塔河油田奥陶系碳酸盐岩油藏岩溶成因类型

塔河油田位于塔里木盆地北部沙雅隆起中段的阿克库勒凸起上。该凸起自加里东中晚期到海西早期的多次构造抬升运动使奥陶系碳酸盐岩地层长期出露于地表,受到强烈的大气淡水淋滤溶蚀作用。该地区还经历了加里东中期海侵和石炭纪海侵以及二叠纪火山作用。以塔河油田主体区内11口井的33份砂泥质充填物为基础样本,作了硼、矾、镓、铷等微量元素和包裹体分析等地球化学的研究,证实研究区内以大气淡水岩溶作用为主,存在后期的淡水-海水混合岩溶作用和热水岩溶(溶蚀)作用。大气淡水岩溶纵向上主要分为三个带,溶洞充填物的伊利石K—Ar同位素定年揭示其呈上老下新的时序性。海水入侵所改造的为浅层第一、二个岩溶带,热水岩溶(溶蚀)改造的为深部第三个岩溶带。

Karst Genesis Classification of Ordovician Carbonate Reservoir in Tahe Oilfield, Tarim Basin

Tahe Oilfield locates in the margin of Akekule uplift in north Tarim Basin.It underwent several times of tectonic uplifts during middle Caledonian to early Hercynian epochs,which led to Ordovician carbonate formations being exposed perennially to the surface and suffering from intense meteoric fresh-water weathering,leaching and dissolving.At the same time,it also went through wide marine transgression from north to south during Mid-Caledonian movement,wide marine transgression from west to east during Carboniferous period,and volcanic events during Permian period in Tahe aera.Geochemical analysis of trace elements including B,V,Ga,Rb,etc.and analysis of fluid inclusions are taken for 33 basic samples of argillite-fillings in karst caverns from 11 wells in the main area of Tahe Oilfield.It is proved that the meteoric water karstification is predominant in this area,succeeding by reconstructing the mixed marine/meteoric water karstification and hydrothermal water karstification.There are three karstification zones in vertical in this area.The isotopic element dating of K-Ar in illite samples from the cavern fillings reveals the karstification chronogenesis that is later in the upper and earlier in the lower.The first and second karstification zones in shallow were reconstructed by marine water transgression and the third karstification zone in deep was by hydrothermal water transgression.