Method for constructing artificial water-conducting channels by pulse fracturing of water drainage boreholes in roof aquifers

Abstract

The present invention relates to the technical field of coal mining, specifically a method for constructing an artificial water channel by pulse fracturing of drainage holes in a roof aquifer. The method forms an artificial water channel in a sandstone fissure aquifer by arranging drainage holes and adopting pulse fracturing in advance through the arranged drainage holes, thereby improving the permeability of a dense and complete sandstone rock mass. The artificial water channel formed by the drainage holes in the sandstone fissure aquifer connects discontinuous water-bearing areas and water-rich areas, and guides the roof sandstone fissure water to the drainage holes through the artificial water channel, thereby achieving effective drainage of the holes and expanding the radiation area of ​​single-hole drainage. The present invention can not only avoid arranging too many drainage holes, significantly improve the drainage efficiency of the exploration and drainage holes, but also play a role in advanced drainage in the mining process. By this method, even under undesirable geological conditions, it can effectively control mine water hazards and ensure safe production in mines.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a method for constructing an artificial water-conducting channel by drilling and pulse fracturing to drain water from a roof aquifer. Background Art

[0002] During coal mining, drainage of mine roof aquifers is a common and challenging problem. As the focus of coal resource mining gradually shifts to the central and western regions, the depth of coal mining gradually increases. The degree of hydrogeological exploration in most mining areas is low. The exploration of roof water characteristics through geophysical drilling and other means is often "difficult to explore and inaccurate", and it is difficult to provide accurate distribution and continuity of water-bearing areas in the coal seam roof. This leads to a lack of effective technical support for the prevention and control of roof water hazards during the mining process, making the drainage of mine roof aquifers more complicated and difficult. Especially in the process of deep mine mining, the water pressure in the roof aquifer is greater, the water level changes are more drastic, and the groundwater penetration capacity is enhanced. The water hazard problem of the mine roof aquifer is becoming more and more challenging.

[0003] If the roof aquifer is not reasonably predicted and evaluated and targeted, it will have a serious impact on the mine construction and mining process. At present, a comprehensive theoretical foundation has been formed in the fields of roof water hazard assessment, aquifer water-richness assessment, and hydrogeological parameter calculation, which can accurately predict and evaluate roof water hazards. However, for complex geological conditions such as good water-richness of sandstone fissure water in the coal seam roof, uneven aquifers and water conductivity, strong locality, and poor rock permeability, the geophysical accuracy is difficult to meet engineering requirements. The use of drilling pre-drainage is somewhat blind, and the drainage of roof sandstone fissure water by encrypting drainage drilling holes has problems such as large engineering volume and long construction period. Traditional treatment methods such as drilling pre-drainage, grouting reinforcement, and sealing and plugging often have limited effects and cannot fully drain and control the roof sandstone water. During the mining process of the working face, large-scale roof water may still appear, which will affect the normal operation and safe production of the mine.

[0004] Especially in the geological environment where the coal seam roof is rich in water but the water conductivity and water content are uneven and localized, the water exploration and drainage method through underground drilling pre-drainage cannot effectively drain the roof sandstone fissure water. At present, the exploration and drainage of coal seam roof with good water richness but uneven water conductivity and water content is mainly based on underground drilling pre-drainage. The permeability of sandstone is controlled by the in-situ sandstone rock mass structure. Under normal conditions, the permeability of dense and complete rock mass is poor, and the drilling drainage effect is not good. Large-area roof water may appear during the mining of the working face, which will affect the normal operation and safe production of the working face. Therefore, it is urgent to solve the problem of efficient drainage of sandstone water in the coal seam roof with good water richness but uneven water conductivity and water content.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] Ensuring sufficient drainage of the mine is the basis for smooth coal mining and ensuring operation safety. Before coal mining in the working face, to effectively control the water disaster of the roof and ensure safe mining of the working face, a certain number of water exploration holes are usually arranged. The water exploration holes not only have the function of advanced exploration but also serve as water drainage. To fully drain the water-rich area of the roof, it is necessary to design a water drainage borehole layout plan according to the hydrogeological characteristics such as the water-bearing area, water-rich area, and its continuity of the mine roof obtained. The water drainage boreholes are generally divided into two types: cross-layer straight holes and directional long boreholes.

[0007] For complex geological conditions where the water-richness of the fissure water in the roof sandstone is good, the water-bearing area is discontinuous, and the permeability of the dense and intact sandstone rock mass is poor, if all discontinuous water-bearing areas are to be fully drained by drilling boreholes, not only is the engineering volume large, but it is also difficult to ensure that the fissure water in the roof sandstone can be completely drained. The core of solving this problem is to form an artificial water-conducting channel in the sandstone fissure aquifer by arranging water drainage boreholes and using technical means in advance through the arranged water drainage and exploration boreholes, improve the permeability of the dense and intact sandstone rock mass, connect the discontinuous water-bearing areas and water-rich areas through the artificial water-conducting channel formed by the water drainage boreholes in the sandstone fissure aquifer, and divert the fissure water in the roof sandstone to the water drainage and exploration boreholes through the artificial water-conducting channel, so as to achieve effective water drainage of the boreholes and expand the radiation area of single-hole water drainage.

[0008] The number of boreholes usually used for drilling is relatively small and it is difficult to meet the requirement of draining the large number and discontinuous fissure water in the roof sandstone. Therefore, to effectively drain the fissure water in the roof sandstone, only by designing additional water drainage boreholes can the problem be solved. By arranging inclined water drainage boreholes with alternating long and short holes and fracturing, not only can all water-bearing areas within the crack propagation radius of the single-hole connection fracturing be connected, effectively increasing the roof water drainage area, but also by arranging the water drainage boreholes in an inclined manner, it can be ensured that during the coal mining process, due to the action of strata movement caused by mining, the fissure water in the roof that has not been fully drained flows along the mining-induced fissures to the water drainage boreholes, realizing advanced water drainage in the working face.

[0009] Fracturing refers to injecting high-pressure fluid (water, gas, etc.) through a borehole. Under the action of fluid-solid coupling, the borehole wall generates fractures and expands. By pre-fracturing the roof water drainage boreholes to form fractures in the sandstone fissure aquifer and constructing an artificial water-conducting channel is an effective technical way to efficiently drain the fissure water in the roof sandstone. The injection displacement of the conventional hydraulic fracturing pump is constant, and the expansion direction of the hydraulic fracture is controlled by the three-dimensional in-situ stress field, expanding perpendicular to the direction of the minimum principal stress, resulting in a small number of hydraulic fractures. Pulse pump injection fracturing uses a high-pressure pulse pump to output high-frequency pulsed pressure water to impact the borehole wall of the rock, causing fatigue damage to the rock, which can overcome the influence of the in-situ stress field on the initiation and expansion direction of the hydraulic fracture and form a dense fracture network in the rock.

[0010] Therefore, a method of constructing an artificial water channel by drilling holes for drainage of the roof aquifer through pulse fracturing is proposed. This method can not only avoid the arrangement of too many drainage holes, significantly improve the drainage efficiency of the exploration and drainage holes, but also play a role in pre-drainage during the mining process. Through this method, even under unsatisfactory geological conditions, mine water hazards can be effectively controlled to ensure safe production in mines.

[0011] The object of the present invention is to provide a method for constructing an artificial water channel by pulse fracturing of a roof aquifer to drain water, so as to solve the problems mentioned in the above background technology.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] A method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer to drain water, comprising the following steps:

[0014] S100. Collect hydrogeological information of the mining area and explore the specific layer and water volume of the roof sandstone fracture aquifer;

[0015] S200, taking rock samples of the roof sandstone fracture aquifer to conduct a segmented pulse fracturing simulation experiment, and determining the optimal pulse frequency, pulse pressure peak, segment length, segment interval length and fracturing time for segmented pulse fracturing in the drainage operation area through the relationship between the pulse pressure peak, pulse frequency, segment length, segment interval length and fracturing time and the fracture development;

[0016] S300, determining the drainage drilling hole arrangement parameters, drainage drilling hole arrangement form and segmented pulse fracturing parameters according to the crack development law in the segmented pulse fracturing simulation experiment and the specific layer position and water volume of the sandstone fracture aquifer in the exploration top plate;

[0017] S400, drilling according to the drainage drilling hole arrangement parameters and drainage drilling hole arrangement form, and after the drilling construction is completed, the site is explored to determine the placement position of the pulse fracturing equipment;

[0018] S500. Install a water stop sleeve and a matching orifice valve at the orifice of the completed drainage borehole to prevent excessive water outflow from the orifice after multiple water-bearing areas are connected by fracturing; connect an external flow meter to the orifice valve to monitor the orifice return water volume, and determine whether the artificial water-conducting channel formed by the pulse fracturing is connected to the roof fissure water by the difference between the pulse pump water injection volume and the rock formation filtration loss and the orifice return water volume, and estimate the water volume of the roof water-bearing area connected by the artificial water-conducting channel;

[0019] S600. Before the fracturing operation, artificial water diversion troughs are arranged in the lanes near the orifices of the drainage boreholes to prevent excessive water outflow from the orifices after the fracturing connects multiple water-bearing areas; after the pulse fracturing equipment is transported to the operation location, the number and integrity of the equipment are checked and the equipment is connected;

[0020]

[0020] After the connection check of the S700 and pulse fracturing equipment is completed, use the drilling rig to sequentially send the stop valve, near-hole bottom packer, check valve, near-hole mouth packer, and high-pressure seal drill to the designed first-stage fracturing position to start the staged pulse fracturing operation. After the first-stage pulse fracturing is completed, use the drilling rig to withdraw part of the high-pressure seal drill pipe. The total length of the withdrawn high-pressure seal drill pipe should be equal to the staged interval length; then perform the next-stage pulse fracturing. Repeat the above operations for the staged pulse fracturing of a single hole until the pulse fracturing of all designed fracturing stages in the single hole is completed.

[0021]

[0021] After the pulse fracturing operation is completed, close the pulse fracturing pump, open the pressure relief valve in the pipeline to release the residual fracturing fluid in the pipeline. After the pressure in the pipeline drops to 0, sequentially push out equipment such as the high-pressure seal drill pipe, near-hole mouth packer, check valve, near-hole bottom packer, and stop valve and check their integrity; repeat the above pulse fracturing process to complete the staged pulse fracturing of all boreholes in sequence.

