关键词: 志留系, 滨岸, 浅海陆棚, 准层序组, 层序格架, 油气藏

Abstract: The Silurian is composed of upper member of Kepingtage Formation, Tataaiertage Formation and Yimugantawu Formation from the bottom to the top.There are grey and grey-white fine sandstone, middle sandstone and siltstone, green-grey mudstone, silty mudstone, mudy siltstone in Silurian in Tazhong area. The author presents the shore-neritic shelf depositional system, in which sandstone body types include shore beach, tidal flat, neritic sand bar, shelf sand and etc. Foreshore-nearshore beach facies, neritic sand bar, neritic shelf facies were developed in the lower bitumen-bearing sandstone member during Silurian period in Tazhong area, Tarim basin. There are mainly tidal flat depositional system in the upper bitumen-bearing sandstone member and Tataaiertage Formation and Yimugantawu Formation. There are transgressive, aggradational and progradational parasequence sets, in which the superimposition by different parasequences constitutes the three third-order sequences of Silurian stratum .Sequence correlation shows Silurian transgression onlapped from northwest to southeast direction. The sandstone body, developed in transgression system tract (TST), better reservoir are mainly located near the maximum marine flooding surface, i.e. the favorable position for marine sandstone body development would be the upper part of TST and the lower part of high system tract (HST). Silurian oil/gas show and bitumen-bearing sandstone mainly distributed in the third-order sequence near the maximum marine flooding surface. Oil/gas reservoirs types include lithologic reservoirs, which are superimposed by many bedded sandstone lens in vertically and horizontally, and fault-anticline reservoirs controlled by structures.