Slopes of the pressure-dependent elastic-electrical correlations in artificial sandstones

Seismic and electromagnetic explorations are two of the most successful geophysical applications for understanding the subsurface earth, and the joint interpretation of seismic and electromagnetic survey data can help to better characterize the rocks because they contain independent and complementary information about the rocks. However, the success of the joint interpretation depends on the understanding of the correlations between the elastic and electrical rock properties and their influencing factors. Confining pressure is an important geological parameter that has been found to give rise to linear elastic-electrical correlations in sandstones. However, it is still poorly known what controls the slopes of the pressure-dependent linear correlations, even though slope is one of the most important parameters determining the linear correlation. We make artificial sandstones with controlled porosity and permeability, respectively, and measure their pressure-dependent elastic (electrical resistivity) and electrical (P-wave velocity) properties simultaneously, as well as porosity. We show that the slopes of the measured electrical resistivity versus P-wave velocity as an implicit function of confining pressure correlate positively with the compliant porosity in all the samples. The results not only reveal the petrophysical parameter that controls the slopes of the pressure-dependent linear elastic-electrical correlations in sandstones, but also provide a basis for the discrimination of the slope-controlling parameter from the simultaneously measured elastic and electrical properties.