CN112253113A - Method for weakening hard gangue layer by coal mine underground directional long drilling and staged hydraulic fracturing - Google Patents
Method for weakening hard gangue layer by coal mine underground directional long drilling and staged hydraulic fracturing Download PDFInfo
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- 238000005553 drilling Methods 0.000 title claims abstract description 113
- 239000003245 coal Substances 0.000 title claims abstract description 81
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- E21C37/06—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole
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Abstract
A method for weakening a hard gangue layer by means of underground coal mine directional long drilling and staged hydraulic fracturing comprises the following steps: the first step is as follows: determining occurrence forms and ranges of hard gangue layers in a stope face; the second step is that: determining drilling hole layout and fracturing technical parameters; the third step: directional long drilling construction is carried out, and directional long drilling construction is carried out by utilizing a drilling machine according to the drilling layout parameters determined in the step two; the fourth step: conveying and fracturing construction in a fracturing equipment hole; therefore, the method can overcome the defects and problems of the existing technology for weakening the hard gangue layer in the stope face, achieves the effect of weakening the hard gangue layer more environmentally, safely and efficiently, achieves the advanced weakening of the hard gangue layer in the fully mechanized face under the coal mine, completes the smooth recovery of the whole set of construction equipment for staged hydraulic fracturing in the directional long drill hole, ensures the fracturing construction efficiency, and solves the technical defect problems in the prior art.
Description
Technical Field
The invention relates to the technical field of coal mine safety production, in particular to the technical field of weakening of a large-range hard gangue layer in a fully mechanized coal mining face under a coal mine, and specifically relates to a method for weakening the hard gangue layer by means of subsection hydraulic fracturing of directional long drill holes under the coal mine.
Background
With the progress of science and technology, coal mining methods, technologies and processes under coal mines are rapidly developed, a single-trend or trend long-arm mining working face enters an era of comprehensive mechanization, automation and intellectualization, coal production enters a high-yield and high-efficiency period, however, many stope working faces are influenced by mining geological conditions with large-range hard gangue layers, safety and high-efficiency high yield are hindered, and the influence is particularly obvious on fully-mechanized mining or fully-mechanized caving working faces with hard gangue layers distributed on the full-length working faces. When the working face is used for stoping, the existence of the hard gangue layer can seriously affect the coal cutting speed of the coal mining machine, so that the coal mining speed and the coal output rate are influenced, meanwhile, when the gear of the coal mining machine cuts the hard gangue layer, friction sparks are generated, the factors greatly restrict the safe and efficient high-yield stoping of the working face under the coal mine, and the method is a great difficult problem needing to be solved urgently at the front of the coal mine production line.
When the thickness of a gangue clamping layer is smaller (less than 0.2m) in the process of mining and cutting coal on a fully mechanized mining face or a fully mechanized caving face, a roller gear of a coal mining machine can easily cut the gangue clamping layer, and the influence on safe mining is small; when the thickness of the gangue layer is large and hard, if the roller of the coal mining machine is cut and mined forcibly, the rocker arm of the coal mining machine is stressed too much, the connecting part is easy to be damaged, and the roller cutting teeth can be damaged seriously. Therefore, the existence of the hard gangue layer seriously influences the advancing speed of the working face, further influences the daily footage of the stope face and causes the rapid reduction of the daily coal yield. Meanwhile, the cutting teeth of the coal mining machine forcibly cut the hard gangue layer can cause the equipment to be over-fatigued, so that the damage is serious, new components need to be continuously replaced, the consumption is also continuously increased, and the equipment cost is greatly increased.
Through the technical survey of the existing weakened hard gangue layer, only one solution is available at present, namely a deep hole blasting method. The deep hole blasting process is complex, the operation requirement is extremely high, and secondary disasters are easily induced due to slightly improper construction operation; the workload is too large, and the operation period is long; the length of the explosive conveyed into the hole is limited, and the influence range after blasting operation is limited; a large amount of dust and harmful and toxic gas can be generated after blasting operation, so that the operation environment is polluted; the initiating explosive device is strictly controlled and has high approval difficulty, and certain potential safety hazard is caused to the mining production of a working face during the operation of the initiating explosive device.
