Micro mechanism of seismoelectric effect in the pore

Abstract

A lot of researches have been done on the acoustoelectric conversion in the pore, but most of them treat the electromagnetic field as a quasi-static field, the streaming current and the conduction current are considered equal and opposite(i.e., current balance conditions), and the electromagnetic field in the pore can be further obtained. However, the conditions are only applicable to the steady situation, and it’s inconsistent with the objective facts in the time-varying case. In this paper, a new method was proposed, which decoupled the acoustic field from the electromagnetic field, calculated the seepage velocity in the slit-like pore, and then obtained the streaming current, considering the refraction and reflection by the pore wall, the electromagnetic field was directly solved without using the current balance condition. The conduction current in the pore was calculated, and it’s proved that the conduction current is not equal to the streaming current, and the current balance condition does not hold in time-varying case. The magnitude of electric force and viscous force were compared, which verifies the rationality of ignoring the influence of electric force on the acoustic field in the acoustoelectric effect. The variation of the amplitude and phase of the electric field with the position in the pore was investigated, and it’s proved that the generated electric field is uniformly distributed in the pore. The influence of salinity, viscosity on the seismoelectric effect in the pore was investigated, which plays an important guiding role for the study of the seismoelectric logging.