Seismogenic Deformation within the Utica/Pt Pleasant Reservoir in Northern Pennsylvania
The Upper Ordovician Utica/Pt Pleasant interval in north-central Pennsylvania has seen significant hydrocarbon exploration and development since 2012. Ongoing activity has provided an inventory of penetrations through an interval previously represented by only a handful of data points. Core from Seneca Resources’ DCNR 007 94H revealed an interval of severely deformed bedding approximately 25 feet (8 meters) thick within the gross reservoir interval of the Utica/Pt Pleasant. This zone is characterized by soft sediment deformation (load structures, possible flame structures), fracturing and brecciation of carbonate-rich zones, significant swings in dip. Bed boundaries immediate above and below this zone return to abruptly to flat bedding. This zone of deformation has been identified in other wells throughout north-central Pennsylvania, including a Seneca Resources’ well in northwestern Cameron County, the SRC WT 2353 214HU. Descriptions of this zone will make the case for deformation soon after deposition. While primary identification of deformation is through core observation and description, correlation with porosity logs indicate that this zone may be identified and mapped without direct visual evidence. The timing of the deformation interval is constrained using a vertical profile of inorganic-fraction 13C measurements. Indications are that the deformed zone was deposited after the widely-recognized Guttenberg Isotopic Carbon Excursion (GICE). Additionally, the position of the deformed zone within the isotopic record indicates that it is synchronous across several counties (at least) within northern Pennsylvania and southern New York. Given the nature of deformation observed in well data, the spatial distribution and thickness of the interval of interest, and the synchronous deposition across the study area, a seismogenic origin is the leading contender for this zone within an active hydrocarbon play.
AAPG Datapages/Search and Discovery Article #90373 © 2019 AAPG Eastern Section Meeting, Energy from the Heartland, Columbus, Ohio, October 12-16, 2019