Study on tectonic fracture characteristics and stage evolution of Longmaxi shale reservoir in Yongchuan, southeastern Sichuan Basin

被引：0
|
作者：
He J. [1 ,2 ]
Li Y. [1 ]
Deng H. [1 ,2 ]
Wang Y. [3 ]
Ma R. [1 ,2 ]
Tang J. [4 ]
机构：
[1] College of Energy, Chengdu University of Technology, Chengdu
[2] State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu
[3] Hainan Branch of China National Offshore Oil Corporation Ltd., Haikou
[4] Exploration and Development Research Institute, Sinopec Southwest Oil & Gas Company, Chengdu
来源：
Earth Science Frontiers | 2024年 / 31卷 / 03期
关键词：
evolution stages; fractures characteristics; southeastern Sichuan Basin; Wufeng-Longmaxi shale; Yongchuan area;
D O I：
10.13745/j.esf.sf.2023.3.2
中图分类号：
学科分类号：
摘要：
Development characteristics and formation stages of natural fractures are of great significance to shale gas accumulation in the complex structural area of southeastern Sichuan. It also significantly influences the effects of hydrofracturing reconstruction and high gas production of shale reservoirs. Currently, there is no systematic study on the characteristics and evolutions of natural fractures with various origins in deep shale gas blocks far from the basin margin in the southeastern Sichuan Basin, which hinders the efficient exploration and development of deep shale gas reservoirs in the basin. Based on field outcrops, drilling cores, thin sections, geochemical data, and apatite dating, the characteristics and formation stages of natural fractures in the Longmaxi Formation shale reservoirs in the Yongchuan area have been studied. The results indicate that the Longmaxi Formation shale mainly developed tectonic fractures, including shear fractures with medium to high angles, low angle slip fractures, and vertical tensile fractures. Additionally, bedding fractures and overpressure fractures are also observed in the cores, with hydrothermal dissolution fractures mainly developed near the main fault zones. Vertically, the density of fracture development gradually decreases from deep to shallow due to variations in mineral compositions. Horizontally, fractures with high angles, distinct single fracture groups, and high vertical penetration capacity are densely developed in the anticline core or wing steep slope area, while fractures with low angles, small scales, and various fracture groups are developed in the gentle areas. Three tectonic movements一the late Yanshan (86-47 Ma), early to middle Himalayan (47-24 Ma), and late Himalayan to present (24-0 Ma)一contributed to the tectonic fractures in this area. The fracture development and filling characteristics in different evolutionary stages are notably different. The study establishes a tectonic fracture development and evolution model of shale in three phases in the Yongchuan area, providing valuable insights into the study of shale gas enrichment and preservation, as well as a deeper understanding of the evolution of shale fractures in the Longmaxi Formation, southeastern Sichuan Basin. © 2024 Science Frontiers editorial department. All rights reserved.
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页码：298 / 311
页数：13
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