This paper describes a new laboratory technique to evaluate the properties of a naturally fractured, low permeability core sample. We specifically determine (1) the porosity of the matrix, (2) the permeability of the matrix, (3) the effective width of the fractures, and (4) the permeability of the fractures.

New laboratory equipment has been designed and constructed to conduct pressure pulse tests in either a homogeneous or a fractured core sample. Analytical solutions have been developed to model gas flow in a fractured core sample during a pressure pulse test. An automatic history matching program has been developed to analyze the laboratory measured pressure transient data using the analytical solutions. The new technique has been used to measure the matrix and fracture properties in twelve naturally fractured, Devonian Shale cores.

The technique we developed in this research is new to the petroleum industry. Our laboratory equipment is unique, and the analytical solutions have not been published in the literature. With this technique, we can measure matrix properties as low as 10−9 md. This is a significant step forward in permeability measurement because the lowest permeability that most existing laboratories can measure is about 10−6 millidarcies.

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