OHIO'S FIRST ORDOVICIAN SHALE-GAS BOOM: IMPLICATIONS FOR CURRENT UTICA-POINT PLEASANT EXPLORATION FROM NINETEENTH-CENTURY WELLS IN WESTERN OHIO

Present-day Ordovician Utica-Point Pleasant oil and gas exploration and production in eastern and central Ohio was preceded by extensive drilling of the same interval in the western part of the state during the 1880s. Spurred by significant oil and gas discoveries in the Trenton Limestone in northwestern Ohio in 1884, numerous wells were drilled along the Cincinnati-Findlay arch between 1885 and 1887. Evaluation of historical drilling records from western Ohio, in conjunction with recent geophysical logs and core, indicate both gas and oil were encountered in the Utica Shlae-Point Pleasant Formation, as well in shales and limestones of the overlying Cincinnati Group. While most gas shows were limited, initial production exceeded 100 MCF per day with production lasting several years in some wells.

Of particular relevance to current Utica-Point Pleasant exploration in the region is the fact that the productive wells of the 1880s are situated in areas considered the thermally "immature" as determined by CAI/R₀ analyses of potential Ordovician hydrocarbon source lithologies. The association of gas with limited oil shows in some wells, as well as gas shows in relatively organic-poor (< 1% TOC) parts of the interval, indicates a likely long-distance (~100 km) migration of hydrocarbon from more deeply-buried source rocks to the east. If this is the case, the most prolific gas occurrences reported from the historical records are likely associated with fracture-related porosity. Additional analyses of potential Ordovician source rocks in western Ohio cores are needed to confirm these hypotheses. Collectively, available data indicate that continuous, internally sourced Ordovician hydrocarbon reservoirs do not exist west of the more thermally mature portions of the basin.