Coupling fracturing method for hard coal bed roof

Abstract

Provided is a coupling fracturing method for a hard coal bed roof. A drilling machine is utilized for drilling fracturing drill holes inside the hard roof till the design position, specifically, each static fracturing guide drill hole is formed between every two pulse hydraulic fracture drill holes so as to form a fracturing system; the fracture drill holes are connected to a pulse water injection pump through an isometric flow distributor with adjustable frequency, and the static fracturing drill holes are filled with static crushing agent slurry; under the action of expansion force of the static crushing agent slurry, initial cracks formed around the drill holes are monitored, released heat irradiates continuously towards the portions around the drill holes, a similarly elliptical temperature field is generated, and the elasticity modulus of a rock stratum is reduced; and under the action of hydraulic pressures of different frequencies, a fracture zone, a fatigue zone and an original stress zone are formed in the positions, around the fracture drill holes, of the rock stratum, when pressure water flows to the rock stratum bearing heat conduction along the cracks, the water and heat effect weakens the strength of the rock stratum, and the through time for crack zones among the drill holes is shortened. The method can sufficiently improve the utilization rate of the drill holes, operation is easy, and construction is safe and reliable.

Description

technical field [0001] The invention relates to a roof coupling fracturing method, in particular to a hard coal seam roof coupling fracturing method suitable for work such as roof fracturing and pressure relief in goafs. Background technique [0002] Cracking the goaf roof and causing it to collapse is an effective way to prevent the abnormal accumulation of gas in the goaf and reduce the impact of rock pressure on the overlying strata and remote strata. Generally, different methods of pressure relief and caving are selected according to the properties of the roof stratum in the goaf. If the direct roof strength is low, the collapse length can be determined according to the initial pressure step of the roof, and the rock stratum will fall and accumulate by itself to prevent The old roof continues to sink downward; if the direct roof is of high strength and it is difficult to settle by the rock's own weight, high-pressure hydraulic fracturing or deep-hole blasting is usually ...

AI Technical Summary

Problems solved by technology

However, in the traditional roof fracturing process, the pilot hole is only used as a medium unit to provide a free weak surface, and there are fewer fracture zones around the drill hole, which are easy to close, and the degree of fracture is reduced, which may result in wasted drilling

Images