Saturation-dependent Coupled Seismic and Electromagnetic Wave Propagation in Porous Media

Abstract:

The seismoelectric effect where acoustic/seismic waves are converted into electromagnetic waves and vice versa, is of importance for hydrocarbon exploration as it is complementary to the conventional seismic surveys. Also for the detection of orebodies (for example massive sulfides), seismoelectric techniques are promising. For hydrological purposes, seismoelectric techniques can provide us with information as well, mapping for example water tables and water-retentive layers. Also for mapping of water-bearing strata beneath glaciers or monitoring of ice fracturing, seismoelectric methods are argued to be very powerful as they can distinguish between conductive and non-conductive layers that have similar acoustic impedances and thus cannot be mapped in conventional seismic surveys.

We designed and developed an experimental setup in which acoustic to electromagnetic (EM) wave conversions at interfaces can be measured. Theoretical results are obtained with an electrokinetic full-waveform theoretical model, where use was made of the Sommerfeld approach. Using bimodal samples, different fluid-solid interface effects and saturating fluids were investigated. The contrast between water and water-saturated porous glass samples is larger than the contrast between water and oil-saturated porous glass samples. The contrast between water and water-saturated Fontainebleau sandstone is larger than the contrast between oil and water-saturated Fontainebleau sandstone. These data are shown to be in good agreement with theoretical predictions on the basis of the Biot-Pride theory.