Seismoelectric monitoring of producing oilfields: A review
Mehran Gharibi, Laurence R. Bentley, Robert R. Stewart
Seismoelectric phenomena associated with seismic waves and activities have been observed in the laboratory and field for several decades. Geophysical techniques using active seismic sources such as reflection seismic can be modified to adapt the requirements for seismoelectric surveys and observations. Electrokinetic potential is a candidate mechanism to explain the seismoelectric phenomena observed in surveys using artificial seismic sources. Coupled electrokinetic signals are observed at the surface or in the borehole using grounded dipole antennas. Efficient power-line and telluric noise (using remote-referencing) reduction is essential to improve the weak amplitude of the seismoelectric signals. Preamplifier and analog notch filtering of the signals are valuable tools in this regard. Properties of pore fluids and solid matrix can be estimated using the linear relationship between seismic and its accompanying seismoelectric waveforms, which make the technique a possible tool for characterization of porous media. Simultaneous multi-component seismic recording will be a key contribution to estimate the rock and fluid properties of interest.
The delay traveltime concept associated with the seismoelectric signals generated by the positive holes mechanism makes it a plausible tool for monitoring seismically active environments undergoing natural or induced microfracturing such as producing oilfields. A processed pilot study using an array of pairs of grounded dipoles over an active area should be able to evaluate the ability of the technique in monitoring of the microfracturing process.