Therefore, on the basis of the defects, a designer researches and designs a method for weakening the hard gangue layer by segmented hydraulic fracturing of the directional long drill hole under the coal mine through intensive research and design, integrates field engineering practical experience and scientific research and attack of related industries for many years, researches and designs a method for weakening the hard gangue layer by segmented hydraulic fracturing of the directional long drill hole under the coal mine on the basis of the technology of controlling the track of the long drill hole under the coal mine, combines the technology of segmented hydraulic fracturing of the long drill hole, realizes advanced weakening of the hard gangue layer of the fully mechanized mining face, improves the advancing speed of the working face, increases daily coal yield, reduces equipment loss, overcomes the technical defects, and provides a more effective technical method for solving the problem of mining the coal layer containing the hard gangue on the working face under the coal mine.
Disclosure of Invention
The invention aims to provide a method for weakening a hard gangue layer by means of subsection hydraulic fracturing in an underground directional long drill hole of a coal mine, which overcomes the defects and problems of the existing technology for weakening the hard gangue layer in a mining working face, realizes the effect of weakening the hard gangue layer more environmentally, safely and efficiently, realizes the advanced weakening of the hard gangue layer in the underground fully mechanized mining working face of the coal mine, completes the smooth recovery of the whole set of construction equipment for subsection hydraulic fracturing in the directional long drill hole, ensures the fracturing construction efficiency, and solves the defect problems in the prior art.
In order to achieve the purpose, the invention discloses a method for weakening a hard gangue layer by using underground coal mine directional long drilling and staged hydraulic fracturing, which is characterized by comprising the following steps of:
the first step is as follows: determining occurrence forms and ranges of hard gangue layers in the stope face, and after the construction of the haulage roadway and the return air roadway on two sides of the stope face is completed, carrying out comprehensive analysis research to determine the occurrence forms and ranges of the hard gangue layers according to the occurrence states of the exposed hard gangue layers in the haulage roadway and the return air roadway and in combination with geological data, underground roadway exploration data and geophysical exploration data during ground exploration;
the second step is that: drilling hole layout and fracturing technical parameter determination;
designing a drill site on one side of a roadway to arrange drill holes, wherein the length direction of the drill holes is parallel to the trend of a working surface, the track of the drill holes is kept consistent with the dip angle of a stratum so as to ensure that the track is kept in the middle of a gangue clamping layer, the depth of the drill holes is determined to be more than 400m according to the width of the working surface and the minimum influence range of gangue clamping, the distance between two fracturing drill holes is D, and the value is 2 times of the fracturing influence radius;
the third step: directional long drilling construction, namely drilling by using a drilling machine, acquiring three-dimensional space track information of a drilled hole through a measurement while drilling system, and adjusting the angle of a tool face of the drilling machine through a hole bottom screw motor to ensure that the drilled hole is accurately controlled to be drilled in a hard gangue clamping layer for construction;
the fourth step: conveying and fracturing construction in a fracturing equipment hole;
firstly, connecting tool strings in holes and pushing the tool strings to a designed position; secondly, connecting the tool string in the hole with a fracturing pump set and an orifice three-way pressure relief valve, connecting well and opening the orifice three-way pressure relief valve to start the fracturing pump set; then starting a fracturing pump set and adopting low-pressure water injection expansion packers, enabling the water injection pressure to reach 5MPa within 5-10 minutes, fully expanding the two packers after the water injection pressure reaches 5MPa in the process of gradual pressurization and expansion, and quickly closing an orifice three-way pressure relief valve; then, the water injection pressure is rapidly increased, after the pressure of the pipe column is stable, the water injection pressure is increased, hydraulic fracturing with large discharge capacity and high pressure is carried out, meanwhile, the discharge capacity and the pressure change of fracturing fluid and the water outlet conditions of adjacent drill holes and coal walls are monitored, after fracturing, obvious pressure drop is generated by the pressure of the pipe column or water is discharged from the coal walls and the return water quantity of the orifices of the adjacent drill holes is obviously increased, the pressure and the discharge capacity are gradually reduced, then, a fracturing pump set is closed, and an orifice three-way pressure relief valve is opened to realize the deblocking; and finally, withdrawing the tool string in the hole, which is put into the hole, out of the hole by using a tunnel drilling machine, then carrying out in-hole peeping to check the fracturing effect, finishing the construction of one fracturing section according to the steps, dragging the packer to a designed position by using the drilling machine, carrying out second-stage fracturing construction, and finishing the fracturing construction of the designed construction section in sequence.
