渝西大足区块早志留世陆架微地貌对深层页岩气沉积-储层的影响  

Influence of Early Silurian intra-shelf microgeomorphology on sedimentation and reservoir of deep shale gas in the Dazu Area, Western Chongqing

作　　者：陈维铭 万翠蓉[2] 李悦 钟铮 严雪齐 蒋威 刘建平 王佳 王敦繁 谭先锋 CHEN Weiming;WAN Cuirong;LI Yue;ZHONG Zheng;YAN Xueqi;JIANG Wei;LIU Jianping;WANG Jia;WANG Dunfan;TAN Xianfeng(Chongqing Shale Gas Exploration and Development Company Limited,Chongqing 401120,China;Chongqing Gas Field of PetroChina Southwest Oil and Gas Field Company,Chongqing 401120,China;College of Oil and Gas Engineering,Chongqing University of Science and Technology,Chongqing 401331,China)

机构地区：[1]重庆页岩气勘探开发有限责任公司,重庆401120 [2]中国石油西南油气田分公司重庆气矿,重庆401120 [3]重庆科技大学石油与天然气工程学院,重庆401331

出　　处：《东北石油大学学报》2024年第6期49-68,108,I0004,I0005,共23页Journal of Northeast Petroleum University

基　　金：国家自然科学基金青年基金项目(42202122);重庆市杰出青年科学基金项目(CSTB2022NSCQ-JQX0031);重庆市自然科学基金项目(CSTB2022NSCQMSX1586);重庆市教委科技重大项目(KJZD-M202101502);重庆市教委科学技术研究项目(KJQN202401512);重庆页岩气勘探开发有限责任公司项目(CYS-FW-2023-0112);重庆科技大学研究生创新计划项目(YKJCX2420119)。

摘　　要：基于岩相学、三维地震、元素地球化学、总有机碳质量分数和X线衍射分析等资料,研究不同微地貌单元对渝西大足区块龙马溪组一段1亚段(龙一1亚段)1—4小层沉积—储层特征的影响,分析优质页岩气储层的分布规律。结果表明:龙马溪组沉积早期,研究区呈3级阶梯状微地貌格局,由北向南划分为陆棚高地、陆棚斜坡和陆棚洼地;中—高碳水平纹层硅质页岩主要沉积于陆棚洼地,向北逐渐过渡至低碳—特低碳无纹层/弱纹层黏土质页岩或硅质页岩。龙一1亚段1和3小层发育中—高碳水平纹层硅质页岩,2和4小层以低碳—特低碳无纹层/弱纹层黏土质页岩为主;识别碳质硅质、硅质泥质和泥质硅质深水陆棚微相,由下至上反映两期海侵—海退沉积旋回,与沉积水体氧化还原条件和古盐度变化特征一致。由陆棚高地至陆棚洼地,沉积微相从泥质硅质过渡为碳质硅质,沉积水体古盐度和还原条件增强。海侵阶段,1和3小层沉积时期,碳质硅质深水陆棚微相向北扩张,沉积水体的还原性强、古盐度高,有利于生物繁盛和有机质保存,在陆棚洼地和陆棚斜坡发育高比例的高碳水平纹层硅质页岩(M8)和中碳水平纹层硅质页岩(M11),高有机孔和脆性指数提高总孔隙度;海退阶段,2和4小层沉积时期,硅质泥质深水陆棚微相向南扩张,主要发育低碳弱纹层黏土质页岩(M5)和特低碳无纹层黏土质页岩(M6),有机孔降低和黏土比例增高导致总孔隙度降低。总有机碳质量分数、孔隙度和脆性指数整体呈向陆棚洼地逐渐增大的特征,受微地貌格局控制显著。该结果为渝西深层页岩气勘探与开发提供指导。Based on petrography,3D seismic,elemental geochemistry,total organic carbon content and X-ray diffraction analysis,this study systematically discussed influence of different microgeomorphic units on sedimentation and reservoir in the first sub-member of the first member of the Longmaxi Formation,Dazu Area,West Chongging,and analyzed the distribution of high-quality shale gas reservoirs.The result shows a 3-step microgeomorphic pattern in the early Longmaxi time in study area,which is divided into shelf plateau,shelf slope and shelf depression from north to south.Medium-to high-carbon laminated siliceous shale was mainly deposited at the shelf depression and transitioned into low-to ultralow-carbon unlaminated/weak-laminated clay shale or siliceous shale northward.Sublayer-1 and sublayer-3 comprise mainly medium-to high-carbon laminated siliceous shale,whereas sublayer-2 and sublayer-4 dominantly consist of low-to ultralow-carbon unlaminated/weak-laminated clay shale.The sedimentary microfacies types have carbonaceous siliceous,siliceous muddy and muddy siliceous deep-water shelf microfacies by shale lithofacies,which responded to transgression-regression sedimentary cycles with two times.Those sedimentary cycles are consistent with variations of redox and paleosalinity of sedimentary water column.From shelf plateau to shelf depression,the sedimentary microfacies transitioned from muddy siliceous to carbonaceous siliceous deep-water shelf,and the paleosalinity and reducing of water column strengthen southward.At the transgressive phase,sublayer-1 and sublayer-3 were deposited and carbonaceous siliceous deep-water shelf microfacies expanded northward,which enhanced reducing condition and biological abundance of water column.High proportions of M8 and M11 lithofacies were developed in shelf depression and slope.High organic pores and brittleness indices improve the porosity.At the regressive phase,sublayer-2 and sublayer-4 were deposited and siliceous muddy deep-water shelf microfacies expanded southward.M5 and M6 l

关 键 词：深层页岩气 微地貌 沉积特征 储层特征 龙马溪组 早志留世 大足区块 渝西地区 

分 类 号：P618.13[天文地球—矿床学]