Pressure-dependent joint elastic-electrical properties of calcite-cemented artificial sandstones

Abstract

Understanding the correlations between the elastic and electrical properties of various types of rocks is the key to the successful joint interpretation of seismic and electromagnetic survey data to provide petrophysical parameters to better assess the subsurface earth. However, the pressure-dependent joint elastic-electrical properties of calcite-cemented sandstones remain poorly understood, even though such rocks are widely distributed in nature and are all experiencing pressures. To obtain such knowledge, a new method has been developed for the manufacture of calcite-cemented artificial sandstones and investigated comprehensively the effects of porosity and cementation content on the confining pressure-dependent joint elastic-electrical properties of the synthetic samples made using the new recipe. Confining pressure is found to more significantly affect the P- and S-wave velocities and electrical resistivity in the samples with higher and lower porosity, respectively, when their cementation content remains the same. On the other hand, cementation content impacts the pressure-dependent elastic and electrical properties more complexly, and the effects of cementation content can be influenced by the minor fluctuation of porosity in the samples, especially at low confining pressures. More interestingly, P- and S-wave velocities are found to approximately linearly correlate with electrical resistivity as confining pressure varies, and the slopes of the linear joint correlations are demonstrated to vary distinctly with porosity and cementation content. The experimental data are interpreted in terms of the competing effects of porosity and cementation content on the microstructure of the samples. The results have helped to reveal the nature that porosity and cementation content find on affecting the joint elastic-electrical properties with varying pressure and have important practical implications for discriminating the porosity and cementation effects that will pave the way to a more successful interpretation of the joint seismic and electromagnetic survey data.