AU2018405437A1 - Method and device for controlling top coal caving property by pulsed hydraulic fracturing - Google Patents
Method and device for controlling top coal caving property by pulsed hydraulic fracturing Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 133
- 238000000034 method Methods 0.000 title claims abstract description 32
- 238000010276 construction Methods 0.000 claims abstract description 20
- 238000006073 displacement reaction Methods 0.000 claims abstract description 8
- 230000000644 propagated effect Effects 0.000 claims abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 44
- 239000002184 metal Substances 0.000 claims description 25
- 125000004122 cyclic group Chemical group 0.000 claims description 16
- 238000005259 measurement Methods 0.000 claims description 16
- 238000007789 sealing Methods 0.000 claims description 13
- 238000002347 injection Methods 0.000 claims description 10
- 239000007924 injection Substances 0.000 claims description 10
- 230000035900 sweating Effects 0.000 claims description 10
- 238000005553 drilling Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 238000005520 cutting process Methods 0.000 claims description 5
- 239000002775 capsule Substances 0.000 claims description 4
- 239000011435 rock Substances 0.000 claims description 4
- 230000008859 change Effects 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims 1
- 238000013467 fragmentation Methods 0.000 abstract description 9
- 238000006062 fragmentation reaction Methods 0.000 abstract description 9
- 239000002699 waste material Substances 0.000 abstract description 3
- 206010017076 Fracture Diseases 0.000 description 28
- 238000005422 blasting Methods 0.000 description 11
- 230000003313 weakening effect Effects 0.000 description 11
- 208000010392 Bone Fractures Diseases 0.000 description 10
- 238000005516 engineering process Methods 0.000 description 10
- 238000005065 mining Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 230000000737 periodic effect Effects 0.000 description 3
- 208000006670 Multiple fractures Diseases 0.000 description 2
- 239000002360 explosive Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000003721 gunpowder Substances 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C45/00—Methods of hydraulic mining; Hydraulic monitors
- E21C45/02—Means for generating pulsating fluid jets
- E21C45/04—Means for generating pulsating fluid jets by use of highly pressurised liquid
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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- Remote Sensing (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Drilling And Exploitation, And Mining Machines And Methods (AREA)
Abstract
The present invention discloses a method and a device for controlling top coal caving property by pulsed hydraulic fracturing. The method combines the advantages of methods of pulsed fracturing and conventional hydraulic fracturing. First, a fracture network is generated in a coal body through pulsed hydraulic fracturing. Then, the fracture network is further propagated through conventional large-displacement hydraulic fracturing, a coal body structure is sufficiently transformed, the top coal fragmentation is reduced, and the top coal caving property is improved. The device in the present invention includes a small-displacement pulse pump and a large-displacement conventional pump which are controlled through a three-way valve and a switch valve. In construction, one path of the pulse pump is first turned on, a conventional high-pressure pump pipeline is closed, a pulse channel is closed after pulsed fracturing is ended, and a conventional fracturing channel is opened. By adopting the method and the device, sufficient fractures can be generated in top coal, the top coal can be weakened, the top coal caving property can be improved, the caving fragmentation of the top coal can be reduced, the construction is convenient, safety and reliability are achieved, and resource waste can be reduced.
Description
METHOD AND DEVICE FOR CONTROLLING TOP COAL
CAVING PROPERTY BY PULSED HYDRAULIC FRACTURING
FIELD OF THE INVENTION [0001] The present invention relates to a method for controlling top coal caving property, and in particular, to a method and device for controlling top coal caving property by pulsed hydraulic fracturing, which belong to the technical field of coal mining.
DESCRIPTION OF RELATED ART [0002] Thick and extra-thick coal seam reserves and production in China account for 40% or more of total coal reserves and total production. Fully mechanized top coal caving is a high-yield and high-efficiency coal mining method for mining thick coal seams developed rapidly in China. Fully mechanized caving mining has become a leading coal mining method for thick and extra-thick coal seams in China presently. The basic requirements for fully mechanized caving mining are complete before supporting and fragmented after supporting. Due to the limitations of technical features, the mine pressure on the hard-thick and extra-thick coal seams or an overburden top coal caving working face is relieved. This pressure cannot achieve timely and sufficient fragmentation of top coal. Therefore, the requirement for top coal caving is not achieved, resulting in a low top coal release rate.
