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Petroleum systems of Chinese nonmarine basins


Wenzhi Zhao, PetroChina Exploration and Production Company, Beijing 100011, China. E-mail:


The petroleum systems of Chinese nonmarine rifted and depression basins, dominated by lacustrine strata, have distinctive source rocks, reservoir types and trap characteristics. The rifted basins are characterized by numerous faults and multiple structural salients and sags (half grabens). Sags include many subdivisions and smaller isolated sags. Most sags constitute relatively independent petroleum systems that have efficiently generated and expelled hydrocarbons, have excellent reservoir properties in a variety of sand-body types, and have multiple traps. These attributes impart a petroliferous character to the entire sag. Depression basins (intracratonic flexural basins) developed on large cratons and hosted large lacustrine systems. They feature very gentle structure, large deltaic sand-bodies, source rocks in extensive contact with sand-bodies, heterogeneous low-porosity-low-permeability reservoirs and large, widespread lithology-controlled pools. In recent years, large oil and gas reserves have been discovered in these two types of lacustrine-dominated basins, contributing significantly to the growth of reserves in onshore China, and stratigraphic oil and gas pools have become the major type of accumulation in nonmarine lacustrine basins.