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

Abstract 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 CO 2 were injected. This experiment shows that the measured value of threshold capillary pressure for supercritical CO 2 is smaller by two-thirds than that for N2 gas. This result also suggests that the measured capillary threshold pressure for supercritical CO 2 is larger than the recalculated value from N 2 gas data with the Laplace equation.