Examination of Methods to Measure Capillary Threshold Pressures of Pelitic Rock Samples

In this work we have examined measurement methodologies of capillary threshold pressure and effects of injected fluid differences. Firstly N-2 gas capillary threshold pressures were directly measured with selected pelitic rock sample using two approaches; step-by-step approach and residual pressure approach. Capillary threshold pressures with these two approaches show different values within the same core sample. Values with residual pressure approach are always lower than those with step-by-step approach. Secondly this pelitic rock sample was also applied for different injected fluids with step-by-step approach; N-2 gas and supercritical CO2 were injected. This experiment shows that the measured value of threshold capillary pressure for supercritical CO2 is smaller by two-thirds than that for N-2 gas. This result also suggests that the measured capillary threshold pressure for supercritical CO2 is larger than the recalculated value from N-2 gas data with the Laplace equation. (c) 2013 The Authors. Published by Elsevier Ltd.