NICK, KEVIN E., Target Reservoir Analysis, Oklahoma City, OK; and BOB SANDRIDGE, Continental Resources Inc., Enid, OK

ABSTRACT: The Ames Crater: Origin and Reservoir Characteristics of a Buried, Ordovician Impact Structure, Major County, Oklahoma

A meteor impact in the early Ordovician is interpreted to be the origin of the Ames Crater and its associated oil and gas reservoirs. Potential reserves of up to 50 MMBO and 40 MMCF of gas are present in and around the crater located in Major County Oklahoma (T20-21N, R9-10W). The morphology of the crater is presently best defined by a structure map on the Sylvan shale which indicates a circular depression with steep walls about 8 miles in diameter. The circular feature is also obvious on gravity maps. The Sylvan structure map also indicates the rim of the circular feature is raised and the depressed floor of the feature contains small, raised and depressed features. The gross size, shape, and details of the floor suggest an impact origin for the crater. Analysis of conventional and s dewall core samples, cuttings, and logs show that the rim of the crater is Arbuckle dolomite and that the crater floor is dominated by a complex assemblage of giant blocks ofArbuckle dolomite; breccias of dolomite; breccias of granite; and mixed granite-dolomite breccias, pebble conglomerates, and litharenites. The crater filling material is allocthonous. Quartz grains with shock lamellae and highly altered, vesicular lithologies have been identified from arenites and conglomerates in the crater floor. These lithologies and textures strongly support the impact origin. The reservoirs are overlain by Simpson shale (Ordovician) and consist of many structural traps with intergranular porosity between clasts and dissolution porosity within dolomite and granite rock fragments.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.