四川盆地中西部筇竹寺组凹槽相区页岩沉积环境及发育模式

Shale Sedimentary Environment and Development Model in the Groove Facies Area of Lower Cambrian Qiongzhusi Formation in the Central and Western Sichuan Basin

魏力民 冯少柯 顾战宇

WEILimin FENGShaoke GUZhanyu

中国石化西南油气分公司勘探开发研究院, 四川 成都 610041 成都理工大学能源学院, 四川 成都 610059

Exploration and Development Research Institute, Southwest Petroleum Branch, SINOPEC, Chengdu, Sichuan 610041, China College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China

四川盆地凹槽相区筇竹寺组贫、富有机质两类页岩气勘探获得重大突破，但其有机质富集程度、页岩气储层特征及形成条件等与龙马溪组表现出极大差异。通过对筇竹寺组凹槽相区的岩性、粒度、矿物组成、有机碳含量、成烃生物和微痕量元素等特征的综合分析，明确了早寒武世筇竹寺期四川盆地中西部“两台夹一槽”的构造格局以及独特的拉张构造背景为筇竹寺组页岩构建了相对稳定的半开放—半封闭沉积环境，高可容纳空间与丰沛的陆源碎屑输入为筇竹寺组粉砂质页岩广泛发育奠定了物质基础，井研地区和资阳地区筇竹寺期沉积水体及沉积微相的变化是导致贫、富有机质两类页岩交替发育的主要原因，建立了四川盆地中西部凹槽相区筇竹寺组浅水亚相—深水亚相页岩发育模式。该模式可以指导此类型的页岩气勘探，为优质页岩分布预测、甜点层段优选提供科学依据。

Significant breakthroughs have been made in the exploration of two types of shale gas, poor and rich in organic matter, in the Qiongzhusi Formation of the groove facies area in the Sichuan Basin. However, the degree of organic matter enrichment, shale gas reservoir characteristics, and formation conditions are significantly different from those of the Longmaxi Formation. Through comprehensive analysis of the lithology, grain size, mineral composition, organic carbon content, hydrocarbon generating organisms, and trace elements of the shale in the groove facies area of the Qiongzhusi Formation, we clarify the structural pattern of the "two platforms sandwiching one trough" in the central and western parts of the Qiongzhusi Formation during the Early Cambrian. The unique extensional tectonic background constructed a relatively stable semi open and semi closed environment for the sedimentation of the Qiongzhusi Formation shale. The high accommodation space and abundant input of terrestrial debris have laid the material foundation for the widespread development of the Qiongzhusi Formation silty shale. The changes in sedimentary water bodies and microfacies during the Qiongzhusi period in the Jingyan and Ziyang areas are the main reasons for the alternating development of two types of shale: poor organic matter and shale with rich organic matter. Therefore, a shallow water subfacies and deep water subfacies shale development model for the Qiongzhusi Formation in the groove facies areaa of the Sichuan Basin has been established, which has important reference value and guiding significance for the exploration of new types of shale gas under the background of extensional structures.

10.11885/j.issn.1674 5086.2024.11.18.03