Abstract: Gas-Producing Submarine-Fan Deposits of Catskill Delta Complex in North-Central West Virginia
The principal gas producer in north-central West Virginia is the upper part of the 40 to 100-ft-thick (12 to 30 m) Benson interval in the lower part of the Upper Devonian Chemung Group. Stratigraphic analysis of geophysical logs from 1,354 wells and 6 cores from the 1,225-sq mi (3,200 sq km) study area suggests that the productive Benson sandstones are turbidites forming a submarine fan at the toe of the Catskill prodelta slope. Four sandstone units composed of aggregate graded beds offlap westward. The oldest sand unit is the thickest and has an erosive base, progressively waning turbidity flow and sediment supply, and gas pay in thicker turbidites near its base. As the fan grew westward, greater distance from supply and gentler depositional slope accounted for thinner, younger sand nits, lack of erosional scour, upward increase in turbidite thickness, and gas pays in the middle and upper part of the sandstone units. Areally, sandstone-unit facies reflect dispersal patterns of turbidity flows similar to the mid-fan regime of modern submarine fans, forming lobes with channels, levees, and bars separated by interlobes. Burrowing of dark shales between turbidites by a Cruziana community indicates spasmodic turbidity flows in neritic waters. Sorting of argillaceous siltstones and sandstones of the productive Benson is never very good. Statistically significant negative correlation is present between porosity and the amount of argillaceous, organic matter and carbonate content. Porosity and gas production are greatest in inner lobe facies where turbidite beds are thickes and best sorted.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC