Control technology for critical rock burst formations by distant and large scale hydraulic fracturing
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China Coal Geology Group Co., Ltd., Beijing 100040, China

Clc Number:

TD324

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    Abstract:

    In view of the situation that rock burst control workers still work in hazardous areas underground, and the requirement that regional control of rock burst goes ahead of underground works cannot be met, the technology for key formation treatment by distant hydraulic fracturing through boreholes to relieve rock burst is put forward. By analyzing the geological conditions in the coal mine threatened by rock bursts and the hazardous characteristics of rock bursts happened in the resent years, it is understood the critical rock burst formation of massive hard rock is commonly developed in the roof of the coalbed, and the energy release in rock burst hazards meets the requirements of the “3 factors” theory on rock burst in north China C-P coal field and Jurassic coal field. According to rock mechanic analysis, the hard and brittle critical formation is easy to fracture. The technology to release rock stress in the key formation by hydraulicly fracturing is suitable. Since drilling technologies for underground long boreholes, deep holes and directional holes from surface have been technically proven, distant rock burst control in large scale by hydraulic fracturing in long borehole is feasible. The industrial tests showed that underground long borehole can be stage?-fracture up to 800m at 40MPa with fracture half-length upto; the vertical borehole drilled from surface can be as deep as 3000m with fracture segment greater than 100m at hydraulic pressure of 80MPa with fracture half-length about 100~200m long; the surface directional borehole can be drilled wi the inseam section as long as 1000m with hydraulic up to 80MPa with fracture half-length about 100~150 m. Analysis showed the pressure on coal seam or on shelf after fracturing was about 10MPa less than that before fracturing. Compared with conventional methods, the technology for key formation treatment by distant hydraulic fracturing through boreholes to release rock burst distantly have many advantages in regional and ahead control, engineering efficiency, safety and environment protection. The unmanned condition in the area threatened by rock burst can be realized in the hazard controlling process, and the requirement of regional and ahead control can be met.

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History
  • Received:July 14,2021
  • Revised:July 14,2021
  • Adopted:July 14,2021
  • Online: December 06,2021
  • Published: September 01,2021