Electro-seismic effect manifests itself as an electrical potential generated in the subsurface by the passage of seismic waves. It has become a hot topic in the exploration of oil and gas reservoirs in recent years. However, various aspects of the experiments are not well described by the current theory. One shortcoming of this theory is that it ignores the presence of liquid menisci at interfaces and within partially saturated porous media. From other fields, however, such as the science of (wet) granular media or more generally from microscale fluid physics, it is well-known that capillary forces play a crucial role in both the mechanical stability and the dynamics of such systems. The goal of this project is to analyze the role of liquid micromenisci in both the electro-seismic as well as in the inverse electro-seismic effect.
Figure 1: Schematic of liquid menisci trapped by a solid support with an incoming pressure wave. a) surface charges at the pore wall and the screening charge within the Debye layer give rise to electroacoustic (EA) coupling in the standard scenario. b) oscillating menisci emit negative pressure waves giving rise to hydrodynamic coupling between adjacent menisci. c) net charge induced at the meniscus by external electric fields can give rise to additional EA and AE coupling. d) AC electric fields drive a meniscus motion at 2ω because of the quadratic relation between the Maxwell stress and the electric field.
In the lab experiments we measure simultaneously the deflection of micromenisci oscillating under the influence of acoustic and electric fields as well as the electrical and acoustic signal generated by them (Fig.1). We use model porous systems in which all relevant external parameters such as the pore geometry, surface chemistry, meniscus shape, external electrical and acoustic fields can be controlled and measured accurately.
More information:
- contact: Frieder Mugele