Research on the ability to explore the edge of electromagnetic removal of electromagnetic remains based on HIE-FDTD simulation

Abstract

Accurate detection of residual oil and gas in deep anisotropic reservoirs is critical for improving the efficiency of energy resource utilization. However, conventional cross-well electromagnetic approaches encounter significant challenges when modeling sub-metered scale geological structures characterized by strong resistivity anisotropy and thin-layer stratifications. To address these limitations, a hybrid implicit-explicit finite-difference time-domain algorithm incorporating a thin plate mesh, enabling high-precision 3D forward modeling of low-frequency cross-well electromagnetic fields. Numerical experiments demonstrate that the proposed method effectively resolves sub-meter-scale geological structures while maintaining computational efficiency. In sandstone-mudstone formations (background conductivity: 0.05 S/m), cross-well electromagnetic measurements achieved optimal signal-to-noise ratios for residual oil detection. By studying the response mechanisms of fine cross-well residual oil to cross-well transient electromagnetic fields, it was found that when a low-conductivity body is located in the center of the cross-well electromagnetic transmitter-receiver coils, the y component of the magnetic field strength (Hy) shows the change process from negative to positive, which serves as a robust diagnostic for residual oil and gas. Further investigation of anomalous bodies with varying conductivity shows that oil-bearing and water-bearing layers can be distinguished according to the onset timing of the negative Hy anomaly. Therefore, this method provides a reliable and high-resolution approach for the accurate localization of cross-well residual oil and gas resources, with substantial strategic value for strengthening national energy security and promoting the efficient development and utilization of oil and gas resources.