Measurements of Streaming Potential and Seismoelectric Conversion in Berea Sandstone

Abstract

When an acoustic wave propagates in an electrolyte-filled porous medium, the relative movement between the solid and the fluid induces a seismoelectric field due to the movable charges in the electric double layer (EDL). In order to investigate the DC streaming potential and the seismoelectric conversion in the same rock sample, we conduct measurements with cylindrical and plate samples of Berea sandstone 500 saturated by NaCl solutions with different conductivities and at different frequencies, respectively. We observe the seismoelectric EM wave induced by a single sine wave at the surface of the rock sample in a water tank. We investigate the standing acoustic fields generated by a continuous acoustic sine wave in the water tank. A multi-cycle acoustic wave burst is applied to induce a seismoelectric signal for measuring the coupling coefficients of the seismoelectric conversion. Using the streaming potentials, we calculate the theoretical coupling coefficients at DC and at high frequency range with Pride’s equations. The experimental and theoretical results compare well. We discuss the agreements and the differences between the measured and theoretical values. Based on the seismoelectric coupling coefficient at high frequencies, we may estimate the electric amplitude of the seismoelectric signals induced in field seismoelectric measurements.