RESERVOIRS IN THE MAJOR OIL-GAS-BEARING DEEPWATER BASINS OF THE WORLD AND THEIR CHARACTERISTICS

A large quantity of oil and gas resources is reserved in the offshore deepwater basins of the world. The occurrence of high quality reservoirs is the necessary condition for forming large hydrocarbon accumulations. A comprehensive study of 24 key deepwater oil-gas-bearing basins of the world, mainly from the Atlantic deepwater and the Neotethyan domain was carried out by the authors, including those in the Gulf of Mexico, eastern Brazilian continental margin, West African passive continental margin, Mid-Norway continental shelf, Northwest Shelf of Australia, South China Sea, Bay of Bengal, and the Mediterranean (Nile Delta). Forming ages, tectonic settings, and depositional environments of the main reservoirs were summarized, and the distribution patterns discussed. Results show that the main reservoirs of the deepwater oil-gas-bearing basins in the world were formed in the time of Cretaceous and Peleogene. The age of main reservoirs in the Atlantic deepwater basins show a distribution pattern of older in the north and younger in the south, whereas the main reservoirs in the Neotethyan deepwater basins are dominanted by the Peleogene. Most of the reservoirs were formed in the drifting stage. In the Atlantic deepwater basins, the main reservoirs are characterized by rifting in the north, and drifting in the south, and the main reservoirs in the Neothetyan deepwater basins were mainly formed in the drifting stage. As far as the sedimentary environment is considered, the main reservoirs in the deepwater basins are dominanted by abyssal turbidite and fluvial-deltaic sandstones. In the Atlantic deepwater basins, the distribution pattern of main reservoirs shows a trend with the littoral-neritic facies in the north, and abyssal facies in the south, while the main reservoirs in the deepwater basins in the Neotethyan domain is characterized by fluvial-delta-littoral-neritic facies.