3D cross-hole resistivity inversion imaging of surrounding rock based on distance weighting constraint algorithm

Aiming at improving the inversion quality of anomalies near the electrodes in boreholes, which has been a large issue interfering in the three-dimensional (3D) cross-hole electrical resistivity tomography (ERT), an inversion method based on the distance weighting constraint is proposed. Different weighting coefficients are assigned to different meshes in the model according to the distances away from the current points in the boreholes, and the computed exponential decay distribution model is established. Under this treatment, the image shape distortion problem of anomalies near the current points in the boreholes resulting from high inversion sensitivity is suppressed, and the resolution of 3D location and reliability of recognition of anomalies by the 3D cross-hole resistivity inversion method is improved. The effectiveness of the distance weighting constraint inversion is further tested and verified through numerical inversion examples and physical model tests. The distribution characteristics such as the spatial location, scale and shape of the anomalies are reflected accurately in the test results.