ABSTRACT: Reservoir Geology of the Basal Pennsylvanian "Buchanan" Sandstone, Lawrence Field, Illinois

BANDY, WILLIAM F., JR., Vincennes University, Vincennes, IN

Fluvial sandstones of the Pennsylvanian-age Caseyville Formation lie directly above the Mississippian-Pennsylvanian unconformity in central Lawrence field. These reservoirs, termed "Buchanan" by local drillers, have produced successfully from hundreds of wells since the pay was first discovered in 1906. In spite of the extensive development history, successful wells can still be drilled in the area. Buchanan sands occur in two paleogeographic settings: sands deposited in a paleovalley, and younger sands deposited in a fluvial complex on the flanks of the paleovalley.

Structure maps on top of the upper Buchanan sands reveal that the best initial production occurred from structural highs. These structural highs still contain significant, unproduced columns of oil. The lower Buchanan sands, while less prolific, have produced oil where thick shale has blocked updip migration, or on structural highs where the upper Buchanan sands are missing. Completion is best achieved with cable tools which can penetrate the top of the reservoir while avoiding the underlying water and preventing mud invasion.

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)