METHOD FOR CONSTRUCTING ARTIFICIAL WATER-CONDUCTING CHANNEL THROUGH PULSE HYDRAULIC FRACTURING OF DRAINAGE BOREHOLES IN ROOF AQUIFER
20250354488 ยท 2025-11-20
Assignee
Inventors
- Xinglong ZHAO (Xuzhou, CN)
- Bingxiang Huang (Xuzhou, CN)
- Zhipeng WEI (Xuzhou, CN)
- Shuliang CHEN (Xuzhou, CN)
Cpc classification
E21C37/12
FIXED CONSTRUCTIONS
International classification
E21C37/12
FIXED CONSTRUCTIONS
Abstract
A method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer includes constructing an artificial water-conducting channel in a sandstone fissure aquifer through arrangement of drainage boreholes and pulse hydraulic fracturing, which improves the permeability of dense and intact sandstone rock masses. The artificial water-conducting channel formed through arrangement of drainage boreholes is connected to discontinuous water-bearing areas and water-rich areas, and water from roof sandstone fissures is diverted to the drainage boreholes through the artificial water-conducting channel, thereby achieving effective drainage of the boreholes and expanding a radiation range of single-borehole drainage. The method not only avoids the arrangement of excessive drainage boreholes and significantly improves the drainage efficiency of prospecting and drainage boreholes, but also facilitates advance drainage during the mining process. The method enables effective control of mine water hazards, thereby ensuring safe production of the mine.
Claims
1. A method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer, comprising the following steps: S100, collecting hydrogeological information of a mining area, and exploring a specific stratigraphic horizon and water volume of a roof sandstone fissure aquifer; S200, extracting rock samples from the roof sandstone fissure aquifer for a segmented pulse hydraulic fracturing simulation experiment to study the relationship of a pulse pressure peak, a pulse frequency, a segment length, a segment interval length, and a fracturing duration with fracture development, so as to determine an optimal pulse frequency, an optimal pulse pressure peak, an optimal segment length, an optimal segment interval length, and an optimal fracturing duration for segmented pulse hydraulic fracturing in a drainage operation area; S300, determining drainage borehole arrangement parameters, drainage borehole arrangement forms, and segmented pulse hydraulic fracturing parameters according to a fracture development law and the specific stratigraphic horizon and water volume of the roof sandstone fissure aquifer derived from the segmented pulse hydraulic fracturing simulation experiment; S400, drilling according to the drainage borehole arrangement parameters and the drainage borehole arrangement forms, and surveying a site after the drilling, to determine placement positions of pulse hydraulic fracturing equipment; S500, installing a water-stopping casing and a matching spherical orifice water shutoff valve at an orifice of the drainage borehole drilled, externally connecting the spherical orifice water shutoff valve to a return flowmeter to monitor a water return volume at the orifice, determining whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of a pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimating a water volume of a water-bearing area of the roof connected to the artificial water-conducting channel; S600, before a fracturing operation, arranging an artificial water-conducting trough in a roadway near the orifice of the drainage borehole; and after the pulse hydraulic fracturing equipment is transported to a designated operation location, checking equipment quantity and integrity, and connecting the equipment; S700, after checking connections of the pulse hydraulic fracturing equipment, sequentially advancing a shutoff valve, a downhole packer, a check valve, a near-orifice packer, and a high-pressure sealed drill rod to a designed first-segment hydraulic fracturing position through a drilling rig to start a segmented pulse hydraulic fracturing operation; after the first-segment pulse hydraulic fracturing is completed, retracting part of the high-pressure sealed drill rod through the drilling rig, wherein a total length of the retracted high-pressure sealed drill rod is equal to a segment interval length; and then performing next-segment pulse hydraulic fracturing, and repeating the above operations for segmented pulse hydraulic fracturing of a single borehole until the pulse hydraulic fracturing of all fracturing segments designed in the single borehole is completed; S800, after the pulse hydraulic fracturing operation is completed, turning off the pulse hydraulic fracturing pump, opening a pressure relief valve in a pipeline to release residual fracturing fluid in the pipeline, and after a pressure in the pipeline drops to 0, sequentially retracting the high-pressure sealed drill rod, the near-orifice packer, the check valve, the downhole packer, the shutoff valve, and other equipment, and checking their integrity; repeating the above pulse hydraulic fracturing process and sequentially completing the segmented pulse hydraulic fracturing of all boreholes; and S900, after completing the pulse hydraulic fracturing operation, monitoring and counting the water return volumes and other parameters of the drainage boreholes, evaluating the effect of pulse hydraulic fracturing on optimizing the drainage of water from the roof sandstone fissure aquifer, and adjusting the spherical orifice water shutoff valve in time to control water outflow from the drainage borehole.
2. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 1, wherein in the step S100: hydrogeological information of the mining area is collected through hydrogeological survey, three-dimensional seismic exploration, geographic information system spatial analysis, and the like; and the specific stratigraphic horizon and water volume of the roof sandstone fissure aquifer are explored in advance by arranging prospecting boreholes in the mining area.
3. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 1, wherein in the step S300: the drainage borehole arrangement parameters comprise a borehole length, a dip angle, a spacing, an azimuth angle, and a diameter; and a terminal end of the drainage borehole arrangement is located at a geometric center point of a geometric figure formed by connecting center points of a plurality of potential discontinuous water-bearing areas facing a radiation zone of pulse hydraulic fracturing-induced fracture development.
4. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 3, wherein in the step S300: a spacing of drainage boreholes is designed based on the distribution and continuity of water-bearing areas; when the water-bearing areas are evenly distributed and have good continuity, the spacing between the drainage boreholes is 30-50 m; when the water-bearing areas are unevenly distributed and have poor continuity, the drainage boreholes are arranged in a way that a single borehole, after pulsed hydraulic fracturing, is fully connected to the water-bearing areas inside the radiation zone of pulse hydraulic fracturing-induced fracture development, and the spacing between adjacent drainage boreholes ensures that all discontinuous water-bearing areas between two adjacent boreholes fall within a fracture development radiation range.
5. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 4, wherein in the step S300: the azimuth angle of the drainage borehole is offset by 30-60 toward an open-off cut of the working face, such that the drainage boreholes enable advance drainage during the mining of the working face; the drainage boreholes have a diameter of 94-120 mm; and a single-segment hydraulic fracturing duration is 20-60 min.
6. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 1, wherein in the step S300: The drainage borehole arrangement forms comprise trans-stratal straight borehole arrangement, directional long borehole arrangement, and combined arrangement of trans-stratal straight boreholes and directional long boreholes.
7. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 6, wherein in the step S300: the trans-stratal straight borehole arrangement comprises fan-shaped borehole arrangement, parallel borehole arrangement, and a combination of the fan-shaped borehole arrangement and the parallel borehole arrangement.
8. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 7, wherein in the step S300: the fan-shaped borehole arrangement refers to arrangement of a plurality of boreholes in a drilling site, and the boreholes are distributed in a fan shape; and the parallel borehole arrangement refers to arrangement of a plurality of groups of alternately long and short boreholes obliquely toward the open-off cut of the working face in two entries of the working face of a coal mine, and plane projections of the alternately long and short boreholes are parallel to each other.
9. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 6, wherein in the step S300: the directional long borehole arrangement refers to arrangement of directional long boreholes in a roof sandstone aquifer of the coal seam using a directional drilling rig in a working face entry; the boreholes have a length of greater than 200 m, and a borehole strike is parallel to an advancing direction of the working face.
10. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 6, wherein in the step S300: the combined arrangement of trans-stratal straight boreholes and directional long boreholes refers to arrangement of both the trans-stratal straight boreholes and the directional long boreholes in the working face entry; first, segmented pulse hydraulic fracturing of the directional long boreholes is performed to form a large range of artificial water-conducting fissures for overall drainage of the roof sandstone fissure aquifer; and then, pulse hydraulic fracturing of the trans-stratal straight boreholes is performed in the water-bearing areas not radiated by the directional long boreholes or highly localized water-bearing areas for local drainage of water.
11. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 1, wherein in the step S600: the connecting the equipment comprises: a water tank is connected to a water supply pipeline through a water tank supply hose to supply liquid to the water tank; the pulse hydraulic fracturing pump is connected to the water tank through a pulse pump return hose and a pulse pump supply hose to supply liquid to the pulse hydraulic fracturing pump; the pulse hydraulic fracturing pump is connected to a high-pressure hose to output pulsed hydraulic fracturing water and inject same into the borehole; the high-pressure hose is connected to a first three-way joint and a pressure relief valve for releasing water pressure in the pipeline; a pressure sensor and a flow sensor are connected to the high-pressure hose to monitor a pulse pressure and flow rate in the pipeline during the pulse hydraulic fracturing process; the pressure sensor is connected to a hydraulic fracturing measurement and control instrument through a pressure sensor signal transmission line, and the flow sensor is connected to the hydraulic fracturing measurement and control instrument through a flow sensor signal transmission line, which is configured to transmit the pulse pressure and flow signals monitored in the pipeline to the hydraulic fracturing measurement and control instrument, display the pulse pressure and flow curves in real time, and store data.
12. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 11, wherein in the step S600: the spherical orifice water shutoff valve and the return flowmeter are connected, the return flowmeter is fixed to a roadway sidewall through a steel band clamp, the return flowmeter is connected to an orifice drainage hose, and the orifice drainage hose is connected to drainage ditches of the two entries.
13. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 1, wherein in the step S900: monitoring operation effects comprise monitoring pulse hydraulic fracturing effects of roof sandstone fissure aquifers and monitoring water drainage effects; the monitoring pulse hydraulic fracturing effects of roof sandstone fissure aquifers comprises monitoring the number and distribution of pulse hydraulic fracturing fractures on drainage borehole walls, and monitoring a propagation range of pulse hydraulic fracturing fractures; and the monitoring water drainage effects mainly comprises counting water return volumes of the drainage boreholes after pulse hydraulic fracturing, and water seepage of a roadway roof during normal mining of the working face.
14. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 13, wherein in the step S900: the monitoring a propagation range of pulse hydraulic fracturing fractures of drainage boreholes is performed by an observation method of taking adjacent boreholes as observation boreholes, and when water outflow or more water outflow occurs in adjacent boreholes during the pulse hydraulic fracturing process, it indicates that pulse hydraulic fracturing fractures have propagated to the adjacent boreholes; and the monitoring the number and distribution of pulse hydraulic fracturing fractures on drainage borehole walls is performed by observing through a borehole inspection apparatus, after borehole drilling is completed, a morphology of borehole walls of the fracturing segments is observed through the borehole inspection apparatus before pulse hydraulic fracturing, and after the pulse hydraulic fracturing, the borehole walls of the fracturing segments are observed again to compare and analyze the number and distribution of pulse hydraulic fracturing fractures on drainage boreholes.
15. The method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer according to claim 13, wherein in the step S900: the counting water return volumes of the drainage boreholes refers to monitoring a pumping flow rate during fracturing through the flow sensor, calculating the filtration loss of a rock stratum according to an indoor hydraulic fracturing similarity simulation experiment in a laboratory, monitoring the water return volume at the orifice after the pulse hydraulic fracturing through the return flowmeter at the orifice, determining whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between the water injection volume of a pulse hydraulic fracturing pump, the filtration loss of a rock stratum, and the water return volume at the orifice, and estimating a water volume of the water-bearing area of the roof connected to the artificial water-conducting channel; and the counting water seepage of the roadway roof during normal mining of the working face refers to observing and recording the water seepage of the roof before and after fracturing and during the mining of the working face, and intuitively evaluating the effect of pulse hydraulic fracturing on optimizing the drainage of water from water-bearing areas of the roof sandstone fissures according to macroscopic phenomena.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] To describe the technical solution in the examples of the present disclosure more clearly, the accompanying drawings required for describing the examples are briefly described below. It should be understood that the following accompanying drawings show merely some examples of the present disclosure, and therefore it should not be construed as a limitation to the scope. Those of ordinary skill in the art can also derive other accompanying drawings from these accompanying drawings without making inventive efforts.
