Sesimic stratigraphy, a technique for improved oil recovery planning at King Field, Jefferson County, Illinois

High-resolution seismic reflection data have been used to delineate reservoir and nonreservoir facies and to provide a means to improve oil recovery in mature fields. Detailed reservoir characterization of the Mississippian-age Aux Vases Formation at King Field, Jefferson County, Illinois, suggests that this reservoir is a compartmentalized, mixed siliciclastic-carbonate system. The Aux Vases reservoir sandstone at King Field occurs at a depth of 2 750 feet, is rarely greater than 20 feet thick, and is considered to be a seismically thin bed because its thickness is below the calculated seismic-tuning thickness of 60 feet. Old electric wireline logs, the principal data available for King Field, were used to create pseudo-velocity logs, which were subsequently used to create synthetic seismogram models of the facies changes. Comparison of synthetic seismograms with seismic data acquired from King Field indicates that amplitude variations of seismic reflectors can differentiate reservoir sandstone facies from laterally adjacent nonreservoir calcareous lithofacies. Seismic reflection character analysis was successfully applied to King Field for the high-velocity, nonreservoir, calcareous facies that laterally separate lower velocity reservoir sandstones into compartments. This type of seismic stratigraphic analysis offers a cost-effective technique for optimizing the placement of injector and producing wells in a secondary or tertiary recovery program. In newer fields, seismic reflection data would be useful for planning the development drilling program. Although this study dealt with a mixed siliciclastic-carbonate depositional system, seismic stratigraphy could be used in other formations in the Illinois Basin where there is a distinct contrast in seismic impedance between reservoir and nonreservoir facies.