四川盆地及其周缘下寒武统筇竹寺组细粒沉积特征与影响因素

Fine-grained sedimentary characteristics and influencing factors of the Lower Cambrian Qiongzhusi Formation in Sichuan Basin and on its periphery

熊亮 邓虎成 吴冬 魏力民 王同 周桦 曹凯旋 解馨慧 马若龙 钟雨萄

XIONG Liang DENG Hucheng WU Dong WEI Limin WANG Tong ZHOU Hua CAO Kaixuan XIE Xinhui MA Ruolong ZHONG Yutao

中国石化 西南油气分公司, 成都 610041 油气藏地质及开发工程国家重点实验室(成都理工大学), 成都 610059 成都理工大学 能源学院, 成都 610059 中国石化 西南油气分公司 勘探开发研究院, 成都 610041 成都理工大学 地球物理学院, 成都 610059

SINOPEC Southwest Oil & Gas Company, Chengdu, Sichuan 610041, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, (Chengdu University of Technology), Chengdu, Sichuan 610059, China College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China Research Institute of Exploration and Development, SINOPEC Southwest Oil & GasCompany, Chengdu, Sichuan 610041, China College of Geophysics, Chengdu University of Technology, Chengdu, Sichuan 610059, China

四川盆地及其周缘下寒武统筇竹寺组页岩气资源丰富，已成为盆地重要的页岩气开发层段之一。受控于复杂的沉积格局，该区筇竹寺组粉砂质页岩纵向储层的岩相多样，非均质性强，制约了页岩气勘探和开发，因此亟需对其沉积特征、沉积相带和沉积模式开展研究。基于前期构造、层序地层研究认识，通过对矿物岩石、钻测井、地球化学和古生物等主要资料开展精细分析，明确四川盆地及其周缘早寒武世为海洋—古陆联合影响、水体深度中等、还原作用普遍发生的沉积背景，认为筇竹寺组主要沉积于滨岸相和陆棚相，并以陆棚相为主体，包括浅水陆棚亚相和深水陆棚亚相。通过对波浪和潮汐联合作用、海水蒸发作用、悬浮作用、上升洋流以及沉积古地貌等细粒沉积影响因素开展分析，结合沉积物空间分布特征，建立了四川盆地及其周缘筇竹寺组细粒岩沉积模式，即沉积初期差异沉降作用显著，层序厚度变化大，不同地区沉积特征及影响因素差异较大；沉积中期差异沉降作用不断减弱，层序厚度差异持续减小；沉积末期稳定沉降，进入“广盆”阶段，层序厚度趋于一致。

The Lower Cambrian Qiongzhusi Formation in Sichuan Basin and on its periphery is rich in shale gas resources, and it has become one of the important shale gas development intervals in Sichuan Basin. Controlled by complex sedimentary setting, the silty shale reservoir in Qiongzhusi Formation has various lithofacies and strong heterogeneity longitudinally, which restricts the exploration and development of shale gas. Therefore, it is urgent to study the sedimentary characteristics, sedimentary facies and sedimentary models. Based on the previous understanding of tectonic setting and sequence stratigraphy, and through detailed analysis of rock data, well logging data, geochemistry data and paleontology data, this paper clarifies the Early Cambrian sedimentary background of combined ocean-paleoland influence, moderate water depth and widespread reduction of Sichuan Basin and its periphery. The paper also believes that the Qiongzhusi Formation is mainly deposited in shore facies and continental shelf facies. The continental shelf facies are dominated, including shallow water continental shelf subfacies and deep water continental shelf subfacies. Based on the analysis of the combined action of wave and tide, seawater evaporation, suspension, rising ocean current, sedimentary paleogeomorphology and other fine-grained sedimentary influencing factors, and combined with the spatial distribution characteristics of sediments, the fine-grained sedimentary model of the Lower Cambrian Qiongzhusi Formation in Sichuan Basin and on its periphery is established, i.e., in the early stage of sedimentation, the effect of differential sedimentation is significant, the sequence thickness varies greatly, and the sedimentary characteristics and influencing factors differ greatly in different regions. In the middle stage of sedimentation, the effect of differential sedimentation is diminished and the difference of sequence thickness decreases continuously. In the late stage of sedimentation, with steady sedimentation, it enters the "open basin" stage, and the sequence thickness tends to be consistent.

国家自然科学基金项目 42072182;中国石化西南油气分公司科研项目 KJ-765-2329;中国石化西南油气分公司科研项目 KJ-766-2330;中国石化西南油气分公司科研项目 KJ-767-2331

https://doi.org/10.11781/sysydz202305857