江汉盆地陈沱口凹陷始新统盐湖古环境对富有机质岩相发育的控制  

Paleoenvironmental controls on organic-rich lithofacies of Eocene saline lacustrine in the Chentuokou Depression, Jianghan Basin

作　　者：俞映月 吴世强[1] 郑有恒[2] 郭丽彬[1] YU Yingyue;WU Shiqiang;ZHENG Youheng;GUO Libin(Exploration and Production Research Institute,Jianghan Oilfield Company,SINOPEC,Wuhan 430223,China;Jianghan Oilfield Company,SINOPEC,Qianjiang Hubei 433124,China)

机构地区：[1]中国石油化工股份有限公司江汉油田分公司勘探开发研究院,武汉430223 [2]中国石油化工股份有限公司江汉油田分公司,湖北潜江433124

出　　处：《地质科技通报》2024年第5期70-80,共11页Bulletin of Geological Science and Technology

基　　金：中国石油化工股份有限公司项目“东部富油气凹陷及周缘资源评价”(P23234);“咸化湖盆碳酸盐岩沉积储层特征研究”(P24048);“咸化湖盆碳酸盐岩成藏富集规律及综合评价研究”(P24044);中国石油化工股份有限公司江汉油田分公司项目“江汉探区湖相碳酸盐岩沉积环境与岩相组合特征研究”(JKD0224002);2022-2023年度湖北省博士后创新实践岗位资助项目。

摘　　要：江汉盆地新沟嘴组下段Ⅱ油组广泛发育页岩与白云岩互层的烃源岩,近期该层系页岩油勘探获得了重大突破,但盐湖沉积背景下沉积的膏盐对于孔隙的影响制约了页岩油的勘探开发,明确低膏盐富有机质岩相发育的控制因素对页岩油勘探具有重要意义。选取陈沱口凹陷的C1系统取心井作为研究对象,通过岩心及岩石薄片的观察鉴定,全岩矿物组成质量分数、有机碳及地球化学元素含量测定,对C1井新沟嘴组下段Ⅱ油组的岩相类型、沉积环境和有机质富集主控因素进行了系统研究,建立了适合江汉盆地新沟嘴组盐湖相岩相划分方案和沉积模式。结果表明:C1井新沟嘴组下段Ⅱ油组共发育4类7种岩相,分别为富碳细纹层状白云岩、富碳粗纹层状白云岩、含碳块状白云岩;富碳细纹层状混合质页岩、富碳粗纹层状混合质页岩;含碳粗纹层状粉砂岩;贫碳块状膏盐岩。古气候、古盐度与古氧化还原协同演化控制了岩相发育的多样性,有机质富集的主控因素为还原性古水介质环境。页岩油勘探有利岩相为富碳(含碳)粗纹层(细纹层)状白云岩(混合质页岩),有利岩相的沉积环境为咸水、还原的半深湖环境。陈沱口凹陷新沟嘴组下段Ⅱ油组富有机质岩相发育控制因素及其沉积环境的揭露,可为江汉盆地相关凹陷新沟嘴组页岩油勘探提供借鉴和参考。Source rocks characterized by shale-dolomite interbeds were widely developed in oil group II,the lower Member of Xingouzui Formation in Jianghan Basin.A breakthrough has been made recently in shale oil exploration of shale-dolomite interbeds,while the presence of gypsum and salt deposites in saline lake on shale porosity restrains the process of shale oil exploration.[Objective]It is of great significance for shale oil exploration to clarify the controlling factors of the organic-rich shale lithofacies with low content of gypsum and salt.[Methods]Well C1 penetrated stratigraphic unit of the Xingouzui Formationin the Chentuokou Depression,Jianghan Basin was studied.Based on the core and thin section observations and the analyses of whole rock mineral compositions,organic carbon contents(TOC),and geochemical elements,a systematic study on lithofacies,sedimentary environment,and main controlling factors of organic matter accumulation were conducted.[Results]The classification of fine-grained sediments and the saline lacustrine sedimentary model in Jianghan Lake Basin were established.Lithofacies of oil group II,the lower Member of Xingouzui Formation Xingouzui Formation in Well C1 can subdivided into seven types:organic-rich laminated dolomite facies,organic-rich layered dolomite facies,organic-contain massive dolomite facies,organic-rich laminated mixed shale facies,organic-rich layered mixed shale facies,organic-contain layered siltstone,and organic-poor massive gypsum-salt rock facies.The co-evolution of paleoclimate,paleosalinity,and paleoredox resulted in the diversity of lithofacies development,and the main controlling factor of organic matter accumulation was the anoxic palaeo-water body.The favorable lithofacies for shale oil exploration are organic-rich/organic-contain laminated/layered dolomite/mixed shale,which deposited in semi-deep lake with brackish water,anoxic condition.[Conclusion]This study reveals the controlling factors for the development of organic-rich lithofacies and its depositional environm

关 键 词：江汉盆地 始新统 盐湖沉积 富有机质岩相 古环境 有机质富集 

分 类 号：P618.13[天文地球—矿床学]