上扬子地区下寒武统筇竹寺组地层特征及页岩气富集段分布  

Stratigraphic characteristics and shale gas enrichment interval distribution of the Lower Cambrian Qiongzhusi Formation,Upper Yangtze region,China

作　　者：王红岩 施振生 赵群[2,3] 周天琪 汪鹏飞[2,3] WANG Hongyan;SHI Zhensheng;ZHAO Qun;ZHOU Tianqi;WANG Pengfei(PetroChina National Institute of Excellence Engineers,Beijing 100096,China;National Energy Shale Gas Research and Development(Experimental)Center,Beijing 100083,China;Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China)

机构地区：[1]中国石油国家卓越工程师学院,北京100096 [2]国家能源页岩气研发(实验)中心,北京100083 [3]中国石油勘探开发研究院,北京100083

出　　处：《煤田地质与勘探》2025年第3期72-89,共18页Coal Geology & Exploration

基　　金：中国石油天然气股份有限公司前瞻性基础性战略性技术攻关项目(2024DJ87)。

摘　　要：【目的】上扬子地区下寒武统筇竹寺组页岩不仅保留重要的原始沉积海洋信息,更是重要的烃源岩和储集层,已展示出巨大的页岩气勘探潜力。【方法】基于地震、钻井和露头资料,通过系统地层划分和对比,开展页岩地层和分布,明确页岩气甜点段。【结果和结论】结果表明:上扬子地区下寒武统筇竹寺组划分为,筇一段(筇一1至筇一4亚段)和筇二段(筇二1至筇二4亚段)。(2)麦地坪组和筇一段主要发育于德阳−安岳克拉通内裂陷内,而筇二段在裂陷外亦有广泛分布。裂陷内部地层结构表现为麦地坪组至筇一段东西两侧终止于灯影组灰岩,西侧厚度变化较缓,东侧地层快速尖灭;南北方向上,筇一段由北向南减薄,筇二段中部薄而南北厚。裂陷外部则以筇二段全区发育为特征,其中筇二1亚段直接超覆于筇一段或灯影组灰岩之上。(3)筇二1亚段页岩具有优越的生烃、储集以及垂向和侧向封堵条件,为页岩气的富集段。内裂陷北段天星1井筇二1亚段页岩微孔隙和微裂缝发育,测井孔隙率为4.93%~6.57%,平均5.08%;德阳−安岳克拉通内裂陷槽中部的威页1井筇竹寺组筇二1亚段页岩有机质孔发育,测井孔隙率为4.20%~4.70%,平均4.51%;内裂陷南部的云南曲靖地区钻井井位有曲页1井、曲地1井等,筇竹寺组黑色页岩孔隙发育,高压压汞孔隙率为1.59%~11.33%,平均5.0%。(4)相比之下,尽管筇一段页岩在生烃和储集条件上表现良好,但其生成的页岩气易侧向沿岩溶带或断层逸散,不利于原地聚集成藏。如,内裂陷北段的川深1井,筇一3亚段厚约40 m,测井TOC含量平均3.5%,测井孔隙率平均6.4%,均为优质烃源岩和储集层,不利于原位聚集成藏。综上,筇二1亚段页岩因其高孔隙率和良好的封堵条件,为页岩气勘探的“甜点段”,为下一步油气勘探提供依据和指导。[Objective]Shales in the Lower Cambrian Qiongzhusi Formation within the Upper Yangtze region preserve critical information about primitive oceans.Furthermore,these shales serve as vital source rocks and reservoirs,having demonstrated considerable potential for shale gas exploration.[Methods]Using seismic,borehole,and outcrop data,this study investigated the shale strata and their distribution in the Qiongzhusi Formation through comparative analysis.Accordingly,the sweet-spot interval was determined.[Results and conclusions]The results indicate that the Lower Cambrian Qiongzhusi Formation in the Upper Yangtze region can be divided into the first and second members(also referred to as the Qiong 1 and 2 members,respectively),with the former consisting of Q1-1 to Q1-4 sub-members and the latter comprising Q2-1 to Q2-4 sub-members.The Maidiping Formation and the Qiong 1 Member predominantly occur within the Deyang-Anyue intracratonic rift,while the Qiong 2 Member is extensively distributed both inside and outside the rift.Within the rift,the west and east sides of the Maidiping Formation-Qiong 1 Member terminates at the limestone of the Dengying Formation,with the west side gradually thinning while the east side pinching out rapidly.In the north-south direction,the Qiong 1 Member thins southward,while the Qiong 2 Member is thin in the central part but thick in the northern and southern parts.Outside the rift,the Qiong 2 Member is distributed throughout the region,with the Q2-1 sub-member directly overlapping either the Qiong 1 Member or the limestone of the Dengying Formation.Shales in the Q2-1 sub-member enjoy superior hydrocarbon generation and reservoir conditions,as well as vertical/lateral sealing performance,emerging as a shale gas enrichment interval.For instance,in the northern part of the intracratonic rift,shales in the Q2-1 sub-member in well Tianxing-1 contain well-developed micropores and microfractures,with logging-derived porosity ranging from 4.93%to 6.57%(average:5.08%).In the central part of the Deya

关 键 词：页岩气 富集段 地层划分 筇竹寺组 下寒武统 上扬子地区 

分 类 号：TE121.3[石油与天然气工程—油气勘探]