Experimental Study on the Relationship Between Capillary Pressure and Resistivity Index in Tight Sandstone Rocks

To further understand the relationship between the capillary pressure and resistivity index of tight reservoir sandstones, we measured these parameters using the semiporous plate method in four tight clayey sandstones from the Junggar Basin, China. To provide a benchmark for analyzing our results, we applied the same experimental procedures to four clay-free, tight Fontainebleau sandstones from the Paris Basin, France. We observed approximate power law relationships between the resistivity index and water saturation for Fontainebleau sandstones and Junggar Basin sandstones, in agreement with the Archie's equation and Waxman-Smits equation, respectively. The capillary pressure and resistivity index data were differently related in the two types of sandstones. We observed a power law correlation for the Fontainebleau sandstones, whereas the Junggar sandstones showed a linear relationship. These differences in behavior appear to be primarily linked to the presence of clays in the Junggar sandstones but not in the Fontainebleau sandstone, and the difference in pore structure between the two types of sandstones.