GUARANTY

Exhibit 10.6

GUARANTY

(Continuing Debt - Unlimited)

DATE AND PARTIES. The date of this Guaranty is November 2, 2007. The parties and their addresses are:

LENDER:

AMERICAN NATIONAL BANK

3033 East First Ave

Denver, Colorado 80208

Telephone: (303) 394-5100

BORROWER:

BUFFALO HIGHLANDS, LLC

a Colorado Limited Liability Company

222 Milwaukee Street, Suite 209

Denver, Colorado 80208

GUARANTOR:

EAGLE EXPLORATION COMPANY

a Colorado Corporation

1801 Broadway, Suite 1010

Denver, Colorado 80202

1. DEFINITIONS. As used in this Guaranty, the terms have the following meanings:

A. Pronouns. The pronouns “I”, “me” and “my” refer to all persons or entities signing this Guaranty, Individually and together. “You” and “your” refer to the Lender.

B. Note. “Note” refers to the document that evidences the Borrower’s indebtedness, and any extensions, renewals, modifications and substitutions of the Note.

C. Property. “Property” means any property, real, personal or intangible, that secures performance of the obligations of the Note, Debt, or this Guaranty.

2. SPECIFIC AND FUTURE DEBT GUARANTY. For good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, and to induce you, at your option, to make loans or engage in any other transactions with the Borrower from time to time. I absolutely and unconditionally agree to all terms of and guaranty to you the payment and performance of each and every Debt, of every type, purpose and description that the Borrower either Individually, among all or a portion of themselves, or with others, may now or at any time in the future owe you, including, but not limited to the following described Debt(s) including without limitation, all principal, accrued interest, attorneys’ fees and collection costs, when allowed by law, that may become due from the Borrower to you in collecting and enforcing the Debt and all other agreements with respect to the Borrower.

A promissory note or other agreement, No. 0134728501, dated November 2, 2007, from Buffalo Highlands, LLC (Borrower) to you, in the amount of $1,000,000.00.

In addition, Debt refers to debts, liabilities, and obligations of the Borrower [including, but not limited to, amounts agreed to be paid under the terms of any notes or agreements securing the payment of any debt, loan, liability or obligation, overdrafts, letters of credit, guaranties, advances for taxes, insurance, repairs and storage, and all extensions, renewals, refinancings and modifications of these debts) whether now existing or created or incurred in the future, due or to become due, or absolute or contingent, including obligations and duties arising from the terms of all documents prepared or submitted for the transaction such as applications, security agreements, disclosures, and the Note.

You may, without notice, apply this Guaranty to such Debt of the Borrower as you may select from time to time.

3. EXTENSIONS. I consent to all renewals, extensions, modifications and substitutions of the Debt which may be made by you upon such terms and conditions as you may see fit from time to time without further notice to me and without limitation as to the number of renewals, extensions, modifications or substitutions.

A. Future Advances. I waive notice of and consent to any and all future advances made to the Borrower by you.

4. UNCONDITIONAL LIABILITY. I am unconditionally liable under this Guaranty, regardless of whether or not you pursue any of your remedies against the Borrower, against any other maker, surety, guarantor or endorser of the Debt or against any Property. You may sue me alone, or anyone else who is obligated on this Guaranty, or any number of us together, to collect the Debt My liability is not conditioned on the signing of this Guaranty by any other person and further is not subject to any condition not expressly set forth in this Guaranty or any Instrument executed in connection with the Debt. My obligation to pay according to the terms of this Guaranty shall not be affected by the Illegality, Invalidity or unenforceability of any notes or agreements evidencing the Debt, their violation of any applicable usury laws, forgery, or any other circumstances which make the indebtedness unenforceable against the Borrower. I will remain obligated to pay on this Guaranty even if any other person who is obligated to pay the Debt, Including the Borrower, has such obligation discharged in bankruptcy, foreclosure, or otherwise discharged by law.

5. BANKRUPTCY. If a bankruptcy position should at any time be filed by or against the Borrower, the maturity of the Debt, so for as my liability is concerned, shall be accelerated and the Debt shall be immediately payable by me. I acknowledge and agree that this Guaranty, and the Debt secured hereby, will remain in full force and effect at all times, notwithstanding any action or undertakings by, or against you or against any Property, in connection with any obligation in any proceeding in the United States Bankruptcy Courts. Such action or undertaking includes, without limitation, valuation of Property, election of remedies or imposition of secured or unsecured claim status upon claims by you pursuant to the United States Bankruptcy Code, as amended. In the event that any payment of principal or interest received and paid by any other guarantor, borrower, surety, endorser or co-maker is deserved, by final order of a court of competent jurisdiction, to have been a voidable preference under the bankruptcy or insolvency laws of the United States or otherwise, then my obligation will remain as an obligation to you and will not be considered as having been extinguished.

6. REVOCATION. I agree that this is an absolute and unconditional Guaranty. I agree that this Guaranty will remain binding on me, whether or not there are any Debts outstanding, until you have actually received written notice of my revocation or written notice of my death or incompetence. Notice of revocation or notice of my death or incompetence will not affect my obligations under this Guaranty with respect to any Debts incurred by or for which you have made a commitment to Borrower before you actually receive such notice, and all renewals, extensions, refinancings, and modifications of such Debts. I agree

that if any other person signing this Guaranty provides a notice of revocation to you, I will still be obligated under this Guaranty until I provide such a notice of revocation to you. If any other person signing this Guaranty dies or is declared incompetent, such fact will not affect my obligations under this Guaranty.

7. PROPERTY. I agree that any Property may be assigned, exchanged, released in whole or in part or substituted without notice to me and without defeating, discharging or diminishing my liability. My obligation is absolute and your failure to perfect any security interest or any act or omission by you which impairs the Property will not relieve me or my liability under this Guaranty. You are under no duty to preserve or protect any Property until you are in actual or constructive possession. For purposes of this paragraph, you will only be in “actual” possession when you have physical, immediate and exclusive control over the Property and have accepted such control in writing. Further, you will only be deemed to be in “constructive” possession when you have both the power and intent to exercise control over the Property.

8. DEFAULT. I will be in default if any of the following occur:

A. Payments. I fail to make a payment in full when due.

B. Insolvency or Bankruptcy. The death, dissolution or insolvency of, appointment of a receiver by or on behalf of, application of any debtor relief law, the assignment for the benefit of creditors by or on behalf of, the voluntary or involuntary termination of existence by, or the commencement of any proceeding under any present or future federal or state insolvency, bankruptcy, reorganization, composition or debtor relief law by or against me, Borrower, or any co-signer, endorser, surety or guarantor of this Guaranty or any Debt.

C. Business Termination. I merge, dissolve, reorganize, end my business or existence, or a partner or majority owner dies or is declared legally incompetent.

D. Failure to Perform. I fail to perform any condition or to keep any promise or covenant of this Guaranty.

E. Other Documents. A default occurs under the terms of any other document relating to the Debt.

F. Other Agreements. I am in default on any other debt or agreement I have with you.

G. Misrepresentation. I make any verbal or written statement or provide any financial information that is untrue, inaccurate, or conceals a material fact at the time it is made or provided.

H. Judgment. I fail to satisfy or appeal any judgment against me.

I. Forfeiture. The Property is used in a manner or for a purpose that threatens confiscation by a legal authority.

J. Name Change. I change my name or assume an additional name without notifying you before making such a change.

K. Property Transfer. I transfer all or a substantial part of my money or property.

L. Property Value. You determine in good faith that the value of the Property has declined or is impaired.

M. M