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REFERENCE NUMERALS IN THE FIGURES
[0074] 1roof sandstone fissure aquifer; 2coal seam; 3discontinuous water-bearing area; 4pulse hydraulic fracturing pump; 5pulse pump supply hose; 6water tank; 7water tank supply hose; 8water supply pipeline; 9high-pressure hose; 10first three-way joint; 11pressure relief valve; 12pressure sensor; 13pressure sensor signal transmission line; 14flow sensor; 15flow sensor signal transmission line; 16hydraulic fracturing measurement and control instrument; 17spherical orifice water shutoff valve; 18water-stopping casing; 19high-pressure sealed drill rod; 20near-orifice packer; 21check valve; 22downhole packer; 23shutoff valve; 24artificial water-conducting channel; 25orifice drainage hose; 26steel band clamp; 27return flowmeter; 28drainage ditch; 29parallel long borehole; 30parallel short borehole; 31tailentry; 32headentry; 33open-off cut of the working face; 34fan-shaped borehole; 35directional long borehole; 36abandoned mine goaf; and 37accumulated goaf water.
DETAILED DESCRIPTIONS OF THE EMBODIMENTS
[0075] The technical solutions in the examples of the present disclosure will be clearly and completely described below in combination with the accompanying drawings in the examples of the present disclosure. Apparently, the examples described are merely some rather than all of the examples of the present disclosure. The assemblies in the examples of the present disclosure described and illustrated in the accompanying drawings usually can be arranged and designed according to various different configurations. Therefore, the following detailed description of the examples of the present disclosure provided in the accompanying drawings is not intended to limit the protection scope of the present disclosure, but only to represent the selected examples of the present disclosure. All other examples acquired by those skilled in the art without making creative efforts based on the examples of the present disclosure fall within the protection scope of the present disclosure. [0076] Example 1: As shown in
[0077] To fully drain water from roof sandstone fissures, reduce water seepage of the roadway during the mining of the working face, and ensure the normal operation and safe production of the working face, the present disclosure provides a method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer in an example. Specifically, a method for constructing an artificial water-conducting channel through segmented pulse hydraulic fracturing of trans-stratal parallel straight boreholes in a roof aquifer is used to solve the problem of low efficiency of conventional drainage of water from a sandstone fissure aquifer of the roof. The specific steps of the method are as follows: [0078] Step 1: Collect hydrogeological information of the mining area through hydrogeological survey, three-dimensional seismic exploration, geographic information system (GIS) spatial analysis, etc., mainly including the stratigraphic horizon of a roof sandstone fissure aquifer 1 and the permeability of the rock strata, and drill a plurality of prospecting boreholes in the mining area for advance exploration, to obtain the specific stratigraphic horizon and water volume of the roof sandstone fissure aquifer 1 and achieve better water drainage. [0079] Step 2: Extract rock samples from the roof sandstone fissure aquifer 1, and transport the rock samples to a laboratory for an indoor segmented pulse hydraulic fracturing simulation experiment to study the relationship of a pulse pressure peak, a pulse frequency, a segment length, a segment interval length, and a fracturing duration with fracture development, so as to determine an optimal pulse frequency, an optimal pulse pressure peak, an optimal segment length, an optimal segment interval length, and an optimal fracturing duration for segmented pulse hydraulic fracturing in a drainage operation area, which further provides a basis for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes. [0080] Step 3: Design a drainage borehole arrangement scheme and a segmented pulse hydraulic fracturing scheme according to a fracture development law and the distribution of water-bearing areas derived from the indoor segmented pulse hydraulic fracturing simulation experiment. Design parallel long boreholes 29 and parallel short boreholes 30 in a long-short alternating manner in a tailentry 31 and a headentry 32 for segmented pulse hydraulic fracturing, where the boreholes have a diameter of 94 mm, the parallel long boreholes 29 have a length of 91 m, an elevation angle of 7.5, and an inclination of 60 towards the working face, and the parallel short boreholes 30 have a length of 47 m, an elevation angle of 12.8, and an inclination of 60 towards the working face, with a borehole spacing of 30 m. The alternating arrangement of long and short boreholes aims to reduce blind zones of pulse hydraulic fracturing modification of aquifers. The inclined arrangement of boreholes toward the working face enables the boreholes to play a role in advance directional drainage during the mining of the working face. [0081] Step 4: Drill the parallel long boreholes 29 and the parallel short boreholes 30 after finalizing the borehole arrangement scheme, and survey the site after the drilling, to determine placement positions of a pulse hydraulic fracturing pump 4 and a water tank 6. [0082] Step 5: Install a water-stopping casing 18 and a matching spherical orifice water shutoff valve 17 at an orifice of the borehole drilled, to prevent excessive water outflow at the orifice after fracturing-induced connectivity between a plurality of water-bearing areas. Externally connect the spherical orifice water shutoff valve to a return flowmeter 27 to monitor a water return volume at the orifice, determine whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of the pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimate a water volume of the water-bearing area of the roof connected to the artificial water-conducting channel. [0083] Step 6: Before a fracturing operation, arrange drainage ditches 28 in the roadways (the tailentry 31 and the headentry 32) near a fracturing orifice, to prevent excessive water discharge at the orifice from causing roadway waterlogging and scouring of the working face; and after the pulse hydraulic fracturing pump 4 and the water tank 6 are transported to a designated operation location, check equipment quantity and integrity, and connect the equipment. The water tank 6 is connected to a water supply pipeline 8 through a water tank supply hose 7 to supply liquid to the water tank 6; the pulse hydraulic fracturing pump 4 is connected to the water tank 6 through a pulse pump return hose and a pulse pump supply hose 5 to supply liquid to the pulse hydraulic fracturing pump 4; the pulse hydraulic fracturing pump 4 is connected to a high-pressure hose 9 to output pulsed hydraulic fracturing water and inject same into the borehole; the high-pressure hose 9 is connected to a first three-way joint 10 and a pressure relief valve 11 for releasing water pressure in the pipeline; a pressure sensor 12 and a flow sensor 14 are connected to the high-pressure hose 9 through the first three-way joint 10 to monitor a pulse pressure and flow rate in the pipeline during the pulse hydraulic fracturing process; the pressure sensor 12 is connected to a hydraulic fracturing measurement and control instrument 16 through a pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the