Wherein: firstly, according to the space parameters of the gangue inclusion in the coal seam revealed by the ground geological exploration drilling, a space geometric form diagram of the gangue inclusion in the mine range is compiled; secondly, inserting the gangue clamping space parameters collected by the shaft, the goaf and the roadway on the basis of the drawn space geometric figure of the gangue clamping in the mine range by combining the shaft position, the goaf and the mining area roadway to actually reveal the gangue clamping parameters of the coal bed, and further drawing the space geometric figure of a hard gangue clamping layer of the coal bed of the panel area where the working face is located; then, after the construction of the haulage roadway, the return air roadway and the working face cut-hole excavation of the stope face is completed, further optimizing and drawing the space geometric form of the hard gangue layer in the coal bed in the working face according to the exposed geometric parameters of the occurrence spaces such as the thickness, the structure, the position and the like of the hard gangue layer in the haulage roadway and the return air roadway; and finally, comprehensively determining the occurrence space geometrical form of the hard gangue layer by combining geophysical prospecting data such as lithologic change of underground geological drilling and rock debris cataloguing, drilling time, drilling efficiency, lithologic change of drill hole peeking and the like.
Wherein: and in the third step, the directional drilling machine of the underground hydraulic tunnel of the coal mine is used for connecting the drilling machine, the navigation drill rod, the directional measurement short circuit, the non-magnetic drill rod, the hole bottom screw motor and the directional drill bit.
Wherein: and then, guiding the designed drilling track into a directional drilling measurement system by combining the determined coal seam hard gangue-containing plane and the profile, measuring the zenith angle and the azimuth angle of the drill hole every 3m of drilling in the process of drilling by the drill bit, acquiring the three-dimensional spatial track information of the drill hole by the measurement-while-drilling system, and timely adjusting the tool face angle of the drilling machine according to the deviation of the measured result and the designed track, thereby ensuring that the drilling track is in the hard gangue-containing layer.
Wherein: and when the drilled hole is drilled to the designed depth or the returned slag lithology is the coal seam, determining that the drilled hole penetrates through the coal seam and is drilled for 3m after gangue is contained, and stopping drilling.
Wherein: and (3) drilling a hole, namely, expanding the hole to 193mm, fixing the pipe by adopting a two-plugging one-injection method after a 146mm casing pipe is 10m below the hole, drilling the pipe to a final hole according to a designed track and a designed diameter after the casing pipe is solidified for 72h, then withdrawing the drilling tool from the bottom of the hole into the hole, and cleaning the drilling hole by using clear water until the sand is removed.
Wherein: and fourthly, assembling and connecting the tool string in the hole of the directional long drilling hole according to the sequence of the deflection guide, the check valve, the first packer, the flow limiter, the second packer and the high-pressure pipeline, and gradually pushing the tool string in the hole to the designed depth position of the long drilling hole by using the directional drilling machine.
Wherein: when the high-pressure fracturing fluid reaches the design pressure, the two packers realize complete setting, and after the continuous pressurization pressure reaches the set pressure value, the flow restrictor 8 is opened, so that the fracturing construction of a fracturing section is realized, and effective cracks are formed.
Wherein: after the construction is finished, the whole set of fracturing equipment is recovered by drawing the directional drilling machine.
According to the content, the method for weakening the hard gangue layer by the underground coal mine directional long borehole staged hydraulic fracturing has the following effects:
1. by implementing directional long drilling and staged hydraulic fracturing at one end of a fully mechanized mining face roadway, a hard gangue layer is weakened, the compressive strength of a coal rock mass is reduced, a coal cutter is continuously operated to cut coal, and the safety production efficiency of the fully mechanized mining face is greatly improved.
