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Exploration and Production Results, Morgan County, Eastern Tennessee: Subsurface Fracturing, Oil Production, and Proposed Extension of Clear Creek-Emory River Fault

Julius Egloff

West of the Ridge and Valley province of the southern Appalachians, in eastern Kentucky and Tennessee, the uplifted, less disturbed Paleozoic carbonates are capped by Pennsylvanian sandstones of the Cumberland Plateau. Great faults and escarpments outline overthrust allochthonous and reentrant autochthonous blocks, and the reentrant blocks presently produces oil and gas. Morgan County, Tennessee, an exploration frontier, occupies much of the reentrant block. The Appalachian orogene changes its trend near Morgan County and the adjoining Oak Ridge-Knoxville area, which is centered on the reentrant block. The Jacksboro fault, striking N30°W on the south side of the Pine Mountain Overthrust block (northeast Tennessee and Kentucky), is the northern boundary of the autocht onous block and is the analog to the Emory River fault, striking N55°W on the southern side of the same block. Where they erode a gorge in the fault trend, the Emory and Obed Rivers and the lower course of Clear Creek mark the distinctive northeastern limit of the Cumberland Overthrust.

Early maps and the east-central geologic map of Tennessee indicate the trace of the Cumberland Overthrust extends from the Emory River (and Obed River) gorge generally marking the cross fault, to the Hatfield Mountain faults trending east-west along the outcrop of the thrust fault. Subsurface tests and varied results in oil and gas production indicate the Emory River fault extends northwest along Clear Creek, where its gorge extends approximately N45°W, and fracturing trends northwest across the Clear Creek and Douglas Branch oil and gas fields. Another study proposed that Clear Creek follows part of the Cumberland Overthrust faulted boundary.

Several Monteagle oil and gas wells had initial potential of hundreds of barrels of oil/day. The Luchin Unit 1 was drilled directly into a highly fractured reservoir and blew out at over several thousand barrels of oil/day. The fracture zone is noted for gas, unusual amounts of condensate, and 40° + API oil. Source beds are probably in the Knox Formation, and migration to the Monteagle Oolitic Limestone is via the cross fault. The Jacksboro fault extends northwest of the south end of Pine Mountain in the same way the Clear Creek-Emory River fault seems to extend northwest of Hatfield Mountain, across the Clear Creek and Douglas Branch fields. The distribution of oil and gas wells and the volume of apparent reservoir and production capacity also indicate relative distribution of f acturing across the cross fault trend. Below the Trenton (Sunnybrook) and Pencil Cave, the deeper formations should differ little due to overthrusting.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.