Distribution of gypsum-salt cap rocks and near-term hydrocarbon exploration targets in the marine sequences of China

Through reverse thinking,we summarize the status of research in the field of subsalt hydrocarbon exploration,analyze the distribution characteristics for gypsum-salt cap rocks,and discuss the potentiality and targets of subsalt hydrocarbon exploration within marine seuences in china.Gypsum and salt are excellent cap rocks which widely occur in the marine sequences of Tarim and Sichuan basins.Subsalt reservoirs are large in resource volume and are the main targets of future exploration.In southern China,gypsum-salt cap rocks mainly occur in the Lower-Middle Cambrian and Lower-Middle Triassic,in addition to the Cretaceous and Paleogene.The gypsum-salt cap rocks are extensive in lateral distribution but large in differences in different areas.For example,the Lower-Middle Triassic gypsum-salt cap rocks are closely related to hydrocarbon distribution in Sichuan Basin.The Cambrian and Lower-Middle Triassic gypsum-salt cap rocks are relatively thick and are the best seals for the marine reservoirs.The Carboniferous gypsum-salt cap rocks also occur in central Hunan province.Moreover,se-veral gypsum-salt cap rocks also exist in Tarim Basin.For the Tarim platform-basin area,there are two sets of major cap rocks,i.e.the Cambrian and the middle-upper Carboniferous gypsum-salt cap rocks,especially the former is the major regional seal.The Cambrian gypsum-salt cap rocks in Bachu-Maigaiti area are large in both areal distribution and continuous thickness.Taking the overall geologic conditions for hydrocarbon accumulation in subsalt area into account,especially the controlling factors of slope and hinge zone for hydrocarbon accumulation,the paper suggest five plays or fields as the major targets of near-term exploration in southern China and Tarim Basin.