[0022]

[0022] After the pulse fracturing operation is completed, monitor and count the water return volume of the drainage boreholes, evaluate the effect of pulse fracturing on improving the drainage of the roof sandstone fissure aquifer. If the water output of the drainage borehole is too large, adjust the orifice spherical water stop valve in time to control the water output of the drainage borehole.

[0023] Preferably, in the step S100:

[0024] The hydrogeological information of the mining area is collected by means of hydrogeological investigation, three-dimensional seismic exploration, and geographic information system spatial analysis;

[0025] The specific horizons and water volume of the roof sandstone fissure aquifer are prospectively explored by arranging several exploration and drainage boreholes in the mining area.

[0026] Preferably, in the step S300:

[0027] The layout parameters of the drainage boreholes include borehole length, dip angle, spacing, azimuth, and diameter;

[0028] The end point of the layout of the drainage boreholes is located at the geometric center of the geometric figure formed by the connection of the central points of multiple discontinuous water-bearing areas that can be included in the radiation area of the pulse fracturing cracks.

[0029] Preferably, in the step S300:

[0030] The spacing of the drainage boreholes is designed according to the distribution and continuity of the water-bearing areas;

[0031] If the distribution of the water-bearing areas is uniform and the continuity is good, the spacing of the drainage boreholes is 30 - 50 m;

[0032] If the water-bearing areas are unevenly distributed and lack good continuity, the water drainage boreholes are arranged such that after single-borehole pulsed fracturing, they can fully connect to the water-bearing areas within the fracture development radiation zone. The spacing between adjacent water drainage boreholes should ensure that all discontinuous water-bearing areas between two adjacent boreholes are within the fracture development radiation range, so as to prevent excessive water output at the borehole orifice after fracturing connects multiple water-bearing areas.

[0033] Preferably, in the step S300:

[0034] The azimuth angle of the water drainage boreholes is offset by 30° to 60° towards the cutting of the working face, enabling the water drainage boreholes to conduct advanced water drainage during the coal mining process of the working face; the diameter of the water drainage boreholes is 94 mm to 120 mm; the single-stage fracturing time is 20 to 60 minutes.

[0035] Preferably, in the step S300:

[0036] The layout forms of the water drainage boreholes include cross-layer straight-hole layout, directional long-hole layout, and a combination of cross-layer straight-holes and directional long-holes.

[0037] Preferably, in the step S300:

[0038] The cross-layer straight-hole layout includes fan-shaped hole arrangement, parallel hole arrangement, and a combination of fan-shaped and parallel hole arrangements.

[0039] Preferably, in the step S300:

[0040] The fan-shaped hole arrangement means arranging multiple boreholes in a drill site, with the boreholes distributed in a fan shape; the fan-shaped hole arrangement has the advantages of fewer drill rig movements and higher borehole construction efficiency, and is suitable for water drainage from locally discontinuous water-bearing areas with relatively concentrated distributions.

[0041] Parallel hole arrangement means arranging multiple groups of alternately long and short boreholes obliquely towards the cutting of the working face in the two gateways of the coal mining face, and the alternately long and short boreholes are parallel to each other in the plane projection. The advantage of parallel boreholes is less construction work, shorter operation time, and can play a role in advanced drainage and water drainage during the coal mining of the working face. The alternately long and short hole arrangement is used to reduce the blind area of pulsed fracturing transformation of the aquifer.

[0042] Preferably, in the step S300:

[0043] The directional long - hole layout means that in the working face gate roadway, a directional drilling rig is used to arrange directional long - holes into the sandstone aquifer in the coal seam roof. The hole length is greater than 200m, and the hole trend is parallel to the working face advancing direction. Since most of the hole trajectories of the directional long - holes are in the sandstone aquifer in the roof, when segmented pulse fracturing is carried out in the directional long - holes, the transformation range of the aquifer is large, and there are many artificial water - conducting fractures formed in the aquifer. Therefore, the water drainage and release coverage area of a single hole is large. At the same time, the hole trend is parallel to the working face advancing direction, and it can also play a role in leading - ahead drainage and water release during the working face mining.

[0044] Preferably, in the step S300:

[0045] The combined layout of cross - seam vertical holes and directional long - holes means that two types of holes, namely cross - seam vertical holes and directional long - holes, are arranged in the working gate roadway. First, segmented pulse fracturing is carried out with the directional long - holes to form a large - range artificial water - conducting fracture for the overall water drainage and release of the roof fractured aquifer. Then, for the water - bearing areas not covered by the directional long - holes or the water - bearing areas with strong locality, cross - seam vertical holes are used for pulse fracturing for local water drainage and release as a supplementary safeguard measure to reduce the blind area of artificial water - conducting fractures and more fully connect the discontinuous water - bearing areas in the roof.

[0046] Preferably, in the step S600:

[0047] The connection equipment specifically includes: the water tank and the water supply pipeline are connected through the water - supply rubber hose of the water tank to supply liquid to the water tank; the pulse fracturing pump and the water tank are connected through the return - water rubber hose of the pulse pump and the water - supply rubber hose to supply liquid to the pulse fracturing pump; the pulse fracturing pump is connected to the high - pressure rubber hose to output pulse fracturing water and inject it into the hole; a three - way joint and a pressure - relief valve are connected between the high - pressure rubber hoses to relieve the water pressure in the pipeline; the pressure sensor and the flow sensor are connected to the high - pressure rubber hose to monitor the pulse pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor is connected to the fracturing measurement and control instrument through the pressure - sensor signal transmission line, and the flow sensor is connected to the fracturing measurement and control instrument through the flow - sensor signal line to transmit the monitored pulse pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument to display the pulse pressure and flow rate curves in real time and store data.

[0048] Preferably, for the connection between the orifice spherical water - stop valve and the return - water flowmeter, the return - water flowmeter is fixed to the roadway sidewall with a steel - belt buckle, the return - water flowmeter is connected to the orifice drainage rubber hose, and the orifice drainage rubber hose is connected to the drainage channels in the two gate roadways.

[0049] Preferably, in the step S900:

[0050] Monitoring and evaluating the operation effect includes monitoring and evaluating the pulse fracturing effect of the roof fractured aquifer and monitoring the water drainage and release effect;

[0051] Monitoring of pulse fracturing effect in roof fracture aquifers includes monitoring of the number and distribution of pulse fracturing cracks on the borehole wall of drainage boreholes, and monitoring of the extension range of pulse fracturing cracks;

[0052] The monitoring of water drainage effect mainly includes the statistics of borehole return water volume after pulse fracturing and the statistics of tunnel roof water dripping during normal mining of the working face.

[0053] Preferably, in step S900:

[0054] The monitoring of the crack extension range of the pulse fracturing in the drainage boreholes is carried out by using the method of using adjacent boreholes as observation holes for each other. If water is produced or the water output increases in the adjacent boreholes during the pulse fracturing process, it indicates that the pulse fracturing cracks have extended to the adjacent boreholes.

[0055] The number and distribution of pulse fracturing cracks in the borehole wall of the drainage water drilling are monitored by observing the borehole peep instrument. After the drilling construction is completed, the borehole peep instrument is used to observe the morphology of the borehole wall of the fracturing section before pulse fracturing. After the pulse fracturing, the borehole wall of the fracturing section is observed again to compare and analyze the number and distribution of pulse fracturing cracks in the drainage water drilling.

[0056] Preferably, in step S900:

[0057] The statistics of borehole return water volume after pulse fracturing refers to monitoring the pumping flow rate during fracturing through a flow sensor, calculating the rock formation filtration loss according to the indoor fracturing similar simulation experiment done in the laboratory, monitoring the orifice return water volume after the pulse fracturing is completed through the orifice return water flowmeter, judging whether the artificial water channel formed by the pulse fracturing is connected to the roof fissure water through the difference between the pulse pump injection volume and the rock formation filtration loss and the orifice return water volume, and estimating the water volume of the roof water-bearing area connected by the artificial water channel;

[0058] The statistics of the water dripping condition of the tunnel roof during the normal mining process of the working face refers to the observation and recording of the water dripping condition of the roof before and after fracturing and the water dripping condition of the roof during the mining process of the working face, and the effect of pulse fracturing on promoting water drainage in the water-bearing area of ​​the roof sandstone fracture is intuitively evaluated through macroscopic phenomena.

[0059] Compared with the prior art, the method of constructing an artificial water channel by drilling holes for drainage of roof aquifers by pulse fracturing can not only avoid the arrangement of too many drainage holes, significantly improve the drainage efficiency of the exploration and drainage holes, but also play a role in advanced drainage during the mining process. Through this method, even under unfavorable geological conditions, mine water hazards can be effectively controlled to ensure safe production in mines.

[0060] Meanwhile, the pulse fracturing of the drainage boreholes in the roof fissure aquifer serves a dual purpose of both drainage and mine pressure control. It can not only enhance the effect of draining water from the fissured water-bearing area in the roof sandstone but also pre-fracture the coal seam roof, reducing the caving step of the roof during the coal face extraction and decreasing the manifestation of mine pressure during the coal face extraction period.

[0061] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, provides a detailed description as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0063] Figure 1 It is a schematic diagram of the overall method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0064] Figure 2 It is a plan view of sectional pulse fracturing of the cross-layer parallel straight boreholes in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0065] Figure 3 It is a sectional view of sectional pulse fracturing of the cross-layer parallel straight boreholes in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0066] Figure 4 It is a plan view of sectional pulse fracturing of the cross-layer fan-shaped straight boreholes in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0067] Figure 5 It is a sectional view of sectional pulse fracturing of the cross-layer fan-shaped straight boreholes in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0068] Figure 6 It is a plan view of sectional pulse fracturing of the cross-layer directional long boreholes in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the drainage boreholes in the roof aquifer provided by the embodiment of the present invention.

[0069] Figure 7The sectional pulse fracturing profile of the directional long borehole in the method for constructing an artificial water-conducting channel by pulse fracturing of the roof aquifer drainage borehole provided by the embodiment of the present invention.

