalty payments and net profit interests) of the Company and the Subsidiaries, and the aggregate accrued production taxes payable by the Company and the Subsidiaries, each as of such date of determination, as set forth in the financial statements included in the Periodic Report for the fiscal quarter or year ended on such date of determination; and minus

(vii) the aggregate Indebtedness of the Company and the Subsidiaries due prior to the Maturity Date (excluding the Notes), as of such date of determination, as set forth in the financial statements included in the Periodic Report for the fiscal quarter or year ended on such date of determination;

divided by

(kk)   “ PUD ” means the total proved undeveloped reserves (in Mcfe) of the Company and the FC Subsidiaries, determined in accordance with SEC guidelines based on an Independent Reserve Report; provided, however, that PUD shall mean zero (0) unless (A) it is based upon an Independent Reserve Report (or a Reserve Update) that was current as of a date within 92 days of such date of determination, (B) the Company has publicly disclosed the PUD in a Periodic Report as of a date within 274 days of such date of determination (based on an Independent Reserve Report that was current as of such date of determination), (C) the PUD is based upon the same Independent Reserve Report or Reserve Update on which the PDNP, PDP and Probable are based as of such date of determination, and (D) if the PUD is not based upon an Independent Reserve Report (or a Reserve Update) that was current as of such date of determination, the Company reasonably believes, based upon its own analysis conducted in good faith and reflecting the Recent Production (and has certified in the applicable Officer’s Certificate that it so reasonably believes), that the PUD is not less than that disclosed in the Independent Reserve Report (or Reserve Update) on which the PUD is based.

(ll)   “ Required Daily Production Average ” means, with respect to any fiscal quarter ending on or after any date set forth below and prior to the next date set forth below, the Daily Production Average set for