More than 60 countries are practising oil and gas exploration in the worldwide deep waters. The regions of deepwater exploration effective are mostly in the passive continental margin basins. The tectonic evolution of these basins can be classified into either rifting-depressing or rifting-drifting ones. In these basins, lacustrine source rock was dominant during the rifting phase and paralic deltaic and transitional source rock during the late rifting and the drifting phases. Organic matter in source rock is commonly sourced from terrigenous detritus. The development of transitional source rock depends on terrestrial sediment supplies while that of marine source rock depends on original productivity of sediments. In the region of South China Sea, the deepwater source rock that developed in various sedimentary environments may be lacustrine, paralic deltaic, transitional or less marine.