Geological Characterization and Site Selection for Enhanced Oil Recovery, Lawrence Field, Illinois

Stephen Whitaker, Bruce Schonert, Jon Brenizer, and Bryan Clayton
Rex Energy Corporation, Bridgeport, Illinois 62417 [email protected]

Whereas the ongoing EOR/ASP project at Lawrence Field in Illinois is showing great promise for improving production from a mature oil field, it has also illustrated the need to conduct detailed geological and engineering studies in order to select optimal sites and to maximize recovery. In-depth geological studies of the lower Pennsylvanian Bridgeport sandstone have revealed numerous individual sandstone deposits with varying degrees of internal heterogeneities. These individual sandstones were deposited in a predominately deltaic environment and exhibit characteristics of incised valley-fill, splay, point bar, and estuarine bar accumulations. Each individual sandstone reservoir exhibits porosity values ranging from 16% - 28%, with average values of about 21.5%. Permeabilities vary up to 1400 millidarcies horizontally and up to 1200 millidarcies vertically. Highly permeable layers affect secondary and tertiary flood performances and can act as thief zones, significantly affecting sweep efficiency. Due to these characteristics, coupled with the varying salinities of fluids used in previous floods, calculating oil saturations and therefore targets for tertiary recovery efforts is somewhat problematic. The use of carbon/oxygen logging is one method that may help define remaining oil-rich targets within the field. Once an area is selected, modeling and simulations can help to determine injection and production patterns in order to optimize sweep efficiency.

AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009