摘要
综合岩石学、矿物学和元素地球化学等研究方法,对柴达木盆地北缘冷湖七号地区下干柴沟组上段(E_(3)^(2))碎屑岩的岩石学特征、成岩作用、沉积微相以及沉积环境进行了综合研究。结果表明:冷湖七号地区下干柴沟组上段碎屑岩以长石质岩屑砂岩为主,其次为岩屑质长石砂岩;孔隙类型多为原生粒间孔和粒间溶蚀孔,胶结物多为方解石;黏土矿物含量平均为15.0%,伊利石含量较高,绿泥石与伊/蒙混层含量次之,成岩环境为碱性环境。碱性成岩环境有利于成岩阶段早期绿泥石包膜和方解石胶结物的形成,前者增加了岩石的机械强度,抑制了硅质胶结作用,有利于原生粒间孔隙的保存;后者含量小于12%时,有利于后期酸性流体介入,发生溶蚀作用而形成一定量的次生溶孔,从而对储层起到一定的改善作用。冷湖七号地区下干柴沟组上段发育水下分流河道、河口坝和远砂坝等砂体,优质储层发育于远砂坝以外的砂体中,成分成熟度和结构成熟度均较高。元素硼、“相当硼”含量和钴元素综合分析结果显示沉积水体为陆相淡水—半咸水,水体深度整体较浅,水动力作用较强。
Based on the methods of petrology,mineralogy and elemental geochemistry,petrological characteristics,diagenesis,sedimentary microfacies and sedimentary environment of clastic rocks of the upper section of the Lower Ganchaigou Formation(E_(3)^(2))of Lenghu No.7 in the northern margin of Qaidam Basin were comprehensively studied.The clastic rocks are mainly feldspathic lithic sandstones,followed by lithic arkose;the pore types are mainly primary intergranular pores and intergranular dissolution pores,and the cement is mostly calcite;the average content of clay mineral is 15.0%,the content of illite is high,followed by chlorite and illite/montmorillonite mixed layer and the diagenetic environment is alkaline environment.Alkaline diagenetic environment is conducive to the formation of chlorite coating and calcite cement in the early diagenetic stage,the former increases the mechanical strength of the rock,inhibits the siliceous cementation,and is conducive to the preservation of primary intergranular pores;when the content of the latter is less than 12%,it is conducive to the intervention of acid fluid in the late diagenetic stage,resulting in the dissolution and formation of a certain amount of secondary dissolved pores,thus playing a certain role in improving the reservoir.Underwater distributary channel,distal bar and estuarine bar are developed,high quality reservoirs are developed in sand-bodies outside distal bar with high maturity of composition and structure.The comprehensive analysis results of element B,“equivalent B”and Co show that the sedimentary water body is continental fresh-brackish water with shallow water depth and strong hydrodynamic effect.
作者
潘世乐
蒋赟
朱文军
刘振宇
王晔桐
孙国强
张顺存
Shi-le PAN;Yun JIANG;Wen-jun ZHU;Zhen-yu LIU;Ye-tong WANG;Guo-qiang SUN;Shun-cun ZHANG(Northwest Institute of Eco?Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;Exploration and Development Research Institute of PetroChina Qinghai Oilfield Company,Dunhuang 736202,China;Exploration and Development Research Institute of PetroChina Xinjiang Oilfield Company,Karamay 834000,China;Key Laboratory of Petroleum Resources Research,Gansu Province,Lanzhou 730000,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2021年第3期393-404,共12页
Natural Gas Geoscience
基金
国家自然科学基金(编号:41872145)
中国科学院“西部之光”人才培养计划(编号:Y304RC1SGQ)
甘肃省自然科学基金(编号:17JR5RA293)
甘肃省重点实验室专项(编号:1309RTSA041)联合资助。
关键词
黏土矿物
主、微量元素
沉积—成岩环境
下干柴沟组
冷湖七号地区
Clay mineral
Major and trace elements
Sedimentary-diagenetic environment
Lower Ganchaigou Formation
Lenghu No.7
