Extension of the Gas Research Institute (GRI) method to measure the permeability of tight rocks

Abstract

Different methods have been proposed to measure the permeability of tight rocks such as shales, mudstones, tight sandstones, and carbonates. The Gas Research Institute (GRI) method has been used to measure permeability and porosity of cuttings, crushed particles, or powders. The conventional pulse-decay method has been used to measure the permeability of bulk samples. The GRI method has a potential drawback in that measured permeability may not represent the original complex pore network properly. In this work, an innovative extension of the GRI method was applied to bulk samples with both regular and irregular shapes. A geocellular model was created, history matching was performed to evaluate permeability after constructing a numerical model based on the configuration of the apparatus and initial conditions. Permeability values measured under similar conditions vary from the order of 1E-5 to1E-2 mD for different samples, and the results were validated using permeability values from conventional pulse-decay tests as the benchmark. This approach highlights the simplicity of operation and applicability to irregularly shaped samples, as cylindrical samples are not always available for testing. In addition, this approach significantly shortens the test duration.