塔里木盆地塔中地区志留系层序格架、砂体类型与油气藏分布

塔中地区志留系由下至上发育有柯坪塔格组上段、塔塔埃尔塔格组和依木干他乌组,主要岩石类型为灰色、灰白色中细粒砂岩、粉砂岩、泥质粉砂岩与绿灰色、浅灰色、灰色粉砂质泥岩、泥岩,总体上为滨岸(海滩、潮坪)—浅海陆棚沉积体系,发育有滨岸海滩、潮坪、浅海砂坝、陆棚砂等砂体类型,其中滨岸海滩、浅海砂坝、陆棚砂等砂体主要发育于柯坪塔格组上段下部,潮坪砂体主要发育于柯坪塔格组上段上部及塔塔埃尔塔格组和依木干他乌组。发育退积型、加积型和进积型三种准层序组类型,不同准层序组叠加构成了志留系三个三级层序,从层序对比分析可看出塔中志留纪海侵是由西北向东南方向逐步上超的过程。砂体主要发育于海侵体系域(TST),最好的储层位于最大海泛面附近,即海侵体系域上部和高水位体系域的下部是海相砂体的最佳发育场所。志留系油气显示及沥青砂岩分布的层段主要分布在三级层序的最大海泛面附近,油气藏类型为由多个层状砂岩透镜体在垂向和平面上叠置的岩性油气藏和受构造控制的断背斜油气藏。

Silurian Sequence Framework, Sandstone Body Types and Oil/gas Reservoirs Distribution in Tazhong Area, Tarim Basin

The Silurian is composed of upper member of Kepingtage Formation, Tataaiertage Formation and Yimugantawu Formation from thebottom to the top.There are grey and grey-white fine sandstone, middle sandstone and siltstone, green-grey mudstone, silty mudstone, mudysiltstone in Silurian in Tazhong area. The author presents the shore-neritic shelf depositional system, in which sandstone body types includeshore beach, tidal flat, neritic sand bar, shelf sand and etc. Foreshore-nearshore beach facies, neritic sand bar, neritic shelf facies were developedin the lower bitumen-bearing sandstone member during Silurian period in Tazhong area, Tarim basin. There are mainly tidal flat depositionalsystem 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-ordersequences of Silurian stratum .Sequence correlation shows Silurian transgression onlapped from northwest to southeast direction. The sandstonebody, developed in transgression system tract (TST), better reservoir are mainly located near the maximum marine flooding surface, i.e. thefavorable 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, andfault-anticline reservoirs controlled by structures.