Analysis of shale gas geological conditions of Paleozoic in Yanyuan area

To further explore the potential of shale gas resources in southwest China, the Chengdu center of China geological survey (CGS) conducted a non-profit basic geological survey of shale gas in Yanyuan area. Based on the systematic geological survey and sedimentology study, the geological conditions of shale gas in the Yanyuan area are analyzed. It is found that two sets of organic-rich shale series,the Silurian Longmaxi Formation and the Devonian Pojiao formation, in Early Paleozoic in Yanyuan area. The Silurian Longmaxi Formation is dominated by carbonaceous siliceous shale and carbonaceous silty shale.It is characterized by rich organic matter, high silica content and development of graptolite, and it developed in the deep shelf environment. The Devonian Pojiao Formation is dominated by calcareous carbonaceous mudstones and calcareous carbonaceous silty mudstones.It is mainly characterized by rich organic matter, high clay content and development of tentaculites, and it developed in the lagoon environment. The two sets of organic-rich shales are with the characteristics of high organic matter contents, the huge deposition thickness, the high degree of thermal evolution, the high brittleness index, the low porosity and the low permeability. A large number of broad-gentle synclines occurred in Yanyuan area, which has good shale gas preservation conditions. Shale gas exploration has also achieved good results, with hydrocarbon shows obtained in the Silurian Baizitian Formation and the Devonian Pojiao Formation in the area. It indicates that shale gas in Yanyuan area has an excellent exploration potential. The research results provide a reference for regional hydrocarbon exploration and evaluation.