Evaluation of Accessible Porosity Using Mercury Injection Capillary Pressure Data in Shale Samples

Abstract

We present a novel approach to correct accessible/fluid-saturated porosity values calculated using mercury injection capillary pressure (MICP) for shale samples. On the basis of recent studies, accessible porosity of shale samples calculated from the MICP test is corrected to consider conformance and grain compressibility. However, we show here that the shale samples experience an additional phenomenon during the MICP test that has not yet been addressed, i.e., compression of inaccessible/unfilled pores. Therefore, we propose a general approach consisting of three distinct corrections to accurately estimate accessible porosity of the shale sample using MICP data: (1) conformance, (2) grain compressibility, and (3) inaccessible pore compressibility. First, we develop a mathematical model to estimate both pore and grain compressibility using MICP data and then calculate accessible porosity using the above-mentioned corrections. In the mathematical formulation, we divide the shale matrix into three constitue...