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Regional Geology Summary

North Central Tennessee is part of a regional oil and gas exploration play that has been ongoing since the early 1900’s. The geological extent of the play ranges from Tennessee north into Canada. Shallow carbonate shelf deposits have been deformed in the North Central America region by tectonic events associated with the uplifting of the Nashville Dome (Cincinnati Arch) and the Appalachian thrust belt (Appalachian Orogeny). In the area associated with these two competing tectonic events a series of wrench fault systems were created in front of the Appalachian thrust belt.  Particularly in North Central Tennessee, faults, fractures, and secondary hydrothermal dolomitization have generated excellent porosity in the Knox, Stones River and Sunny Brook formations.

 

Potential hydrocarbon accumulations in North Central Tennessee are associated with the Ordovician Knox, Stones River (Murfreesboro) and the Sunny Brook formations. These reservoirs are contained in primary facies-controlled porosity of the Knox and secondary dolomite brecciated leaching (including karst collapse) in the Stones River and Sunny Brook. The secondary reservoir porosity, evidenced by the dolomitization of the limestone, is activated along faults by the upward migration of magnesium rich hydrothermal waters. This dolomitization of the limestone produces alterations in rock matrix, voids and a weakness of the limestone structure that can result in collapse and a slump of the overlying Devonian Chattanooga shale. This HTD reservoir environment has produced large amounts of oil and gas from relatively shallow and inexpensive well locations.

 

       The Davis Field in Overton County, TN was the site of a single well HTD reservoir discovery in 2000. The # 5 well had an open flow at discovery of 1,100+ bbls per day and produced 125 bbls per day under shut-in gas pressure for the first year of production. Seismic studies of the #5 well showed evidence of a Sunny Brook formation collapse and hydrothermal alteration leading to the development of an HTD reservoir. Currently, on the west and south sides of the property, new discoveries within the last year have had initial production rates from 50 to 400+ bbls per day.