The Cambrian-age Potosi Dolomite of the Knox Group in Illinois is a significant reservoir target for the sequestration of carbon dioxide (). The Potosi was originally deposited in a shallow intertidal to subtidal environment and has a major diagenetic overprint of karst processes. There were vuggy intervals (up to 2.1-m [7-ft] thick) present that have caused lost circulation of drilling fluid to occur when penetrating through these intervals. This article used data from Decatur, Illinois, to illustrate a case study of integrating well data, core, and 3D seismic reflection data inversion to create a reservoir model, extrapolating the 3D seismic porosity cube to a larger area beyond the 3D seismic volume and then performing reservoir simulation of injection into the Potosi. A waste injection project approximately 64 km (40 mi) to the east suggested that high volumes of injection are possible. Project results illustrated that seismic inversion might reduce the uncertainty of the distribution of the lost circulation intervals. The reservoir flow simulation suggested that the Potosi is a viable target for sequestration.