1 EXHIBIT 23 CONSENT OF GAFFNEY, CLINE & ASSOCIATES, INC. As Harken Energy Corporation's (Harken's) independent reserve engineers, Gaffney, Cline & Associates, Inc. (GCA) consents to the reference to GCA's reserve report dated June 30, 2000, as included in this Form 10-Q. Very truly yours, GAFFNEY, CLINE & ASSOCIATES, INC. Dallas, Texas August 14, 2000