CN109826629B - Coal mine ground fracturing hard roof process selection method - Google Patents
Coal mine ground fracturing hard roof process selection method Download PDFInfo
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Abstract
The invention relates to a fracturing process selection method for fracturing a hard roof by adopting a ground fracturing technology, in particular to a coal mine ground fracturing hard roof process selection method, which solves the problem that the selection method for the coal mine hard roof ground fracturing process is lacked at present. The method comprises the following steps: firstly, marking the three-dimensional stress of a fracturing target layer; marking two different horizontal well arrangement modes according to the horizontal well arrangement direction and the working face mining direction; thirdly, testing the three-dimensional stress distribution state of the fracturing target layer; fourthly, determining a reasonable fracturing mode according to the three-dimensional stress distribution state and by combining the arrangement characteristics of the fracturing well; and fifthly, arranging the fracturing well on the ground for fracturing according to the fracturing well selection result. The method is comprehensive, reliable, high in flexibility and wide in application prospect.
Description
Technical Field
The invention belongs to a method for performing fracturing control on an overlying hard roof of a coal seam by using a ground fracturing method, and particularly relates to a process selection method for fracturing the hard roof on the coal mine ground.
Background
The control of rock stratum is the core in underground coal seam mining, and especially for a hard roof, because the strength is large, the breaking step distance is wide, and the large-area breaking of the hard roof easily causes the strong mine pressure of a stope to appear, even brings about storm disasters, and is a great difficulty in roof control. At present, for the control of a hard top plate, hydraulic fracturing or blasting and other control technical means are usually adopted underground, but the control is limited by underground construction environment, drilling length and other construction conditions, the top plate is generally weakened only in roadways on two sides of a working face, the weakening range is limited to 50m above a coal seam, and the control effect is limited. Therefore, aiming at the limitation of the current control technology, a ground fracturing method can be innovatively adopted, namely fracturing is carried out on the top plate from the ground surface to the lower fracturing drill hole through ground fracturing equipment. According to the arrangement method of the fracturing wells, the ground fracturing hard top plate can adopt a vertical well fracturing mode and a horizontal well fracturing mode, wherein the fracturing cost of the vertical well is relatively low; when the ground is fractured, the fracture expansion form is closely related to the three-dimensional stress of the stratum, so that the fracture expansion effect is different under different fracturing well arrangement modes and rock stratum three-dimensional stress conditions, and the fracturing effect is influenced accordingly. Therefore, a proper fracturing well arrangement mode is selected according to the rock stratum stress state and the fracturing requirements, the fracturing requirements of the hard top plate are met to the greatest extent, and the ground fracturing cost is reduced as much as possible.
Disclosure of Invention
The invention provides a coal mine ground fracturing hard roof process selection method, aiming at solving the problem of ground fracturing hard roof process selection during coal seam mining in a hard roof mining area.
The invention adopts the following technical scheme: a coal mine ground fracturing hard roof process selection method comprises the following steps,
a. recording the three-dimensional stress of a fracturing target layer, wherein the stress parallel to the mining direction of the working face is sigmahStress perpendicular to the face direction of mining is σHStress in the vertical direction is σv。
b. The ground fracturing can adopt two fracturing modes of a vertical well and a horizontal well, wherein the horizontal well fracturing comprises two arrangement modes, the arrangement mode that the horizontal section of the horizontal well is parallel to the mining direction of the working face is a horizontal well fracturing mode I, and the arrangement mode that the horizontal section of the horizontal well is vertical to the mining direction of the working face is a horizontal well fracturing mode II.
c. Testing and analyzing the three-dimensional stress state of the fracturing target layer by using a ground stress testing device;
when sigma isH＞σh＞σvwhen in use, a horizontal well fracturing mode ① is adopted for fracturing,
when sigma isH＞σv＞σhwhen the fracturing method is used, a vertical well or horizontal well fracturing mode ① or a horizontal well fracturing mode ② can be used for fracturing, and the fracturing modes with low cost are selected compared with the three fracturing wells;
when sigma appearsh＞σH＞σv、σh＞σv＞σH、σv＞σH＞σhAnd σv＞σh＞σHand in several stress states, fracturing is carried out by adopting a horizontal well fracturing mode ②.
d. And arranging the fracturing well on the ground for fracturing according to the fracturing well selection result.
Compared with the prior art, the invention has the following advantages: 1) the possible distribution state of all three-dimensional stresses of the rock stratum is covered, and the comprehensiveness and reliability of the selection method are guaranteed; 2) the arrangement mode and technical characteristics of each fracturing method are fully considered, and a proper fracturing mode is selected according to different stress environments; 3) the selection method is simple in flow, the ground fracturing mode can be judged only according to the mining state of the working face and the three-dimensional stress distribution characteristics of the rock stratum, the applicability is strong, and the application prospect is wide.