hydraulic fracturing measurement and control instrument 16 through a flow sensor signal transmission line 15, which is configured to transmit the pulse pressure and flow signals monitored in the pipeline to the hydraulic fracturing measurement and control instrument, display the pulse pressure and flow curves in real time, and store data; and the spherical orifice water shutoff valve 17 and the return flowmeter 27 are connected through an orifice drainage hose 25, the return flowmeter 27 is fixed to a roadway sidewall through a steel band clamp 26, the return flowmeter 27 is connected to the orifice drainage hose 25, and the orifice drainage hose 25 is connected to the drainage ditches 28 of the two entries. [0084] Step 7: After checking connections of the pulse hydraulic fracturing pump 4, the pulse pump supply hose 5, the water tank 6, and the water tank supply hose 7, sequentially advance a shutoff valve 23, a downhole packer 22, a check valve 21, a near-orifice packer 20, and a high-pressure sealed drill rod 19 to a designed first-segment hydraulic fracturing position through a drilling rig to start the segmented pulse hydraulic fracturing operation, where the long borehole is fractured in three segments, the short borehole is fractured in two segments, and a single-segment hydraulic fracturing duration is 40-50 min; after the first-segment pulse hydraulic fracturing is completed, retract part of the high-pressure sealed drill rod through the drilling rig, where a total length of the retracted high-pressure sealed drill rod should be equal to a segment interval length; and then perform next-segment pulse hydraulic fracturing, and repeat the above operations for segmented pulse hydraulic fracturing of a single borehole until the pulse hydraulic fracturing of all fracturing segments designed in the single borehole is completed. [0085] Step 8: After completing the pulse hydraulic fracturing operation, sequentially retract the high-pressure sealed drill rod 19, the near-orifice packer 20, the check valve 21, the downhole packer 22, the shutoff valve 23, and other equipment, and check their integrity. Then repeat the above pulse hydraulic fracturing process and sequentially complete the segmented pulse hydraulic fracturing of all boreholes. [0086] Step 9: After completing the pulse hydraulic fracturing operation, monitor and count the water return volumes and other parameters of the drainage boreholes, and evaluate the effect of pulse hydraulic fracturing on optimizing the drainage of water from the roof sandstone fissure aquifer. Specifically, monitor the changes in the return flowmeter 27 at the orifice over a monitoring cycle of seven days, compare the water return volume after fracturing recorded by the return flowmeter 27 with the water injection volume recorded by the hydraulic fracturing measurement and control instrument 16, and estimate the volume of water drained from the roof aquifer through the artificial water-conducting channel constructed by pulse hydraulic fracturing within one cycle.
[0087] In case of excessive water outflow from the drainage borehole, adjust the spherical orifice water shutoff valve 17 in time to control the water outflow from the drainage borehole and achieve fully controllable drainage.
[0088] As shown in
[0099] In case of excessive water outflow from the drainage borehole, adjust the spherical orifice water shutoff valve 17 in time to control the water outflow from the drainage borehole and achieve fully controllable drainage. [0100] Example 3: As shown in
[0101] To solve the problems, the present disclosure provides a method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer in an example. Specifically, a method for constructing an artificial water-conducting channel through segmented pulse hydraulic fracturing of directional long boreholes in a roof aquifer is used to fully drain water from roof sandstone fissures. The specific steps of the method are as follows: [0102] Step 1: Collect hydrogeological information of the mining area through hydrogeological survey, three-dimensional seismic exploration, geographic information system (GIS) spatial analysis, and the like, mainly including the stratigraphic horizon of a roof sandstone fissure aquifer 1 and the permeability of the rock strata, and drill a plurality of prospecting boreholes in the mining area for advance exploration, to obtain the specific stratigraphic horizon and water volume of the roof sandstone fissure aquifer 1 and achieve better water drainage. [0103] Step 2: Extract rock samples from the roof sandstone fissure aquifer 1, and transport the rock samples to a laboratory for an indoor segmented pulse hydraulic fracturing simulation experiment to study the relationship of a pulse pressure peak, a pulse frequency, a segment length, a segment interval length, and a fracturing duration with fracture development, so as to determine an optimal pulse frequency, an optimal pulse pressure peak, an optimal segment length, an optimal segment interval length, and an optimal fracturing duration for segmented pulse hydraulic fracturing in a drainage operation area, which further provides a basis for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes. [0104] Step 3: Design a drainage borehole arrangement scheme and a segmented pulse hydraulic fracturing scheme according to a fracture development law and the distribution of water-bearing areas derived from the indoor segmented pulse hydraulic fracturing simulation experiment. Design a group of directional long boreholes 35 in a drilling site of working face entry for segmented pulse hydraulic fracturing, including three directional long boreholes with a diameter of 120 mm and lengths of 549 m, 575 m, and 574 m respectively, where a single-segment hydraulic fracturing zone has a length of 20 m, and an interval between two adjacent segments of fracturing zone is 10 m. [0105] Step 4: Drill the directional long boreholes 35 after finalizing the borehole arrangement scheme, and survey the site after the drilling, to determine placement positions of a pulse hydraulic fracturing pump 4 and a water tank 6. [0106] Step 5: Install a water-stopping casing 18 and a matching spherical orifice water shutoff valve 17 at an orifice of the borehole drilled, to prevent excessive water outflow at the orifice after fracturing-induced connectivity between a plurality of water-bearing areas. Externally connect the spherical orifice water shutoff valve to a return flowmeter 27 to monitor a water return volume at the orifice, determine whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of the pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimate a volume of water accumulated in the low-lying areas of the roof connected to the artificial water-conducting channel. [0107] Step 6: Before a fracturing operation, arrange drainage ditches 28 in the roadways (the tailentry 31 and the headentry 32) near a fracturing orifice, to prevent excessive water discharge at the orifice from causing roadway waterlogging and scouring of the working face; and after the pulse hydraulic fracturing pump 4 and the water tank 6 are transported to a designated operation location, check equipment quantity and integrity, and connect the equipment. The water tank 6 is connected to a water supply pipeline 8 through a water tank supply hose 7 to supply liquid to the water tank; the pulse hydraulic fracturing pump 4 is connected to the water tank 6 through a pulse pump return hose and a