Microwave-Induced Thermoacoustic Imaging of Subsurface 3D Water-Oil
Displacement in Porous Sand
Abstract
The process of two-phase fluid displacement in the porous medium is
still poorly understood partly due to the absence of effective
reconstruction methods featured in a 3D real-time fashion. This
manuscript proposes the application of thermoacoustics (TA) imaging, an
emerging real-time imaging technique, to reconstruct the dynamic
surfactant-enhanced imbibition process into the oil-saturated sand. It
is both theoretically and experimentally demonstrated that a significant
TA contrast exists between the water-saturated sand and oil-saturated
sand under the same microwave power. In the experiment, a U-shaped
infiltration path is embedded 20mm underneath the oil-saturated sand as
the ground truth profile of the water flow. A calibration process is
conducted to account for the amplitude attenuation and velocity
dispersion effects of the TA wave in the sand, and a two-layered medium
sensing matrix is built for the inversion process. The reconstructed
images match well with the infiltration path, which makes it feasible to
monitor the subsurface 3D water-oil displacement in non-transparent
porous sand in a real-time fashion.