--> Unconventional Resource Potential of the Sunbury Shale, Berea Sandstone, and Antrim Shale in Central Michigan

AAPG Eastern Section Meeting

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Unconventional Resource Potential of the Sunbury Shale, Berea Sandstone, and Antrim Shale in Central Michigan

Abstract

The Early Mississippian to Late Devonian Sunbury Shale, Berea Sandstone and Antrim Shale are part of a total petroleum system found throughout the Appalachian and Michigan basins which is responsible for significant petroleum generation, migration and production. The Antrim Shale is known for its high TOC's although it has various degrees of maturity across the area. The Berea sandstone is a shallow oil and gas reservoir in the Appalachian Basin and has limited production in the Michigan Basin. Some of the oldest production in Michigan is from the Berea sandstone where it has produced from several fields in and around Midland County. The latest significant Berea production was developed in the Williams field starting in 1980. The Berea sandstone in the Williams field is a deltaic to marine deposit with offshore bar development. The Williams field is a combination strat-structural trap and to date nearly 2 million barrels of oil has been produced in the field from the Berea sandstone. Although the Berea is primarily a conventional target in the last few years operators started using horizontal wells to explore for these sands especially in eastern Kentucky. The production in Kentucky is from shallow (<2000'), half-mile laterals which can produce as much as 40 MBO per well. Operators are considering horizontal drilling in the Sunbury-Berea-Antrim interval in central Michigan however, poor data on Berea reservoir character combined with low commodity prices have stalled new development. An interesting characteristic of the upper Antrim shale under and around Williams field is the resistivity changes from an average of 100 ohm-m outside of Midland County to an average of more than 1000 ohm-m underneath the field area. Maps of the high resistivity area show an apparent relationship between shallow oil production in central Michigan. The initial thought was this area of high-resistivity represented areas of mature hydrocarbon (oil-prone) generation however, maturity studies showed the Antrim to be barely mature in the area. Additional migration studies are needed to understand the hydrocarbon potential of the Sunbury-Berea-Antrim sequence.