EXHIBIT 10.20 Amendment To Apache Corporation Money Purchase Retirement Plan Apache Corporation ("Apache") maintains the Apache Corporation Money Purchase Retirement Plan (the "Plan"). In section 9.4 of the Plan, Apache reserved the right to amend the Plan from time to time. Apache hereby exercises such right as follows, by replacing the chart at the end of Appendix C with the following chart, effective as of January 1, 2003. <Table> <Caption> Former Employer New Employees --------------- ------------- Crescendo Resources, L.P. ("Crescendo") All individuals hired from April 30, 2000 through June 1, 2000 from Crescendo and related companies in connection with an April 30, 2000 asset acquisition from Crescendo. Collins & Ware ("C&W") and Longhorn All individuals hired from C&W, Longhorn, and Disposal, Inc. ("Longhorn") related companies in connection with a May 23, 2000 asset acquisition from C&W and Longhorn. Occidental Petroleum Corporation ("Oxy") All individuals hired from Oxy and related companies in connection with an August 2000 asset acquisition from an Oxy subsidiary. Private company ("Private") All individuals hired in January 2003 from Private and related companies in connection with an asset acquisition of certain property in Louisiana effective as of December 1, 2002. </Table> EXECUTED this 27th day of January 2003. APACHE CORPORATION By: /s/ Jeffrey M. Bender ---------------------------------- Name: Jeffrey M. Bender Title: Vice President, Human Resources Page 1 of 1