The thinking about selecting strategic areas of oil-gas resourcesfor marine facies basins in China

摘要

The strategic principle of oil and gas exploration is two "lay equal stress on both", is decided by the tectonic evolution of Paleo-contiental in China, the nature and forming of basins, the transforming process of basins and mountains, the distribution of oil and gas of China and so on. Strategic disposition of oil and gas exploration all of country should be lay equal stress on both marine and land territory, and on land territory should be lay equal stress on both marine facies basins and land continental facies basins. In view of global tectonic, Tethyan structural territory, one of four tectonic territories in global scale, is concentrated 68% oil and gas resources reserves, and especially concentrated marine basin in Mesozoic. The marine basin in paleo-continent in China are mainly belonged to Paleozoic Era, and only early to middle Triassic Period in Mesozoic Era. The stable marine basins developed on the cratonic basement, including Tarim basin, Sichuan basin and Ordos basin, are important exploring and exploiting areas of oil-gas resources. The three basins contain one-third oil resources and half of proved reserves of China, especially they hold in 66% of gas resources and 87% proved reserves of China. Two tectonic layers of marine basins are developed in Calidonian epoch and Hercynian-early Indochina epoch. In Early Paleozoic, the hydrocarbon rocks of Marine basins deposited transgressive sequence and regressive sequence separately. From late Paleozoic to early Indo-Chinese epoch, the transgressive sequence of sea level principal ascending times developed reservoirs primarily, hydrocarbon rocks secondly. The deposition of the regressive sequence in sea level principal descending times developed hydrocarbon rocks and reservoirs equally. Oil-gas exploring and exploiting practice has recovered that the middle -western three big marine basins had generality in the developing of hydrocarbon rocks, reservoirs and pool-forming features. The middle-western marine prototype basins have the same depositional evolution and depositional sequence, developed five sets hydrocarbon rocks: Upper Sinian series, Lower Cambrian series, Lower Ordovician series, Middle-Upper Ordovi-cian series, Lower Silurian series. Caledonian movement formed failed foreland basins, paleo-uplifts, deep basins with hydrocarbon-bearing strata by tectonic tilting, many paleo-exposed and erosional surfaces, and erosional zones. Carbonate rocks with paleo-karst and overlapping in late Paleozoic formed the system of reserving and accumulating. Paleogeographic migration and time deference of tectonic evolution resulted in the diversity between Northern basin and Southern basins in China.