Method for reducing mine earthquake level by using perforating gun and hydraulic fracturing

Abstract

The present invention relates to a perforating gun for reducing the level of mine earthquakes and a method for reducing the level of mine earthquakes by hydraulic fracturing. In order to overcome the above-mentioned defects of the prior art, the perforating gun for reducing the level of mine earthquakes of the present invention comprises a gun barrel and a perforating bullet fixing seat, the firing holes and the corresponding perforating bullets are opposite to each other, the axis lines of the opposite perforating bullets coincide and intersect perpendicularly with the axis line of the gun barrel, and the axis lines of all firing holes and perforating bullets are parallelly distributed on a vertical plane. The present invention also relates to a method for reducing the level of mine earthquakes by hydraulic fracturing. The perforating gun for reducing the level of mine earthquakes of the present invention has the advantages of simple structure and easy use. The method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention can effectively split a plurality of hydraulic fracturing surfaces parallel to the working face on the roof of the key layer, so that when the working face passes, the roof collapses in an orderly manner, thereby effectively reducing the level of mine earthquakes.

Description

Technical Field

[0001] The invention relates to a perforating gun for reducing the mine earthquake level and a method for reducing the mine earthquake level by hydraulic fracturing. Background Art

[0002] As the intensity and depth of coal mining continue to increase, mine tremors frequently occur in the thick strata above the goaf, which brings great challenges to coal mining. Therefore, mine tremor control has received extensive attention from the government, society and enterprises. To this end, a process for reducing the level of mine tremors through ground drilling hydraulic fracturing is proposed.

[0003] According to data research, the existing mine earthquake control technology mainly adopts methods such as adjusting coal mining process parameters, directional fracturing in tunnels, and directional blasting in tunnels to carry out prevention and control.

[0004] The "Experimental Study on Directional Hydraulic Fracturing Technology for Hard Roof Treatment" studied the construction process of tunnel directional hydraulic fracturing technology and its control over the collapse of hard roof. Tunnel directional hydraulic fracturing technology is limited by tunnel space, small equipment, and limited fracturing scale. It is only effective for hard strata within tens of meters above the roof.

[0005] Patent "A method for preventing and controlling impact-type mine tremors in coal seams" CN 106437711A discloses a method for preventing and controlling impact-type mine tremors by excavating a pressure-relief tunnel in the stop-mining line area of ​​the mine tremor protection zone and drilling and blasting in the coal wall of the working face. This method is only effective for hard rock formations near the roof. The blasting may cause pollution of underground air and may cause sudden accidents such as gas explosions. CN 106150503A, CN 111058819 A, CN 109339786 B, CN 108999636 A.

[0006] The above-mentioned mine earthquake control technologies all have limitations and cannot solve the problem of mine earthquakes that occur in extremely thick and hard strata hundreds of meters away from the direct top.

[0007] The Chinese invention patent with the authorization announcement number CN 106150503 B discloses a method for treating hard roof by hydraulic fracturing. The invention discloses a method for treating hard roof by hydraulic fracturing, comprising the following steps: 1) clarifying the stress state of the hard roof to be fractured; 2) selecting two corresponding different fracturing schemes according to the obtained stress state; 3) selecting the drilling position and drilling parameters and constructing the fracturing drilling; 4) performing hydraulic fracturing on the hard roof.

[0008] The advantage of the invention is that it can adopt two different fracturing schemes according to the specific situation of different ground stresses. Compared with the previous fracturing methods, the present invention is more comprehensive, the selection of fracturing methods is more flexible, the fracturing operation is more targeted, and it is easier to form fracturing cracks that are conducive to weakening the hard roof overlying the coal seam, so as to weaken the hard roof, and finally achieve timely breaking of the hard roof, shorten the roof pressure step, reduce the strong mine pressure on the working face, and benefit the safety production of coal mines.

[0009] The invention selects two different fracturing schemes according to the obtained stress state: if the stress state of the hard roof to be fractured is that the horizontal stress is greater than the vertical stress, the vertical drilling hydraulic jet layered fracturing method is used to divide the fracturing target layer into multiple layers for fracturing, as shown in the attached manual. Figure 1-2 ;

[0010] If the stress state of the hard roof to be fractured is that the horizontal stress is less than the vertical stress, the L-type drilling hydraulic jet staged fracturing method is used to fracture the target layer, as shown in the attached manual. Figure 3-4 .

