南羌塘古油藏白云岩成因机制及其油气地质意义  

Genetic mechanism and its oil and gas geological significance of dolomites of the Long’eni-Angdarco-Dazuoma palaeo-reservoir in southern Qiangtang Basin,China

作　　者：张健[1,2,3] 王剑[3,4] 张建勇[5,6] 熊绍云 郑波 沈利军 ZHANG Jian;WANG Jian;ZHANG Jianyong;XIONG Shaoyun;ZHENG Bo;SHEN Lijun(Chinese Academy of Geological Sciences;China University of Geosciences(Beijing);Southwest Petroleum University,Chengdu,Sichuan 610500,China;National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation;State Energy Key Laboratory for Carbonate Oil and Gas;Key Laboratory of Carbonate Reservoir,CNPC)

机构地区：[1]中国地质科学院 [2]中国地质大学(北京) [3]西南石油大学,四川省成都市610500 [4]油气藏地质与开发工程全国重点实验室 [5]国家能源碳酸盐岩油气重点实验室 [6]中国石油集团碳酸盐岩储层重点实验室

出　　处：《海相油气地质》2024年第2期147-163,共17页Marine Origin Petroleum Geology

基　　金：国家自然科学基金项目“羌塘盆地侏罗纪成盐环境与盐构造演化及其油气赋存效应”(编号:42241202);“羌地-17井低温热年代学记录对羌塘盆地早期隆升的约束”(编号:42102131);中国石油“十四五”前瞻性基础性课题“羌塘盆地构造沉积演化与基本石油地质条件研究”(编号:2021DJ0801)的联合资助。

摘　　要：南羌塘隆鄂尼—昂达尔错—达卓玛古油藏白云岩是羌塘盆地最有利的碳酸盐岩储层之一,其成因机制对于羌塘盆地油气勘探突破具有十分重要的意义。在岩石薄片鉴定的基础上,结合碳氧稳定同位素、锶同位素、微量和稀土元素等测试分析,对古油藏白云岩成因机制及白云岩储层的形成演化开展研究。结果表明:(1)研究区共发育6种类型白云岩(石),分别为泥—粉晶残余结构白云岩、他形—半自形细晶白云岩、自形细晶白云岩、他形中—粗晶白云岩、雾心亮边晶粒白云岩和后期孔洞充填的马鞍形白云石。(2)古油藏白云岩存在多种成因。泥—粉晶残余结构白云岩成因为准同生期微生物白云石化作用,他形—半自形细晶白云岩和他形中—粗晶白云岩成因为浅埋藏阶段回流渗透白云石化作用,自形细晶白云岩成因为埋藏白云石化作用,雾心亮边晶粒白云岩是后期抬升至近地表混合水白云石化作用的产物。古油藏白云岩孔洞中大量充填的马鞍形白云石是热液白云石化作用的产物。(3)南羌塘古油藏白云岩储层受白云石化、大气淡水淋滤和热液溶蚀等成岩作用改造形成次生孔隙,形成了良好的规模储层,可作为油气勘探目的层之一。建立了南羌塘古油藏白云岩成因模式,为羌塘盆地油气成藏演化研究与优质碳酸盐岩储层预测提供了新的理论依据。The oil-bearing dolomites exposed in the Long’eni-Angdarco-Dazuoma region have been proven to be a favorable carbonate reservoir in the Qiangtang Basin.Its genetic mechanism is significant for oil and gas exploration in the Qiangtang Basin.In this study,comprehensive analysis of rock thin section identification,carbon and oxygen isotopes,trace and rare earth elements and strontium isotopes are conducted to investigate the genetic mechanisms of the palaeoreservoir dolomites and the formation and evolution process of the dolomites reservoirs.The main findings are as follows:(1)Dolomite types are subdivided into micritic-very fine crystalline residual structure dolomite,fine crystalline subhedral-anhedral dolomite,fine crystalline euhedral dolomite,medium-coarse crystalline subhedral dolomite,cloudy core and clear rim structure crystalline dolomite and saddle dolomite with late filling holes.(2)The petrological and diagenetic fluid geochemical studies indicate that the micritic-very fine crystalline residual structure dolomite is formed by syngenetic microbial dolomitization.The fine crystalline subhedral-anhedral dolomite and medium-coarse crystalline subhedral dolomite are formed via reflux dolomitization,which occurred during the shallow burial stage.The fine crystalline euhedral dolomite is formed by the deep burial dolomitization.The cloudy core and clear rim structure crystalline dolomite is formed by the near-surface mixing-zone dolomitization during the uplift stage.The saddle dolomite is formed by the hydrothermal dolomitization.(3)The genetic mechanism of dolomites in the palaeo-reservoir reveals the evolution process of burial conditions and reservoir space of dolomites.Secondary pores are formed by dolomitization,meteoric freshwater leaching and hydrothermal dissolution,forming a good dolomite scale reservoir,which can be used as one of the target reservoirs for oil and gas exploration.These understandings provide new theoretical references for the study of hydrocarbon accumulation evolution and the pr

关 键 词：地球化学特征 白云岩成因 储层演化 古油藏 南羌塘 

分 类 号：TE122.2[石油与天然气工程—油气勘探]