[0003] The traditional methods for controlling top coal caving property mainly include a deep hole pre-blasting technology, a coal seam water injection fracturing technology, and a blasting-water injection combined pre-integrated weakening technology. But for hard-thick and extra-thick coal seams, the three methods of top coal fragmentation have the following problems:
[0004] The deep hole pre-blasting technology and the blasting-water injection combined pre-integrated weakening technology both involve the management and transportation of explosives and detonators. The once-blasting three-inspection system and the three-person linked blasting system are strictly enforced for blasting. The safety management is complex. A large amount of harmful gas such as i
CO generated instantaneously by large-scale blasting has a large impact on the safety management of mine ventilation. For a high gas mine, blasting fragmented coal columns are not suitable due to a hidden danger of gas explosion induced by blasting sparks. A fully mechanized mining face is generally approximately 200 m, deep hole blasting is carried out in upper and lower lanes, boreholes should radiate the whole area, and the boreholes are long, so a large number of pyrotechnics such as gunpowder and detonators are needed, and the economic cost is high. For explosive blasting, dense boreholes are usually arranged within a particular range, so a single hole control range is small.
[0005] According to the coal seam water injection fracturing technology, since the pressure of coal seam water injection is generally approximately 5MP, the expansion direction of fractures caused by hydraulic fracturing is controlled by a three-dimensional stress field, and the fractures generated are fewer and sparse, and the weakening degree of coal body strength is limited. Therefore, enough fractures cannot be formed, so an effect of fragmenting top coal is not obvious.
SUMMARY OF THE INVENTION [0006] To overcome the above-mentioned shortcomings of the prior art, the present invention provides a method and device for controlling top coal caving property by pulsed hydraulic fracturing, which can generate sufficient fractures in top coal, weaken the top coal, improve the top coal caving property, and reduce the caving fragmentation of the top coal. The method is convenient in construction, safe and reliable, and reduces resource waste.
[0007] To solve the above-mentioned problems, the present invention provides a device for controlling top coal caving property by pulsed hydraulic fracturing, which includes a hydraulic fracturing pump set, a high-pressure hose, a packer, and a high-pressure seal mounting rod. An end of the high-pressure seal mounting rod extending to the bottom of a borehole is provided with the packer. The other end of the high-pressure seal mounting rod is connected to the hydraulic fracturing pump set through the high-pressure hose. The packer is connected to a hand pump through a high-pressure thin hose. The hydraulic fracturing pump set includes a hydraulic fracturing high-pressure pump and a hydraulic fracturing pulse pump. The high-pressure hose output from the hydraulic fracturing high-pressure pump and the high-pressure hose output from the hydraulic fracturing pulse pump are connected through a three-way valve. A pipeline between the hydraulic fracturing high-pressure pump and the three-way valve is provided with a switch valve I. A pipeline between the hydraulic fracturing pulse pump and the three-way valve is provided with a switch valve II. The other end of the three-way valve is connected to the high-pressure seal mounting rod through the high-pressure hose. The high-pressure hose is connected to the high-pressure seal mounting rod through an adapter.
[0008] Further, a high-pressure hose pipeline between the three-way valve and the adapter is provided with a pressure relief valve.
[0009] Further, a high-pressure hose pipeline between the three-way valve and the pressure relief valve is provided with a hydraulic fracturing measurement and control instrument.
[0010] A method for controlling top coal caving property by pulsed hydraulic fracturing includes the following steps:
[0011] step 1. Construct oriented long boreholes parallel to each other and perpendicular to a coal wall in a cut coal seam, and construct inclined long boreholes I and inclined long boreholes II parallel to each other and perpendicular to the coal wall in a transport gate road and a return air gate road respectively, the boreholes of the two gate roads being arranged in a staggered manner;
[0012] step 2. Mount and debug a hydraulic fracturing pulse pump;
[0013] step 3. Send a packer to the bottom of the borehole, connect a high-pressure seal mounting rod, an adapter and a high-pressure hose sequentially, and connect the high-pressure hose to the hydraulic fracturing pulse pump;
[0014] step 4. Inject high-pressure water into the packer by using a hand pump, so that the packer is expanded for hole sealing;
[0015] step 5. Open a switch valve II, start the hydraulic fracturing pulse pump for pulsed hydraulic fracturing, and monitor, in real time, the change in a water pressure of fractured boreholes and water seepage in the coal wall of a fractured area by observing a hydraulic fracturing measurement and control instrument mounted in a pipeline during the fracturing process;
[0016] step 6. When the hydraulic fracturing measurement and control instrument monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of a coal stratum exceeds 5 to 7 min, close the hydraulic fracturing pulse pump, open a pressure relief valve, withdraw the packer to a designed second fracturing position for re-sealing fracturing, and repeat this step until the entire drilling section is fractured; and [0017] step 7. Remove the packer, mount the packer to a next borehole, and repeat steps c-f until all the boreholes are fractured.
