A laboratory test program was performed to evaluate the physical characteristics of Devonian Shale reservoirs from six wells in the Appalachian Basin, four in Ohio and two in New York. As hydraulic fracturing is a mainstay for increasing well production, the interaction between fracturing fluids, the formation, and proppant in the induced fracture becomes of prime importance. In analyzing the physical characteristics of the core material, three types of tests were performed: physical properties, matrix permeability damage, and fracture conductivity damage.

Results of the physical properties testing indicate that the typical Devonian shale matrix was dense and of low porosity, averaging 2.75 gm/cc and 6 percent, respectively. In situ permeability values of the tested samples averaged 66 μd, with 9 of 13 samples below 10 μd. Fracturing fluid matrix damage tests were performed with three different fracturing fluids for comparison: a water-based gel (cellulose thickener), a nitrogen foamed liquid (75 percent quality), and a brine/CO2 mixture fracturing fluid. Recovery was based on the calculated ratio of final permeability to initial permeability. Results from these tests show better recoveries from those samples exposed to the nitrogen foam, up to 18 percent. Fracture conductivity damage tests were performed with the same fracturing fluids. Results of these tests give recovery values of 35 to 100 percent. Nitrogen foam gave better results. All testing of reservoir material, except some basic physical properties, was conducted at simulated in situ conditions.

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