川南下寒武统筇竹寺组沉积格局及沉积体系

Sedimentary Patterns and Depositional Systems of the Lower Cambrian Qiongzhusi Formation in the Southern Sichuan Basin

熊亮 钟怡江 董翼昕 彭明鸿

XIONGLiang ZHONGYijiang DONGYixin PENGMinghong

中国石化西南油气分公司, 四川 成都 610041 成都理工大学沉积地质研究院, 四川 成都 610059 四川轻化工大学经济学院, 四川 自贡 643000

Southwest Petroleum Branch, SINOPEC, Chengdu, Sichuan 610041, China Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, Sichuan 610059, China School of Economics, Sichuan University of Science and Engineering, Zigong, Sichuan 643000, China

川南下寒武统筇竹寺组页岩气勘探连续重大突破，揭示该套层系成为继五峰组—龙马溪组页岩气重要接替层系的可能。该套页岩层系具有展布不均匀、沉积相特征差异明显且变化大的特点，制约了下一步勘探开发进展。为了解决这一问题，结合国内外细粒沉积学最新理论研究进展，以新近钻井、录井和地震沉积学分析为基础，剖析细粒沉积物质岩石学、地球化学和沉积组构综合特征，明确沉积格局、沉积环境和沉积体系发育特征。结果表明：1) 受同沉积断裂活动影响，中上扬子克拉通发育南北贯穿的川中凹槽和鄂西—渝东裂陷槽，形成了“三台夹两槽”的沉积格局。2) 建立了川南地区受绵阳—长宁凹槽构造-沉积分异控制下的滨岸—海槽—陆棚沉积体系，且将海槽体系分为浅水缓坡、深水缓坡、槽盆和陡坡4个亚相，井研地区和资阳地区分别发育于浅水缓坡和深水缓坡。3) 建立了川南地区来自西部物源区的细粒沉积物质在缓坡带内受到风暴流、浊流和底流的交互作用改造形成浅水缓坡浊积体和底流丘以及深水缓坡内浊积体和底流席的沉积模式。4) 以细粒沉积学为指导建立的沉积格局控制的沉积微相发育模式对筇竹寺组新类型页岩气勘探有着重要的指导作用。

Recent advancements in shale gas exploration of the Qiongzhusi Formation in the southern Sichuan suggest that this interval has the potential to become a significant successor to the Wufeng-Longmaxi shale gas play. The shale sequences exhibit uneven lateral distribution, with notable variations in sedimentary facies characteristics, which pose challenges to further exploration and development. Drawing on the latest advances in fine-grained sedimentology, along with new drilling, well logging, and seismic data, this study analyzes the lithology, geochemistry, and sedimentary fabric of fine-grained sediments to elucidate sedimentary patterns, depositional environments, and sedimentary system development. The results indicate that: 1) synsedimentary fault activity led to the formation of a north-south-trending groove facies area in central Sichuan and the Exi-Yudong Region, generating a sedimentary deep-water gentle slope pattern characterized by "three platforms and two troughs". 2) controlled by the Mianyang-Changning groove facies area, a coastal-shelf-basin sedimentary system was established in southern Sichuan, with four subfacies: shallow-water gentle slope, deep-water gentle slope, steep slope and trough-basin. The Jingyan and Ziyang areas are dominated by shallow-water gentle slope and deep-water gentle slope subfacies, respectively. 3) fine-grained sediments sourced from the west were modified by storm currents, turbidity flows, and bottom currents, forming shallow-water gentle slope turbidites, bottom-current mounds, and deep-water gentle slope turbidites microfacies. 4) we established the sedimentary model based on fine-grained sedimentology and sedimentary patterns, providing crucial insights for the exploration of new shale gas plays within the Qiongzhusi Formation.

10.11885/j.issn.1674 5086.2024.11.16.15