The Evolution and Hydrocarbon Accumulation of Foreland Basins in Eastern Section of Tethys

Zhang, Guangya ¹; Ma, Feng ¹; Liu, Zuodong ¹; Wang, Suhua ¹
(1)Department of Global Resources and Strategy Research, Research Institute of Petroleum Exploration & Development(RIPED),PetroChina, Beijing, China.

The eastern sector of Tethys located in the southern edge of Eurasian Plate and the northern edge of Indian plate. It is mainly consist of stable Cratons and a series of thrust fold belts. During the late Permian-early Triassic, the closure of the Paleo-Asian Ocean forming foreland basins; In the Triassic, Paleo-Tethys closed leaded the formation of Southeast sag of the Tarim Basins etc; In the Neogene, Neo-Tethys was closing, the large-scale foreland thrust belt formed around the hinge of small cratonic basins, forming the renewable foreland basins. Horizontal distribution is characterized by “cratonic basin surrounded by active thrust belt”; vertical distribution is characterized by multiphase structural superposition of marine facies craton in earlier period, the late Paleozoic marine continental facies craton, the Mesozoic continental depressed basin and the Cenozoic renewable forland basin. In the earlier period marine-facies craton basin, the source rocks are the Cambrian-Ordovician marine carbonate rocks. High quality reservoir is the Paleozoic Reefs beach body. The main cap consists of Marine mudstone in deepwater and evaporite rocks of restricted platform and lithologic trap developed well around the area mentioned above. The Carboniferous-Permian transitional facies source rocks developed in the late Paleozoic cratonic basin, two sets of reservoir are the Carboniferous-Permian volcanic rocks and marine quartz sandstone. In the Mesozoic land facies depressed basin, the Triassic lacustrine/swamp facies mudstone and coal series are major source rocks. The Cenozoic renewable foreland basin develop fan dalta-braided river delta sand as the excellent reservoir during foreland thrust- depression period , evaporate rocks and lacustrine facies compose the main cap in these area. The upper Jurassic evaporate is widely distributed in Central Asia, whereas Western China develop lacustrine facies mudstone and the Cretaceous- Paleogene evaporate in lagoon. The major lithologic traps are the Cenozoic sandstone lens; compressional anticline and faults-related anticline are mainly structure traps. They are common in Western China renewable foreland basin which experienced strongly thrust drape deformation from the Neogene to the Quaternary. The relationship between the formation of thrust belt and the stages of oil-gas reservoirs decides the hydrocarbon potential of Central-western China and Central Asia.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.