Electrokinetic experimental studies in borehole model II: localized and radiated seismoelectric field

Electrokinetic effects which refer to the coupling between elastic and electromagnetic fields in fluid-saturated porous media have wide geophysical applications, and potential usage in the petroleum exploration. Such effects are related to the relative motion between the solid phase and the pore fluid, due to the electric double layer existing nearby the solid-fluid surface. In this study, electrokinetic measurements are conducted in different borehole models, the localized electrokinetic signals generated in homogeneous medium and radiating electrokinetic signals generated at an interface between different media are recorded and analyzed. Then the conditions of these two kinds of electrokinetic signal and its propagation properties are compared with electrokinetic theory. The relationship between electrokinetic signals and acoustic signals is studied based on experimental data. Then we discuss the influences of source excitation mode, electrode reception mode on electrokinetic signals. The results show that the source modes(monopole or dipole) have great influences on the propagation properties of electrokinetic signals, which is important for the design of electrokinetic logging instrument and the logging data process. The experimental measurements in different boreholes also suggested that the electrokinetic logging might be a potential technique for the oil exploration.