[0070] Figure 8 The plan view of the combined sectional pulse fracturing of the vertical through-layer borehole and the directional long borehole in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the roof aquifer drainage borehole provided by the embodiment of the present invention.

[0071] Figure 9 The sectional pulse fracturing profile of the combined vertical through-layer borehole and the directional long borehole in the roof aquifer in the method for constructing an artificial water-conducting channel by pulse fracturing of the roof aquifer drainage borehole provided by the embodiment of the present invention.

[0072] Figure 10 The sectional pulse fracturing diagram of the vertical through-layer borehole for the accumulated water in the old goaf of the roof in the method for constructing an artificial water-conducting channel by pulse fracturing of the roof aquifer drainage borehole provided by the embodiment of the present invention.

[0073] As shown in the figure:

[0074] 1. Roof sandstone fractured aquifer; 2. Coal seam; 3. Discontinuous water-bearing area; 4. Pulse fracturing pump; 5. Pulse pump water supply rubber hose; 6. Water tank; 7. Water tank water supply rubber hose; 8. Water supply pipeline; 9. High-pressure rubber hose; 10. First three-way joint; 11. Pressure relief valve; 12. Pressure sensor; 13. Pressure sensor signal transmission line; 14. Flow sensor; 15. Flow sensor signal transmission line; 16. Fracturing measurement and control instrument; 17. Orifice spherical water stop valve; 18. Water stop casing; 19. High-pressure sealed drill pipe; 20. Near-orifice packer; 21. Check valve; 22. Near-bottom packer; 23. Stop valve; 24. Artificial water-conducting channel; 25. Orifice drainage rubber hose; 26. Steel belt buckle; 27. Return water flowmeter; 28. Drainage channel; 29. Parallel long borehole; 30. Parallel short borehole; 31. Return air heading; 32. Conveyor heading; 33. Working face cut-through; 34. Fan-shaped borehole; 35. Directional long borehole; 36. Old kiln goaf; 37. Accumulated water in goaf. Detailed implementation manners

[0075] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention described and illustrated herein usually can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0076] Embodiment 1: As Figure 1-3 shown, in a certain mine working face, geophysical exploration reveals that there are discontinuous strip-shaped water-bearing areas above the coal seam being mined. The water-bearing area is approximately 200 - 300 m, the coal seam dip angle is 6°, and the average thickness is 1.9 m. During roadway driving, obvious water gushing occurs on the roof. In the early stage of mine geophysical exploration, roof water was drained by drilling water exploration holes. Due to the unevenness of the rock formation, the efficiency of draining water only through water exploration holes is low and the cycle is long. For two adjacent water exploration and drainage holes, the water inflows are non-uniform. The water inflow of one water exploration and drainage hole is approximately 17 m 3 / h, and the water inflow of another adjacent water exploration and drainage hole is approximately 3 m 3 / h.

[0077] To fully drain the roof sandstone fissure water, reduce roadway water gushing during the working face mining, and ensure the normal operation and safe production of the working face, the embodiments of the present invention provide a method for constructing an artificial water-conducting channel by pulse fracturing of roof aquifer drainage holes. In this method, the method of using cross-layer parallel straight holes for segmented pulse fracturing in the roof aquifer is adopted to solve the problem of low efficiency of conventional roof sandstone fissure aquifer drainage measures. The specific steps are as follows:

[0078] The first step: Collect mine hydrogeological information through means such as hydrogeological investigation, three-dimensional seismic exploration, and geographic information system (GIS) spatial analysis. The information mainly includes the distribution horizon of the roof sandstone fissure aquifer 1 and the permeability of the rock formation, etc. Arrange several water exploration holes in the mine area for advanced exploration to obtain the specific horizon and water volume of the roof sandstone fissure aquifer 1, and at the same time use them for water drainage.

[0079] The second step: Take rock samples from the roof sandstone fissure aquifer 1, transport the taken rock samples to the laboratory for indoor segmented pulse fracturing simulation experiments, study the relationship between the peak pulse pressure, pulse frequency, segmented length, segmented interval length, and fracturing time and the fracture development situation, so as to determine the optimal pulse frequency, peak pulse pressure, segmented length, segmented interval length, and fracturing time for segmented pulse fracturing in the water drainage operation area, and provide a basis for constructing an artificial water-conducting channel by pulse fracturing of roof aquifer drainage holes.

[0080] Step 3: Design a water drainage borehole layout plan and a segmented pulse fracturing plan based on the fracture development law and the distribution of water-bearing areas obtained from the indoor segmented pulse fracturing simulation experiment. In the return air crossheading 3 and the conveyor crossheading 32, parallel long boreholes 29 and parallel short boreholes 30 with alternating lengths are designed for segmented pulse fracturing. The borehole diameter is 94 mm. Among them, the length of the parallel long borehole 29 is 91 m, the elevation angle is 7.5°, and it inclines 60° towards the working face direction. The length of the parallel short borehole 30 is 47 m, the elevation angle is 12.8°, and it inclines 60° towards the working face direction. The borehole spacing is 30 m. The arrangement of long and short boreholes is adopted to reduce the blind area of the pulse fracturing transformation of the aquifer. The inclined arrangement of the boreholes towards the working face direction can enable the boreholes to play a role in advance drainage and water release during the mining of the working face.

[0081] Step 4: After the borehole layout plan is determined, construct the parallel long borehole 29 and the parallel short borehole 30. After the borehole construction is completed, explore the site to determine the placement positions of the pulse fracturing pump 4 and the water tank 6.

[0082] Step 5: Install a water stop casing 18 and a supporting orifice spherical water stop valve 17 at the orifice of the completed borehole to prevent the situation of excessive water output at the orifice after the fracturing connects multiple water-bearing areas. The orifice valve is externally connected to a backwater flowmeter 27 to monitor the backwater volume at the orifice. Determine whether the artificial water-conducting channel formed by pulse fracturing connects to the roof fissure water by the difference between the injection volume of the pulse pump and the filtration loss of the rock formation and the backwater volume at the orifice, and estimate the water volume of the roof water-bearing area connected by the artificial water-conducting channel.

[0083] Sixth step: Before the fracturing operation, drainage channels 28 are arranged in the roadways near the fracturing orifice, namely the return air crossheading 3 and the transportation crossheading 32, to prevent water accumulation in the roadways caused by a large amount of water flowing out of the orifice during the fracturing process and to wash the working face. After the pulse fracturing pump 4 and the water tank 6 are transported to the operation position, check the quantity and integrity of the equipment and connect the equipment. The water tank 6 is connected to the water supply pipeline 8 through the water supply rubber hose 7 of the water tank to supply liquid to the water tank; the pulse fracturing pump 4 is connected to the water tank 6 through the return water rubber hose and the water supply rubber hose 5 of the pulse pump to supply liquid to the pulse fracturing pump 4; the pulse fracturing pump 4 is connected to the high-pressure rubber hose 9 to output pulsed fracturing water ice into the borehole; a first three-way joint 10 and a pressure relief valve 11 are connected between the high-pressure rubber hoses 9 to relieve the water pressure in the pipeline; the pressure sensor 12 and the flow sensor 14 are connected to the high-pressure rubber hose 9 through the first three-way joint 10 to monitor the pulsed pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor 12 is connected to the fracturing measurement and control instrument 16 through the pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the fracturing measurement and control instrument 16 through the flow sensor signal line 15 to transmit the monitored pulsed pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument, and to display the pulsed pressure and flow rate curves in real time and store the data; the orifice spherical water stop valve 17 is connected to the return water flowmeter 27 through the orifice drainage rubber hose 25, and the return water flowmeter 27 is fixed to the roadway side with a steel belt buckle 26. The return water flowmeter 27 is connected to the orifice drainage rubber hose 25, and the orifice drainage rubber hose 25 is connected to the drainage channels 28 in the two crossheadings.

[0084] Seventh step: After the connection check of the pulse fracturing pump 4, the pulse pump water supply rubber hose 5, the water tank 6, and the water tank water supply rubber hose 7 is completed, use the drill rig to send the stop valve 23, the near-hole bottom packer 22, the check valve 21, the near-hole orifice packer 20, and the high-pressure sealing drill 19 to the designed first-stage fracturing position in sequence to start the segmented pulse fracturing operation. Among them, the long borehole is fractured in 3 segments, the short borehole is fractured in 2 segments, and the single-stage fracturing time is 40 min to 50 min. After the first-stage pulse fracturing is completed, use the drill rig to withdraw part of the high-pressure sealing drill pipe. The total length of the withdrawn high-pressure sealing drill pipe should be equal to the segmented interval length. Then, carry out the next-stage pulse fracturing. The segmented pulse fracturing of a single hole repeats the above operations until the pulse fracturing of all the designed fracturing segments in the single hole is completed.

[0085] Eighth step: After the pulse fracturing operation is completed, push out the high-pressure sealing drill pipe 19, the near-hole orifice packer 20, the check valve 21, the near-hole bottom packer 22, the stop valve 23 and other equipment in sequence and check their integrity. Then repeat the above pulse fracturing process to complete the segmented pulse fracturing of all the boreholes in sequence.

[0086] Step 9: After the pulsed fracturing operation is completed, monitor and count the water return volume of the drainage boreholes, etc., and evaluate the effect of pulsed fracturing on improving the drainage of the roof sandstone fissure aquifer. Specifically, monitor the change of the water return flowmeter 27 at the orifice. The monitoring period is 7 days. Compare the water return volume after fracturing recorded by the water return flowmeter 27 with the water injection volume recorded by the pulsed fracturing control instrument 16 to estimate the water content of the roof discharged through the artificial water-conducting structure constructed by pulsed fracturing within one cycle.

[0087] If the water output of the drainage borehole is too large, the orifice spherical water stop valve 17 should be adjusted in time to control the water output of the drainage borehole and achieve fully controllable drainage.

[0088] As Figure 1 、 Figure 4-5 As shown in the figure, there are many low-lying areas in the coal seam roof of a certain mine, with a large amount of accumulated water, discontinuous distribution, strong locality, uneven distribution horizons. During the coal mining process, affected by mining, the roof becomes unstable, and the accumulated water in the low-lying areas may suddenly be released, which may affect the operation area of the coal mining face below.

