Scholarlink

<p>To enhance coal seam permeability and promote the formation of shear-dominated, complex fracture networks, this study investigates three CO<sub>2</sub> fracturing schemes based on the dynamic equilibrium between fluid injection and fracture propagation: constant-rate continuous injection (CCI), stepwise-rate continuous injection (SCI), and cyclic progressive injection (CPI). The evolution of pump pressure–time curves, acoustic emission (AE) characteristics, fracture geometries, and microcrack development under these schemes was systematically analyzed. In the CPI scheme, numerous shear microcracks were generated, producing a highly complex fracture network. The results show that: (1) AE energy in the CCI scheme was concentrated before fracture initiation (12.12&#xa0;MPa); in the SCI scheme, high-energy AE events occurred twice—at an injection rate of 70&#xa0;mL/min and prior to failure; in the CPI scheme, cyclic AE energy peaks corresponded to multiple fracturing events in different directions, with an average initiation pressure of 9.16&#xa0;MPa. (2) All schemes produced primary and secondary fractures, but the CPI scheme generated five main fractures, activated four natural fractures (NFs), and exhibited the greatest tortuosity, consistent with numerical simulations. (3) Under the CPI scheme, cyclic variations in flow velocity (rise–hold–decline) effectively stimulated NFs, producing 91.23% shear microcracks through microcrack aggregation and shear slip. (4) A cyclic progressive CO<sub>2</sub> fracturing technology is proposed for coalbed methane (CBM) recovery, forming a three-tier fracture network dominated by hydraulic fractures, activated by natural fractures, and branched by offset-intersecting fractures.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Fracture Network Evolution Mechanisms in Coal Through Cyclic Progressive CO2 Shear Fracturing Under True Triaxial Stress

  • 期刊论文

  • 发表日期：

    2026年1月29日

查看全文
  • Chen Jing,
  • Changbao Jiang,
  • Zhuchun Wang,
  • Jian Hou,
  • Erhu Jiang,
  • Jianfeng Liu

摘要

To enhance coal seam permeability and promote the formation of shear-dominated, complex fracture networks, this study investigates three CO2 fracturing schemes based on the dynamic equilibrium between fluid injection and fracture propagation: constant-rate continuous injection (CCI), stepwise-rate continuous injection (SCI), and cyclic progressive injection (CPI). The evolution of pump pressure–time curves, acoustic emission (AE) characteristics, fracture geometries, and microcrack development under these schemes was systematically analyzed. In the CPI scheme, numerous shear microcracks were generated, producing a highly complex fracture network. The results show that: (1) AE energy in the CCI scheme was concentrated before fracture initiation (12.12 MPa); in the SCI scheme, high-energy AE events occurred twice—at an injection rate of 70 mL/min and prior to failure; in the CPI scheme, cyclic AE energy peaks corresponded to multiple fracturing events in different directions, with an average initiation pressure of 9.16 MPa. (2) All schemes produced primary and secondary fractures, but the CPI scheme generated five main fractures, activated four natural fractures (NFs), and exhibited the greatest tortuosity, consistent with numerical simulations. (3) Under the CPI scheme, cyclic variations in flow velocity (rise–hold–decline) effectively stimulated NFs, producing 91.23% shear microcracks through microcrack aggregation and shear slip. (4) A cyclic progressive CO2 fracturing technology is proposed for coalbed methane (CBM) recovery, forming a three-tier fracture network dominated by hydraulic fractures, activated by natural fractures, and branched by offset-intersecting fractures.