塔河地区三叠系主要砂体沉积相类型分析

RE-ANALYSIS OF SEDIMENTARY TYPES OF TRIASSIC SYSTEM IN TAHE AREA

塔河地区三叠系主要为厚层砂岩夹泥岩沉积,砂岩分选性中等-好,颗粒呈次棱角状,成岩矿物以岩屑和石英为主.综合岩心资料、岩石矿物及粒度分析、测井和钻井等资料分析认为,3个油组的厚层砂体主要为辫状河流相沉积,各油组厚层砂体之上的砂泥岩主要为滨浅湖、半深湖-深湖及三角洲相沉积.通过地震资料和测钻井资料分析,研究区南部中油组可识别出湖底扇相和下切水道相.沉积相演化分析表明,湖平面较低时,研究区沉积厚层辫状河流相砂体,湖平面上升时为沉积滨浅湖-半深湖-深湖暗色泥岩和三角洲砂泥岩,研究区三叠系可识别出4次湖平面升降变化,形成4套厚层砂岩夹泥岩的沉积组合(包括柯吐尔组泥岩).

sandstone interbeded with mudstone are mainly present in Triassic System of Tahe area.The sandstone is lithic quartz sandstone with middle to perfect sorting and mineral grains present hypo-edge angle,and rock minerals mainly include cutting and quartz.Based on core data,rock mineral and grain size analysis data,logging and drilling data,the main facies of thick sandstone of three oil-member in study area is braided river.The mudstone and sandstone interbeded in thick sandstone of oil-member are deposited in shore-shallow lacustrine,semi-deep lake to deep lake and delta.Based on seismic data and logging data and drilling data,sublacustrine fan and canyon can be identified in middle oil-member in southern study area.Through the study of facies evolution,braided river sandstone is present during lower lake level,and dark mudstone and sandstone are present in shore-shallow lacustrine,semi-deep lake to deep lake and delta during rising of lake level.Four lake level changes can be identified in Triassic System in study,which form four sets association of thick sandstone and mudstone（including Ketuer formation）.