[0018] Since the caving fragmentation of the top coal is a feature parameter reflecting the caving property of the top coal, the caving property of the top coal is mainly controlled by two key factors: physical and mechanical properties of the top coal and mining-induced stress, i.e. mine pressure. Pulsed hydraulic fracturing is used to control top coal caving property with a principle that high-pressure water with periodic displacement is injected into boreholes of a coal seam by a pulsed high-pressure pump, so that borehole walls undergo multiple fractures under periodic fatigue loading, thereby generating more fractures beyond the control of a three-dimensional stress field. Moreover, a high-frequency shock wave can activate natural fractures in the coal seam to make the natural fractures re-expanded and propagated through, thus forming a complex fracture network in the coal seam, fully cutting a coal body, and weakening the overall mechanical properties of the coal body. Meanwhile, the permeability of the coal body can also be changed, so that the coal body can be moistened by fully absorbing water, and further softening the coal body. Therefore, a hard top coal pulsed hydraulic fracturing control technology refers to: using a pulsed hydraulic fracturing method to pre-destroy the macro- and micro-structures of top coal, weakening the coal body strength by fracturing and softening, and thus meeting the requirement of improving the top coal caving property depending on the coal breaking of mine pressure.
[0019] As a further improvement of the present invention, based on pulsed hydraulic fracturing and weakening top coal, combined with the advantages of pulsed hydraulic fracturing and conventional hydraulic fracturing, a top coal weakening technology of pulsed hydraulic fracturing, followed by conventional hydraulic fracturing is proposed.
[0020] Based on the above-mentioned method, in step 2, a hydraulic fracturing high-pressure pump is mounted and debugged while the hydraulic fracturing pulse pump is mounted, and the hydraulic fracturing pulse pump and the hydraulic fracturing high-pressure pump are connected in parallel together by a three-way valve.
[0021] In step 5, after the hydraulic fracturing pulse pump is subjected to pulsed hydraulic fracturing for 30 minutes, the hydraulic fracturing pulse pump and the switch valve II are closed, then the switch valve I and the hydraulic fracturing high-pressure pump are opened, a fracture generated by pulsed hydraulic fracturing is further propagated by large-displacement pumping injection, and the fracture propagation range is increased.
[0022] In step 6, when the hydraulic fracturing measurement and control instrument monitors that the water pressure of the fractured borehole is less than 5MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, the hydraulic fracturing high-pressure pump is closed, the pressure relief valve is opened, the packer is withdrawn to the designed second fracturing position for re-sealing fracturing, and this step is repeated until the entire drilling section is fractured.
[0023] The improved method includes: first injecting high-frequency pulsed high-pressure water into a coal seam through a pulsed high-pressure pump, and repeatedly impacting the coal seam by periodic high-pressure to generate multiple fractures in the coal seam; and then, using conventional large-displacement hydraulic fracturing to further propagate a fracture network generated by pulsed hydraulic fracturing, so that the fractures between adjacent boreholes are propagated through, a coal body is cut into masses of a particular size and shape, a coal structure is fully transformed, the integrity of the coal seam is destroyed, the coal body strength is reduced, and the overall mechanical properties of top coal are weakened, thereby making it more fully crushed during the process of propelling a working face, reducing the fragmentation of the top coal and improving top coal caving property.
[0024] Further, in step 1, cut boreholes are constructed first, and then the boreholes of the two gate roads are constructed, two-gate road boring being sequentially performed from the direction of cutting to the direction of a main roadway; and a hydraulic fracturing sequence in step 3 to step 6 is the same as a borehole construction sequence, hydraulic fracturing and borehole construction are carried out simultaneously and operated in parallel, and if the construction speed is to be matched, the boreholes may be constructed in advance.
