Fracturing relief method for stress concentration of remaining ore pillars in overlying goaf

Patent metadata

Field	Value
Publication number	US-11299954-B2
Application number	US-201816768889-A
Country	US
Kind code	B2
Filing date	Nov 2, 2018
Priority date	May 31, 2018
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

Abstract

Provided is a fracturing relief method for stress concentration of remaining ore pillars in an overlying goaf, including first, performing directional fracturing on a roof to optimize the stress of the roof and reduce the source of force; secondly, performing pulse fracturing on a coal pillar to produce a crack network, weaken the stiffness of the coal pillar and reduce the bearing capacity of the coal pillar; and finally, performing pulse fracturing on a floor strata of the coal pillar to reduce the ability of transferring stress concentration thereof. A drilling machine is used for separately constructing fracturing drill holes in a roadway to a set depth at an interval in a direction oblique to the coal pillar in an upper goaf. The roof, the coal pillar and the floor can be fractured by an oblique fracturing hole in a sublevel retreating manner. The position of the directional fracturing of the roof is approximately 1 m above the middle of a main roof above the coal pillar. The method reduces the width of the lower coal pillar, improves the coal mining rate, reduces the deformation of the lower coal roadway, effectively solves the problems of mine pressure passing through the coal pillar on the working face of the lower coal seam, rock burst, and coal and gas outburst in the mining of the lower coal seam, and simultaneously has the advantages of high safety factor, simple method, convenient construction and low cost.

First claim

What is claimed is:

1. A fracturing relief method for stress concentration of remaining ore pillars in an overlying goaf, comprising the following steps:
step 1: separately constructing three rows of fracturing drill holes in a roadway to a set depth at an interval in a direction oblique to a coal pillar in an upper goaf by using a drilling machine, wherein a position of a final hole of a first row of the fracturing drill holes is 1 m above a middle of a main roof above the coal pillar, a position of a final hole of a second row of the fracturing drill holes is 1 m above a middle of the coal pillar, and a position of a final hole of a third row of the fracturing drill holes is at a section of ¾ of the coal pillar;
step 2: mounting and commissioning a hydraulic fracturing high-pressure pump and a hydraulic fracturing pulse pump;
step 3: sending a packer to a to-be-fractured area of a to-be-fractured drill hole, sequentially connecting a high-pressure seal mounting rod, a transfer joint and a high-pressure pipeline, and separately connecting the high-pressure pipeline to the hydraulic fracturing pulse pump and the hydraulic fracturing high-pressure pump through a three-way valve;
step 4: performing high-pressure hydraulic fracturing on a main roof area in the first row of the fracturing drill holes, and then performing pulse hydraulic fracturing on a coal pillar area in the first row of the fracturing drill holes;
step 5: performing pulse hydraulic fracturing on the second row of the fracturing drill holes; and
step 6: performing pulse hydraulic fracturing on the coal pillar area in the third row of the fracturing drill holes, and then performing pulse hydraulic fracturing again on a floor area in the third row of the fracturing drill holes.

2. The fracturing relief method for the stress concentration of the remaining ore pillars in the overlying goaf according to claim 1 , wherein, in step 4, the specific step of performing hydraulic fracturing on the first row of the fracturing drill holes comprises following steps:
(a) connecting the high-pressure seal mounting rod with the packer, sending the packer to a corresponding first-row drill hole main roof fracturing zone in a first fracturing drill hole of the first row, then connecting the high-pressure pipeline connected to the hydraulic fracturing high-pressure pump and the hydraulic fracturing pulse pump onto the high-pressure seal mounting rod, and using a hand pump to infuse high-pressure water into the packer through a high-pressure thin hose to expand the packer and seal the hole, wherein a pressure relief valve and a hydraulic fracturing measuring and controlling instrument are arranged on the high-pressure pipeline;
(b) closing a switch valve II, opening a switch valve I, turning on the hydraulic fracturing high-pressure pump, and infusing high-pressure water into the drill hole through the high-pressure pipeline to perform hydraulic fracturing; when a construction pressure monitored by the hydraulic fracturing measuring and controlling instrument is smaller than 5 MPa or when a coal seam sweats for more than 5-7 minutes, turning off the hydraulic fracturing high-pressure pump and opening the pressure relief valve;
(c) retreating the packer to a corresponding first-row drill hole coal pillar fracturing zone by adopting sublevel retreating fracturing, sealing the hole again, closing the switch valve I, opening the switch valve II, and performing fracturing again by using the hydraulic fracturing pulse pump; and
(d) removing the packer and the high-pressure seal mounting rod.

