Well-LOG Method for Evaluating the Devonian Shales in the Appalachian Basin

摘要

The Devonian Shale formations of the Appalachian, Illinois, and Michigan Basins are being studied by the Morgantown Energy Technology Center (US Department of Energy) and industry (Eastern Gas Shales Project) in order to accelerate the development of the natural gas potential of the shales. Total gas resource estimates for the Appalachian Basin along range from 3 to 2400 TCFG. Although relatively complete well log suites have been recorded in wells drilled for characterization and stimulation research experiments, the Devonian Shale is an unconventional gas resource and the reservoir is not readily evaluated by conventional well log analysis. The economics of shale wells and the sensitivity of the shales to drilling muds require that an operator be able to evaluate a well using a minimum of well logs, preferably recorded in an empty borehole. Log suites recorded in empty and liquid-filled boreholes have been analyzed from a total of seven wells in three states in the Appalachian Basin. Several techniques were attempted to identify gas- and kerogen-rich and naturally fractured intervals, including construction of resistivity and porosity overlays, calculation of Production Indices, analysis of temperature, bulk density compensation and Sibilation curves. The information extracted from the logs was compared to conventional core desorption (offgas), fracture and geochemical data as well as to computer-generated synergetic logs. A suite of empty-borehole logs has been defined which will yield maximum formation evaluation data at a minimum cost. 10 figures. (ERA citation 08:025546)