[0011] Although the invention proposes two solutions, vertical drilling fracturing and L-shaped drilling fracturing, based on the difference in the magnitude of horizontal stress and vertical stress, the perforations are pointed in all directions and cannot produce the same concentrated vertical cleavage fractures, and the fracturing effect needs to be further improved. Summary of the invention

[0012] The technical problem to be solved by the present invention is how to overcome the above-mentioned defects of the prior art and provide a method for reducing the mine earthquake level by using a perforating gun and hydraulic fracturing.

[0013] In order to solve the above technical problems, the present invention discloses a perforating gun for reducing the mine earthquake level, comprising a gun barrel and a perforating bullet fixing seat, wherein the gun barrel is provided with a plurality of firing holes, the perforating bullet fixing seat is arranged in the gun barrel, and a perforating bullet is provided on the perforating bullet fixing seat opposite to each firing hole, and the axis line of the perforating bullet coincides with the axis line of the corresponding firing hole, and is characterized in that: the firing holes and their corresponding perforating bullets are opposite to each other, the axis lines of the opposite perforating bullets coincide and intersect with the axis line of the gun barrel at right angles, and the axis lines of all the firing holes and the perforating bullets are parallelly distributed on a vertical plane.

[0014] When using, try to make the axis lines of all the firing holes on the same vertical plane and trigger them at the same time, so that the perforating bullets are concentrated on one vertical plane and the resulting trajectory is also distributed on one vertical plane. This design helps the cracks to extend mainly along the pre-designed vertical plane during hydraulic fracturing.

[0015] As an optimization, the distance between the axis lines of the upper and lower adjacent emission holes of the key is controlled in the range of 0.4 to 0.6 meters, preferably 0.5 meters. With such a design, practice has proved that the above distance range has a good effect, preferably 0.5 meters.

[0016] The method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention comprises the following steps:

[0017] ①. Determine the location of each key layer: Determine the location of the key layer and isolation layer where mine earthquakes frequently occur in the stratum through ore layer measurement data and geological drilling information.

[0018] ②. Plan the vertical drilling positions: arrange the vertical drilling holes vertically and horizontally on the ground, with the spacing between adjacent vertical drilling holes in the horizontal direction controlled within 100 to 120 meters, and the spacing between adjacent vertical drilling holes in the vertical direction controlled within 120 to 150 meters.

[0019] ③. Drilling, casing and cement slurry injection: Drill holes according to the vertical drilling positions obtained in step ②, install a casing in each borehole, and then inject cement slurry between each casing and the borehole wall where it is located until all vertical drilling, casing and cement slurry injection work is completed;

[0020] ④.Perforate and hydraulically fracture each key layer from bottom to top in sequence. The method is as follows: After the cement slurry solidifies, divide each casing into multiple horizontal rows.

[0021] Starting from one end of each row of casings, two or more casings adjacent to each other in the horizontal direction are selected as a synchronous perforation and fracturing group, and lower sealers and the aforementioned perforating guns for reducing the mine seismic level are sequentially and respectively installed in each casing of the same synchronous perforation and fracturing group, so that each perforating gun for reducing the mine seismic level is located exactly in the key layer of the lowest layer, and the axis line of each firing hole on at least one side of the perforating gun for reducing the mine seismic level is on the same vertical plane as the axis line of the adjacent casing in the horizontal direction, and each perforating gun for reducing the mine seismic level is triggered at the same time to perform perforation, and then an upper sealer is installed in the corresponding casing, and then each casing of the synchronous perforation and fracturing group is connected to a hydraulic fracturing device to perform hydraulic fracturing,

[0022] Then, according to the aforementioned method, the key layer of the upper layer where the synchronous perforating and fracturing group is located is equipped with a sealer and the aforementioned perforating gun for reducing the mine earthquake level, perforating is performed, the sealer is installed, and then hydraulic fracturing operations are performed until the perforation and hydraulic fracturing operations of each casing of the same synchronous perforating and fracturing group in each key layer are completed.

