Eastern Section Meeting

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Exploitation Methods to Rejuvenate Old Oil Fields in Northern Wayne County, Illinois


The Clay City Anticlinal Belt stretches for over 70 miles southwest to northeast from roughly southern Wayne County to northern Jasper County in Illinois. This giant field has produced in excess of 350 million barrels of oil since its discovery in 1937. This study focuses on a small area (600 acres) for detailed geological mapping of multiple Middle Mississippian reservoirs on the southern end of this trend, in order to uncover the proverbial “needle in a haystack.”

Previous production (1950s to 2005) was from the Aux Vases Sandstone (at 3,050 ft) and oolitic limestone members of the deeper Ste. Genevieve Formation, known locally as the McClosky Limestone. Regional studies by the first author over the last 35 years in Clay and northern Wayne counties have identified 5 or more producing intervals in the McClosky Limestone, ranging from 28′ to 130′ below the top of the Ste, Genevieve Formation. By reviewing previous producing intervals relative to regional trends, new potential targets can be identified by drilling deeper in old fields. The study area is on the eastern edge of a large abandoned waterflood, where the Aux Vases was the major producer. There initially appeared to be low or no oil potential. However, drilling of 6 new, deeper wells between 2006 and 2011 by DDC Oil Company of Mattoon, IL, resulted in a rejuvenated oil exploitation target. This drilling extended the field, uncovering new reserves in the Aux Vases reservoir, and deeper oolitic to fossiliferous limestone production in the McClosky member of the Ste. Genevieve. This type of exploitation project, along with maintaining low operating costs can be used as a model for re-exploration and development of what has been termed a “cashcow project”, even in the economic environment of sub $60 per barrel of oil today, and possible near future in the Illinois Basin or mature producing areas.