[0089] Example 2: Since it is difficult to completely explore the distribution of the complete low-lying area through geophysical exploration and other means, in order to fully drain the accumulated water in the roof low-lying area, reduce the roof water inrush during the coal face mining, and ensure the normal operation and safe production of the coal face, the embodiment of the present invention provides a method for constructing an artificial water-conducting channel by pulsed fracturing of the drainage borehole in the roof aquifer. This method uses the method of pulsed fracturing of the cross-layer fan-shaped straight boreholes in the low-lying water-bearing area of the roof to construct an artificial water-conducting channel to solve the problem of low efficiency of conventional drainage measures in the low-lying water-bearing area of the roof. The specific steps are as follows:

[0090] Step 1: Collect the hydrogeological information of the mining area through means such as hydrogeological investigation, three-dimensional seismic exploration, and geographic information system (GIS) spatial analysis. The main information includes the distribution horizons of the roof sandstone fissure aquifer 1 (low-lying water accumulation area) and the permeability of the rock strata, etc. Arrange several water exploration boreholes in the mining area for advanced exploration to obtain the specific horizons and water volume of the roof sandstone fissure aquifer 1 (low-lying water accumulation area), and at the same time use them for drainage.

[0091] Step 2: Take rock samples from the roof sandstone fissure aquifer 1, transport the taken rock samples to the laboratory for indoor segmented pulsed fracturing simulation experiments, study the relationship between the pulsed pressure peak value, pulsed frequency, segmented length, segmented interval length, and fracturing time and the fracture development, so as to determine the optimal pulsed frequency, pulsed pressure peak value, segmented length, segmented interval length, and fracturing time for segmented pulsed fracturing in the drainage operation area, and provide a basis for constructing an artificial water-conducting channel by pulsed fracturing of the drainage borehole.

[0092] Step 3: Design the water drainage borehole layout plan and the segmented pulse fracturing plan according to the fracture development law and the distribution of water-bearing areas obtained from the indoor segmented pulse fracturing simulation experiment. Design a set of fan-shaped boreholes 34 in the working face crossheading drill yard for segmented pulse fracturing, with a borehole diameter of 94 mm. The fan-shaped boreholes 34 are symmetrically arranged with the plane where the middle long and short boreholes are located as the symmetry plane, and the boreholes on both wings are symmetrically arranged. Among them, the length of the middle long borehole is 101 m, the elevation angle is 9°, and it is arranged parallel to the working face cutting eye 33. The length of the middle section borehole is 69 m, the elevation angle is 12°, and it is arranged parallel to the working face cutting eye 33. The right-wing short borehole is inclined 45° towards the working face, with a borehole length of 74 m and an elevation angle of 13°. The right-wing long borehole is inclined 70° towards the working face, with a borehole length of 89 m and an elevation angle of 11°. The left-wing boreholes can be symmetrically arranged with the right-wing boreholes with the plane where the middle long and short boreholes are located as the symmetry plane. The spacing between adjacent two sets of fan-shaped holes is 60 m. The fan-shaped hole arrangement method can effectively connect the low-lying water with strong locality and uneven horizons, and has the advantages of fewer times of drilling rig movement and high borehole construction efficiency, and is suitable for water drainage in relatively concentrated local discontinuous water-bearing areas.

[0093] Step 4: After the borehole layout plan is determined, construct the fan-shaped boreholes 34. After the borehole construction is completed, explore the site to determine the placement positions of the pulse fracturing pump 4 and the water tank 6.

[0094] Step 5: Install a water-stop casing 18 and a supporting orifice spherical water-stop valve 17 at the orifice of the constructed borehole to prevent the situation of excessive water output at the orifice after fracturing connects multiple water-bearing areas. The orifice valve is externally connected to a flowmeter 27 to monitor the water return volume at the orifice. Judge whether the artificial water-conducting channel formed by pulse fracturing connects the roof fissure water by the difference between the water injection volume of the pulse pump and the rock formation filtration loss volume and the water return volume at the orifice, and estimate the water accumulation volume in the low-lying area of the roof connected by the artificial water-conducting channel.

[0095] Sixth step: Before the fracturing operation, drainage channels 28 are arranged in the roadways near the fracturing orifice, namely the return air crossheading 3 and the transportation crossheading 32, to prevent water accumulation in the roadways and scouring of the working face caused by a large amount of water discharging from the orifice during the fracturing process. After the pulse fracturing pump 4 and the water tank 6 are transported to the operation position, check the quantity and integrity of the equipment and connect the equipment. The water tank 6 is connected to the water supply pipeline 8 through the water supply rubber hose 7 of the water tank to supply liquid to the water tank; the pulse fracturing pump 4 is connected to the water tank 6 through the return water rubber hose of the pulse pump and the water supply rubber hose 5 to supply liquid to the pulse fracturing pump 4; the pulse fracturing pump 4 is connected to the high-pressure rubber hose 9 to output pulsed fracturing water ice into the borehole; a first three-way joint 10 and a pressure relief valve 11 are connected between the high-pressure rubber hoses 9 to relieve the water pressure in the pipeline; the pressure sensor 12 and the flow sensor 14 are connected to the high-pressure rubber hose 9 through the first three-way joint 10 to monitor the pulsed pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor 12 is connected to the fracturing measurement and control instrument 16 through the pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the fracturing measurement and control instrument 16 through the flow sensor signal line 15 to transmit the monitored pulsed pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument, and to display the pulsed pressure and flow rate curves in real time and store the data; the orifice spherical water stop valve 17 is connected to the return water flowmeter 27 through the orifice drainage rubber hose 25, and the return water flowmeter 27 is fixed to the roadway side with a steel belt buckle 26. The return water flowmeter 27 is connected to the orifice drainage rubber hose 25, and the orifice drainage rubber hose 25 is connected to the drainage channels 28 in the two crossheadings.

[0096] Seventh step: After the connection inspection of the pulse fracturing pump 4, the pulse pump water supply rubber hose 5, the water tank 6, and the water tank water supply rubber hose 7 is completed, use the drill rig to successively send the stop valve 23, the near-hole-bottom packer 22, the check valve 21, the near-hole-orifice packer 20, and the high-pressure sealing drill 19 to the designed first-stage fracturing position to start the staged pulse fracturing operation. Among them, the long borehole is fractured in 3 stages, the short borehole is fractured in 2 stages, and the single-stage fracturing time is 40 min to 50 min. After the first-stage pulse fracturing is completed, use the drill rig to withdraw part of the high-pressure sealing drill pipe. The total length of the withdrawn high-pressure sealing drill pipe should be equal to the sectional interval length. Then, carry out the next-stage pulse fracturing. The staged pulse fracturing of a single hole repeats the above operation until the pulse fracturing of all the designed fracturing stages in the single hole is completed.

[0097] Eighth step: After the pulse fracturing operation is completed, successively push out the high-pressure sealing drill pipe 19, the near-hole-orifice packer 20, the check valve 21, the near-hole-bottom packer 22, the stop valve 23 and other equipment and check their integrity. Then repeat the above pulse fracturing process to successively complete the staged pulse fracturing of all the boreholes.

[0098] Ninth step: After the pulsed fracturing operation is completed, monitor and count the water return volume of the drainage boreholes, etc., and evaluate the effect of pulsed fracturing on improving the drainage of the low-lying area of the roof. Specifically, monitor the change of the water return flowmeter 27 at the orifice. The monitoring period is 7 days. Compare the water return volume after fracturing recorded by the water return flowmeter 27 with the water injection volume recorded by the pulsed fracturing control instrument 16 to estimate the water content in the low-lying area of the roof discharged through the artificial water-conducting structure formed by pulsed fracturing within one cycle.

[0099] If the water output of the drainage borehole is too large, the orifice spherical water stop valve 17 should be adjusted in time to control the water output of the drainage borehole and achieve fully controllable drainage.

[0100] Example 3: As Figure 1 , Figure 6-7 shown, the average thickness of the coal seam in a certain mining area is 2.8 m. The direct roof of the coal seam is mudstone with an average thickness of 2.5 m, and the main roof is fine sandstone with an average thickness of 11.4 m. The roadway is driven along the roof of the coal seam. There is rich water about 40 m above the roof of the coal seam, and the water quality is stable. The main water filling source is the fissure water in the roof sandstone, and the water-richness is good. However, during the roadway driving period, the roof has the characteristic of discontinuous water gushing, and an obvious dry-wet demarcation line can be observed. The adjacent 1-m anchor cables installed in the roadway also show the characteristic of discontinuous water gushing, indicating that the water conductivity and water content in the water-bearing area of the mining area are non-uniform and have strong locality, and the dense sandstone has poor permeability. The previous geophysical exploration cannot effectively reflect the water-bearing area of the roof, and only through the drilled exploration holes, the roof water cannot be effectively drained. During the working face mining period, problems such as large-area water gushing on the roof may occur, affecting normal operation and safe production.

[0101] To solve this problem, the embodiment of the present invention provides a method for constructing an artificial water-conducting channel by pulsed fracturing of the drainage borehole in the roof aquifer. This method uses the method of directional long-hole sectional pulsed fracturing in the roof aquifer to construct an artificial water-conducting channel to fully drain the roof sandstone water. The specific steps are as follows:

[0102] First step: Collect the hydrogeological information of the mining area through means such as hydrogeological investigation, three-dimensional seismic exploration, and geographic information system (GIS) spatial analysis. The information mainly includes the distribution horizon of the roof sandstone fissure aquifer 1 and the permeability of the rock formation, etc. Arrange several water exploration holes in the mining area for advanced exploration to obtain the specific horizon and water volume of the roof sandstone fissure aquifer 1, and at the same time use them for drainage.

[0103] Step 2: Take rock samples from the fissure aquifer 1 of the roof sandstone, transport the taken rock samples to the laboratory for indoor segmented pulse fracturing simulation experiments, study the relationships between the peak pulse pressure, pulse frequency, segmented length, segmented interval length, and fracturing time and the fracture development, so as to determine the optimal pulse frequency, peak pulse pressure, segmented length, segmented interval length, and fracturing time for segmented pulse fracturing in the water drainage operation area, and provide a basis for constructing an artificial water-conducting channel for pulse fracturing of water drainage boreholes.

