The seismoelectric coupling coefficient indicates the strength of seismoelectric conversion. In our study, an experimental apparatus was designed to record the seismoelectric signals induced in water-saturated sandstones in the frequency range from 10K to 500 KHz. The results were interpreted using a micro-capillary model for the porous medium to describe the seismoelectric coupling. The relationship between seismoelectric coupling coefficients and the permeability and porosity of sandstones were also examined theoretically. A general agreement between the theory and the test data indicates that seismoelectric conversion is enhanced by increases in porosity over a range of different frequencies. However, seismoelectric conversion has a complex relationship with rock permeability, that changes with frequency. In the low frequency range (0-50KHz), seismoelectric coupling strengthens with the increase of permeability logarithmically. In the high frequency range (50K-10000KHz), the seismoelectric coupling is at first enhanced, with small increases of permeability leading to small increases in seismoelectric coupling. However, continued increases of permeability lead to a slight decrease in size and image conversion again. The experimental and theoretical results indicate that seismoelectric conversion seems to be more sensitive to the changes of low-permeability samples. This suggests that seismic conversion may have advantages in characterizing low permeability reservoirs.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)