Experimental studies of streaming potential and high frequency seismoelectric conversion in porous samples

Streaming potential across a porous medium is induced by a fluid flow due to an electric double layer between a solid and a fluid. When an acoustic wave propagates through a porous medium, the wave pressure generates a relative movement between the solid and the fluid. The moving charge in the fluid induces an electric field due to the seismoelectric conversion. In order to investigate the streaming potential and the seismoelectric conversion in the same rock sample, we conduct quantitative measurements with cylindrical and plate samples of Berea sandstone 500 saturated by NaCl solutions with different conductivities. We measure the electric voltage (streaming potential) across a cylinder sample in solutions with different conductivities and under different pressures. In a solution container, we measure the seismoelectric signals induced by acoustic waves at different frequencies and solution conductivities. We calculate the quantitative coupling coefficients of the seismoelectric conversion at DC and high frequencies with samples saturated by solutions with different conductivities. According to the streaming potentials, we calculate the theoretical coupling coefficients at the DC and high frequency range. The experimental and theoretical results are compared quantitatively and their differences are discussed.Massachusetts Institute of Technology. Earth Resources Laborator