Roadway roof fracturing and outburst prevention method

Abstract

The invention discloses a roadway roof fracturing and outburst prevention method. The roadway roof fracturing and outburst prevention method is applicable to outburst prevention of deep high-gas and low-permeability coal seam roadways. According to the roadway roof fracturing and outburst prevention method, a horizontal well is drilled on the ground in the direction consistent with the roadway tunneling direction, the well path trajectory is controlled in a top plate within a certain range away from the top limit of a reserved coal pillar coal seam, and the horizontal well is in butt joint with a discharging and exploiting straight well; a perforation technology is adopted, downward perforation is carried out at fixed points in a segmented manner in the horizontal section of the horizontalwell, and perforated holes do not communicate with the reserved coal pillar coal seam; then, supercritical CO2 serves as a fracturing fluid, crushed particles of a top plate of the reserved coal pillar coal seam serve as supporting agents, large-displacement cross-interface segmented fracturing is carried out on the reserved coal pillar coal seam, and cracks are expanded on the left side and theright side in the direction perpendicular to the horizontal section of the horizontal well by 20-30m respectively, so that the high-efficiency fracturing and outburst prevention of a to-be-dug transportation flat roadway and a to-be-dug air return roadway can be realized at one time, the roadway tunneling speed can be greatly improved, defects of traditional hydraulic fracturing are avoided, the increase of the yield of coal seam gas is facilitated, and a plurality of effects are realized through one action.

Description

technical field [0001] The invention relates to a method for cracking and preventing outbursts on the roof of a roadway, which is especially suitable for preventing outbursts in deep high-gas and low-permeability coal seam roadways, and belongs to the fields of coal mine safety and gas drainage. Background technique [0002] At present, the outburst prevention methods for coal seam roadways are mainly drilling gas drainage holes, arranging gas drainage roadways, hydraulic punching and hydraulic cutting, etc., but these methods usually have the disadvantages of slow roadway excavation speed, difficult operation, and high operating costs. question. [0003] In the field of coalbed methane mining, by arranging vertical wells on the ground, the roadway and working face can be relieved and prevented from bursting while mining coalbed methane. However, this method has the disadvantages of requiring a large number of wells, low gas production per well, and occupying a lot of land. ...

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Problems solved by technology

[0002] At present, the outburst prevention methods for coal seam roadways are mainly drilling gas drainage holes, arranging gas drainage roadways, hydraulic punching and hydraulic cutting, etc., but these methods usually have the disadvantages of slow roadway excavation speed, difficult operation, and high operating costs. question

[0003] In the field of coalbed methane mining, by arranging vertical wells on the ground, the roadway and working face can be relieved and prevented from bursting while mining coalbed methane. However, this method has the disadvantages of requiring a large number of wells, low gas production per well, and occupying a lot of land. , will inevitably lead to poor anti-burst effect

[0004] Arranging horizontal wells in the coal seam to extract coalbed methane requires hard coal quality. Although it can improve the extraction efficiency of coalbed methane to a certain extent, thereby reducing the gas content and achieving a certain anti-outburst effect, but because the horizontal wellbore is arranged in the coal seam, it is difficult for the follow-up The excavation of the roadway has a lot of interference, and the fracturing scale is generally small, and the fracturing fluid uses active water, which has problems such as difficult flowback, pollution of formations and groundwater, and consumption of water resources.

[0005] In order to solve the problems of drill sticking and hole collapse in horizontal well layout of structural soft coal, the "A method for enhanced drainage of coalbed methane staged fracturing horizontal wells" (CN103967472 A) proposed by Xi'an Research Institute of China Coal Science and Technology Group Flat wells are arranged in the roof between 0.5 and 1.5m away from the top of the coal seam, and the perforation is connected to the coal seam. This method provides guidance for the construction of soft coal bed methane drainage and roadway outburst prevention, but because the perforation is deep into the coal seam, Failure to utilize the energy released by the brittle fracture of the roof results in additional consumption of fracturing fluid. At the same time, because activated water is used as the fracturing fluid, in addition to defects such as difficult flowback and easy contamination of formations and groundwater, the interaction between activated water and structural soft coal It may lead to the softening of the coal structure, and the strength of quartz sand as a proppant is much higher than that of structural soft coal, which can easily lead to its embedding into the coal body under the action of high ground stress and high water injection pressure, resulting in narrower fracturing fractures or even blockage. In the end, the effects of coalbed methane drainage and outburst prevention may be different from expectations

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