关键词: 鄂尔多斯盆地, 苏里格大气田, 单斜, 岩性圈闭, 河流—三角洲砂体

Abstract: Sulige gas field in Ordos Basin is the largest natural gas field in China.At present,the gas reserves in Carboniferous-Permian have been proven since the beginning of systematic evaluation and exploration in 2000.Sulige gas field is located in the central part of the basin, where there is the favorable geological conditions for forming natural gas.The source rock widely distributed in Ordos Basin was deposited widely in the paralic environment during the Paleozoic.With the deepening and thermal evolution,organic matters were matured or highly matured,which provides the abundant gas sources.The superimposed fluvial-delta sandstones distributed approximately from north to south have constituted the complex sandstone reservoir body in a large area.Under the background of the gentle west-dip monocline,the fluvial-bay pelitic rocks to the east acted as the barriers laterally,and the various deposition face belt to north part as lithologic tight barrier,and the lacustrine pelitic rocks of the Upper Permian as a good regional seal.As a result,a large-area lithologic trap was formed in Sulige area.High content of quarts in continental facies as well as the dissolution and erosion of volcanic matters were favorable for forming the high-porosity and high-permeability reservoirs.The perfect timing of sources,reservoirs,seals,traps and the conditions of preservation provided a fundamental guarantee for forming and preserving the Sulige gas field.

Key words: Ordos Basin, Sulige gas field, monocline, lithologic trap, fluvial-delta sandstone