[0023] Then, in the same row of casings, two or more casings adjacent to each other in the horizontal direction are selected as the next synchronous perforation and fracturing group, and the above method is repeated until the perforation and hydraulic fracturing operations of all casings in the same row are completed.

[0024] ⑤. Select the next row of casings and repeat the steps described in step ④ to perform perforation and hydraulic fracturing operations until the perforation and hydraulic fracturing operations of all casings are completed.

[0025] The present invention can simultaneously perform perforation on the same key layer of the same synchronous perforation and fracturing group, and the resulting trajectory is also distributed on the vertical plane accordingly. The above trajectory and vertical drilling have already carried out preliminary directional destruction of the rock in the corresponding key layer. Then hydraulic fracturing is carried out simultaneously, and the resulting hydraulic cracks mainly extend along the corresponding vertical planes, and large vertical cracks like axe splitting are generated on both sides of the corresponding casing. Such a design can make the cracks generated by hydraulic fracturing distributed in the required direction as much as possible, with as little hydraulic operation as possible, and minimize the mine earthquake level.

[0026] As an optimization, in step ①, the stress magnitude of the rock in each key layer in the horizontal direction is measured, and the direction with large stress is selected as the lateral direction described in step ②. This design facilitates the generation of a vertical lateral fracture surface during hydraulic fracturing.

[0027] As an optimization, the horizontal direction of the vertical drilling in step ② is preferably parallel to the direction of the working face in the well. Such a design facilitates the orderly collapse of the roof above the goaf during the advancement of the working face.

[0028] As an optimization, it also includes the sixth step: during the advancement of the working face, real-time monitoring of mine earthquakes is carried out. If a high-level mine earthquake event occurs, the number and density of vertical drilling holes need to be increased, and then perforation and hydraulic fracturing operations are carried out. This design is suitable for use in complex and changeable geological conditions.

[0029] The perforating gun for reducing the mine earthquake level of the present invention has the advantages of simple structure and easy use. The hydraulic fracturing method for reducing the mine earthquake level of the present invention can effectively split a plurality of hydraulic fracturing surfaces parallel to the working surface on the roof of the key layer, so that the roof collapses in an orderly manner when the working surface passes, thereby effectively reducing the mine earthquake level. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The following is a further description of the method for reducing the mine earthquake level by using a perforating gun and hydraulic fracturing to reduce the mine earthquake level according to the present invention in conjunction with the accompanying drawings:

[0031] Figure 1 It is a schematic diagram of the structure of a perforating gun for reducing the mine earthquake level according to the present invention;

[0032] Figure 2 Schematic diagram of the cross-sectional structure of the fourth step of the method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention (a vertical plane section along the axis of the casing and the axis of the launch hole);

[0033] Figure 3This is a schematic diagram of the cross-sectional structure of the fourth step of the method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention (II) (cut along the vertical plane passing through the axis of the casing and the axis of the launch hole);

[0034] Figure 4 It is a structural schematic diagram of step ⑤ of the method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention.

[0035] In the figure: 1 is a gun barrel, 2 is a perforating charge fixing seat, 3 is a launching hole, 4 is a perforating charge, 5 is a key layer, 6 is an isolation layer, 7 is a goaf, 8 is a vertical borehole, 9 is a casing, 10 is a lower sealer, 11 is an upper sealer, 12 is a working face, 13 is a trajectory produced after the perforating charge is fired, and 14 is a crack. DETAILED DESCRIPTION

[0036] Implementation method 1: Figure 1 As shown, the perforating gun for reducing the mine earthquake level includes a barrel 1 and a perforating bullet fixing seat 2, the barrel 1 is provided with a plurality of firing holes 3, the perforating bullet fixing seat is arranged in the barrel 1, and a perforating bullet 4 is provided on the perforating bullet fixing seat 2 facing each firing hole 3, and the axis of the perforating bullet 4 coincides with the axis of the corresponding firing hole 3, and is characterized in that: the firing holes 3 and their corresponding perforating bullets 4 are opposite to each other, the axis of the opposite perforating bullets 4 coincides, and intersects vertically with the axis of the barrel 1, and the axis of all firing holes 3 and perforating bullets 4 are parallelly distributed on a vertical plane. The distance between the axis of the upper and lower adjacent firing holes 3 is controlled in the range of 0.4 to 0.6 meters, preferably 0.5 meters.

