Yates Field, West Texas: Geology of a Permian Basin Giant

Abstract

Yates field, which produces oil largely from Late Permian San Andres dolomites, was discovered in 1926 and logged its billionth barrel in 1985. It is remarkable for the size of its original oil in place (four billion barrels estimated) and for its early ability to produce hundreds to thousands of barrels per hour from individual wells at depths of less than 2,000 ft. The high quality of the reservoir has been related to the following geologic characteristics: (1) a broad anticline with significant closure located at the apex of regional structure which formed a trap for large volumes of primary and secondary oil; (2) a vast integrated system of porosity (ranging from intergrain/intercrystal pores to joints, fractures, and small caves) that imparts high storage capacity and transmissivity to the reservoir dolomites; (3) a thick, efficient seal of anhydrite capping the reservoir sequence; and (4) high flowing pressures during much of the history of the field. The western area of the Yates field reservoir is dominated by peritidal to lagoonal mudstones and wackestones; the eastern area, by shallow subtidal packstones and grainstones. These depositional facies reflect both aggradation and eastward progradation of upper San Andres carbonates. Effective engineering management of the more » field has followed from a recognition of the quite different reservoir qualities in the two areas of the field and from adapting secondary and tertiary recovery techniques to constraints imposed by the geologic factors listed above. « less