ABSTRACT: An Overview of Sub-Devonian Plays in the Appalachian and Black Warrior Basins

MILICI, ROBERT C., Virginia Division of Mineral Resources, Charlottesville, VA

Lower Paleozoic strata in the Appalachian and Black Warrior basins produce and have the potential for producing significant amounts of hydrocarbons. In the Black Warrior basin, production is from Cambrian and Ordovician carbonate strata (Knox, Middle Ordovician).

Cambrian, Ordovician, and Silurian carbonate and siliciclastic strata produce hydrocarbons around the periphery of the Appalachian basin. A little production occurs in the deformed belt on the east side of the basin (Knox, Trenton, Tuscarora); more production occurs to the north (Theresa, Trenton, Queenston, Medina, Lockport); and even more to the west, on the Cincinnati arch (Knox, Trempeleau, Rose Run, Stones River, Trenton, Clinton).

Lower Paleozoic shales and limestones apparently are the chief sources for hydrocarbons produced from sub-Devonian strata. In some places, however, overlying Devonian shales are the source for these hydrocarbons.

Thermal maturation increases eastward across the Appalachian basin. With minor exception, oil occurs only to the west of the Allegheny front. The eastern limit of gas production is in the western Valley and Ridge.

Porosity in older carbonate sequences is related to solution and pervasive alteration caused by fluid migration from regional unconformities, and to tectonically induced fractures. Fractures are the dominant type of porosity in overlying Middle and Upper Ordovician limestones and shales. In Silurian sandstones, intergranular porosity commonly is augmented by fractures.

Trapping mechanisms include a variety of geologic structures and stratigraphic traps.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)