Reservoir-forming condition analysis and favorable zone prediction for the shale gas in the Upper Paleozoic Taiyuan Formation in the Ordos Basin

摘要

Shale gas is a hydrocarbon gas occurring in organic-rich argillaceous shale in a free and adsorbed state. The shale in shale gas reservoirs is source rock and also container rock, which is different from the situation in conventional gas reservoirs; the gas content in shale is mainly related to the abundance, type, and evolution degree of organic matter. The Taiyuan Formation in the Ordos Basin is marine-continental transitional sediments; the argillaceous shale of the Taiyuan Formation has features such as high organic matter abundance and high thermal evolution degree and has better reservoir-forming conditions, compared with the shale gas reservoirs outside China. The argillaceous shale in the Taiyuan Formation strata is mixed with thin gas-bearing sand layers, which indicates a high hydrocarbon-generating potential of the argillaceous shale. According to the main reservoir-forming conditions of shale gas, it is predicted that the favorable zones of shale gas in the Taiyuan Formation are primarily located in areas such as the northwestern corner of the Tianhuan Depression, the northeastern corner of the Shanbei Slope Belt, and the central and southern parts of the Ordos Basin. With the rapid progress in shale gas exploration and exploitation technologies, the shale gas in the Taiyuan Formation in the Ordos Basin has become an important exploration target because of its huge potential.