Method and equipment for controlling top coal cavability with pulse hydraulic fracturing

Abstract

The invention discloses a method and equipment for controlling top coal cavability with pulse hydraulic fracturing. According to the method, advantages of methods of pulse fracturing and common hydraulic fracturing are combined, a crack network is generated in coal through pulse hydraulic fracturing firstly, secondly, the crack network is further expanded through common large-displacement hydraulic fracturing, then a coal structure can be sufficiently transformed, the top coal breakage degree can be reduced, and the top coal cavability can be improved. The equipment disclosed by the inventioncomprises a small-displacement pulse pump and a large-displacement common pump which are controlled through a three-way valve and a switch valve, in construction, one path of the pulse pump is firstlycommunicated, a common high-pressure pump pipeline is closed, a pulse channel is closed after pulse fracturing is completed, and a common fracturing channel is opened. By adopting the method and theequipment, sufficient cracks can be generated in top coal, an effect of weakening the top coal can be achieved, the top coal cavability can be improved, the top coal cavability breakage degree can bereduced, convenience in construction is achieved, safety and reliability are achieved, and resource waste can be reduced.

Description

Technical field [0001] The invention relates to a method for controlling the caving of top coal, in particular to a method and equipment for controlling the caving of top coal by pulse hydraulic fracturing, and belongs to the technical field of coal mining. Background technique [0002] The reserves and output of thick and extra-thick coal seams in my country account for more than 40% of the total coal reserves and total output. Fully-mechanized top coal caving is a high-yield and efficient coal mining method for thick coal seams that has developed rapidly in my country. At present, fully-mechanized caving Mining has become the dominant coal mining method for thick and extra-thick coal seams in my country. The basic requirement of fully mechanized caving mining is "complete before the support, broken after the support". Due to the limitation of its technical characteristics, the mine pressure on the overlying rock layer on the hard and thick coal seam or the caving coal face appea...

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Problems solved by technology

[0004] The deep hole pre-blasting technology, blasting and water injection combined pre-comprehensive weakening technology all involve the management and transportation of explosives and detonators, and the "one shot, three inspection system" and "three-person chain firing system" must be strictly implemented for blasting, and the safety management is complicated; A large amount of harmful gases such as CO produced instantly by large-scale blasting have a huge impact on mine ventilation safety management; for high-gas mines, blasting broken coal pillars should not be used due to the hidden danger of gas explosion induced by blasting sparks; fully mechanized mining faces are generally about 200m , deep-hole blasting is carried out in the upper and lower alleys, the drill holes need to radiate the whole area, and the drill holes are long, so a large amount of explosives, detonators and other pyrotechnics are required, and the economic cost is high; explosive blasting usually arranges dense drill holes within a certain range, Single hole control range is small

[0005] Coal seam water injection fracturing technology Since the pressure of coal seam water injection is generally around 5 MPa, the crack propagation direction of hydraulic fracturing is controlled by the three-dimensional stress field, and the cracks produced are few and sparse, and the degree of weakening of the strength of the coal body is limited, so it is impossible to form enough cracks. cracks, so the effect of breaking the top coal is not obvious

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