[0037] The method for reducing the level of mine earthquakes by hydraulic fracturing of the present invention comprises the following steps:

[0038] ①. Determine the position of each key layer 5: Determine the position of the key layer 5 and the isolation layer 6 in the stratum where mine earthquakes frequently occur through ore layer measurement data and geological drilling information. The key layer 5 is preferably a large section of sandstone layer above the goaf 7.

[0039] ②. Plan the position of vertical boreholes 8: arrange the vertical boreholes 8 vertically and horizontally on the ground, with the spacing between adjacent vertical boreholes 8 in the horizontal direction controlled within the range of 100 to 120 meters, and the spacing between adjacent vertical boreholes 8 in the vertical direction controlled within the range of 120 to 150 meters.

[0040] ③. Drilling, casing 9, and cement slurry injection: According to the vertical drilling position obtained in step ②, drilling is performed, and a casing 9 is installed in each borehole. Then, cement slurry is injected between each casing and the borehole wall in which it is located until all vertical drilling 8, casing 9 and cement slurry injection work are completed;

[0041] ④. Perform perforation and hydraulic fracturing on each key layer 5 from bottom to top in sequence. The method is as follows: After the cement slurry solidifies, divide each casing 9 into multiple horizontal rows.

[0042] Starting from one end of each row of casings 9, two or more casings adjacent to each other in the transverse direction are selected as a synchronous perforation and fracturing group, and lower sealers 10 and the aforementioned perforating guns for reducing the mine earthquake level are sequentially and respectively installed into each casing 9 of the same synchronous perforation and fracturing group, so that each perforating gun for reducing the mine earthquake level is located just in the key layer 5 of the lowest layer, and the axis line of each firing hole 3 on at least one side of the perforating gun for reducing the mine earthquake level is on the same vertical plane as the axis line of the laterally adjacent casing 9, and each perforating gun for reducing the mine earthquake level is triggered at the same time to perform perforation, and then an upper sealer 11 is installed in the corresponding casing 9, and then each casing 9 of the synchronous perforation and fracturing group is connected to a hydraulic fracturing device (not shown in the figure) to perform hydraulic fracturing, such as Figure 2 shown.

[0043] Then, according to the aforementioned method, the key layer 5 of the upper layer where the synchronous perforating and fracturing group is located is installed with the lower sealer 10 and the aforementioned perforating gun for reducing the mine earthquake level, perforated, installed with the sealer 11, and then hydraulic fracturing operations are carried out until the perforation and hydraulic fracturing operations of each casing 9 of the same synchronous perforating and fracturing group in each key layer 5 are completed.

[0044] Then, in the same row of casings 9, two or more casings 9 adjacent to each other in the horizontal direction are selected as the next synchronous perforation and fracturing group, and the above method is repeated until the perforation and hydraulic fracturing operations of all casings 9 in the same row are completed. Figure 3 shown.

[0045] ⑤. Select the next row of casings 9 and repeat the steps in step ④ to perform perforation and hydraulic fracturing operations until the perforation and hydraulic fracturing operations of all casings 9 are completed.

[0046] The lateral direction of the vertical borehole 8 in step ② is preferably parallel to the direction of the working surface 12 downhole. Figure 4 shown.

[0047] Implementation method 2: In step ①, measure the stress magnitude of the rock in each key layer 5 in the horizontal direction, and select the direction with large stress as the lateral direction described in step ②.

[0048] The method of reducing the level of mine tremors by hydraulic fracturing of the present invention also includes step ⑥: during the advancement of the working face 12, the mine tremors are monitored in real time. If a high-level mine tremor event occurs, the number and density of vertical drilling holes need to be supplemented and increased, and then perforation and hydraulic fracturing operations are performed. The remaining steps are as described in Implementation Method 1 and are omitted.