2. The problems of large mechanical loss and high energy consumption per ton of coal of hard gangue cutting of a fully mechanized mining working face are solved, the damage degree of equipment is reduced, the starting operation time of a coal mining machine is greatly improved, the production efficiency of the working face is improved, the daily coal yield is greatly increased, and the safe and efficient production of the working face is realized.
3. When the directional long borehole drilling and the staged hydraulic fracturing operation are carried out, the directional long borehole drilling and the staged hydraulic fracturing operation are carried out in respective independent areas, the mutual interference is small, the parallel operation can be realized, and the drilling and fracturing construction efficiency is greatly improved.
The details of the present invention can be obtained from the following description and the attached drawings.
Drawings
FIG. 1 shows a floor plan for a directional long bore staged hydraulic fracturing construction of the present invention;
FIG. 2 shows a cross-sectional view of a directional long bore staged hydraulic fracturing construction of the present invention;
FIG. 3 shows a schematic diagram of the connection of the directional long bore staged hydraulic fracturing apparatus of the present invention;
fig. 4 shows a schematic diagram of the effect of the directional long-drill-hole staged hydraulic fracturing of the invention.
Reference numerals:
1-coal bed; 2-hard gangue layer; 3-a goaf; 4-fracturing the borehole; 5-oblique guiding; 6-a check valve; 7-a first packer; 8-a flow restrictor; 9-a second packer; 10-high pressure line; 11-fracturing the fracture.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings.
Referring to fig. 1 to 4, the invention discloses a method for weakening a hard gangue layer by using staged hydraulic fracturing of an underground directional long borehole of a coal mine, which specifically comprises the following steps:
the first step is as follows: and determining the occurrence form and range of the hard gangue layer in the stope face.
The method can be specifically realized through the following processes that firstly, according to the spatial parameters (such as the thickness of the clamped gangue, the lithology of the clamped gangue, the base plate mark of the clamped gangue and the like) of the clamped gangue in the coal bed 1 exposed by the ground geological exploration drilling, a spatial geometric form map (such as a thickness distribution contour map, a lithology distribution map and a base plate elevation contour map) of the clamped gangue in a mine range is compiled; secondly, inserting the gangue clamping space parameters collected by the shaft, the goaf and the roadway on the basis of the drawn space geometric figure of the gangue clamping in the mine range by combining the shaft position, the goaf and the mining area roadway to actually reveal the gangue clamping parameters of the coal bed, and further drawing the space geometric figure of a hard gangue clamping layer of the coal bed of the panel area where the working face is located; then, after the construction of the two roadways of the haulage roadway and the return air roadway of the stope face and the cut hole excavation is completed, further optimizing and drawing the space geometric form of the hard gangue layer in the coal bed in the working face according to the exposed geometric parameters of the occurrence space such as the thickness, the structure, the position and the like of the hard gangue layer in the haulage roadway and the return air roadway; and finally, comprehensively determining the occurrence space geometrical form of the hard gangue layer by combining geophysical prospecting data such as lithologic change of underground geological drilling and rock debris cataloguing, drilling time, drilling efficiency, lithologic change of drill hole peeking and the like.
The second step is that: and (4) determining the drilling layout and fracturing technical parameters.
In order to accurately design the drill hole in the hard gangue layer, a drill site is designed on one side of a roadway (which can be a transportation roadway) to arrange the drill hole, the length direction of the drill hole is parallel to the trend of a working surface, the track of the drill hole is kept basically consistent with the dip angle of a stratum so as to ensure that the track is kept in the middle of the gangue layer, the depth of the drill hole is determined to be more than 400m according to the width of the working face and the minimum influence range of the gangue, therefore, the depth can be timely adjusted according to the drilling rock debris record, the drilling time and the drilling effect change condition in the actual drilling process, the ineffective drilling is avoided, the distance between two fracturing drill holes is D, the value is 2 times of the fracturing influence radius, the fracturing radius is determined according to construction experience, and hole spacing parameters can be properly adjusted and optimized according to the change of the return water amount of the orifices during the fracturing process of two adjacent drill holes, the water outlet condition of peeping hole walls in the fractured drill holes in the fracturing process, the change of fracturing monitoring curves and the like. The plan layout of the directional long-drill-hole staged hydraulic fracturing construction is shown in a figure 1, the left side in the figure 1 is a goaf 3, the right side determines the position of each fracturing drill hole 4, the right side of the goaf is a working face cutting hole, the upper side and the lower side of the goaf are respectively a return air roadway and a transportation roadway, and the sectional view of the directional long-drill-hole staged hydraulic fracturing construction is shown in a figure 2.