[0104] Step 3: Design a water drainage borehole layout plan and a segmented pulse fracturing plan according to the fracture development law obtained from the indoor segmented pulse fracturing simulation experiment and the distribution of water-bearing areas. Design a group of directional long boreholes 35 for segmented pulse fracturing in the working face gate roadway drill field, including 3 directional long boreholes with a hole diameter of 120 mm and lengths of 549 m, 575 m, and 574 m respectively. The length of the single-segment fracturing area is 20 m, and the interval between adjacent two-segment fracturing areas is 10 m.

[0105] Step 4: After the borehole layout plan is determined, construct the directional long boreholes 35. After the borehole construction is completed, explore the site to determine the placement positions of the pulse fracturing pump 4 and the water tank 6.

[0106] Step 5: Install a water-stop casing 18 and a supporting orifice spherical water-stop valve 17 at the orifice of the constructed borehole to prevent the situation of excessive water output at the orifice after fracturing connects multiple water-bearing areas. The orifice valve is externally connected to a flowmeter 27 to monitor the water return volume at the orifice. Judge whether the artificial water-conducting channel formed by pulse fracturing connects the roof fissure water by the difference between the water injection volume of the pulse pump and the rock formation filtration loss volume and the water return volume at the orifice, and estimate the accumulated water volume in the low-lying area of the roof connected by the artificial water-conducting channel.

[0107] Step 6: Before the fracturing operation, drainage channels 28 are arranged in the roadways near the fracturing orifice, namely the return airway 3 and the conveyor gateway 32, to prevent water accumulation in the roadways caused by a large amount of water flowing out of the orifice during the fracturing process and scouring the working face. After the pulse fracturing pump 4 and the water tank 6 are transported to the operation position, check the quantity and integrity of the equipment and connect the equipment. The water tank 6 is connected to the water supply pipeline 8 through the water supply rubber hose 7 of the water tank to supply liquid to the water tank; the pulse fracturing pump 4 is connected to the water tank 6 through the return water rubber hose and the water supply rubber hose 5 of the pulse pump to supply liquid to the pulse fracturing pump 4; the pulse fracturing pump 4 is connected to the high-pressure rubber hose 9 to output pulsed fracturing water ice and inject it into the borehole; a first three-way joint 10 and a pressure relief valve 11 are connected between the high-pressure rubber hoses 9 to relieve the water pressure in the pipeline; the pressure sensor 12 and the flow sensor 14 are connected to the high-pressure rubber hose 9 through the first three-way joint 10 to monitor the pulsed pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor 12 is connected to the fracturing measurement and control instrument 16 through the pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the fracturing measurement and control instrument 16 through the flow sensor signal line 15 to transmit the monitored pulsed pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument, and to display the pulsed pressure and flow rate curves in real time and store the data; the orifice spherical water stop valve 17 is connected to the return water flowmeter 27 through the orifice drainage rubber hose 25, and the return water flowmeter 27 is fixed on the roadway sidewall with the steel belt buckle 26. The return water flowmeter 27 is connected to the orifice drainage rubber hose 25, and the orifice drainage rubber hose 25 is connected to the drainage channels 28 in the two gateways.

[0108] Step 7: After the connection check of the pulse fracturing pump 4, the pulse pump water supply rubber hose 5, the water tank 6, and the water tank water supply rubber hose 7 is completed, use the drill rig to send the stop valve 23, the near-bottom packer 22, the check valve 21, the near-orifice packer 20, and the high-pressure sealing drill 19 to the designed first-stage fracturing position in sequence to start the segmented pulse fracturing operation. Among them, the long borehole is fractured in 3 segments, the short borehole is fractured in 2 segments, and the single-stage fracturing time is 40 min - 50 min. After the first-stage pulse fracturing is completed, use the drill rig to withdraw part of the high-pressure sealing drill pipe. The total length of the withdrawn high-pressure sealing drill pipe should be equal to the segmented interval length. Then, perform the next-stage pulse fracturing. The segmented pulse fracturing of a single hole repeats the above operations until the pulse fracturing of all the designed fracturing segments in the single hole is completed.

[0109] Step 8: After the pulse fracturing operation is completed, push out the equipment such as the high-pressure sealing drill pipe 19, the near-orifice packer 20, the check valve 21, the near-bottom packer 22, and the stop valve 23 in sequence and check their integrity. Then repeat the above pulse fracturing process to complete the segmented pulse fracturing of all the boreholes in sequence.

[0110] Step 9: After completing the pulsed fracturing operation, monitor and count the water return volume of the drainage boreholes, etc., and evaluate the effect of pulsed fracturing on improving the drainage of the roof sandstone fissure aquifer. Specifically, monitor the change of the water return flowmeter 27 at the orifice. The monitoring period is 7 days. Compare the water return volume after fracturing recorded by the water return flowmeter 27 with the water injection volume recorded by the pulsed fracturing measurement and control instrument 16 to estimate the water content of the roof sandstone fissure aquifer discharged through the artificial water-conducting structure formed by pulsed fracturing within one cycle.

[0111] If the water output of the drainage borehole is too large, the orifice spherical water stop valve 17 should be adjusted in time to control the water output of the drainage borehole and achieve fully controllable drainage.

[0112] Since most of the hole trajectories of the directional long boreholes are in the roof sandstone aquifer, segmented pulsed fracturing is carried out in the directional long boreholes. The transformation range of the aquifer is large, and many artificial water-conducting fissures are formed in the aquifer. Therefore, the drainage coverage range of a single borehole is large. At the same time, the borehole trend is parallel to the working face advancing direction, and it can also play a role in leading and draining water in advance during the working face mining.

[0113] Example 4: There is accumulated water in the goaf of an old kiln above the coal seam currently being mined in a certain mining area. If the accumulated water in the goaf is not drained through technical means, serious mine water disasters may occur during coal seam mining, affecting normal operation and safe production.

[0114] Due to the large scope and high horizon of the old kiln goaf, it is difficult to determine the specific location of the accumulated water area in the goaf through geophysical exploration means. To solve this problem, the embodiment of the present invention provides a method for constructing an artificial water-conducting channel by pulsed fracturing of the roof aquifer drainage boreholes. This method conducts segmented pulsed fracturing to drain the accumulated water in the old kiln goaf by designing multiple groups of single-inclined cross-layer holes near the old kiln goaf. The specific steps are as follows:

[0115] Step 1: Collect the hydrogeological information of the mining area through means such as hydrogeological investigation, three-dimensional seismic exploration, and geographical information system (GIS) spatial analysis, mainly including the general distribution horizon and area of the old kiln goaf 36, etc.

[0116] Step 2: Take rock samples from the horizon near the old kiln goaf, transport the taken rock samples to the laboratory for indoor segmented pulsed fracturing simulation experiments, study the relationship between the peak pulsed pressure, pulse frequency, segmented length, segmented interval length, and fracturing time and the fracture development, so as to determine the optimal pulse frequency, peak pulsed pressure, segmented length, segmented interval length, and fracturing time for segmented pulsed fracturing in the drainage operation area, and provide a basis for constructing an artificial water-conducting channel by pulsed fracturing of the drainage boreholes.

[0117] Step 3: Design a water drainage borehole layout plan and a segmented pulse fracturing plan according to the fracture development law obtained from the indoor segmented pulse fracturing simulation experiment and the distribution of old goafs. In the crossheading drill site of the working face, design multiple groups of single inclined cross-layer parallel long boreholes 29 for segmented pulse fracturing, with a borehole diameter of 94 mm, a borehole length of 176 m, an elevation angle of 21°, and an inclination of 60° towards the working face direction.

[0118] Step 4: After the borehole layout plan is determined, construct the parallel long boreholes 29. After the borehole construction is completed, explore the site to determine the placement positions of the pulse fracturing pump 4 and the water tank 6.

[0119] Step 5: Install a water stop casing 18 and a supporting orifice spherical water stop valve 17 at the orifice of the completed borehole to prevent the situation of excessive water output at the orifice after fracturing connects multiple water-bearing areas. The orifice valve is externally connected to a flowmeter 27 to monitor the water return volume at the orifice. Determine whether the artificial water-conducting channel formed by pulse fracturing connects to the roof fissure water by the difference between the water injection volume of the pulse pump and the rock formation filtration volume and the water return volume at the orifice, and estimate the water accumulation volume in the low-lying area of the roof connected by the artificial water-conducting channel.

[0120] Step 6: Before the fracturing operation, arrange drainage channels 28 in the roadways near the fracturing orifice, i.e., the return air crossheading 3 and the transportation crossheading 32, to prevent waterlogging in the roadways caused by a large amount of water output at the orifice during the fracturing process and scouring the working face; wait until the pulse fracturing pump 4 and the water tank 6 are transported to the operation position, check the quantity and integrity of the equipment, and connect the equipment. The water tank 6 is connected to the water supply pipeline 8 through the water tank water supply rubber hose 7 to supply liquid to the water tank; the pulse fracturing pump 4 is connected to the water tank 6 through the pulse pump return water rubber hose and the water supply rubber hose 5 to supply liquid to the pulse fracturing pump 4; the pulse fracturing pump 4 is connected to the high-pressure rubber hose 9 to output pulsed fracturing water ice and inject it into the borehole; a first three-way joint 10 and a pressure relief valve 11 are connected between the high-pressure rubber hoses 9 to relieve the water pressure in the pipeline; the pressure sensor 12 and the flow sensor 14 are connected to the high-pressure rubber hose 9 through the first three-way joint 10 to monitor the pulsed pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor 12 is connected to the fracturing measurement and control instrument 16 through the pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the fracturing measurement and control instrument 16 through the flow sensor signal line 15 to transmit the monitored pulsed pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument, and display the pulsed pressure and flow rate curves in real time and store the data; the orifice spherical water stop valve 17 is connected to the water return flowmeter 27 through the orifice drainage rubber hose 25, and the water return flowmeter 27 is fixed to the roadway sidewall with a steel belt buckle 26. The water return flowmeter 27 is connected to the orifice drainage rubber hose 25, and the orifice drainage rubber hose 25 is connected to the drainage channels 28 in the two crossheadings.

