Experimental study on electrokinetic properties of porous rock samples

This paper presents the streaming potential experiments conducted in the laboratory with saturated porous rocks in the low frequency domain. The streaming potentials and streaming currents of ten rock samples are recorded by a lock in amplifier. Then the streaming potential coefficients are calculated and analyzed at six different saturation concentrations. The influences of solution concentration, rock permeability and clay content on streaming potential coefficient are studied in order to reveal the relationship between the coefficient and these parameters. The experimental results show that the streaming potential coefficient decreases with increasing solution concentration, while the electrokinetic phenomenon still exists even in solution with relatively high concentration. The results also show that the concave that appeared in the frequency response of streaming potential coefficient is not caused by the electrokinetic property, but the resonance of core-holder. In addition, this work demonstrates that the amplitude of streaming potential coefficient can be directly used to evaluate permeability in the lower concentration that is less than 0.4 mol/L. This study verifies the feasibility of electrokinetic well logging and indicates its application conditions for the experimental measurements.