The third step: and (5) directional long drilling construction.
Firstly, connecting a drilling machine, a navigation drill rod, a directional measurement short circuit, a non-magnetic drill rod, a hole bottom screw motor and a directional drill bit by utilizing a coal mine underground hydraulic tunnel directional drilling machine; secondly, guiding the designed drilling track into a directional drilling measurement system by combining the determined coal seam hard gangue clamping plane and the profile; then, measuring the zenith angle and the azimuth angle of the drill hole every 3m when the drill bit starts to perform directional drilling in the drilling process, obtaining three-dimensional space track information of the drill hole through a measurement while drilling system, timely adjusting the tool face angle of the drilling machine according to the deviation of the measured result and the designed track, specifically, measuring and obtaining parameters of the zenith angle and the azimuth angle of the position of the drill bit in the directional drilling process, calculating the plane deviation and the vertical deviation of the three-dimensional space track information of the drill bit and the designed three-dimensional space track information according to the parameters, and adjusting the working face angle when any one exceeds 20cm, so that the drill track is ensured to be in a hard gangue layer; and finally, after the drilled hole is drilled to the designed depth or the returned slag is the coal seam, drilling for 3m after the coal seam is determined to be torn through and the waste rock is contained, and stopping drilling. And (3) drilling a hole, namely, expanding the hole to 193mm, fixing the pipe by adopting a two-plugging one-injection method after a 146mm casing pipe is 10m below the hole, drilling the pipe to a final hole according to a designed track and a designed diameter after the casing pipe is solidified for 72h, then withdrawing the drilling tool from the bottom of the hole into the hole, and cleaning the drilling hole by using clear water until the sand is removed.
The fourth step: conveying in hole of fracturing equipment and fracturing construction
During the haplopore staged fracturing, will draw downthehole tool string of slope, packer, high-pressure line etc. to send to downthehole design degree of depth, utilize two packers on the downthehole tool string to sit and seal, realize that two single cards are staged fracturing target section position, concrete step is as follows: firstly, connecting tool strings in a hole, and pushing the tool strings to a designed position by using a drilling machine and a drill rod; secondly, connecting the tool string in the hole with a fracturing pump set and an orifice three-way pressure relief valve, and starting the fracturing pump set by opening the orifice three-way pressure relief valve; then, starting low-pressure water injection and expansion packers of the fracturing pump set, slowly closing an orifice three-way pressure relief valve, observing by a pressure gauge to enable water injection pressure to reach 5MPa within 5-10 minutes, gradually increasing the pressure of the two packers in the gradual expansion process, and completely expanding the two packers after the pressure reaches 5MPa and quickly closing the orifice three-way pressure relief valve; then, the pressure is quickly increased, the water injection pressure is increased after the pressure is stable, hydraulic fracturing with large discharge capacity and high pressure is carried out, and meanwhile, the discharge capacity and the pressure change of fracturing fluid and the water outlet conditions of adjacent drill holes and coal walls are monitored; then, after fracturing until pressure generates obvious pressure drop or coal wall water flows out and the adjacent drilling hole openings return water obviously, gradually reducing the pressure and the discharge capacity, closing a fracturing pump set, and opening a hole opening three-way pressure relief valve to realize deblocking of the two packers; and finally, withdrawing the tool string in the hole from the hole by using the tunnel drilling machine, and then carrying out in-hole peeping inspection on the fracturing effect. And after one fracturing section construction is completed according to the steps, dragging the packer to a designed position by using a drilling machine, performing second-stage fracturing construction, and sequentially completing the fracturing construction of the designed construction section. After the construction is finished, the tool string in the whole set of holes is recovered by simply pulling and pulling the drilling machine. The connection schematic diagram of the directional long drilling staged hydraulic fracturing equipment is shown in figure 3.
