PETROLEUM GEOLOGICAL CHARACTERISTICS AND OIL-PROSPECT EVALUATION OF THE TRIASSIC AND THE JURASSIC IN THE QIANGTANG BASIN, TIBET

The Qiangtang Basin, which is developed on the Pre-Devonian crystalline basement and the Upper Paleozoic epimetamorphic folded basement, is a composite residual basin dominated by the Mesozoic marine deposit. It consists of the North Qiangtang Geotectogene, the Central Mole Track and the South Qiangtang Geotectogene three secondary tectonic units, and mainly developed the Triassic and the Jurassic two sets of source rock-reservoir-cap rock assemblages. The Triassic and the Jurassic assemblages developed well in the North Qiangtang Geotectogene. There is scarcely the Jurassic assemblage and the Triassic assemblage is only distributed in the pitching parts within the Central Mole Track. In the South Qiangtang Geotectogene, the Ttiassic assemblage developed well, and the Jurassic assemblage exists well in some regions. The hydrocarbon exploration practice in the Qingzang Plateau shows that the oil prospect of this area depends on the strong and weak of tectonic movement and the good and bad of preservation conditions. Considered the information of source rock-reservoir-cap rock assemblages, the Qiangtang Basin can be divided into three types of prospective oil lands: the North Qiangtang Geotectogene favorable region, the South Qiangtang Geotectogene favorable region and the Central Mole Track subfavorable region.