[0025] Further, to ensure the fracturing effect of the long boreholes and to increase the uniformity of the fractures and the number of the fractures, the hydraulic fracturing process employs segmented retreated fracturing, the length of segmented fracturing is to 20 m, and the steps are specifically as follows:
[0026] (a) starting the hydraulic fracturing pulse pump or the hydraulic fracturing high-pressure pump;
[0027] (b) injecting water into one fractured borehole for a cyclic hydraulic fracturing;
[0028] (c) when the hydraulic fracturing measurement and control instrument monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, closing the hydraulic fracturing pulse pump or the hydraulic fracturing high-pressure pump, and opening the pressure relief valve to complete the cyclic hydraulic fracturing;
[0029] (d) then, retreating the packer by 10 to 20 m toward the direction of an orifice of the borehole, and performing a cyclic hydraulic fracturing again;
[0030] (e) repeating the operation until the packer is retreated to a depth of 15 m from the orifice of the fractured borehole for the last cyclic hydraulic fracturing; and [0031] (f) withdrawing the packer to complete the retreated segmented hydraulic fracturing.
[0032] Further, the hydraulic fracturing pulse pump outputs a hydraulic pulse having a pressure range of 0 to 20 MP and a rated flow rate of 6.7 m /h.
[0033] The packer includes a front expansion hose hole-sealer and a rear expansion hose hole-sealer. The front expansion hose hole-sealer and the rear expansion hose hole-sealer are spaced apart in the borehole. A connecting pipe and a high-pressure thin hose are disposed between the front and rear hose hole-sealers. The front hose hole-sealer includes a first hydraulic quick connector, a first fixed sleeve, a first sliding sleeve, a first metal pipe, and a first hole-sealer cavity. One end of the first metal pipe passes through the first sliding sleeve and is connected to the first hydraulic quick connector, and the other end passes through the first sliding sleeve. The rear hose hole-sealer includes a second hydraulic quick connector, a third hydraulic quick connector, a threaded connector, a second sliding sleeve, a second fixed sleeve, a second metal pipe, and a second hole-sealer cavity. One end of the second metal pipe passes through the second sliding sleeve and is connected to the second hydraulic quick connector, and the other end is connected to the second sliding sleeve. The first hydraulic quick connector is connected to the second hydraulic quick connector through the connecting pipe. One end of the high-pressure thin hose passes through the first fixed sleeve and is connected to the front expansion hose hole-sealer, and the other end sequentially passes through the second fixed sleeve, the second hole-sealer cavity, the second sliding sleeve and the threaded connector and is connected to an outer hand pump. When the hand pump pressurizes, a capsule hole-sealer expands radially and retracts longitudinally, and the first sliding sleeve and the second sliding sleeve are freely slidable on the first metal pipe and the second metal pipe respectively. The connecting pipe is provided with a through hole for releasing high-pressure water to fracture a coal-rock mass.
[0034] Compared with conventional blasting top coal weakening and conventional hydraulic fracturing weakening technologies, the pulsed hydraulic fracturing top coal weakening technology adopted by the present invention has the following beneficial effects:
[0035] 1. More hydraulic fractures may be generated in a coal seam by pulsed hydraulic fracturing, meanwhile primary fractures in the coal seam are activated, and a complex fracture network is formed in a coal body to cut the coal body, thereby fully weakening the top coal, improving top coal caving property, and reducing the caving fragmentation of the top coal.
[0036] 2. Retreated segmented pulsed hydraulic fracturing is adopted, thereby improving the uniformity of fractures in the coal body and the number of the fractures, which is conducive to improving the overall caving fragmentation of the top coal.
[0037] 3. Holes are sealed by using a hydraulic fracturing packer. Compared with a conventional hydraulic fracturing single-channel hole-sealer, a double-channel packer may seal high-pressure water between two capsule hole-sealers to achieve segmented fracturing of one borehole, thereby greatly reducing the possibility of punching, and improving the stability of the fracturing process.
[0038] 4. The method for controlling top coal caving property by pulsed hydraulic fracturing is simple, convenient for construction, safe and reliable, and conducive to improving the caving rate of top coal in a fully mechanized caving face and reducing resource waste, and has wide practicality.
BRIEF DESCRIPTION OF THE DRAWINGS [0039] FIG. 1 is a device and construction view according to a first embodiment of the present invention;
[0040] FIG. 2 is a device and construction view according to a second embodiment of the present invention;
[0041] FIG. 3 is a borehole arrangement view of a method according to the present invention;
[0042] FIG. 4 is a sectional view taken along line 1-1 in FIG. 3;
[0043] FIG. 5 is a sectional view taken along line 2-2 in FIG. 3;
[0044] FIG. 6 is a sectional view taken along line 3-3 in FIG. 3; and [0045] FIG. 7 is a schematic structure view of a packer.
