Oil and Gas Exploration in Appalachian Overthrust Belt of Southwestern Virginia: ABSTRACT

Abstract

Hydrocarbon exploration is on the upswing in the southwestern Virginia portion of the Eastern Overthrust Several potential reservoir horizons have been identified on surface exposures, but remain untested. Major faults, including the Saltville and Pulaski thrusts, have as much as 16,000 ft (4,877 m) of displacement, suggesting potential structural traps in the largely allochthonous belt. Excluding the Early Grove gas field and the oil fields of Lee County, only a small number of wells have tested the strongly folded and faulted 20,000-ft-thick (6,100 m) sequence of Paleozoic sediments in the Valley and Ridge province. Seismic and leasing activities indicate several significant tests in the near future. The Early Grove gas field was developed on an anticlinal flexure within the Greendale syncline. The field produced gas from porous anhydrite beds in the Lower Mississippian Little Valley Formation until shut-in in 1957. Five new wells since March 1980 have encountered near-virgin pressures in the old Little Valley pay zone and have discovered significant gas in the sandstones of the Price Formation. Detailed field mapping near Rose Hill, Lee County, identified several fensters through the folded Pine Mountain overthrust block, and most oil exploration efforts have been concentrated in those windows. Recently, fensters near Ben Hur have also proved successful targets. Production is from shallow fractured carbonates of the Ordovician Trenton formation. An 8,020-ft (2,444 m) test by Shell Oil discovered a deeper major thrust, proving the allochthonous structure of the area, and indicating potential deep targets. An ARCO test now being drilled will help to evaluate the deeper possibilities. End_of_Article - Last_Page 1165------------