Drawings
FIG. 1 is a schematic diagram of a surface fracturing well fracturing arrangement;
FIG. 2 is a flow chart of a process selection for fracturing a hard roof on the ground;
in the figure: 1-working face, 2-fracturing target layer, 3-horizontal well fracturing mode with horizontal section parallel to working face mining direction, 4-horizontal well fracturing mode with horizontal section perpendicular to working face mining direction.
Detailed Description
The invention is further described by taking the hard roof surface fracturing of the great homogeneous mining area as an example and combining the attached drawings.
Fig. 1 is a schematic diagram of a fracturing well arrangement mode of the method for selecting the process for fracturing the hard roof on the coal mine ground, fig. 2 is a flow chart of specific fracturing process selection, and a proper fracturing process is selected according to a three-dimensional stress state of a fracturing target layer and by combining a hydraulic fracture expansion characteristic, and the specific steps are as follows.
a. Recording the three-dimensional stress of the fracturing target layer 2 according to the mining state of the working face 1, wherein the stress parallel to the mining direction of the working face 1 is sigmahStress perpendicular to the working face 1 in the direction of mining is σHStress in the vertical direction is σv。
b. Recording an arrangement mode that a horizontal section of the horizontal well is parallel to the mining direction of the working face 1 as a horizontal well fracturing mode I3, and recording an arrangement mode that the horizontal section of the horizontal well is vertical to the mining direction of the working face 1 as a horizontal well fracturing mode II 4;
c. the ground stress testing device is adopted to test and analyze the three-dimensional stress state of the fracturing target layer, and the result shows that the three-dimensional stress distribution state in the fracturing target layer is sigmaH＞σh＞σv。
d. According to the figure 2, a horizontal well fracturing mode is adopted for fracturing.
e. And arranging a horizontal well on the ground for fracturing according to the fracturing well selection result.
The field monitoring result shows that the maximum principal stress sigma of the crack parallel isHDirection, vertical minimum principal stress σvThe direction is expanded, a horizontal crack surface is formed in the fracturing target layer, and the thickness of the hard top plate is reduced; the mine pressure monitoring shows that after ground fracturing, the mine pressure action strength of the fracture instability of the hard roof is obviously reduced, the working face support resistance is reduced by 15%, the roadway deformation is reduced by 45%, and the correctness of the ground fracturing process selection is verified. By adopting the method for reasonably selecting the process for fracturing the hard roof on the ground, the method has important significance for efficiently controlling the hard roof, weakening the mining field intensity mine pressure disaster and ensuring the safe and efficient mining of the coal seam in the mining area with the hard roof.
Claims (1)
1. A coal mine ground fracturing hard roof process selection method is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
a. recording the three-dimensional stress of a fracturing target layer, wherein the stress parallel to the mining direction of the working face is sigmahStress perpendicular to the face direction of mining is σHStress in the vertical direction is σv；
b. The ground fracturing can adopt two fracturing modes of a vertical well and a horizontal well, wherein the horizontal well fracturing comprises two arrangement modes, the arrangement mode that the horizontal section of the horizontal well is parallel to the mining direction of a working face is a horizontal well fracturing mode I, and the arrangement mode that the horizontal section of the horizontal well is vertical to the mining direction of the working face is a horizontal well fracturing mode II;
c. testing and analyzing the three-dimensional stress state of the fracturing target layer by using a ground stress testing device;
when sigma isH＞σh＞σvwhen in use, a horizontal well fracturing mode ① is adopted for fracturing,
when sigma isH＞σv＞σhwhen the fracturing method is used, a vertical well or horizontal well fracturing mode ① or a horizontal well fracturing mode ② can be used for fracturing, and the fracturing modes with low cost are selected compared with the three fracturing wells;
when sigma appearsh＞σH＞σv、σh＞σv＞σH、σv＞σH＞σhAnd σv＞σh＞σHin several stress states, a horizontal well fracturing mode ② is adopted for fracturing;
d. and arranging the fracturing well on the ground for fracturing according to the fracturing well selection result.
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| CN110295880B (en) * | 2019-07-04 | 2021-05-14 | 中国矿业大学 | Method for optimizing stoping line of multi-dimensional hydraulic fracturing coal seam roof |
| CN112160792B (en) * | 2020-08-31 | 2022-12-30 | 太原理工大学 | Staged hydraulic fracturing working method for underground hard top plate |
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| CN102279131B (en) * | 2011-07-18 | 2013-04-24 | 中国石油大学(北京) | Simulation experiment method of coal seam hydraulic fracture |
| CN103390108B (en) * | 2013-07-25 | 2016-08-31 | 中国石油大学(北京) | A kind of well type method for designing based on fracturing geology body compressibility and device |
| CN105952429B (en) * | 2016-05-17 | 2018-11-20 | 中国地质大学（武汉） | Terrestrial facies shale air cleft network pressure splits parameter preferred method |
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| CN106150503B (en) * | 2016-07-05 | 2018-06-01 | 重庆大学 | A kind of method that tight roof is administered in hydraulic fracturing |
| CN107589020B (en) * | 2017-07-17 | 2018-07-27 | 华北水利水电大学 | A kind of hydraulic fracturing test method based on stress path |
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