To understand the deep structure characteristics and the distribution and lithology of the main Devonian-Permian shale gas strata on the southwestern side of Southeast Hunan Depression, the authors carried out the processing and qualitative-quantitative analysis of data from four magnetotelluric sounding profiles in Yuanjia syncline. Based on the apparent resistivity section, impedance phase analysis and two-dimensional continuous media inversion of magnetotelluric sounding data and combined with the geological characteristics and physical properties of the study area, the authors found out the location, nature and development characteristics of main fractures as well as the spatial distribution of the main geological formation (electrical layer). On such a basis, the favorable shale gas strata exploration was discussed. The results show that the majority of the faults trend in SN, NE and NW directions in the Yuanjia syncline, showing structures such as "listric style" and "flat and ramp style" in the section. The Upper Permian Longtan Formation has high quality gas-bearing coalbed and good exploration prospect of coalbed methane. The low resistance shale of the lower member of Middle Devonian Qiziqiao Formation is continuous and thick, and hence it can be regarded as a favorable exploration shale formation.
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