Genetic types and migration-accumulation characteristics of natural gas in China's offshore areas
The major gas-bearing basins(sags)in the offshore areas of China include three basins and four sags,namely the Qiongdongnan Basin,Yinggehai Basin,East China Sea Basin,Baiyun Sag,Huizhou Sag,Bozhong Sag,and Liaozhong Sag.A considerable amount of data reveals that the geological conditions for natural gas accumulation in the offshore areas of China are complex.The genetic types of gas source rocks are diverse;the gas generation intensity and the gas expulsion efficiency vary significantly;the accumulation and transportation patterns are different,and the main controlling factors for gas accumulation differ.This requires that the focus of exploration research should change accordingly.In the Neogene gas-bearing basins in the offshore areas of China,three main types of gas source rocks are developed:The first type is the coal-measure gas source rocks in the transitional marine-terrestrial facies,featuring high organic matter abundance and strong gas generation intensity.Fault-sand bodies are the main accumulation and transportation channels,and faulted anticlines are the main gas accumulation traps.The scale of the coal-measure gas source rocks is the main controlling factor for gas accumulation.The second type is the terrestrial-marine gas source rocks in the littoral and shallow sea environments,with relatively low organic matter abundance and weak gas generation intensity.Mud diapirs are important accumulation and transportation channels,and diapir anticlines and lithologic traps in deep-water channels are the main gas accumulation traps.The accumulation and transportation channels are the main controlling factors for gas accumulation.The third type is the argillaceous gas source rocks in the medium-deep lacustrine facies,with moderate organic matter abundance and relatively high gas generation intensity.Unconformity-sand bodies are the main accumulation and transportation channels,and buried hills and draping anticlines are important gas accumulation traps.The degree of thermal evolution of hydrocarbon source rocks is the main controlling factor for gas accumulation.
China's offshore areanatural gasgas source rockgenetic typemigration and accumulation characteristicmain controlling factor for gas accumulation
万方数据
