DISTRIBUTION OF HEAT FLOW IN CENOZOIC BASINS OF SOUTH CHINA SEA AND ITS CONNECTION WITH OIL AND GAS MIGRATION AND ACCUMULATION

The South China Sea is located in the juncture of the three tectonic blocks of Eurasia, India-Australia and the Pacific. The regional geological background and earth dynamic conditions are rather complicated. The characteristics of deep crust vary in different types of continental margin, and as the result the distribution of heat flow are of difference significantly. The north continental margin of the South China Sea is prevailed by rift basins with typical double-layer structure. With the thining of the continental crust from north to south, and the occurrence of transitional crust, heat flow increases accordingly. Taking the distribution of hydrocarbon into account, there is oil in the north and gas in the south. However, the south and southwest continental margin of the South China Sea is a composite continental margin under a complicated dynamic condition characterized by the superimposition of bending-stretching, compression and strike-sliping. There form the bending-stretching and compression composite basins and strike-sliping composite basins. Heat flow is higher here rather than in the north continental margin. Therefore, this region is rich in gas with a small amount of condensate oil and light oil. Many gas fields but a little of oil fields have been discovered. Data suggest that heat flow is one of the controlling factors on oil and gas migration, accumulation and distribution. And the distribution pattern of heat flux depends on the geological background, the nature of deep crust and the alteration of earth's crust thickness of the region. Oil and gas accumulation and distribution are closely related to the heat flow distribution pattern.