[0046] In the figures: 1: Transport gate road; 2: Coal seam; 3: Roof; 4: Inclined long borehole I; 5: High-pressure seal mounting rod; 6: Packer; 6-1: Front expansion hose hole-sealer; 6-2: Rear expansion hose hole-sealer; 6-3: Connecting pipe; 6-4: First hydraulic quick connector; 6-5: First fixed sleeve; 6-6: First sliding sleeve; 6-7: First metal pipe; 6-8: Second hydraulic quick connector; 6-9: Third hydraulic quick connector; 6-10: Second fixed sleeve; 6-11: Second metal pipe; 6-13: Second sliding sleeve; 6-14: First hole-sealer cavity; 6-15: Second hole-sealer cavity; 6-16: Threaded connector; 7: Hydraulic fracturing pump set; 7-1: Hydraulic fracturing pulse pump; 7-2: Hydraulic fracturing high-pressure pump; 8: High-pressure hose; 9: Pressure relief valve; 10: Hydraulic fracturing measurement and control instrument; 11: Cut coal seam; 12: Return air gate road; 13: Switch valve II; 14: Switch valve I; 15: Three-way valve; 16: Adapter; 17: High-pressure thin hose; 18: Hand pump; 19: Oriented long borehole; and 20: Inclined long borehole II.
DETAILED DESCRIPTION OF THE INVENTION [0047] The present invention will be described in detail below with reference to the accompanying drawings.
[0048] First embodiment [0049] As shown in FIG. 1 and FIG. 3 to FIG. 6, an average thickness of a coal seam of a mine is 7.5 m; an immediate roof is pebbly coarse sandstone, sometimes mudstone and sandy mudstone, with an average thickness of 6.32 m; an upper roof is coarse sandstone, with an average thickness of 4.06 m; and an immediate floor is siltstone, with an average thickness of 2.10 m. Working face cut: an anchor, a net and a cable are combined to support a rectangular roadway with a net width of 8.5 m, a net height of 3.2 m and a net sectional area of 27.2 m . Working face transport gate road: an anchor, a net and a cable are combined to support a rectangular roadway with a net width of 4.6 m, a net height of 3.2 m and a net sectional area of 14.72 m . Working face return air gate road: a supporting mode is the same as that of the transport gate road, a rectangular roadway having a net width of 4.6 m, a net height of 3.2 m and a net sectional area of 14.72 m .
[0050] As shown in FIG. 3 and FIG. 4, oriented long boreholes 19 parallel to each other and perpendicular to a coal wall are constructed in a cut coal seam, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, and the boreholes have a length of 50 m and a diameter of 75 mm.
[0051] As shown in FIG. 3 and FIG. 5, inclined long boreholes 14 parallel to each other and perpendicular to the coal wall are constructed in a transport gate road, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, and the boreholes have a length of 105 m and a diameter of 75 mm.
[0052] As shown in FIG. 3 and FIG. 6, inclined long boreholes 1120 parallel to each other and perpendicular to the coal wall are constructed in a return air gate road, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, the boreholes have a length of 105 m and a diameter of 75 mm, and the boreholes of the two gate roads are arranged in a staggered manner. The arrangement of the boreholes should avoid geological structural belts such as faults as far as possible according to geological data, and avoid the influence of geological structures on the fracturing effect of the top coal.
[0053] Cut boreholes are constructed first, and then the boreholes of the two gate roads are constructed, two-gate road boring being sequentially performed from the direction of cutting to the direction of a main roadway. A hydraulic fracturing sequence is the same as a borehole construction sequence, hydraulic fracturing and borehole construction are carried out simultaneously and operated in parallel, and if the construction speed is to be matched, the boreholes may be constructed in advance.
[0054] To ensure the fracturing effect of the long boreholes and to increase the uniformity of the fractures and the number of the fractures, segmented retreated fracturing is employed, a special packer is used for sealing the holes, the length of segmented fracturing is 10 to 20 m, and it is determined after multiple tests according to the actual situation on site.
