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ABSTRACT: Atoka Detrital--A Rediscovered Pay in the Midland Basin, West Texas

Magell P. Candelaria

Since the dramatic downturn in the oil and gas industry in 1986, there has been increasing emphasis placed on exploration in mature basins close to existing production and on maximizing recovery from existing fields through low-risk recompletions. An example of a long-unrecognized recompletion interval that also provided renewed exploration potential in a mature basin is the Atoka detrital in the Midland basin of west Texas. The Atoka was aggressively pursued by a variety of operators, small independents, and majors alike, before unstable oil prices, among other factors, forced many operators to curtail their activity. The Atoka play consists of one or more 10-20 ft porous detrital bioclastic to siliciclastic turbidite and/or density current deposits within deep-water org nic-rich, siliceous shale. The Atoka detrital had produced from isolated one-well fields for over 20 yr before being rediscovered several times, purely by chance, by different operators. In each of four discoveries a gas kick was noted in the Atoka shale while drilling on structure for deeper objectives. Chance completion of one well in the detrital interval in each of four instances led to discovery of four Atoka detrital fields with combined cumulative recovery of over 10 MMBO to date.

A drilling show that was previously attributed to shale gas was reinterpreted as evidence of a thin, widespread reservoir that offered significant recompletion potential and lay behind casing in many well bores. This reservoir was subsequently developed into several new fields.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990