Claims

1. A method for reducing the level of mine earthquakes by hydraulic fracturing, comprising the following steps: ①. Determine the location of each key layer: Determine the location of the key layer and isolation layer where mine earthquakes frequently occur in the stratum through ore layer measurement data and geological drilling information. ②. Plan the vertical drilling positions: arrange the vertical drilling holes vertically and horizontally on the ground, with the spacing between adjacent vertical drilling holes in the horizontal direction controlled within 100 to 120 meters, and the spacing between adjacent vertical drilling holes in the vertical direction controlled within 120 to 150 meters. ③. Drilling, casing and cement slurry injection: Drill holes according to the vertical drilling positions obtained in step ②, install a casing in each borehole, and then inject cement slurry between each casing and the borehole wall where it is located until all vertical drilling, casing and cement slurry injection work is completed; ④.Perforate and hydraulically fracture each key layer from bottom to top in sequence. The method is as follows: After the cement slurry solidifies, divide each casing into multiple horizontal rows. Starting from one end of each row of casings, two or more casings adjacent to each other in the horizontal direction are selected as a synchronous perforation and fracturing group, and lower sealers and perforating guns for reducing the mine seismic level are sequentially and respectively installed in each casing of the same synchronous perforation and fracturing group, so that each perforating gun for reducing the mine seismic level is located exactly in the key layer of the lowest layer, and the axis line of each firing hole on at least one side of the perforating gun for reducing the mine seismic level is on the same vertical plane as the axis line of the adjacent casing in the horizontal direction, and each perforating gun for reducing the mine seismic level is triggered at the same time to perform perforation, and then an upper sealer is installed in the corresponding casing, and then each casing of the synchronous perforation and fracturing group is connected to a hydraulic fracturing device to perform hydraulic fracturing, Then, according to the aforementioned method, the key layer of the upper layer where the synchronous perforating and fracturing group is located is installed with a sealer and a perforating gun for reducing the mine earthquake level, perforating is performed, the sealer is installed, and then hydraulic fracturing is performed until the perforation and hydraulic fracturing operations of each casing of the same synchronous perforating and fracturing group in each key layer are completed. The perforating gun for reducing the mine earthquake level includes a gun barrel and a perforating bullet fixing seat, the gun barrel is provided with a plurality of firing holes, the perforating bullet fixing seat is arranged in the gun barrel, and a perforating bullet is provided on the perforating bullet fixing seat facing each firing hole, and the axis of the perforating bullet coincides with the axis of the corresponding firing hole, characterized in that: The firing holes and their corresponding perforating bullets are opposite to each other, the axis lines of the perforating bullets are coincident and perpendicularly intersect with the axis line of the barrel, all the firing holes and the axis lines of the perforating bullets are parallelly distributed on a vertical plane, and the distance between the axis lines of the upper and lower adjacent firing holes is controlled within the range of 0.4-0.6 meters. Then, in the same row of casings, two or more casings adjacent to each other in the horizontal direction are selected as the next synchronous perforation and fracturing group, and the above method is repeated until the perforation and hydraulic fracturing operations of all casings in the same row are completed. ⑤. Select the next row of casings and repeat the steps described in step ④ to perform perforation and hydraulic fracturing operations until the perforation and hydraulic fracturing operations of all casings are completed.

2. The method for reducing mine earthquake level by hydraulic fracturing according to claim 1, characterized in that: In step ①, measure the stress magnitude of the rock in each key layer in the horizontal direction, and select the direction with large stress as the lateral direction described in step ②.

3. The method for reducing mine earthquake level by hydraulic fracturing according to claim 1, characterized in that: The horizontal direction of the vertical drilling in step ② is parallel to the working surface in the well.

4. The method for reducing mine earthquake level by hydraulic fracturing according to any one of claims 1 to 3, characterized in that: It also includes step ⑥: During the advancement of the working face, mine earthquakes are monitored in real time. If high-level mine earthquakes occur, the number and density of vertical drilling holes need to be supplemented and increased, and then perforation and hydraulic fracturing operations need to be carried out.

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