柴达木盆地北缘南八仙地区下干柴沟组沉积相研究

Study on Sedimentary Facies of Xiaganchaigou Formation in Nanbaxian Area of Northern Qaidam Basin

通过对南八仙地区岩心、钻井、录井和测井等资料的研究,认为柴达木盆地北缘南八仙地区下干柴沟组(E3)主要发育三角洲相和湖泊相,进而可细分为分流河道、天然堤、分流间湾、决口扇、水下分流河道、水下分流河道间、河口砂坝、远砂坝-席状砂、前三角洲泥、滩、坝和泥坪微相。E13(下干柴沟组下段)沉积时期为干燥气候下的咸化坳陷湖泊环境,研究区主要为滨浅湖沉积和远砂坝-席状砂沉积;由于构造抬升,E23(下干柴沟组上段)沉积时期,水体变浅,物源由东北进一步向西南推进,研究区逐步演变为三角洲和滨浅湖滩坝多期叠加沉积,其中三角洲前缘沉积尤其发育。

By researching the date of core and drilling and well logging,it was considered that the sedimentary facies,such as delta and lake facies were developed in Xiaganchaigou Formation of Nanbaxian Area.The two facies could be subdivided into distributary channel,natural barrier,inter-distributary bay,crevasse splay,underwater distributary channel,underwater inter-distibutary area,channel mouth bar,distal bar-sand sheet,delta front,predelta and shore shallow lake.Sedimentary evolution of the formation was separated into two stages.One was the lower segment(E 1 3),the other was the upper segment(E 2 3).In E 1 3 the area mainly developed shore shallow lake and distal bar-sand sheet.Sand body was at low development degree.In E 2 3,water became shallow,provenance was moved forward from northeast to south-west.Sand body is abnormally developed,delta and shore shallow lake deposit is multistage superposition.The delta front facies is especially well developed.