Application of complex resistivity method to the exploration of marine shale gas in the Nanling Basin, Anhui Province
YIN Qi-Chun1,2(), WANG Yuan-Jun1, ZHOU Dao-Rong1, ZHANG Li3, SUN Tong2
1. Nanjing Center, China Geological Survey, Nanjing 210016, China 2. Harbin Comprehensive Survey Center of Natural Resources, China Geological Survey, Harbin 150081, China 3. Geological Exploration Technology Institute of Anhui Province, Hefei 230041, China
The main part of the Nanling Basin in Anhui Province is a red Mesozoic continental basin, under which the distribution of marine strata is still undetermined and the potential of shale gas resources is unidentified. Based on the physical property characteristics that the Permian organic-rich shale reservoirs around the study area contain pyrite, this study carried out a geological survey of shale gas using the complex resistivity method. Specifically, this study designed an observation system suitable for the different geological characteristics inside and outside the basin, conducted fitting and inversion using Cole-Brown and Cole-Cole models, and plotted maps of near-field parameters electromagnetic resistivity and apparent charging rate. The results show that: (1) The Permian organic-rich shale contains high carbonaceous content and rich pyrite particles and has distinct characteristics of low resistivity and high polarizabi-lity. Therefore, it can be effectively distinguished from its surrounding rocks, which is favorable for the shale gas exploration using the complex resistivity method; (2) Polarizability is an effective parameter that can be used to identify deep organic-rich shale strata and even shale gas reservoirs; (3) Drilling tests were carried out based on the exploration results obtained using the complex resistivity method, successfully discovering the Triassic carbonate strata and predicting that below the red basin in the Nanling Basin is the favorable area of Permian shale gas reservoirs. This study demonstrates that the complex resistivity method can detect pyrite-bearing shale strata with a depth of greater than 2,000 m and a cumulative thickness of about 200 m in the Nanling Basin and is the only method that can directly indicate shale gas reservoirs in electromagnetic exploration. Therefore, the complex resistivity method can be applied to the geophysical prospecting of the marine shale gas in the Nanling Basin with complex geological conditions and even Southern China. The results of this exploration also provide a basis for the further exploration of the marine shale gas in the Nanling Basin.
殷启春, 王元俊, 周道容, 张丽, 孙桐. 复电阻率法在安徽南陵盆地海相页岩气勘探中的应用[J]. 物探与化探, 2022, 46(3): 668-677.
YIN Qi-Chun, WANG Yuan-Jun, ZHOU Dao-Rong, ZHANG Li, SUN Tong. Application of complex resistivity method to the exploration of marine shale gas in the Nanling Basin, Anhui Province. Geophysical and Geochemical Exploration, 2022, 46(3): 668-677.
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