Study of Low-Permeability Sandstone by Unidirectional Mercury Intrusion Porosimetry

Abstract

In light of the fact that the results of conventional mercury intrusion porosimetry experiments may not always be accurate, unidirectional (linear) mercury intrusion porosimetry was employed to construct capillary pressure curves, determine the pore size distribution and pore structure of four low-permeability sandstones under different effective stress. Analysis results show that for the same sandstone sample, the capillary pressure curve obtained by unidirectional mercury intrusion porosimetry deviates from the curve obtained by conventional mercury intrusion porosimetry, and the deviation becomes more apparent with increasing effective stress; the inlet capillary pressure in the unidirectional mercury intrusion porosimetry experiment is higher than that in the conventional mercury intrusion porosimetry experiment; with the same mercury saturation, the capillary pressure in the unidirectional mercury intrusion porosimetry experiment is higher than that in the conventional mercury intrusion porosimehy experiment; the maximum mercury injection saturation in the unidirectional mercury intrusion porosimetry experiment is lower than that in the conventional mercury intrusion porosimehy experiment and decreases with increasing effective stress; the average mercury injection value in the unidirectional mercury intrusion porosimetry experiment is higher than that in the conventional mercury intrusion porosimetry experiment and increases with increasing effective stress; the sorting coefficient determined by unidirectional mercury intrusion porosimetry is slightly different from that found by conventional mercury intrusion porosimetry; finally, the skewness of the capillary pressure curve obtained by unidirectional mercury intrusion porosimetry is greater than that obtained by conventional mercury intrusion porosimetry. Therefore, unidirectional mercury intrusion porosimetry makes it possible to measure capillary pressure with a high level of accuracy.