Seismoelectric effect in a Laboratory setting for Characterizing Geological Cores saturated with either Water or Oil.

Abstract:

Seismoelectric effect belongs to a wide family of Electrokinetic phenomena that arises in heterogeneous systems due to electric charge separation at interfaces. Resulting structure is called an Electric Double Layer (EDL), which is characterized by electric potential drop – Zeta potential. This parameter serves as a major characteristic of liquid-solid interface in liquid dispersion and in porous materials, including geological ones. It varies roughly (in absolute value) from 0 to 100 mV and, therefore, play a major role in the seismoelectric effect, which is proportional to it. Siesmoelectric effect offers opportunity for measuring Zeta potential in geological cores. Phase of the seismoelectric current is pore size dependent, which can be used for characterizing this parameter as well. There are currently hundreds of instruments worldwide that are based on ultrasound for characterizing heterogeneous systems. There are even ISO standards providing guidelines for these characterization techniques, but mostly for concentrated dispersions and emulsions. We are attempting to extend application of these techniques for characterizing geological cores and other porous materials. This talk will present general features of the underlying theory, experimental setup and results for geological cores and several other porous materials. Studying seismoelectric effect in laboratory setting seems to be useful not for characterization purposes only but also for its better understanding on the large scale during seismological tests. This preliminary laboratory experiments reveal factors that affect seismoelectric signal and would allow more adequate interpretation of the seismoelectric signals.