Genetic Types,Migration and Accumulation of Oil & Gas and Exploration Proposal in North Marginal Basins,South China Sea

Different types of oil gas in the Cenozoic passive continental margin basin of Northern South Sea show a certain regularity based on the complex geologic setting,earth dynamics,and diversified appearance of oil and gas geology.Until present reseach and exploration of oil and gas,the discovered oil and gas can be divided into three types,such as biogenic and sub-biogenic gas,normal mature oil gas,high-and over-mature oil gas.Three types of non-hydrocarbon gas can also be identified.Types of gas hydrates include thermally decomposed gas(mature and high mature gas),biogenic gas and sub-biogenic gas,and the later is prior.The biogenic and sub-biogenic gases are wide distributed in the shallow study area and sea floor.The normal mature continental paraffin oil gas were mainly distributed in the North Sea basin and the faulted depression zone of the Pearl River Mouth basin.The high-and over-mature coal-type condensates were mainly found in the Yanan sag of Qiongdongnan basin and continental shelf area of the Zhusan depression in the western Pearl River Mouth basin.Coal-type gas and non-hydrocarbon gas(i.e.CO2) were mainly accumulated in muddy diapiric zones of the Yinggehai basin,the Eastern Qiongdongnan basin and deeply faulting areas of the Pearl River Mouth basin.Oil gas in deep water and gas hydrates were accumulated in the faulted depression zones of the southern Qiongdongnan basin and the continental slope deep water of the faulted depression zones in the southern Pearl River Mouth basin.So it enhances the exploration success rate by selecting the expected oil gas areas and optimizing the drilling well at favorable accumulation of oil and gas,base on the spatial distribution of different types oil and gas.