Geology of Wasson Field, Yoakum and Gaines Counties, Texas

ABSTRACT The Wasson field is near the central part of the Staked Plains or “Llano Estacado,” in southern Yoakum and northwestern Gaines counties, Texas. It occupies a triangular area 15 miles long and 14 miles wide, containing approximately 55,000 acres or 86 square miles, and is defined at only a few points by dry holes. Geologically, the field lies on the extended axis of the Central Basin platform, but appears to be separated from it by a trough in northern Gaines County. For the purpose of this paper the structural-stratigraphic feature under discussion is referred to as part of North Basin platform. Two major axes, one trending N. 60° W., the other N. 30° E., combine with several minor parallel axes to form a compound structure. The combined effect of the structural elements gives the whole the appearance of a terraced platform tilted northeast by post-Permian movement. The stratigraphy is typical of West Texas, in that massive, porous dolomites with few clastics are present and grade basinward into thicker sections of interbedded dolomite and anhydrite containing more clastic material. The section penetrated by wells consists of: Recent, Tertiary, Cretaceous, Triassic, and Permian rocks. The reservoir is in porous dolomite 300–600 feet below the top of the San Andres formation. Detailed examination of the well cuttings show the body of the reservoir to have a reef-like cross section which may be accounted for by (1) physico-chemical deposition on a submarine “high,” and (2) reef growth with attendant chemical deposition and recrystallization of the dolomite. The combination of Permian structure and stratigraphy appear to have controlled the permeability, porosity, and the accumulation of fluids. Later folding has modified the position of these fluids somewhat but for the field as a whole there is no direct relationship between the present structural elevation and the ability to produce oil. The discovery well, the Honolulu Oil Corporation and the Davidson Drilling Company’s Bennett No. 1, found oil on September 28, 1935. Development has been continuous since 1936 and 42,631,627 barrels of oil had been recovered from the field by Jan. 1, 1943.