--> Abstract: Exploration in Mature Areas, by S. S. Foland; #90990 (1993).

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FOLAND, SARA S., Amoco Production Co., Denver, CO

ABSTRACT: Exploration in Mature Areas

The Choctaw play, Arkoma basin, southeastern Oklahoma, is one of the active exploration plays in the United States. The first wells discovered porous Pennsylvanian Spiro sandstone in "blind-imbricate" thrust plates beneath the hanging wall Choctaw thrust fault. Secondary reservoirs were discovered in the Upper Pennsylvanian (Brazil and Cecil) sandstones and in the Lower Pennsylvanian Wapanucka limestone and Cromwell sandstone.

Amoco Production Company has operated or participated in 65 of the total 102 wells drilled since 1987, with an economic success rate of >65%. Approximately 180 mmcf of natural gas is produced daily from these wells. Amoco's success rate is attributed to the innovative use of technologies to define source characteristics and reservoir/trap configurations.

The following geotechnical problems exist: timing of thrusting relative to generation and expulsion, geothermal history of the basin and source maturity, imaging small (+/- 450 ac) imbricate plates at depths in excess of 12,000 ft through hanging-wall section dipping >70 degrees, understanding productive analogies in the basin (the giant Red Oak and Wilburton fields), and determination of the paleogeography of the Spiro shelf.

Amoco used various technologies to address these geotechnical problems, including basin modeling, fission track analysis,

fluid inclusion analysis, depth migration before stack processing, and palinspastic restoration. The Spiro play has matured and the Atokan sand play is the next viable exploration target. The Atokan sands are depositionally more discontinuous than the Spiro, and further disruption by thrusting creates a very complex geometry. To be successful in this new subtle play, Amoco must continue to apply innovative technologies creatively.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.