塔北南坡志留系柯坪塔格组下段底部砂岩亚段沉积体系分析

Analysis of Depositional System of Bottom Sandstone Sub-member in Lower Member of Kalpintag Formation,Silurian in Southern Slope of Tabei Uplift

据岩心、录井、测井等资料,分析塔北南坡志留系柯坪塔格组下段底部砂岩亚段沉积体系类型及空间分布特征。塔北南坡志留系柯坪塔格组下段底部砂岩亚段发育一套海侵背景下形成的碎屑滨岸一浅海沉积体系,其中,碎屑滨岸体系可进一步划分为后滨、前滨、临滨沉积。后滨亚相以砂泥岩互层为特征,见泥砾;前滨亚相以中粗砂岩为主,泥岩较少;临滨亚相为砂泥岩不等的厚互层,上临滨砂岩所占比例较高,下临滨泥岩增多。浅海相以泥岩为主。平面上,沉积体系自NW向ES呈后滨-前滨-临滨-浅海不规则带状展布,垂向上,自下而上呈后滨-前滨-临滨-浅海演化序列。该沉积相格局的确定,为分析有利储层及确定下一步有利勘探目标奠定了基础。

Based on logging and core data,the depositional system of bottom sandstone sub-member in lower kalpingtagformation,Silurian in southern slope of Tabei uplift,was analysised and the spatial distribution of depositional systemwas found out.The depositional system of bottom sandstone sub- member in lower kalpingtag formation,Silurian in southernslope of Tabei uplift was clastic shore-shallow sea under the background of transgressive.The clastic shore can befuther divided into backshore,foreshore and shoreface.Backshore in sandstone and mudstone interbed feature,visible boulderclay.Foreshore facies in the moderate coarse sandstone,mudstone less.Shoreface of sandstone and mudstone interbededin different thickness.Upper shoreface had a higher proportion of sandstone. Mudstone increased in lower shoreface.Shallow sea development more mudstone.The plane,the sedimentary system is from northwest to southeast“ backshore -foreshore-shoreface-shallow sea”irregular zonal distribution.Vertical,buttom-up exhibit sequence evolution“backshoreforeshore-shoreface-shallow sea”.Determination of sedimentary facies pattern lay the foundation of analyzing favorablereservoir.