Abstract

The search for the elusive fracture-type oil and gas reservoirs in southwestern Virginia’s Lee County has continued intermittently since the opening of the Rose Hill oil field in 1942. Tests as early as 1910 were based on surface oil seeps. Charles Butts, a pioneer Appalachian geologist, recognized several windows eroded through the Pine Mountain thrust plate. Three Lee County oil fields were developed within or near these windows, but a recent increase in drilling has expanded onto the overthrust sheet.

The Ben Hur oil field, 16 mi (26 km) northeast of the Rose Hill pool, was opened in 1963. Since 1981, a burst of exploration has enlarged these two fields and added one new oil field and the first commercial gas well.

Production is obtained principally from a nonporous biomicrite with secondary fracturing, which is locally intense. From 1943 to 1980, 42 wells recorded production of nearly 123,000 bbl or about 3,000 bbl/well. Since 1981, increased oil prices created heightened interest in Lee County drilling, which resulted in production of 128,112 bbl of oil in a 3-yr span, more than during the previous 39 yr.

The Trenton Limestone is generally 400-500 ft (122-152 m) thick, and production has been obtained at depths between 1,300 and 2,500 ft (396 and 762 m). The fracture identification log run by Schlumberger has proven quite useful, but oil shows are also readily noted while air drilling. Many wells respond to an acidfrac stimulation. Exploration for the more highly fractured reservoir areas is presently frustrating, and logical geologic concepts have not replaced plain good luck.

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