[0121] Step 7: After the connection inspection of the pulse fracturing pump 4, the pulse pump water supply hose 5, the water tank 6, and the water tank water supply hose 7 is completed, use the drilling rig to send the stop valve 23, the near-bottom packer 22, the check valve 21, the near-orifice packer 20, and the high-pressure sealing drill 19 to the designed first-stage fracturing position in sequence to start the segmented pulse fracturing operation. Among them, the long borehole is fractured in 3 segments, the short borehole is fractured in 2 segments, and the single-segment fracturing time is 40 min to 50 min. After the first-stage pulse fracturing is completed, use the drilling rig to withdraw part of the high-pressure sealing drill pipe. The total length of the withdrawn high-pressure sealing drill pipe should be equal to the segmented interval length. Then, perform the next-stage pulse fracturing. The segmented pulse fracturing of a single hole repeats the above operations until the pulse fracturing of all the designed fracturing segments in a single hole is completed.

[0122] Step 8: After the pulse fracturing operation is completed, push out the equipment such as the high-pressure sealing drill pipe 19, the near-orifice packer 20, the check valve 21, the near-bottom packer 22, and the stop valve 23 in sequence and check their integrity. Then repeat the above pulse fracturing process to complete the segmented pulse fracturing of all the boreholes in sequence.

[0123] Step 9: After the pulse fracturing operation is completed, monitor and count the water return volume of the water drainage boreholes, etc., and evaluate the water drainage effect of the pulse fracturing in improving the water accumulation in the goaf of the roof old kiln. Specifically, monitor the change of the water return flowmeter 27 at the orifice. The monitoring period is 7 days. Compare the water return volume after fracturing recorded by the water return flowmeter 27 with the water injection volume recorded by the pulse fracturing measurement and control instrument 16 to estimate the water accumulation volume in the goaf of the roof old kiln discharged through the artificial water conduction structure formed by the pulse fracturing within a cycle.

[0124] If the water output of the water drainage borehole is too large, the orifice spherical water stop valve 17 should be adjusted in time to control the water output of the water drainage borehole and achieve full and controllable water drainage.

[0125] Example 5: As Figure 1 、 Figure 8-9 shown, a method for constructing an artificial water conduction channel by pulse fracturing of a water drainage borehole in a roof aquifer provided by an embodiment of the present invention. In this method, a combination of vertical holes through the roof aquifer and directional long boreholes is used for segmented pulse fracturing. The specific steps are as follows:

[0126] Step 1: Collect the hydrogeological information of the mining area through means such as hydrogeological investigation, three-dimensional seismic exploration, and geographic information system (GIS) spatial analysis. The main information includes the distribution horizon of the roof sandstone fissure aquifer 1 and the permeability of the rock formation, etc. Arrange several water exploration holes in the mining area for advanced exploration to obtain the specific horizon and water volume of the roof sandstone fissure aquifer 1, and at the same time use them for water drainage.

[0127] Step 2: Take rock samples from the fissure aquifer 1 of the roof sandstone. Transport the taken rock samples to the laboratory for indoor segmented pulse fracturing simulation experiments to study the relationships between the peak pulse pressure, pulse frequency, segmented length, segmented interval length, and fracturing time and the fracture development, so as to determine the optimal pulse frequency, peak pulse pressure, segmented length, segmented interval length, and fracturing time for segmented pulse fracturing in the water drainage operation area, and provide a basis for constructing artificial water-conducting channels for pulse fracturing of water drainage boreholes.

[0128] Step 3: Design the water drainage borehole layout plan and the segmented pulse fracturing plan according to the fracture development law obtained from the indoor segmented pulse fracturing simulation experiment and the distribution of the water-bearing areas. Specifically, for the borehole layout plan, combined segmented pulse fracturing is carried out using cross-layer vertical holes and directional long boreholes.

[0129] Step 4: After the borehole layout plan is determined, construct directional boreholes. After the borehole construction is completed, explore the site to determine the placement positions of the pulse fracturing pump 4 and the water tank 6.

[0130] Step 5: Install a water-stop casing 18 and a supporting orifice spherical water-stop valve 17 at the orifice of the completed borehole to prevent the situation of excessive water output at the orifice after fracturing connects multiple water-bearing areas. The orifice valve is externally connected to a flowmeter 27 to monitor the water return volume at the orifice. Judge whether the artificial water-conducting channel formed by pulse fracturing connects the roof fissure water by the difference between the water injection volume of the pulse pump and the rock formation filtration loss volume and the water return volume at the orifice, and estimate the accumulated water volume in the low-lying area of the roof connected by the artificial water-conducting channel.

[0131] Sixth step: Before the fracturing operation, drainage channels 28 are arranged in the roadways near the fracturing orifice, namely the return airway 3 and the conveyor roadway 32, to prevent waterlogging in the roadways caused by a large amount of water discharging from the orifice during the fracturing process and scouring the working face. After the pulse fracturing pump 4 and the water tank 6 are transported to the operation position, check the quantity and integrity of the equipment and connect the equipment. The water tank 6 is connected to the water supply pipeline 8 through the water supply rubber hose 7 of the water tank to supply liquid to the water tank; the pulse fracturing pump 4 is connected to the water tank 6 through the return water rubber hose of the pulse pump and the water supply rubber hose 5 to supply liquid to the pulse fracturing pump 4; the pulse fracturing pump 4 is connected to the high-pressure rubber hose 9 to output pulsed fracturing water ice into the borehole; a first three-way joint 10 and a pressure relief valve 11 are connected between the high-pressure rubber hoses 9 to relieve the water pressure in the pipeline; the pressure sensor 12 and the flow sensor 14 are connected to the high-pressure rubber hose 9 through the first three-way joint 10 to monitor the pulsed pressure and flow rate in the pipeline during the pulse fracturing process; the pressure sensor 12 is connected to the fracturing measurement and control instrument 16 through the pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the fracturing measurement and control instrument 16 through the flow sensor signal line 15 to transmit the monitored pulsed pressure and flow rate signals in the pipeline to the fracturing measurement and control instrument, and to display the pulsed pressure and flow rate curves in real time and store the data; the orifice spherical water stop valve 17 is connected to the return water flowmeter 27 through the orifice drainage rubber hose 25, and the return water flowmeter 27 is fixed to the roadway sidewall with the steel belt buckle 26. The return water flowmeter 27 is connected to the orifice drainage rubber hose 25, and the orifice drainage rubber hose 25 is connected to the drainage channels 28 in the two roadways.

[0132] Seventh step: After the connection inspection of the pulse fracturing pump 4, the pulse pump water supply rubber hose 5, the water tank 6, and the water tank water supply rubber hose 7 is completed, use the drill rig to send the stop valve 23, the near-hole-bottom packer 22, the check valve 21, the near-hole-orifice packer 20, and the high-pressure seal drill 19 to the designed first-stage fracturing position in sequence to start the segmented pulse fracturing operation. Among them, the long borehole is fractured in 3 segments, the short borehole is fractured in 2 segments, and the single-stage fracturing time is 40 min - 50 min. After the first-stage pulse fracturing is completed, use the drill rig to withdraw part of the high-pressure seal drill pipe. The total length of the withdrawn high-pressure seal drill pipe should be equal to the segmented interval length. Then, carry out the next-stage pulse fracturing. The segmented pulse fracturing of a single hole repeats the above operation until the pulse fracturing of all the designed fracturing segments in the single hole is completed.

[0133] Eighth step: After the pulse fracturing operation is completed, push out the equipment such as the high-pressure seal drill pipe 19, the near-hole-orifice packer 20, the check valve 21, the near-hole-bottom packer 22, and the stop valve 23 in sequence and check their integrity. Then repeat the above pulse fracturing process to complete the segmented pulse fracturing of all the boreholes in sequence.

[0134] Step 9: After the pulsed fracturing operation is completed, monitor and count the water return volume of the drainage boreholes, etc., and evaluate the effect of pulsed fracturing on improving the drainage of the roof sandstone fissure aquifer. Specifically, monitor the change of the water return flowmeter 27 at the borehole outlet. The monitoring period is 7 days. Compare the water return volume after fracturing recorded by the water return flowmeter 27 with the water injection volume recorded by the pulsed fracturing control instrument 16 to estimate the water content of the roof sandstone fissure aquifer discharged through the artificial water-conducting structure formed by pulsed fracturing within one cycle.

[0135] If the water output of the drainage borehole is too large, the orifice spherical water stop valve 17 should be adjusted in time to control the water output of the drainage borehole and achieve fully controllable drainage.

[0136] In the present invention, ensuring sufficient drainage of the mine is the basis for realizing smooth coal mining and ensuring operation safety. Before the coal face is mined, to effectively control the roof water hazard and ensure the safe mining of the coal face, a certain number of water exploration boreholes are usually arranged. The water exploration boreholes not only have the function of advanced exploration but also serve as drainage holes. If sufficient drainage of the water-rich area in the roof is required, a drainage borehole layout plan needs to be designed according to the hydrogeological characteristics such as the water-bearing area, water-rich area, and its continuity in the mine roof obtained. The drainage boreholes are generally divided into two types: cross-layer straight holes and directional long holes.

[0137] For complex geological conditions where the roof sandstone fissure water is rich in water, the water-bearing area is discontinuous, and the permeability of the dense and intact sandstone rock mass is poor. If all discontinuous water-bearing areas are to be fully drained by drilling boreholes, not only is the engineering volume large, but it is also difficult to ensure complete drainage of the roof sandstone fissure water. The core of solving this problem is to form an artificial water-conducting channel in the sandstone fissure aquifer through the arranged drainage boreholes by technical means, improve the permeability of the dense and intact sandstone rock mass, connect the discontinuous water-bearing areas and water-rich areas through the artificial water-conducting channel formed in the sandstone fissure aquifer by the drainage boreholes, and divert the roof sandstone fissure water to the drainage boreholes through the artificial water-conducting channel to achieve effective drainage of the boreholes and expand the radiation area of single-hole drainage.

