Computer Analysis and Synthesis of Stratigraphy and Petroleum Geology, Upper Cambrian Strata, Morrow County, Ohio: ABSTRACT

Abstract

Computer analysis indicates that hydrocarbon accumulations found at the tops of paleogeomorphic features on the Knox unconformity surface of Morrow County, Ohio, are controlled primarily by structural trapping. In the subsurface of Morrow County, the Knox unconformity separates dolomite of the Copper Ridge formation (Cambrian) from the shales, limestones, and dolomites of the Middle Ordovician Chazy formation. A computer-generated three-dimensional plot of the Copper Ridge Dolomite surface reveals a pattern of northwest-southeast trending erosional remnants which exhibit up to 150 ft (46 m) of local relief and resemble a karst topography. The distribution of erosional remnants is believed to be controlled by paleodrainage patterns. The primary reservoir rock is the Copper Ridge Dolomite. The rocks of the overlying Chazy Limestone have buried the erosional remnants and serve as the trap for Copper Ridge Dolomite accumulations. Trend surface analysis of horizons above and below the Knox unconformity indicates a regional structural dip of 50 to 55 ft/mi (9.5 to 10.4 m/km) toward the east. Negative residuals from the trend surface analysis, which border the eastern edge of production, indicate folding and the existence of a structural trap in Morrow County. Hydrocarbons migrating up structural dip (to the west) were initially caught in the structural trap and then accumulated at the tops of erosional remnants on the Knox unconformity surface. End_of_Article - Last_Page 563------------