Tectonic Evolution and Petroleum Potential of Tarim Basin in the Northwestern China: ABSTRACT

Abstract

The Mesozoic-Cenozoic Tarim basin is 560,000 km{sup 2} in area and overlaps the Precambrian Tarim craton. The sharp unconformity on top of the basement marks the Tarim movement through which the Tarim craton was converted into a stable area. There are numerous oil-generating rocks in Tarim basin. Based on comprehensive studies, it is concluded that the oil of Shacan 2 well in the Northern uplift is derived from marine algae and lower aquatic precursors and is a highly matured, migrated, and biodegraded petroleum. The oil was sourced from Ordovician and Cambrian source rocks, which are the main sources of petroleum in Tarim and are widely distributed. The Carboniferous-Lower Permian carbonaceous mudstone and carbonate of marine facies in the western Tarim are also source rocks, but of secondary importance compared with those of the lower Paleozoic. Dark mudstone and coal seams in Upper Triassic and Jurassic lacustrine-swamp facies are also important source rocks in Tarim basin. They are widely distributed in Baicheng, the Southwestern and the Central depressions and are proved to be oil sources in Yiqikelike and Kekeya oil fields and in the oil seeps of the Kashi area. Upper Cretaceous-Paleogene carbonate, clastic, and salt-gypsum assemblages could be source rocksmore » in the Southwestern depression, but need to be studied. Miocene dark mudstones of lacustrine facies are probably source rocks in Kashi, Kuqa, Awati and Yiecheng areas. The petroleum reserves of Tarim basin are hard to estimate because large-scale exploration has been going on for just a few years. The Chinese explorationists believe that the reserve of petroleum in the whole Tarim basin is in the range of 70 to 130 billion barrels. After recent testing of the Tazhong 1 well in the Central depression, some Chinese experts have even more optimistic estimates.« less