Application of mercury injection capillary pressure to mudrocks: Conformance and compression corrections

Mercury injection capillary pressure (MICP) is a commonly-used technique for measurements of porosity, pore throat size distribution, and injection pressure vs. mercury saturation for many types of rocks. The latter two are correlated to and can be used to estimate permeability. Problems for MICP application in mudrocks are associated with two types of system errors: conformance and compression effects. These two sources of error are well-recognized, but no standard procedures to correct them exist. In this study, a new method for conformance and compression corrections was developed, and the method applied to five Eagle Ford Shale samples. Conformance correction is based on comparison of mercury injection volume vs. pressure curves between epoxy-coated and uncoated samples. Compression correction is based on calculation of compressions before and after mercury intrusion in MICP experiment. Different types of compressions are quantified and compression corrections on porosity, pore throat size distribution, and injection pressure vs. mercury saturation are performed. Porosity and permeability were calculated based on corrected MICP data. Results show that both conformance and compression corrections are important for accurate MICP porosity calculation, whereas conformance correction is more important than compression correction in permeability calculation.