The Theory of Hydrocarbon Genernation Controlled by Source Rock and Heat from Circle Distribution of Outsideoil Fields and Insidegas Fields in South China Sea

Key words: 
• South China Sea

Abstract: After experiencing threephase tectonic evolution in the Cenozoic, respectively Indiananhai rift period, intercontinent rift period and regional subsidence stage, the South China Sea (in short the SCS) possesses of three tectonic units, respectively continental shelf, continental slope and ocean crust. Surrounding the ocean crust, the distribution of the continental shelf and the continental slope is approximate to ringzone. The sedimentary basins are mainly located in the continental shelf and the continental slope. The basins surround to the center ocean crust zone, too. In the SCS, the action of the petroleum exploration flourished from the end of the 60s in last century and the hundreds hydrocarbon fields, located in the south\\north\\west continental margin, have been discovered so far. Those hydrocarbon fields character as the outsideoil and the insidegas. The oil fields locate mainly in the continental shelf or the area near the land. The gas fields locate mainly in the continental slope or the area near the ocean. In the sags which located in the outsideoil belts, the middledeep lake face mud and Ⅰ&Ⅱ1 types kerogen are dominated in the source rocks. In those sags, the crust is relatively thick and the heat flow is relatively lower. The source rocks are in the oilwindow and produce the crude oil. In the sags which located in the innersidegas belts, the marine facies mud & the onshoreoffshore mud and Ⅱ2Ⅲ types kerogen are dominated in the source rocks. In those sags, the crust is relatively thin and the heat flow is relatively higher. The source rocks produce mainly the gas. In the outsideoil zone, there are several petroleum plays. The sandstone, which formed in the environment of the lake and the shallow marine, is the main reservoir. In the innersidegas zone, there are two petroleum plays, respectively the shallow water sediments and the deep water sediments. The deepwater fan and the reef are the main reservoir. The seal is mainly the marinefacies mud stone. According to the 300m depth, the outsideoil zone, with high exploration, locates mainly in shallow water. The insidegas zone, with lower exploration, locates mainly in the bottom of the continental shelf and the continental slope. Nowadays, in the SCS, the exploration is transferring from the shallow water area to the deepwater area. With the development of petroleum exploration, the SCS, with the enormous hydrocarbon resource that is comparative to that in the rift area in the eastern China or in the Bohai gulf basins, would be the significant potential hydrocarbon area. 