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.