3. The fracturing relief method for the stress concentration of the remaining ore pillars in the overlying goaf according to claim 2 , wherein steps of drilling holes and hydraulic fracturing are synchronously performed in parallel and both the drilling holes and the hydraulic fracturing are conducted according to a sequence of a first fracturing drill hole of the first row, a first fracturing drill hole of the second row, a first fracturing drill hole of the third row, a second fracturing drill hole of the first row, a second fracturing drill hole of the second row, a second fracturing drill hole of the third row . . . an Nth fracturing drill hole of the first row, an Nth fracturing drill hole of the second row and an Nth fracturing drill hole of the third row.

4. The fracturing relief method for the stress concentration of the remaining ore pillars in the overlying goaf according to claim 1 , wherein, in step 5, the specific step of performing hydraulic fracturing on the second row of the fracturing drill holes comprises following steps:
(a) connecting the high-pressure seal mounting rod with the packer, sending the packer to a corresponding second-row drill hole coal pillar fracturing zone in a first fracturing drill hole of the second row, then connecting the high-pressure pipeline connected to the hydraulic fracturing high-pressure pump and the hydraulic fracturing pulse pump onto the high-pressure seal mounting rod, and using a hand pump to infuse high-pressure water into the packer to expand the packer and seal the hole, wherein a pressure relief valve and a hydraulic fracturing measuring and controlling instrument are arranged on the high-pressure pipeline;
(b) closing a switch valve I, opening a switch valve II, turning on the hydraulic fracturing pulse pump, and infusing pulse water into the first fracturing drill hole of the second row through the high-pressure pipeline to perform hydraulic fracturing; when a construction pressure monitored by the hydraulic fracturing measuring and controlling instrument is smaller than 5 MPa or when a coal seam sweats for more than 5-7 minutes, turning off the hydraulic fracturing pulse pump and opening the pressure relief valve; and
(c) removing the packer and the high-pressure seal mounting rod.

5. The fracturing relief method for the stress concentration of the remaining ore pillars in the overlying goaf according to claim 4 , wherein steps of drilling holes and hydraulic fracturing are synchronously performed in parallel and both the drilling holes and the hydraulic fracturing are conducted according to a sequence of a first fracturing drill hole of the first row, a first fracturing drill hole of the second row, a first fracturing drill hole of the third row, a second fracturing drill hole of the first row, a second fracturing drill hole of the second row, a second fracturing drill hole of the third row . . . an Nth fracturing drill hole of the first row, an Nth fracturing drill hole of the second row and an Nth fracturing drill hole of the third row.

6. The fracturing relief method for the stress concentration of the remaining ore pillars in the overlying goaf according to claim 1 , wherein, in step 6, specific step of performing hydraulic fracturing on the third row of the fracturing drill holes comprises following steps:
(a) connecting the high-pressure seal mounting rod with the packer, sending the packer to a corresponding third-row drill hole coal pillar fracturing zone in a first fracturing drill hole of the third row, then connecting the high-pressure pipeline connected to the hydraulic fracturing high-pressure pump and the hydraulic fracturing pulse pump onto the high-pressure seal mounting rod, and using a hand pump to infuse high-pressure water into the packer to expand the packer and seal the hole, wherein a pressure relief valve and a hydraulic fracturing measuring and controlling instrument are arranged on the high-pressure pipeline;
(b) closing a switch valve I, opening a switch valve II, turning on the hydraulic fracturing pulse pump, and infusing pulse water into the first fracturing drill hole of the third row through the high-pressure pipeline to perform hydraulic fracturing; when a construction pressure mon

Assignees

• Univ China Mining
• Xuzhou Usure Mining Tech Co Ltd

Inventors

• Huang Bingxiang
• Shao Luying
• Zhao Xinglong
• Chen Shuliang

Classifications

• E21C45/04 Primary

  by use of highly pressurised liquid · CPC title

• E21B43/26

  by forming crevices or fractures · CPC title

• E21D7/00

  Shaft equipment, e.g. timbering within the shaft {(lifts in hoistways or mines B66B15/00 - B66B19/00)} · CPC title

• E21B33/127 Primary

  with inflatable sleeve (E21B33/122, E21B33/124 take precedence) · CPC title

• E21B4/02

  Fluid rotary type drives · CPC title