Integrated Exploration Method Used in Search for Stratigraphic Traps in Illinois Basin: ABSTRACT

Abstract

A new oil pool was discovered in Marion County, Illinois, during 1988, using this integrated approach. The discovery is within 2.5 mi of the Salem field, which was discovered in 1938 and has produced more than 387 million bbl of oil. Numerous seismic surveys have been conducted in the area since the Salem field discovery over 50 years ago. Using structure maps developed from the available seismic data, well control, and depositional models, a Ste. Genevieve (middle Mississippian Valmeyeran) prospect was developed on the northeast flank of the Salem anticline. The initial well encountered 8 ft of oil-saturated oolitic limestone in the McClosky zone of the Ste. Genevieve Limestone. Subsequent drilling resulted in four additional oil wells. The size of the reservoir is approximately 120 ac with primary recovery estimated at 200,000 bbl of oil. The depth of the reservoir is 2,250 ft, with an average porosity of 14% and permeability of 300 md. The trapping mechanism is stratigraphic - an oolite bar draped across a gentle nose, which was originally interpreted from the seismic information. Numerous analogous situations exist in the Salem anticline area as well as near other large structures in the basin. An integrated exploration approach canmore » help define these areas and lead to commercial discoveries in mature areas.« less