Referring to fig. 3 and 4, the tool string in the hole of the directional long drilling hole is assembled and connected according to the sequence of the deflection 5, the check valve 6, the first packer 7, the flow restrictor 8, the second packer 9 and the high-pressure pipeline 10, and the tool string in the hole is gradually pushed to the designed depth position of the long drilling hole by using the directional drilling machine. And (4) starting a high-pressure fracturing pump set to promote the two packers to expand and set, and fracturing a target section by a single clamp. When the high-pressure fracturing fluid reaches the design pressure, the two packers are completely set, and after the continuous pressurization pressure reaches the set pressure value, the flow restrictor 8 is opened to realize the fracturing construction of a fracturing section and form an effective crack 11 (see fig. 4); after the first stage of fracturing construction is completed, the fracturing orifice fracturing pump injection equipment is closed, the orifices are drained and pressure relief is carried out, and the two packers automatically contract to the original state; and dragging the orifice high-pressure pipe column by using a directional drilling machine, dragging the two packers to the designed positions, performing second-stage fracturing construction, and sequentially completing fracturing construction of the designed construction section to form effective three-dimensional cracks (the directional long drilling staged hydraulic fracturing effect is shown in figure 4). After the construction is finished, the whole set of fracturing equipment is recovered by simply pulling and pulling the directional drilling machine.
It should be apparent that the foregoing description and illustrations are by way of example only and are not intended to limit the present disclosure, application or uses. While embodiments have been described in the embodiments and depicted in the drawings, the present invention is not limited to the particular examples illustrated by the drawings and described in the embodiments as the best mode presently contemplated for carrying out the teachings of the present invention, and the scope of the present invention will include any embodiments falling within the foregoing description and the appended claims.
Claims (9)
1. A method for weakening a hard gangue layer by means of coal mine underground directional long drilling and staged hydraulic fracturing is characterized by comprising the following steps:
the first step is as follows: determining occurrence forms and ranges of hard gangue layers in the stope face, and after the construction of the haulage roadway and the return air roadway on two sides of the stope face is completed, carrying out comprehensive analysis research to determine the occurrence forms and ranges of the hard gangue layers according to the occurrence states of the exposed hard gangue layers in the haulage roadway and the return air roadway and in combination with geological data, underground roadway exploration data and geophysical exploration data during ground exploration;
the second step is that: drilling hole layout and fracturing technical parameter determination;
designing a drill site on one side of a roadway to arrange drill holes, wherein the length direction of the drill holes is parallel to the trend of a working surface, the track of the drill holes is kept consistent with the dip angle of a stratum so as to ensure that the track is kept in the middle of a gangue clamping layer, the depth of the drill holes is determined to be more than 400m according to the width of the working surface and the minimum influence range of gangue clamping, the distance between two fracturing drill holes is D, and the value is 2 times of the fracturing influence radius;
the third step: directional long drilling construction, namely drilling by using a drilling machine, acquiring three-dimensional space track information of a drilled hole through a measurement while drilling system, and adjusting the angle of a tool face of the drilling machine through a hole bottom screw motor to ensure that the drilled hole is accurately controlled to be drilled in a hard gangue clamping layer for construction;
the fourth step: conveying and fracturing construction in a fracturing equipment hole;
firstly, connecting tool strings in holes and pushing the tool strings to a designed position; secondly, connecting the tool string in the hole with a fracturing pump set and an orifice three-way pressure relief valve, connecting well and opening the orifice three-way pressure relief valve to start the fracturing pump set; then starting a fracturing pump set and adopting low-pressure water injection expansion packers, enabling the water injection pressure to reach 5MPa within 5-10 minutes, fully expanding the two packers after the water injection pressure reaches 5MPa in the process of gradual pressurization and expansion, and quickly closing an orifice three-way pressure relief valve; then, the water injection pressure is rapidly increased, after the pressure of the pipe column is stable, the water injection pressure is increased, hydraulic fracturing with large discharge capacity and high pressure is carried out, meanwhile, the discharge capacity and the pressure change of fracturing fluid and the water outlet conditions of adjacent drill holes and coal walls are monitored, after fracturing, obvious pressure drop is generated by the pressure of the pipe column or water is discharged from the coal walls and the return water quantity of the orifices of the adjacent drill holes is obviously increased, the pressure and the discharge capacity are gradually reduced, then, a fracturing pump set is closed, and an orifice three-way pressure relief valve is opened to realize the deblocking; and finally, withdrawing the tool string in the hole, which is put into the hole, out of the hole by using a tunnel drilling machine, then carrying out in-hole peeping to check the fracturing effect, finishing the construction of one fracturing section according to the steps, dragging the packer to a designed position by using the drilling machine, carrying out second-stage fracturing construction, and finishing the fracturing construction of the designed construction section in sequence.
2. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 1, wherein: firstly, according to the space parameters of the gangue inclusion in the coal seam revealed by the ground geological exploration drilling, a space geometric form diagram of the gangue inclusion in the mine range is compiled; secondly, inserting the gangue clamping space parameters collected by the shaft, the goaf and the roadway on the basis of the drawn space geometric figure of the gangue clamping in the mine range by combining the shaft position, the goaf and the mining area roadway to actually reveal the gangue clamping parameters of the coal bed, and further drawing the space geometric figure of a hard gangue clamping layer of the coal bed of the panel area where the working face is located; then, after the construction of the haulage roadway, the return air roadway and the working face cut-hole excavation of the stope face is completed, further optimizing and drawing the space geometric form of the hard gangue layer in the coal bed in the working face according to the exposed geometric parameters of the occurrence spaces such as the thickness, the structure, the position and the like of the hard gangue layer in the haulage roadway and the return air roadway; and finally, comprehensively determining the occurrence space geometrical form of the hard gangue layer by combining geophysical prospecting data such as lithologic change of underground geological drilling and rock debris cataloguing, drilling time, drilling efficiency, lithologic change of drill hole peeking and the like.
3. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 1, wherein: and in the third step, the directional drilling machine of the underground hydraulic tunnel of the coal mine is used for connecting the drilling machine, the navigation drill rod, the directional measurement short circuit, the non-magnetic drill rod, the hole bottom screw motor and the directional drill bit.
4. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 3, wherein: and then, guiding the designed drilling track into a directional drilling measurement system by combining the determined coal seam hard gangue-containing plane and the profile, measuring the zenith angle and the azimuth angle of the drill hole every 3m of drilling in the process of drilling by the drill bit, acquiring the three-dimensional spatial track information of the drill hole by the measurement-while-drilling system, and timely adjusting the tool face angle of the drilling machine according to the deviation of the measured result and the designed track, thereby ensuring that the drilling track is in the hard gangue-containing layer.
5. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 4, wherein: and when the drilled hole is drilled to the designed depth or the returned detritus is the coal seam, determining that the drilling is stopped 3m after the coal seam is torn off and the waste rock is contained.
6. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 5, wherein: and (3) drilling a hole, namely, expanding the hole to 193mm, fixing the hole by adopting a two-plugging one-injection method after a 146mm casing pipe is 10m below the hole, drilling the hole to a final hole according to a designed track and a designed diameter after the casing pipe is solidified for 72h, then withdrawing the drilling tool from the bottom of the hole one by one, and cleaning the drilling hole by using clear water while pushing out the drilling tool until the sand is removed.
7. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 1, wherein: and fourthly, assembling and connecting the tool string in the hole of the directional long drilling hole according to the sequence of the deflection guide, the check valve, the first packer, the flow limiter, the second packer and the high-pressure pipeline, and gradually pushing the tool string in the hole to the designed depth position of the long drilling hole by using the directional drilling machine.
8. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 1, wherein: when the high-pressure fracturing fluid reaches the design pressure, the two packers realize complete setting, and after the continuous pressurization pressure reaches the set pressure value, the flow restrictor is opened, so that the fracturing construction of a fracturing section is realized, and effective cracks are formed.
9. The method for weakening the hard gangue layer by means of underground coal mine directional long borehole staged hydraulic fracturing as claimed in claim 1, wherein: after the construction is finished, the whole set of fracturing equipment is recovered by drawing the directional drilling machine.
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