pulse pump supply hose 5 to supply liquid to the pulse hydraulic fracturing pump 4; the pulse hydraulic fracturing pump 4 is connected to a high-pressure hose 9 to output pulsed hydraulic fracturing water and inject same into the borehole; the high-pressure hose 9 is connected to a first three-way joint 10 and a pressure relief valve 11 for releasing water pressure in the pipeline; a pressure sensor 12 and a flow sensor 14 are connected to the high-pressure hose 9 through the first three-way joint 10 to monitor a pulse pressure and flow rate in the pipeline during the pulse hydraulic fracturing process; the pressure sensor 12 is connected to a hydraulic fracturing measurement and control instrument 16 through a pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the hydraulic fracturing measurement and control instrument 16 through a flow sensor signal transmission line 15, which is configured to transmit the pulse pressure and flow signals monitored in the pipeline to the hydraulic fracturing measurement and control instrument, display the pulse pressure and flow curves in real time, and store data; and the spherical orifice water shutoff valve 17 and the return flowmeter 27 are connected through an orifice drainage hose 25, the return flowmeter 27 is fixed to a roadway sidewall through a steel band clamp 26, the return flowmeter 27 is connected to the orifice drainage hose 25, and the orifice drainage hose 25 is connected to the drainage ditches 28 of the two entries. [0108] Step 7: After checking connections of the pulse hydraulic fracturing pump 4, the pulse pump supply hose 5, the water tank 6, and the water tank supply hose 7, sequentially advance a shutoff valve 23, a downhole packer 22, a check valve 21, a near-orifice packer 20, and a high-pressure sealed drill rod 19 to a designed first-segment hydraulic fracturing position through a drilling rig to start the segmented pulse hydraulic fracturing operation, where the long borehole is fractured in three segments, the short borehole is fractured in two segments, and a single-segment hydraulic fracturing duration is 40-50 min; after the first-segment pulse hydraulic fracturing is completed, retract part of the high-pressure sealed drill rod through the drilling rig, where a total length of the retracted high-pressure sealed drill rod should be equal to a segment interval length; and then perform next-segment pulse hydraulic fracturing, and repeat the above operations for segmented pulse hydraulic fracturing of a single borehole until the pulse hydraulic fracturing of all fracturing segments designed in the single borehole is completed. [0109] Step 8: After completing the pulse hydraulic fracturing operation, sequentially retract the high-pressure sealed drill rod 19, the near-orifice packer 20, the check valve 21, the downhole packer 22, the shutoff valve 23, and other equipment, and check their integrity. Then repeat the above pulse hydraulic fracturing process and sequentially complete the segmented pulse hydraulic fracturing of all boreholes. [0110] Step 9: After completing the pulse hydraulic fracturing operation, monitor and count the water return volumes and other parameters of the drainage boreholes, and evaluate the effect of pulse hydraulic fracturing on optimizing the drainage of water from the roof sandstone fissure aquifer. Specifically, monitor the changes in the return flowmeter 27 at the orifice over a monitoring cycle of seven days, compare the water return volume after fracturing recorded by the return flowmeter 27 with the water injection volume recorded by the hydraulic fracturing measurement and control instrument 16, and estimate the volume of water drained from the roof fissured sandstone aquifer through the artificial water-conducting channel constructed by pulse hydraulic fracturing within one cycle.
[0111] In case of excessive water outflow from the drainage borehole, adjust the spherical orifice water shutoff valve 17 in time to control the water outflow from the drainage borehole and achieve fully controllable drainage.
[0112] Since the vast majority of trajectories of the directional long boreholes are in the roof sandstone aquifer, segmented pulse hydraulic fracturing of the directional long boreholes causes significant modification of the aquifer and formation of many artificial water-conducting fissures in the aquifer. Therefore, the drainage coverage of a single borehole is large. Additionally, the borehole strike is parallel to the advancing direction of the working face, which enables the boreholes to also play a role in advance directional drainage during the mining of the working face. [0113] Example 4: There exists accumulated water in an abandoned mine goaf above a coal seam currently mined in a mining area, and failure to drain water in the goaf through technical means may lead to severe mine water hazards during coal seam mining, and even affect normal operations and safe production.
[0114] Since the abandoned mine goaf has a large area and an elevated stratigraphic position, it is very difficult to accurately locate a water accumulation area of the goaf through geophysical prospecting. To solve this problem, the present disclosure provides a method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer in an example. According to the method, a plurality of groups of single-inclined trans-stratal boreholes are arranged near the abandoned mine goaf for segmented pulse hydraulic fracturing to drain the water accumulated in the abandoned mine goaf. The specific steps of the method are as follows: [0115] Step 1: Collect hydrogeological information of the mining area through hydrogeological survey, three-dimensional seismic exploration, geographic information system (GIS) spatial analysis, etc., mainly including the general stratigraphic horizon and region of the abandoned mine goaf 36. [0116] Step 2: Extract rock samples from the strata near the abandoned mine goaf, and transport the rock samples to a laboratory for an indoor segmented pulse hydraulic fracturing simulation experiment to study the relationship of a pulse pressure peak, a pulse frequency, a segment length, a segment interval length, and a fracturing duration with fracture development, so as to determine an optimal pulse frequency, an optimal pulse pressure peak, an optimal segment length, an optimal segment interval length, and an optimal fracturing duration for segmented pulse hydraulic fracturing in a drainage operation area, which further provides a basis for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes. [0117] Step 3: Design a drainage borehole arrangement scheme and a segmented pulse hydraulic fracturing scheme according to a fracture development law and the distribution of the abandoned mine goaf derived from the indoor segmented pulse hydraulic fracturing simulation experiment. Design a plurality of groups of single-inclined trans-stratal parallel long boreholes 29 in a drilling site of working face entry for segmented pulse hydraulic fracturing, where the boreholes have a diameter of 94 mm, a length of 176 m, an elevation angle of 21, and an inclination of 60 toward the working face. [0118] Step 4: Drill the parallel long boreholes 29 after finalizing the borehole arrangement scheme, and survey the site after the drilling, to determine placement positions of a pulse hydraulic fracturing pump 4 and a water tank 6. [0119] Step 5: Install a water-stopping casing 18 and a matching spherical orifice water shutoff valve 17 at an orifice of