Sedimentary facies of the Middle-Upper Triassic Yanchang Formation in Ordos Basin and breakthrough in petroleum exploration
Deng Xiuqin1,2,3, Fu Jinhua1,2, Yao Jingli1,2, Pang Jinlian1,2, Sun Bo1,2
1 Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company，Xi'an 710018，Shaanxi 2 National Engineering Laboratory for Exploration and Development of Low-permeability Oil & Gas Fields，Xi'an 710018，Shaanxi 3 Key Laboratory for Continental Dynamics of Ministry of Education，Northwest University，Xi'an 710069，Shaanxi
Abstract：The Ordos Basin lies across Shaanxi，Gansu，Ningxia，Inner Mongolia and Shanxi Provinces of middle-western China.Its area reaches 2.5×105 km2.The Middle-Upper Triassic Yanchang Formation，more than 1000 m thick，is widely developed in the basin.Alluvial fan，fluvial，delta and lacustrine facies developed well during the Middle and Upper Triassic，and formed the key oil- and gas-bearing layers of the basin.According to the data collected from more than 100 drilling wells in the hinterland basin and many outcrops in the surrounding areas，as well as the long-term exploration and research experiences，we compiled 7 sedimentary facies maps of different oil-bearing intervals of the Middle-Upper Triassic Yanchang Formation of the Ordos Basin.The features of sedimentary facies in different depositional periods of the Yanchang Formation，especially the distribution and evolution of the dark mudstone and shale of the deltas and lacustrine facies，as well as the sand body of the various strand-bars and the gravity flow facies，were illustrated in detail.By the theoretical guidance of the sedimentary facies and lithofacies palaeogeography，the oil exploration of the Yanchang Formation has made great breakthrough constantly in the Ordos Basin.Several large oilfields，with the proved reserve more than 1×108t，such as Shanbei，Xifeng，Jiyuan and Huaqing oilfields，have been discovered in recent years.
Deng Xiuqin,Fu Jinhua,Yao Jingli et al. Sedimentary facies of the Middle-Upper Triassic Yanchang Formation in Ordos Basin and breakthrough in petroleum exploration[J]. JOPC, 2011, 13(4): 443-455.
