RESEARCH AND APPLICATION OF PERMAFROST DETECTION BASED ON ELECTRICAL RESISTIVITY TOMOGRAPHY

After degradation of permafrost, the periodic freezing and melting in thawing areas will seriously damage the stability of oil pipelines. The 2D and 3D electrical resistivity tomography(ERT) are used respectively to detect the distribution and development status of permafrost in the buried area of crude oil pipelines. To further study the effectiveness of different exploration modes of ERT and resistivity response characteristics of permafrost, firstly, three models for unthawed, half-thawed and through-thawed permafrost are established in the space beneath the pipeline, and EarthImager 2D and EarthImager 3D software are applied for the forward modeling of finite element method and smoothness constrained least-squares inversion. On the basis of numerical simulation results, then, the resistivity response characteristics and differences of inversion results between the three models are compared and the exploration effects of 2D and 3D ERT are summarized. Finally, the results are further verified by exploration practice. The results show that the ERT is an effective method in permafrost survey. The detection effect of 2D ERT on the unthawed and through-thawed permafrost is better than on half-thawed permafrost. The data collected by 3D ERT is more abundant, the display of object morphology is more intuitive and precise, and the inversion results are closer to the theoretical model, which is suitable for permafrost of various melting states. The field examples further verify the numerical simulation results, and the application of 3D ERT also provides a new idea in the field of permafrost fine detection.