the borehole drilled, to prevent excessive water outflow at the orifice after fracturing-induced connectivity between a plurality of water-bearing areas. Externally connect the spherical orifice water shutoff valve to a return flowmeter 27 to monitor a water return volume at the orifice, determine whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of the pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimate a volume of water accumulated in the low-lying areas of the roof connected to the artificial water-conducting channel. [0120] Step 6: Before a fracturing operation, arrange drainage ditches 28 in the roadways (the tailentry 31 and the headentry 32) near a fracturing orifice, to prevent excessive water discharge at the orifice from causing roadway waterlogging and scouring of the working face; and after the pulse hydraulic fracturing pump 4 and the water tank 6 are transported to a designated operation location, check equipment quantity and integrity, and connect the equipment. The water tank 6 is connected to a water supply pipeline 8 through a water tank supply hose 7 to supply liquid to the water tank; the pulse hydraulic fracturing pump 4 is connected to the water tank 6 through a pulse pump return hose and a pulse pump supply hose 5 to supply liquid to the pulse hydraulic fracturing pump 4; the pulse hydraulic fracturing pump 4 is connected to a high-pressure hose 9 to output pulsed hydraulic fracturing water and inject same into the borehole; the high-pressure hose 9 is connected to a first three-way joint 10 and a pressure relief valve 11 for releasing water pressure in the pipeline; a pressure sensor 12 and a flow sensor 14 are connected to the high-pressure hose 9 through the first three-way joint 10 to monitor a pulse pressure and flow rate in the pipeline during the pulse hydraulic fracturing process; the pressure sensor 12 is connected to a hydraulic fracturing measurement and control instrument 16 through a pressure sensor signal transmission line 13, and the flow sensor 14 is connected to the hydraulic fracturing measurement and control instrument 16 through a flow sensor signal transmission line 15, which is configured to transmit the pulse pressure and flow signals monitored in the pipeline to the hydraulic fracturing measurement and control instrument, display the pulse pressure and flow curves in real time, and store data; and the spherical orifice water shutoff valve 17 and the return flowmeter 27 are connected through an orifice drainage hose 25, the return flowmeter 27 is fixed to a roadway sidewall through a steel band clamp 26, the return flowmeter 27 is connected to the orifice drainage hose 25, and the orifice drainage hose 25 is connected to the drainage ditches 28 of the two entries. [0121] Step 7: After checking connections of the pulse hydraulic fracturing pump 4, the pulse pump supply hose 5, the water tank 6, and the water tank supply hose 7, sequentially advance a shutoff valve 23, a downhole packer 22, a check valve 21, a near-orifice packer 20, and a high-pressure sealed drill rod 19 to a designed first-segment hydraulic fracturing position through a drilling rig to start the segmented pulse hydraulic fracturing operation, where the long borehole is fractured in three segments, the short borehole is fractured in two segments, and a single-segment hydraulic fracturing duration is 40-50 min; after the first-segment pulse hydraulic fracturing is completed, retract part of the high-pressure sealed drill rod through the drilling rig, where a total length of the retracted high-pressure sealed drill rod should be equal to a segment interval length; and then perform next-segment pulse hydraulic fracturing, and repeat the above operations for segmented pulse hydraulic fracturing of a single borehole until the pulse hydraulic fracturing of all fracturing segments designed in the single borehole is completed. [0122] Step 8: After completing the pulse hydraulic fracturing operation, sequentially retract the high-pressure sealed drill rod 19, the near-orifice packer 20, the check valve 21, the downhole packer 22, the shutoff valve 23, and other equipment, and check their integrity. Then repeat the above pulse hydraulic fracturing process and sequentially complete the segmented pulse hydraulic fracturing of all boreholes. [0123] Step 9: After completing the pulse hydraulic fracturing operation, monitor and count the water return volumes and other parameters of the drainage boreholes, and evaluate the effect of pulse hydraulic fracturing on optimizing the drainage of water accumulated in the abandoned mine goaf of the roof. Specifically, monitor the changes in the return flowmeter 27 at the orifice over a monitoring cycle of seven days, compare the water return volume after fracturing recorded by the return flowmeter 27 with the water injection volume recorded by the hydraulic fracturing measurement and control instrument 16, and estimate the volume of water drained from the abandoned mine goaf of the roof through the artificial water-conducting channel constructed by pulse hydraulic fracturing within one cycle.
[0124] In case of excessive water outflow from the drainage borehole, adjust the spherical orifice water shutoff valve 17 in time to control the water outflow from the drainage borehole and achieve fully controllable drainage. [0125] Example 5: As shown in
[0135] In case of excessive water outflow from the drainage borehole, adjust the spherical orifice water shutoff valve 17 in time to control the water outflow from the drainage borehole and achieve fully controllable drainage.
[0136] In the present disclosure, sufficient drainage of the mine is fundamental to achieve smooth mining and ensure safe operation. Before mining of the working face, a certain number of prospecting boreholes are usually arranged to effectively control roof water hazards and ensure safe mining of the working face. The prospecting boreholes have functions of both advance exploration and drainage. To fully drain water from the water-rich areas of the roof, the drainage borehole arrangement scheme needs to be designed based on the distribution and continuity of water-bearing areas and water-rich areas of the roof in the mining area, and other hydrogeological characteristics. Drainage boreholes are generally divided into trans-stratal straight boreholes and directional long boreholes.
[0137] Under the complex geological conditions such as good water abundance of roof sandstone fissures, discontinuity of the water-bearing areas, and poor permeability of dense and intact sandstone rock masses, drilling boreholes to fully drain water from all discontinuous water-bearing areas not only is labor-intensive but also fails to ensure that the water from roof sandstone fissures is fully drained. The core of solving the above problem is to construct an artificial water-conducting channel in the sandstone fissure aquifer through advance arrangement of drainage boreholes and other technical means, so as to improve the permeability of the dense and intact sandstone rock masses. The artificial water-conducting channel formed in the sandstone fissure aquifer through arrangement of drainage boreholes is connected to the discontinuous water-bearing areas and water-rich areas, and water from roof sandstone fissures is diverted to the drainage boreholes through the artificial water-conducting channel, which achieves effective drainage of the boreholes and expansion of the radiation range of single-borehole drainage.
