Electrical Detection of Shale Gas Layers Based on Wide-Field Electromagnetic Method
摘要
The drilling gas production situation indicates a certain correlation between the shale gas reservoir in the Sichuan Basin and the high and low changes in formation resistivity. These variations are observed in the first member of the Longmaxi Formation to the Wufeng Formation at the bottom of the Longmaxi Formation. Given this correlation and based on the logging electrical data, this study employs the wide-field electromagnetic method (WFEM) to experimentally detect the electrical characteristics of the deep shale gas target layer in the Yibin area of southern Sichuan. The study also tests the regularity and effectiveness of the electrical parameters for evaluating favorable areas of shale gas reservoirs. In terms of specific operation, the structural pattern of the study area is implemented based on the wide-field electromagnetic results and geological data for comprehensive analysis, which identifies the main hidden faults and their influence range on low resistance. The detailed spatial distribution of the upper Ordovician Wufeng Formation and the lower Silurian Longmaxi Formation in the target layer with a buried depth of 2000–5000m is described. This layer exhibits the characteristics of a continuous and stable distribution of organic shale. After verifying the subsequent electrical logging data, the electrical logging curve is found to be essentially consistent with the shape and trend of the wide-field resistivity curve. This consistency demonstrates the effectiveness of WFEM in detecting shale gas layers.