【摘要】 塔中地区志留系柯坪塔格组下沥青砂岩段是塔里木盆地古生界碎屑岩层系油气主要富集层段之一。以钻井岩心观察描述为基础,结合测井、地震和分析测试资料进行综合分析,提出了塔中地区志留系下沥青砂岩段发育海侵背景下的滨岸-潮坪-辫状河三角洲沉积体系的观点。其中滨岸相沉积中主要发育上临滨和下临滨沉积微相,岩性以细砂岩、粉砂岩、含砾不等粒砂岩为主;潮坪沉积相中障壁砂坝、潮砂滩、潮汐水道、砂坪沉积微相发育,潮道沉积的岩性以砂岩、粗砂岩和含砾砂岩为主,发育楔形、板状和羽状交错层理,底部见侵蚀冲刷面和较多黄铁矿团块;辫状河三角洲中发育辫状河水下分流河道、分流间湾、前缘席状砂等沉积微相。海侵时期,下沥青砂岩段存在4期超覆砂体,从盆地中部向南部的塔中低隆逐期超覆,沉积微相在平面上也由此存在着复合超覆规律的演变,整体表现为滨岸相至潮坪相、辫状河三角洲沉积相沉积的演变。4期超覆沉积微相的平面分布在控制因素、展布范围和海侵方向上具有一定的继承性、相似性和规律性。更多还原

【Abstract】 The lower bitumen-bearing sandstone Member of Kepingtage Formation in Tazhong Area is one of the major oil and gas-rich layers in Palaeozoic clastic rock series in Tarim basin.Based on description of drilling cores,combined with logging,seismic and test data,it is showed that transgressive shore-tidal-braided-river delta depositional system was developed in target stratum.Littoral facies is made up of up-nearshore and down-nearshore microfacies,whose lithology includes fine sandstone,siltstone,pebbled anisomerous sandstone.Tidal flat facies is made up of tidal sand bar,tidal channel,sand flat microfacies.The sediments of tidal channel mainly include sandstone,gritstone and pebbled sandstone.Its sedimentary structures include wedge shaped cross bedding,tabular cross-stratification,and herringbone cross-bedding.There are some erosion surfaces and lots of pyrite in the bottom of tidal channel.Braided-river delta is made up of underwater distributary channel,interdistributary bay,and sand sheet microfacies.During marine transgressive period,there are four depositional periods sandbodies from the basin central to the south overlapping onto Tazhong low uplift one by one.According to sedimentary overlap evolution law,the microfacies of these four periods of sandbodies are littoral,tidal flat and braided-river delta facies in the plane.In terms of controlling factors,distribution range and transgression direction,the four periods microfacies have similarity and regularity.更多还原