[0138] The boreholes usually used for exploration are relatively limited, which cannot meet the needs of draining water from numerous and discontinuous roof sandstone fissures. Therefore, to effectively drain water from the roof sandstone fissures, it is necessary to design and add drainage boreholes. Arrangement and fracturing of inclined drainage boreholes in a long-short alternating manner not only enable connection to all water-bearing areas within a fracture propagation radius through a single borehole, and effectively increase an area of water drainage from the roof. Additionally, inclined arrangement of drainage boreholes ensures that during the mining process, the water from roof fissures that is not fully drained will flow to the drainage boreholes along the mining-induced fissures due to the rock stratum movement caused by mining, thereby achieving advance water drainage from the working face.
[0139] Fracturing refers to the process of injecting a high-pressure fluid (such as water, gas, or the like) through a borehole, which causes the borehole wall to fracture and expand under the action of fluid-solid coupling. An effective technical approach to efficiently drain the water from roof sandstone fissures is to pre-fracture the roof drainage boreholes to form fractures in the sandstone fissure aquifer so as to construct an artificial water-conducting channel. The pumping displacement of conventional hydraulic fracturing is constant, the hydraulic fracture propagation direction is controlled by a three-dimensional geostress field and is perpendicular to the direction of a minimum principal stress, and few hydraulic fractures are formed. In pulse pump fracturing, a high-pressure pulse pump outputs high-frequency pulse pressure water to impact the rock borehole walls, which causes fatigue damage to the rock, and reduces the impact of the geostress field on the initiation and propagation direction of hydraulic fractures, with a dense fracture network formed in the rock.
[0140] Therefore, a method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer is provided. The method not only avoids the arrangement of excessive drainage boreholes and significantly improves the drainage efficiency of the prospecting and drainage boreholes, but also facilitates advance drainage during the mining process. The method enables effective control of mine water hazards even under unfavorable geological conditions, thereby ensuring safe production of the mine.
[0141] In the above examples, the drainage boreholes include the prospecting and drainage boreholes used for geophysical prospecting and drainage and drainage boreholes used for advance drainage and construction of an artificial water-conducting channel through pulse hydraulic fracturing, and the drainage boreholes are divided into trans-stratal straight boreholes and directional trans-stratal long boreholes.
[0142] The borehole arrangement scheme includes borehole arrangement parameters and borehole arrangement forms.
[0143] The drainage borehole arrangement parameters include a borehole length, a dip angle, a spacing, an azimuth angle, and a diameter; an orientation of the borehole should point towards a geometric center point of a geometric figure formed by connecting center points of a plurality of potential discontinuous water-bearing areas facing a radiation zone of pulse hydraulic fracturing-induced fracture development; and after a borehole opening location is determined, the borehole length may be determined based on a distance between the borehole opening location and the geometric center point of a geometric figure formed by connecting center points of a plurality of discontinuous water-bearing areas. An included angle formed by connecting the borehole opening location, a horizontal line, and the geometric center point of a geometric figure formed by connecting center points of a plurality of discontinuous water-bearing areas is the borehole dip angle.
[0144] The borehole spacing mainly depends on the distribution and continuity of water-bearing areas, and when the water-bearing areas are evenly distributed and have good continuity, the borehole spacing is usually 30-50 m; when the water-bearing areas are unevenly distributed and have poor continuity, the boreholes are arranged in a way that a single borehole, after pulsed hydraulic fracturing, is fully connected to the water-bearing areas inside the radiation zone of pulse hydraulic fracturing-induced fracture development, and the spacing between adjacent boreholes ensures that all discontinuous water-bearing areas between two adjacent boreholes fall within a fracture development radiation range, thereby ensuring that each water-bearing area is fully drained. The specific spacing should be determined according to actual conditions.
[0145] To improve the single-borehole utilization rate and enhance single-borehole versatility, the azimuth angle of the drainage borehole is usually offset by 30-60 toward an open-off cut of the working face, such that the boreholes enable advance drainage during the mining of the working face.
[0146] The boreholes have a diameter of usually 94-120 mm, and the borehole of a corresponding size can also be customized according to construction requirements.
[0147] The borehole arrangement forms include trans-stratal straight borehole arrangement, directional long borehole arrangement, and combined arrangement of trans-stratal straight boreholes and directional long boreholes.
[0148] The trans-stratal straight borehole arrangement refers to the arrangement of trans-stratal straight boreholes for constructing the artificial water-conducting channel through segmented pulse hydraulic fracturing in the working face entry, and the trans-stratal straight boreholes are arranged in the fan-shaped or parallel manner: [0149] the fan-shaped borehole arrangement refers to arrangement of a plurality of boreholes in a drilling site, and the boreholes are distributed in a fan shape; and the fan-shaped borehole arrangement has the advantages of fewer drilling rig movements and high drilling efficiency, and is suitable for draining water from relatively concentrated local discontinuous water-bearing areas. [0150] the parallel borehole arrangement refers to arrangement of a plurality of groups of alternately long and short boreholes obliquely toward the open-off cut of the working face in two entries of the working face of a coal mine, and plane projections of the alternately long and short boreholes in the borehole arrangement plan view are parallel to each other. Parallel drilling has the advantages of reduced construction workload and shortened operation time, and plays a role in advance directional drainage during the mining of the working face. The alternating arrangement of long and short boreholes aims to reduce blind zones of pulse hydraulic fracturing modification of aquifers.
[0151] The directional long borehole arrangement refers to arrangement of directional long boreholes in a roof sandstone aquifer of the coal seam using a directional drilling rig in the working face entry; the boreholes have a length of generally greater than 200 m, and a borehole strike is parallel to an advancing direction of the working face. Since the vast majority of trajectories of the directional long boreholes are in the roof sandstone aquifer, segmented pulse hydraulic fracturing of the directional long boreholes causes significant modification of the aquifer and formation of many artificial water-conducting fissures in the aquifer. Therefore, the drainage coverage of a single borehole is large. Additionally, the borehole strike is parallel to the advancing direction of the working face, which enables the boreholes to also play a role in advance directional drainage during the mining of the working face.
