塔里木盆地塔中地区志留系柯坪塔格组沉积相与沉积模式

塔中地区志留系自下而上包括柯坪塔格组(下沥青砂岩段、灰色泥岩段、上沥青砂岩段)、塔塔埃尔塔格组（红色泥岩段和砂泥岩段）、依木干他乌组。通过对塔中地区志留系钻井岩心观察和盆地西北部阿克苏、柯坪、巴楚等地露头剖面的观察，塔中地区志留系下沥青砂岩段岩石类型主要为绿灰色泥岩、粉砂质泥岩、泥质粉砂岩、粉砂岩、极细砂岩和细砂岩，部分井发育中细砂岩和中砂岩，砂岩层中常见大量撕裂状泥砾和黄铁矿，发育水平纹理、平行层理、低角度交错层理和楔状交错层理，在露头剖面中可见槽状交错层理。发育的主要沉积相类型为前滨-临滨、浅海陆棚、受风暴影响的浅海砂坝或潮汐砂脊等。在部分井的志留系底部还可见砂砾岩沉积，砾石磨圆较好，砾石成分为石英岩、燧石、泥砾、砂岩砾及其它变质岩砾，向上过渡为中粗砂岩和中细砂岩，发育板状和槽状交错层理，具向上变细的粒序结构，具河流相沉积特征，如塔中30、塔中161井的志留系底部。总体认为塔中地区志留系柯坪塔格组下沥青砂岩段为无障壁滨线-陆棚为主的沉积体系，具有海侵背景下受风暴控制的滨线－陆棚沉积模式, 随海侵发展形成宽度几十公里以上的滨线－陆棚砂岩沉积体，垂向上为滨岸砂到陆棚砂的演化序列。上沥青砂岩段以潮坪沉积为主，并有部分前滨和临滨沉积，横向相变，垂向交互叠置，在砂体发育程度和规模上较下沥青砂岩段差。根据岩心物性和测井物性分析，浅海陆棚沙坝和滨岸沙坝砂岩储集性好于潮坪相砂岩。

Sedimentary facies and models of the Kepingtage Formation of Silurian in Tazhong Area,Tarim Basin

The Silurian is composed of Kepingtage Format ion,Tataaiertage Formatio n and Yimugantawu Formation.Based on analysis of drilling cores and outcrops s uch as Akesu,Keping and Bachu in northwestern Tarim Basin,there are green-grey mudstone,silty mudstone,mudy siltstone,siltstone,fine-grained s andstone a nd medium-grained sandstone in the Lower Part of Silurian in Tazhong Area,with a lot of muddy gravels and pyrites in the sandbodies.The sedimentary structures i nclude horizontal bedding,parallel bedding,lower angle cross bedding,wedge-shap ed cross bedding and trough cross bedding.The authors present that the shore-neritic sedimentary system was developed in the lower bitumen-bearing sandstone member during the Silurian Period in Tazhong Area of Tarim Basin,which is made up of foreshore-nearshore facies,neritic shelf facies,neritic sand bar,tidal ridge facies with m ore storm sediments.There is mainly tidal flat sedimentary system in the uppe r bitumen-bearing sandstone member,which includes foreshore and nearshore faci es.The width of the shore-neritic sedimentary system is tens of kilometers.T he shore-neritic sandstones are good reservoir.