[0138] The number of boreholes usually used for drilling is relatively small and difficult to meet the requirement of draining the numerous and discontinuous roof sandstone fissure water. Therefore, to effectively drain the roof sandstone fissure water, only by designing and drilling additional drainage boreholes and arranging and fracturing inclined drainage boreholes with alternating long and short holes can not only connect all water-bearing areas within the fracture propagation radius of single-hole connection and fracturing, effectively increase the roof drainage area, but also, by arranging the drainage boreholes in an inclined manner, ensure that during the coal mining process, due to the action of strata movement caused by mining, the insufficiently drained roof fissure water flows along the mining-induced fissures to the drainage boreholes to achieve advanced water drainage at the coal face.

[0139] Fracturing refers to the process of injecting high-pressure fluid (water, gas, etc.) through a borehole, which causes the borehole wall to crack and expand under the action of fluid-solid coupling. Pre-fracture of the roof drainage boreholes to form cracks in the sandstone fissure aquifer and construct artificial water-conducting channels is an effective technical approach to efficiently drain the roof sandstone fissure water. The conventional hydraulic fracturing pumping volume is constant, and the expansion direction of the hydraulic fracture is controlled by the three-dimensional geostress field, expanding perpendicularly to the direction of the minimum principal stress, and the number of hydraulic fractures formed is small. Pulse pumping fracturing uses a high-pressure pulse pump to output high-frequency pulse pressure water to impact the rock borehole wall, causing fatigue damage to the rock. It can overcome the influence of the geostress field on the initiation and expansion direction of hydraulic fractures and form a dense fracture network in the rock.

[0140] Therefore, the method of constructing artificial water channels by drilling holes for drainage of roof aquifers through pulse fracturing can not only avoid the arrangement of too many drainage holes, significantly improve the drainage efficiency of the exploration and drainage holes, but also play a role in pre-drainage during the mining process. Through this method, even under unfavorable geological conditions, mine water hazards can be effectively controlled to ensure safe production in mines.

[0141] In the above embodiment, the hydrophobic boreholes include water exploration and drainage boreholes used for geophysical exploration and drainage and hydrophobic boreholes used for pulse fracturing to construct water channels and advance drainage. The hydrophobic boreholes are divided into through-layer straight holes and directional through-layer long holes.

[0142] The drilling arrangement plan includes drilling arrangement parameters and drilling arrangement form.

[0143] The drilling arrangement parameters include the length, inclination, spacing, azimuth and diameter of the drilling hole. The direction of the drilling hole should be towards the geometric center point of the geometric figure formed by the connection of the center points of multiple discontinuous water-bearing areas that can be included in the pulse fracturing fracture development radiation area. The drilling hole opening position is to be determined, that is, the drilling length can be determined by the distance between the opening position and the geometric center point of the geometric figure formed by the connection of the center points of multiple discontinuous water-bearing areas. The angle between the geometric center point of the geometric figure formed by the connection of the opening position and the center points of multiple discontinuous water-bearing areas and the horizontal line is the drilling inclination.

[0144] The borehole spacing is mainly based on the distribution and continuity of the water-bearing areas. If the water-bearing areas are evenly distributed and have good continuity, the borehole spacing is usually 30 to 50 meters. If the water-bearing areas are unevenly distributed and have poor continuity, the boreholes should be arranged so that a single borehole can fully connect the water-bearing areas within the fracture development radiation area after pulse fracturing. The spacing between adjacent boreholes should ensure that all discontinuous water-bearing areas between two adjacent boreholes are within the fracture development radiation range, ensuring that each water-bearing area can be fully drained. The specific spacing should be determined according to actual conditions.

[0145] To improve the utilization rate of a single borehole and enable a single drilling to perform multiple functions, the azimuth angle of the borehole generally deviates by 30° to 60° towards the cut-eye of the working face, so that the borehole can drain water ahead during the coal mining process of the working face.

[0146] The diameter of the said borehole is usually 94 mm to 120 mm, and corresponding-sized boreholes can also be customized according to construction requirements.

[0147] The layout forms of the said boreholes include cross-layer straight borehole layout, directional long borehole layout, and the combination layout of cross-layer straight boreholes and directional long boreholes.

[0148] The cross-layer straight borehole layout means arranging cross-layer straight boreholes for segmented pulse fracturing to construct artificial water-conducting channels in the crossheading of the working face. There are two cases for the cross-layer straight boreholes: fan-shaped layout and parallel layout:

[0149] Fan-shaped hole layout means arranging multiple boreholes in a drill site, and the distribution of the boreholes is fan-shaped; the fan-shaped hole layout method has the advantages of fewer times of rig movement and high borehole construction efficiency, and is suitable for draining water from local discontinuous water-bearing areas with relatively concentrated distribution.

[0150] Parallel hole layout means arranging multiple groups of long and short alternate boreholes obliquely towards the cut-eye of the working face in the two crossheadings of the coal mining working face, and the plane projections of the long and short alternate boreholes are parallel to each other in the borehole layout plan. The advantage of parallel boreholes is less construction volume, short operation time, and can play the role of advanced drainage and water drainage during the coal mining of the working face. The long and short hole alternate layout method is used to reduce the blind area of pulse fracturing transformation of the aquifer.

[0151] The directional long borehole layout means using a directional drill rig in the crossheading of the working face to arrange directional long boreholes towards the sandstone aquifer in the coal seam roof. The length of the borehole is generally greater than 200 m, and the borehole trend is parallel to the working face advancing direction. Since most of the borehole trajectories of the directional long boreholes are in the sandstone aquifer in the roof, segmented pulse fracturing is carried out in the directional long boreholes, the transformation range of the aquifer is large, and many artificial water-conducting fissures are formed in the aquifer. Therefore, the water drainage coverage range of a single borehole is large. At the same time, the borehole trend is parallel to the working face advancing direction, and it can also play the role of advanced drainage and water drainage during the coal mining of the working face.

[0152] The combination layout of cross-layer straight boreholes and directional long boreholes means arranging two forms of boreholes, cross-layer straight boreholes and directional long boreholes, in the working crossheading. First, use the directional long boreholes for segmented pulse fracturing to form a large range of artificial water-conducting fissures for overall water drainage of the roof fissure aquifer, and then for the water-bearing areas not covered by the directional long boreholes or the water-bearing areas with strong locality, use the cross-layer straight boreholes for pulse fracturing for local water drainage as a supplementary safeguard measure to reduce the blind area of artificial water-conducting fissures and more fully connect the discontinuous water-bearing areas in the roof.

[0153] The single-stage fracturing length and the sectional interval length are determined according to the indoor sectional pulse fracturing simulation experiment after on-site sampling, the lithology of the rock formation, the rock mechanical parameters, the pulse peak value and frequency.

[0154] The single-stage fracturing time is generally about 20 - 60 minutes. It should be combined with the geological characteristics of the mining area to ensure that the artificial water-conducting channels of the structure can effectively improve the permeability of the rock formation, connect the water-bearing areas with each other, and achieve the purpose of effective water drainage.

[0155] The statement that the arranged water drainage boreholes can also be used as monitoring boreholes for each other means that during the fracturing process, the expansion range of the pulse fracturing artificial water-conducting channel can be evaluated by observing the water outflow situation at the borehole mouth of the adjacent boreholes around the fracturing borehole before and after fracturing, and it can be judged whether the constructed artificial water-conducting channel has penetrated the adjacent boreholes.

[0156] The water-bearing area also includes unexplored old goaf water above the coal seam roof. Directional long boreholes or cross-cutting holes are arranged in the gate road, and a water-stop casing and a borehole mouth valve are installed at the borehole mouth. Pulse fracturing is carried out for the water drainage boreholes that have not discharged water to construct an artificial water-conducting channel to communicate with the old goaf, and the accumulated water in the old goaf is fully drained. During fracturing, the water drainage situation is monitored in a timely manner. If a large amount of water flows out at the borehole mouth after fracturing, the borehole mouth water-stop valve should be adjusted in a timely manner to control the water outflow volume of the water drainage borehole, achieve fully controllable water drainage, and ensure operation safety.

[0157] The monitoring and evaluation of the operation effect include two aspects: the monitoring and evaluation of the pulse fracturing effect of the roof fissure aquifer and the monitoring of the water drainage effect.

[0158] The monitoring of the pulse fracturing effect of the roof fissure aquifer includes the monitoring of the number and distribution pattern of pulse fracturing cracks on the borehole wall of the water drainage borehole, the monitoring of the expansion range of the pulse fracturing cracks, etc.

[0159] The monitoring of the number and distribution pattern of pulse fracturing cracks on the borehole wall of the water drainage borehole is observed through a borehole peephole. After the borehole construction is completed, the borehole wall shape of the fracturing section is observed by a borehole peephole before pulse fracturing, and then a borehole wall peephole observation of the fracturing section is carried out again after pulse fracturing, and the number and distribution pattern of pulse fracturing cracks in the water drainage borehole are analyzed by comparison.

[0160] The monitoring of the expansion range of the pulse fracturing cracks in the water drainage borehole is observed by using the method that adjacent boreholes are used as observation boreholes for each other. If water outflow or an increase in the water outflow volume occurs in the adjacent boreholes during the pulse fracturing process, it indicates that the pulse fracturing cracks have extended to the adjacent boreholes.

[0161] The monitoring of the water drainage effect mainly includes two aspects: the statistics of the water return volume of the borehole after pulse fracturing and the statistics of the water gushing situation on the roadway roof during the normal coal face mining process.

[0162] The statistics of the water return volume of the borehole after pulsed fracturing refers to monitoring the pumping flow rate during fracturing through a flow sensor, calculating the formation filtration loss based on the indoor fracturing similarity simulation experiment conducted in the laboratory, monitoring the water return volume at the orifice of the borehole after pulsed fracturing through an orifice water return flowmeter, and judging whether the artificial water-conducting channel formed by pulsed fracturing is connected to the roof fissure water by the difference between the pulsed pumping water volume, the formation filtration loss and the water return volume at the orifice, and estimating the water volume of the roof water-bearing area connected by the artificial water-conducting channel.

[0163] The statistics of the roof water gushing situation in the roadway during the normal coal face mining process refers to observing and recording the roof water gushing situation before and after fracturing and the roof water gushing situation during the coal face mining process, and visually evaluating the effect of pulsed fracturing on promoting the drainage of the roof sandstone fissure water-bearing area through macroscopic phenomena.

