Exhibit 10.27 [First Amendment to Credit Agreement] NationsBank Energy Banking Group P.O. Box 830104 Dallas, TX 75283-0104 Tel 214 508-1200 December 22, 1998 St. Mary Land & Exploration Company Mr. David L. Henry, Chief Financial Officer 1776 Lincoln Street, 11th Floor Denver, Colorado, 80203 RE: Credit Agreement dated June 30, 1998 between St. Mary Land & Exploration Company and NationsBank, N.A., as Agent, and Lenders. Dear David: Pursuant to Section 7.5 Limitation on Sales of Property, Lenders hereby consent to Borrower's sale of certain oil and gas properties located in Oklahoma. Additionally, upon the sale of such properties, the Aggregate Borrowing Base is reduced to $105,000,000 until the next Determination Date. For purposes of this reduction, the effective date of ther revised Aggregate Borrowing Base is December 21, 1998. David, please feel free to call me if you have any questions or if I can be of additional assistance. Sincerely, David C. Rubenking Senior Vice President Cc: Tom Foncannon Mark Thompson