[0055] The steps are specifically implemented as follows:
[0056] As shown in FIG. 3, in step 1, oriented long boreholes 19 parallel to each other and perpendicular to a coal wall are constructed in a cut coal seam 11, and inclined long boreholes I 14 and inclined long boreholes II 1120 parallel to each other and perpendicular to the coal wall are constructed in a transport gate road 1 and a return air gate road 20 respectively, the boreholes of the two gate roads being arranged in a staggered manner.
[0057] As shown in FIG. 1, in step 2, a hydraulic fracturing pulse pump 7-1 is mounted and debugged.
[0058] In step 3, a packer 6 is conveyed to the bottom of the borehole 4, the borehole 19 or the borehole 20, a high-pressure seal mounting rod 5, an adapter 16 and a high-pressure hose 8 are connected sequentially, and the high-pressure hose is connected to the hydraulic fracturing pulse pump 7-1.
[0059] In step 4, high-pressure water is injected into the packer by using a hand pump 18, so that the packer 6 is expanded for hole sealing.
[0060] In step 5, a switch valve II is opened, and the hydraulic fracturing pulse pump 7-1 is started for pulsed hydraulic fracturing, where the hydraulic fracturing pulse pump 7-1 outputs a hydraulic pulse having a pressure of 20 MP and a rated flow rate of 6.7 m /h; and the change in a water pressure of fractured boreholes and water seepage in the coal wall of a fractured area are monitored in real time by observing a hydraulic fracturing measurement and control instrument 10 mounted in a pipeline during the fracturing process.
io [0061] In step 6, when the hydraulic fracturing measurement and control instrument 10 monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of a coal stratum exceeds 5 to 7 min, the hydraulic fracturing pulse pump 7-1 is closed, a pressure relief valve 9 is opened, and the packer 6 is withdrawn to a designed second fracturing position for re-sealing fracturing. This step is repeated until the entire drilling section is fractured.
[0062] In step 7, the packer is removed and mounted to a next borehole. Steps 3-6 are repeated until all the boreholes are fractured.
[0063] The steps of segmented retreated fracturing are specifically as follows:
[0064] (a) Start the hydraulic fracturing pulse pump 7-1.
[0065] (b) Inject water into one fractured borehole for a cyclic hydraulic fracturing.
[0066] (c) Close, when the hydraulic fracturing measurement and control instrument 10 monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, the hydraulic fracturing pulse pump 7-1, and open the pressure relief valve 9 to complete the cyclic hydraulic fracturing.
[0067] (d) Then, retreat the packer 6 by 10 to 20 m toward the direction of an orifice of the borehole, and perform a cyclic hydraulic fracturing again.
[0068] (e) Repeat the operation until the packer 6 is retreated to a depth of 15 m from the orifice of the fractured borehole for the last cyclic hydraulic fracturing.
[0069] (f) Withdraw the packer 6 to complete the retreated segmented hydraulic fracturing.
[0070] Second embodiment [0071] As shown in FIG. 2, FIG. 3 to FIG. 6, an average thickness of a coal seam of a mine is 9 m. An immediate roof is pebbly coarse sandstone, sometimes mudstone and sandy mudstone, with an average thickness of 7 m; an upper roof is coarse sandstone, with an average thickness of 4 m; and an immediate floor is siltstone, with an average thickness of 2 m. Working face cut: an anchor, a net and a cable are combined to support a rectangular roadway with a net width of 9 m, a net height of 3 m and a net sectional area of 27 m . Working face transport gate road: an anchor, a net and a cable are combined to support a rectangular roadway with a net width of 4.6 m, a net height of 3.2 m and a net sectional area of 14.72 m . Working face return air gate road: a supporting mode is the same as that of the transport gate road, a rectangular roadway having a net width of 4.6 m, a net height of 3.2 m and a net sectional area of 14.72 m .
[0072] As shown in FIG. 3 and FIG. 4, oriented long boreholes 19 parallel to each other and perpendicular to a coal wall are constructed in a cut coal seam, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, and the boreholes have a length of 50 m and a diameter of 75 mm.
[0073] As shown in FIG. 3 and FIG. 5, inclined long boreholes 14 parallel to each other and perpendicular to the coal wall are constructed in a transport gate road, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, and the boreholes have a length of 105 m and a diameter of 75 mm.
[0074] As shown in FIG. 3 and FIG. 6, inclined long boreholes 1120 parallel to each other and perpendicular to the coal wall are constructed in a return air gate road, a hole starting position is spaced apart from a floor by 1.2 m, a hole ending position is spaced apart from a roof by 1 m, the boreholes have a length of 105 m and a diameter of 75 mm, and the boreholes of the two gate roads are arranged in a staggered manner. The arrangement of the boreholes should avoid geological structural belts such as faults as far as possible according to geological data, and avoid the influence of geological structures on the fracturing effect of the top coal.
