Delineating the Utica Shale/Point Pleasant Formation Play System to Determine the Influence of the Precambrian Basement on Deposition in Northeastern Ohio, Jarrod R. Bridges, S.F. Austin State University
The Utica Shale/Point Pleasant Formation system has recently become a highly developed unconventional target for oil and natural gas production, leading to an increased desire for knowledge of the controls on deposition of this system. Precambrian basement features have long been known to affect deposition of older strata near these features across Ohio, but the effects of far field tectonics is not fully agreed upon. Precambrian faults and lineaments are known to exist and have been mapped, but are thought to have ceased their influence on deposition by the time of the Knox unconformity during the Cambrian. In the cases of the Ordovician Utica Shale, Point Pleasant Formation, Trenton Limestone, and the Black River Group, many believe that the deposition of these strata were not affected by Precambrian faults/lineaments or other basement features, rather their main influence was changes in sea level due to basin loading, climatic changes, and localized uplift/subsidence. The objective of this study was to determine if the deposition of these younger strata was influenced by Precambrian faults and basement features. This was to be done by analyzing a group of oil and gas wells in Lorain, Cuyahoga Lake, Geauga, Ashtabula, Trumbull, Mahoning, Stark, Portage, Summit, Wayne, Ashland, and Medina counties in northeastern Ohio. Electric well logs from these wells were added to Petra, a geological mapping program, and the tops of the Utica Shale, Point Pleasant Formation, Trenton Limestone, and the Black River Group were picked. These tops were then contoured into four structure maps and four isopach thickness maps. These maps were analyzed with known Precambrian faults and lineaments, along with known Precambrian basement features, to determine if these Precambrian influences affected the deposition of these Ordovician strata. It is known that high spatial resolution structure maps show contour offsets across known and inferred structural features. It is also known that high spatial resolution isopach maps show thinning and thickening across known and inferred structural features. The purpose of this study was to take these methods and apply them to the Utica Shale/Point Pleasant Formation system in order to determine structural influence from the Precambrian basement on Ordovician strata in northeastern Ohio.