1 EXHIBIT 15(a) Arthur Andersen LLP Suite 5600 901 Main Street Dallas TX 75202 Tel 214-741-8300 www.arthurandersen.com Anadarko Petroleum Corporation 17001 Northchase Drive Houston, Texas 77060-1714 July 13, 2001 We are aware that Anadarko Finance Company has incorporated by reference in its Registration Statement on Form S-4 the Form 10-Q for Union Pacific Resources Group Inc. for the quarter ended March 31, 2000, which includes our report dated April 26, 2000, covering the unaudited interim financial information contained therein. Pursuant to Regulation C of the Securities Act of 1933, that report is not considered a part of the registration statement prepared or certified by our firm or a report prepared or certified by our firm within the meaning of Sections 7 and 11 of the Act. Very truly yours, /s/ Arthur Andersen LLP