Tectonic fracture stages and evolution model of Longmaxi Formation shale, Dingshan structure,Southeast Sichuan

被引：0
|
作者：
Fan C. [1 ,2 ]
Li H. [1 ,2 ,3 ]
Zhong C. [1 ,2 ]
Qin Q. [1 ,2 ]
Hu D. [4 ]
Zhang Y. [1 ,2 ]
He S. [1 ,2 ]
Zhang W. [3 ]
机构：
[1] School of Science and Technology, Southwest Petroleum University, Chengdu, 610500, Sichuan
[2] State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Sichuan, Chengdu, 610500, Sichuan
[3] Sinopec Exploration Company, Chengdu, 610041, Sichuan
[4] PetroChina Tarim Oilfield Company, Korla, 841100, Xinjiang
来源：
Shiyou Xuebao/Acta Petrolei Sinica | 2018年 / 39卷 / 04期
关键词：
Dingshan structure; Evolution model; Formation stage; Longmaxi Formation shale; Tectonic fractures;
D O I：
10.7623/syxb201804002
中图分类号：
学科分类号：
摘要：
Huge shale gas reserves exist in Longmaxi Formation,Dingshan structure,Southeast Sichuan,where fractures have an important effect on shale gas enrichment and productivity. Based on field outcrop,core,image log,inclusion analysis,acoustic emission experiment and (U-Th)/ He dating,the formation stages and evolution models of tectonic fractures in this area are comprehensively studied. The research shows that the high-angle plane shear fractures and low-angle profile shear fractures of tectonic origin are mainly developed in field outcrops with various types of core fractures,dominated by high-angle shear fractures of tectonic origin. The fracture occurrence of field outcrop is better consistent with the core and image logging interpretation. The tectonic fractures of Longmaxi Formation can be divided into three stages. In the first stage,tectonic fractures were formed in the late Yanshanian movement (82.5-72.1 MPa). The fillings of fractures are mainly calcite,followed by silicon or iron,showing a high filling degree. The homogenization temperature is 295.6-325.2℃,the maximum effective principal stress of paleo-geostress is 97.06 MPa,and the direction of principal stress is 135°±15°. The fracture orientation is mainly shown as the horizontal "X" conjugate shear fractures with NWW-SEE and NNE-SSW trending as well as the NE profile shear fractures. In the second stage,tectonic fractures were formed in the late Yanshanian movement and the middle Himalayan movement (72.1-31.2 Ma). The fracture fillings are calcite with low filling degree. The homogenization temperature is 189.1-232.4℃,the maximum effective principal stress of paleo-geostress is 90.71 MPa,the direction of principal stress is 45°±15°,and the fracture orientation is mainly shown as the plane "X" conjugate shear fractures with near-SN and NEE trending as well as NW-trending shear fractures on the profile. In the third stage,tectonic fractures were formed in the late Himalayan movement till now (31.2-0 Ma),and only a few NW-trending shear fractures have been formed on the profile. The fractures are basically unfilled. The maximum effective principal stress of paleo-geostress is 76.55 Mpa. The first and second stages are the main fracture formation stages,while the third stage is to transform the earlier fractures. Combined with the theory of geomechanics,the genetic model of fracture development in three phases was established in this study. © 2018, Editorial Office of ACTA PETROLEI SINICA. All right reserved.
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页码：379 / 390
页数：11
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