Method for improving permeability through coal mine downhole slotting pressure-maintaining guide fracturing

Abstract

The invention discloses a method for improving the permeability of a coal seam through coal mine downhole slotting pressure-maintaining guide fracturing. The method is suitable for permeability improving operation of the low-permeability coal seam. The method for improving the permeability through guide fracturing is characterized in that guide holes are also formed while fracturing holes are formed, and appropriate slotting parameters are designed according to the coal seam stratum condition; the fracturing holes and guide holes are slotted; and then certain water pressure of the guide holesis kept, and the fracturing holes are fractured hydraulically. Compared with a common hydraulic fracturing method, the method for improving the permeability through guide fracturing has the advantagesthat fracture propagation can be effectively guided and controlled, the hydraulic fracturing blank zone is reduced, and the fracturing range of the fracturing holes is increased; and meanwhile, through the method, a local pressure relief area can be generated in a coal mass, the fracture initiation pressure of hydraulic fracturing is effectively reduced, the defect that a top plate and a bottom plate are damaged and consequently secondary disasters occur and other defects are overcome, the fracture morphology is strengthened, and finally the purposes of improving the fracturing effect and extracting gas efficiently are achieved.

Description

technical field [0001] The invention relates to an underground coal mine slit pressure-maintaining guided fracturing anti-permeability method, which belongs to the technical field of gas control in the underground area of ​​the coal mine, and is especially suitable for mines with unbalanced fracturing effects and a large number of fracturing "blank zones". Background technique [0002] Gas (coalbed methane), as an unconventional natural gas that is mainly stored in coal seams in an adsorbed state, is the main factor that threatens the safety of coal mine production, and it is also a clean energy that will be developed in my country in the future. In recent years, my country has paid more and more attention to coal mine gas control in order to eliminate the threat of gas to coal mine safety production and comprehensively utilize gas to improve economic benefits. Since the "hydraulic" gas control method was popularized and applied, many scholars at home and abroad have devoted...

AI Technical Summary

Problems solved by technology

However, there are still deficiencies: high fracture initiation pressure, great damage to roof and floor stability, unfavorable for subsequent excavation and support work, and difficulty in controlling the initiation position and extension of fractures in the coal seam. It is easy to turn to the roof and floor and expand and extend, making it difficult to effectively fracturing the coal seam. A single main fracture can easily form a fracturing "blank zone", and the gas drainage concentration decays quickly, the drainage efficiency is low, and the drainage effect is not obvious. Gas outburst accidents are prone to occur from time to time, the construction cost is high, and the fracturing effect is incomplete, etc. (Wang Yaofeng, He Xueqiu, Wang Enyuan, et al. Research progress and development trend of hydraulic coal seam anti-permeability technology[J]. Coal Journal, 2014, 39(10 ):1945-1955.)

However, it was found in the field application that the effect of the above-mentioned guided fracturing is not ideal

The analysis found that the main reason is that the control ability of the disc-shaped slit to the crack initiation position is poor, and the pilot hole without hydraulic pressure has a weak guiding ability to the crack.

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