[0164] The pulsed fracturing of the drainage borehole in the roof fissure aquifer has the dual functions of drainage and mine pressure control. It can not only promote the drainage effect of the roof sandstone fissure water-bearing area, but also pre-fracture the coal seam roof, reduce the caving step distance of the roof during the coal face mining process, and reduce the mine pressure manifestation during the coal face mining period.

[0165] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0166] In addition, the terms "horizontal", "vertical", "hanging", etc. do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0167] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0168] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

Claims

1. A method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer to drain water, characterized in that: The steps include: S100. Collect hydrogeological information of the mining area and explore the specific layer and water volume of the roof sandstone fracture aquifer; S200, taking rock samples of the roof sandstone fracture aquifer to conduct a segmented pulse fracturing simulation experiment, and determining the optimal pulse frequency, pulse pressure peak, segment length, segment interval length and fracturing time for segmented pulse fracturing in the drainage operation area through the relationship between the pulse pressure peak, pulse frequency, segment length, segment interval length and fracturing time and the fracture development; S300, determining the drainage drilling hole arrangement parameters, drainage drilling hole arrangement form and segmented pulse fracturing parameters according to the crack development law in the segmented pulse fracturing simulation experiment and the specific layer position and water volume of the sandstone fracture aquifer in the exploration top plate; S400, drilling according to the drainage drilling hole arrangement parameters and drainage drilling hole arrangement form, and after the drilling construction is completed, the site is explored to determine the placement position of the pulse fracturing equipment; S500, installing a water stop casing and a matching orifice valve at the orifice of the completed drainage borehole, connecting the orifice valve to an external flow meter, monitoring the orifice return water volume, judging whether the artificial water conduction channel formed by the pulse fracturing is connected to the roof fissure water through the difference between the pulse pump water injection volume and the rock formation filtration loss and the orifice return water volume, and estimating the water volume of the roof water-bearing area connected by the artificial water conduction channel; S600. Before the fracturing operation, an artificial water channel is arranged in the tunnel near the opening of the drainage borehole; After the pulse fracturing equipment is transported to the operation location, check the quantity and integrity of the equipment and connect the equipment; S700, after the pulse fracturing equipment connection inspection is completed, the stop valve, near-bottom packer, one-way valve, near-hole mouth packer, and high-pressure seal drill are sent to the designed first-stage fracturing position by the drilling rig in sequence to start the segmented pulse fracturing operation. After the first-stage pulse fracturing is completed, part of the high-pressure seal drill pipe is withdrawn by the drilling rig. The total length of the withdrawn high-pressure seal drill pipe should be equal to the segment interval length; then the next segment of pulse fracturing is carried out. The segmented pulse fracturing of a single hole repeats the above operations until the pulse fracturing of all designed fracturing sections in the single hole is completed; S800, after the pulse fracturing operation is completed, turn off the pulse fracturing pump, open the pressure relief valve in the pipeline to release the remaining fracturing fluid in the pipeline, and after the pressure in the pipeline drops to 0, push out the high-pressure sealing drill pipe, near-hole mouth packer, one-way valve, near-hole bottom packer, stop valve and other equipment in turn and check their integrity; repeat the above pulse fracturing process to complete the segmented pulse fracturing of all boreholes in turn; S900. After completing the pulse fracturing operation, monitor and count the return water volume of the drainage borehole, evaluate the effect of pulse fracturing on improving the drainage of the roof sandstone fracture aquifer, and if the water output of the drainage borehole is too large, adjust the ball water stop valve at the orifice in time to control the water output of the drainage borehole; Among them, the roof sandstone fracture aquifer contains multiple discontinuous aquifers; In the step S300: the drainage water drilling arrangement parameters include the drilling length, inclination, spacing, azimuth and diameter; the end point of the drainage water drilling arrangement is located at the geometric center point of a geometric figure formed by connecting the center points of multiple discontinuous water-bearing areas that can be included in the pulse fracturing fracture development radiation area; In the step S300: the spacing of the drainage water drilling holes is designed according to the distribution and continuity of the water-bearing area; if the water-bearing area is evenly distributed and has good continuity, the spacing of the drainage water drilling holes is 30 to 50 meters; if the water-bearing area is unevenly distributed and has poor continuity, the drainage water drilling holes are arranged so that the water-bearing areas in the fracture development radiation area can be fully connected after pulse fracturing of a single borehole, and the spacing between adjacent drainage water drilling holes should be able to ensure that all discontinuous water-bearing areas between two adjacent boreholes are within the fracture development radiation range; In the step S300, the azimuth angle of the drainage borehole is offset by 30° to 60° toward the cut-off point of the working face, so that the drainage borehole has the function of advanced drainage during the mining process of the working face; the diameter of the drainage borehole is 94 mm to 120 mm; and the single-stage fracturing time is 20 to 60 minutes; In the step S300: the drainage drilling hole arrangement includes a through-layer straight hole arrangement, a directional long drilling hole arrangement, and a combination of a through-layer straight hole and a directional long drilling hole arrangement; In the step S300: the arrangement of the through-layer straight holes includes fan-shaped hole arrangement, parallel hole arrangement and a combination of fan-shaped hole arrangement and parallel hole arrangement; In step S300: the fan-shaped hole arrangement refers to arranging multiple holes in a drilling site, and the holes are distributed in a fan shape; the parallel hole arrangement refers to arranging multiple groups of long and short alternating holes in the two inclined working faces of the coal mining working face, and the long and short alternating holes are parallel to each other in the plane projection; In the step S300: directional long borehole arrangement refers to arranging directional long boreholes in the coal seam roof sandstone aquifer using a directional drilling rig in the working face slot, the borehole length is greater than 200m, and the borehole strike is parallel to the working face advancement direction; In the step S300: the combination of through-layer straight holes and directional long boreholes refers to arranging two types of boreholes, namely through-layer straight holes and directional long boreholes, in the working drift. First, segmented pulse fracturing of directional long boreholes is used to form large-scale artificial water-conducting fractures, and the overall water drainage of the roof fracture aquifer is carried out. Then, for the water-bearing areas not radiated by the directional long boreholes or the water-bearing areas with strong localization, through-layer straight hole pulse fracturing is used to locally drain water.

2. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 1, characterized in that: In step S100: The hydrogeological information of the mining area is collected by means of hydrogeological survey, three-dimensional seismic survey and geographic information system spatial analysis; The specific layer position and water volume of the roof sandstone fracture aquifer are advanced explored by laying a number of exploration holes in the mining area.

3. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 1, characterized in that: In step S600: The connection equipment specifically includes: the water tank and the water supply pipeline are connected through the water tank water supply hose to supply liquid to the water tank; the pulse fracturing pump is connected to the water tank through the pulse pump return hose and the water supply hose to supply liquid to the pulse fracturing pump; the pulse fracturing pump is connected to the high-pressure hose to output pulse fracturing water and inject it into the borehole; the high-pressure hose is connected with a three-way joint and a pressure relief valve to relieve the water pressure in the pipeline; the pressure sensor and the flow sensor are connected to the high-pressure hose to monitor the pulse pressure and flow in the pipeline during the pulse fracturing process; the pressure sensor is connected to the fracturing measurement and control instrument through the pressure sensor signal transmission line, and the flow sensor is connected to the fracturing measurement and control instrument through the flow sensor signal line, which are used to transmit the monitored pulse pressure and flow signals in the pipeline to the fracturing measurement and control instrument, display the pulse pressure and flow curves in real time and store data.

4. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 3, characterized in that: In step S600: The connection between the orifice ball check valve and the return water flowmeter is that the return water flowmeter is fixed to the side of the lane with a steel belt buckle, the return water flowmeter is connected to the orifice drainage hose, and the orifice drainage hose is connected to the drainage channel of the two chute.

5. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 1, characterized in that: In step S900: Monitoring and evaluation of operation effects include monitoring and evaluation of pulse fracturing effects in roof fracture aquifers and monitoring of water drainage effects; Monitoring of pulse fracturing effect in roof fracture aquifers includes monitoring of the number and distribution of pulse fracturing cracks on the borehole wall of drainage boreholes, and monitoring of the extension range of pulse fracturing cracks; The monitoring of water drainage effect mainly includes the statistics of borehole return water volume after pulse fracturing and the statistics of tunnel roof water dripping during normal mining of the working face.

6. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 5, characterized in that: In step S900: The monitoring of the crack extension range of the pulse fracturing in the drainage boreholes is carried out by using the method of using adjacent boreholes as observation holes for each other. If water is produced or the water output increases in the adjacent boreholes during the pulse fracturing process, it indicates that the pulse fracturing cracks have extended to the adjacent boreholes. The number and distribution of pulse fracturing cracks in the borehole wall of the drainage water drilling are monitored by observing the borehole peep instrument. After the drilling construction is completed, the borehole peep instrument is used to observe the morphology of the borehole wall of the fracturing section before pulse fracturing. After the pulse fracturing, the borehole wall of the fracturing section is observed again to compare and analyze the number and distribution of pulse fracturing cracks in the drainage water drilling.

7. The method for constructing an artificial water channel by drilling and pulse fracturing of a roof aquifer according to claim 5, characterized in that: In step S900: The statistics of borehole return water volume after pulse fracturing refers to monitoring the pumping flow rate during fracturing through a flow sensor, calculating the rock formation filtration loss according to the indoor fracturing similar simulation experiment done in the laboratory, monitoring the orifice return water volume after the pulse fracturing is completed through the orifice return water flowmeter, judging whether the artificial water channel formed by the pulse fracturing is connected to the roof fissure water through the difference between the pulse pump injection volume and the rock formation filtration loss and the orifice return water volume, and estimating the water volume of the roof water-bearing area connected by the artificial water channel; The statistics of the water dripping condition of the tunnel roof during the normal mining process of the working face refers to the observation and recording of the water dripping condition of the roof before and after fracturing and the water dripping condition of the roof during the mining process of the working face, and the effect of pulse fracturing on promoting water drainage in the water-bearing area of ​​the roof sandstone fracture is intuitively evaluated through macroscopic phenomena.

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