UNCONVENTIONAL RESOURCE POTENTIAL OF ORGANIC-RICH DEVONIAN SHALE FORMATIONS, EASTERN OHIO, USA

The United States has become the leading producer of hydrocarbons, largely through unconventional shale development. Approximately 50% of all dry shale gas production and 25% of all tight oil production in the country is attributed to Devonian shales. Eastern Ohio hosts seven organic-rich shale units throughout the Devonian interval. Despite the abundance of these organic-rich shales, most of the reservoir characterization effort has focused solely on the Marcellus Shale. The Ohio Department of Natural Resources, Division of Geological Survey currently is engaged in a project appraising the hydrocarbon and CO₂-sequestration potential of organic-rich Devonian shales in eastern Ohio. This research is being conducted with funding provided, in part, by the Midwest Regional Carbon Sequestration Partnership funded by the U.S. Department of Energy.

Geophysical well log interpretation, source rock analysis, and thermal maturity data characterize the nature of these units. Two organic-rich shales of significant thickness occur in the area of interest: the Huron Member of the Ohio Shale and the Rhinestreet Member of the West Falls Formation. Gross isopach maps suggest relatively uniform deposition across the basin throughout the Rhinestreet Member interval and a shift in depocenter from north to south during deposition of the Huron Member. Net reservoir maps suggest organic constituents were deposited and preserved in the deepest part of the basin throughout deposition of the Rhinestreet Member. However, net reservoir maps of the Huron Member suggest that organic constituents were either not deposited or not preserved in the deepest parts of the basin. The relationship between net and gross isopach maps of the Huron Member suggests organic matter was deposited and preserved on a distal ‘shelf’ beyond the prograding Catskill Delta Complex. Coupled with source rock analyses and thermal maturity maps, these data indicate significant hydrocarbon and CO₂-sequestration potential in the Rhinestreet and Huron Members of eastern Ohio.