[0152] The combined arrangement of trans-stratal straight boreholes and directional long boreholes refers to arrangement of both the trans-stratal straight boreholes and the directional long boreholes in the working face entry; first, segmented pulse hydraulic fracturing of the directional long boreholes is performed to form a large range of artificial water-conducting fissures for overall drainage of the roof sandstone fissure aquifer; and then, pulse hydraulic fracturing of the trans-stratal straight boreholes is performed in the water-bearing areas not radiated by the directional long boreholes or highly localized water-bearing areas for local drainage of water. As a supplementary safeguard measure, this reduces the blind spots of artificial water-conducting fissures and ensures more full connection to the discontinuous water-bearing areas of the roof.
[0153] The single-segment hydraulic fracturing length and the segment interval length are determined based on the indoor segmented pulse hydraulic fracturing simulation experiment after field sampling, rock stratum lithology, rock mechanics parameters, a pulse peak, and a pulse frequency.
[0154] The single-segment hydraulic fracturing duration is generally about 20-60 min, and geological characteristics of the mining area should be considered to ensure that the constructed artificial water-conducting channel effectively improves the permeability of rock strata, and the water-bearing areas are connected to each other, thereby achieving effective water drainage.
[0155] The arranged drainage boreholes also serve as monitoring boreholes, and during the fracturing process, the propagation range of the artificial water-conducting channel formed by pulse hydraulic fracturing may be evaluated by observing the orifice water outflow from the adjacent boreholes around the fracturing borehole before and after fracturing, so as to determine whether the constructed artificial water-conducting channel has been connected to the adjacent boreholes.
[0156] The water-bearing areas also include the unexplored abandoned mine goaf above the coal seam roof. Directional long boreholes or trans-stratal boreholes are arranged in the entry, the water-stopping casing and the spherical orifice water shutoff valve are mounted at the orifice, pulse hydraulic fracturing is performed on the drainage boreholes that have not produced water, and the artificial water-conducting channel is constructed for connection to the abandoned mine goaf to fully drain the water accumulated in the abandoned mine goaf. During fracturing, the drainage situation is monitored in time, and when excessive water discharge occurs at the orifice after fracturing, the spherical orifice water shutoff valve should be adjusted in time to control the water outflow of the drainage boreholes, so as to achieve fully controllable drainage and ensure operational safety.
[0157] The monitoring operation effects include monitoring pulse hydraulic fracturing effects of roof sandstone fissure aquifers and monitoring water drainage effects.
[0158] The monitoring pulse hydraulic fracturing effects of roof sandstone fissure aquifers comprises monitoring the number and distribution of pulse hydraulic fracturing fractures on drainage borehole walls, and monitoring a propagation range of pulse hydraulic fracturing fractures.
[0159] The number and distribution of pulse hydraulic fracturing fractures on drainage borehole walls are observed through the borehole inspection apparatus. After borehole drilling is completed, the morphology of borehole walls of the fracturing segments is observed through the borehole inspection apparatus before pulse hydraulic fracturing, and after the pulse hydraulic fracturing, the borehole walls of the fracturing segments are observed again to compare and analyze the number and distribution of pulse hydraulic fracturing fractures on drainage boreholes.
[0160] The monitoring a propagation range of pulse hydraulic fracturing fractures of drainage boreholes is performed by an observation method of taking adjacent boreholes as observation boreholes. when water outflow or more water outflow occurs in adjacent boreholes during the pulse hydraulic fracturing process, it indicates that pulse hydraulic fracturing fractures have propagated to the adjacent boreholes.
[0161] The monitoring water drainage effects mainly comprises counting water return volumes of the drainage boreholes after pulse hydraulic fracturing, and water seepage of the roadway roof during normal mining of the working face.
[0162] The counting water return volumes of the drainage boreholes refers to monitoring a pumping flow rate during fracturing through a flow sensor, calculating the filtration loss of a rock stratum according to an indoor hydraulic fracturing similarity simulation experiment in a laboratory, monitoring the water return volume at the orifice after the pulse hydraulic fracturing through the return flowmeter at the orifice, determining whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of a pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimating a water volume of the water-bearing area of the roof connected to the artificial water-conducting channel.
[0163] The counting water seepage of the roadway roof during normal mining of the working face refers to observing and recording the water seepage of the roof before and after fracturing and during the mining of the working face, and intuitively evaluating the effect of pulse hydraulic fracturing on optimizing the drainage of water from water-bearing areas of the roof sandstone fissures according to macroscopic phenomena.
[0164] Pulse hydraulic fracturing of drainage boreholes in roof sandstone fissure aquifers has dual functions of drainage and mine pressure control, which not only optimizes the drainage of water from water-bearing areas of the roof sandstone fissures, but also enables to pre-fracture the coal seam roof, reduces a caving interval of the roof during the mining of the working face, and reduces the mine pressure manifestation during the mining of the working face.
[0165] In the descriptions of the present disclosure, it should be noted that the terms center, upper, lower, left, right, vertical, horizontal, inner, outer, and the like indicate orientation or position relations based on those shown in the accompanying drawings, or of common placement when the product of the present disclosure is used, which are only for ease of description of the present disclosure and for simplicity of description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation and be constructed and operated in a particular orientation, and thus may not be construed as a limitation on the present disclosure. Moreover, the terms first, second, third, and the like are used merely to distinguish between descriptions and may not be construed as indication or implication of relative importance.
[0166] Further, the terms such as horizontal, vertical, and overhanging do not necessarily mean that the components are absolutely horizontal or overhanging, but can be slightly inclined. For example, compared to vertical, horizontal only means that a structure is more horizontal in terms of direction, but does not mean that the structure must be completely horizontal, but can be slightly inclined.
[0167] In the description of the present disclosure, it should be further noted that, unless otherwise clearly specified, meanings of terms arrange, mount, connected, and connect should be understood in a board sense. For example, the connection may be a fixed connection, a detachable connection, an integral connection; may be a mechanical connection or an electrical connection; may be a direct connection or an indirect connection by using an intermediate medium; or may be intercommunication between two components. For those of ordinarily skilled in the art, specific meanings of the above terms in the present disclosure could be understood according to specific circumstances.
[0168] The above descriptions are only preferred examples of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modifications, equivalent replacements, improvements, and the like made within the spirit and principles of the present disclosure should fall within the scope of protection of the present disclosure. It should be noted that similar reference numerals and letters represent similar terms in the following accompanying drawings. Therefore, once defined in one accompanying drawing, a term is not needed to be further defined or explained in subsequent accompanying drawings.