[0075] Cut boreholes are constructed first, and then the boreholes of the two gate roads are constructed, two-gate road boring being sequentially performed from the direction of cutting to the direction of a main roadway. A hydraulic fracturing sequence is the same as a borehole construction sequence, hydraulic fracturing and borehole construction are carried out simultaneously and operated in parallel, and if the construction speed is to be matched, the boreholes may be constructed in advance.
[0076] To ensure the fracturing effect of the long boreholes and to increase the uniformity of the fractures and the number of the fractures, segmented retreated fracturing is employed, a special packer is used for sealing the holes, the length of segmented fracturing is 10 to 20 m, and it is determined after multiple tests according to the actual situation on site.
[0077] The steps are specifically implemented as follows:
[0078] In step 1, oriented long boreholes 19 parallel to each other and perpendicular to a coal wall are constructed in a cut coal seam 11, and inclined long boreholes 14 and inclined long boreholes 1120 parallel to each other and perpendicular to the coal wall are constructed in a transport gate road 1 and a return air gate road 12 respectively, the boreholes of the two gate roads being arranged in a staggered manner.
[0079] In step 2, a hydraulic fracturing high-pressure pump 7-2 is mounted and debugged while the hydraulic fracturing pulse pump 7-1 is mounted, and the hydraulic fracturing pulse pump 7-1 and the hydraulic fracturing high-pressure pump 7-2 are connected in parallel together by a three-way valve.
[0080] In step 3, a packer 6 is conveyed to the bottom of the borehole 4, a high-pressure seal mounting rod 5, an adapter 16 and a high-pressure hose 8 are connected sequentially, and the high-pressure hose is connected to the hydraulic fracturing pulse pump 7-1 and the hydraulic fracturing high-pressure pump 7-2.
[0081] In step 4, high-pressure water is injected into the packer by 6 using a hand pump 18, so that the packer 6 is expanded for hole sealing.
[0082] In step 5, a switch valve 1113 on the pipeline of the hydraulic fracturing pulse pump 7-1 is opened, a switch valve 114 on the pipeline of the hydraulic fracturing high-pressure pump 7-2 is closed, the hydraulic fracturing pulse pump 7-1 is started for pulsed hydraulic fracturing, and the hydraulic fracturing pulse pump 7-1 outputs a hydraulic pulse having a pressure of 20 MP and a rated flow rate of 12 m /h.
[0083] In step 6, after the hydraulic fracturing pulse pump 7-1 is subjected to pulsed hydraulic fracturing for 30 minutes, the hydraulic fracturing pulse pump 7-1 and the switch valve 1113 are closed, then the switch valve 114 and the hydraulic fracturing high-pressure pump 7-2 are opened, a fracture generated by pulsed hydraulic fracturing is further propagated by large-displacement pumping injection, the fracture propagation range is increased, and the hydraulic fracturing high-pressure pump 7-2 has a rated pressure of 63 MP and a rated flow rate of 12 m /h.
[0084] In step 7, when the hydraulic fracturing measurement and control instrument 10 monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of a coal stratum exceeds 5 to 7 min, the hydraulic fracturing high-pressure pump 7-2 is closed, a pressure relief valve 9 is opened, and the packer 6 is withdrawn to a designed second fracturing position for re-sealing fracturing. This step is repeated until the entire drilling section is fractured.
[0085] In step 8, the packer 6 is removed and mounted to a next borehole. Steps 3-7 are repeated until all the boreholes are fractured.
[0086] The steps of segmented retreated fracturing are specifically as follows:
[0087] (a) Start the hydraulic fracturing pulse pump 7-1 or the hydraulic fracturing high-pressure pump 7-2.
[0088] (b) Inject water into one fractured borehole for a cyclic hydraulic fracturing.
[0089] (c) Close, when the hydraulic fracturing measurement and control instrument 10 monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, the hydraulic fracturing pulse pump 7-1 or the hydraulic fracturing high-pressure pump 7-2, and open the pressure relief valve 9 to complete the cyclic hydraulic fracturing.
[0090] (d) Then, retreat the packer 6 by 10 to 20 m toward the direction of an orifice of the borehole, and perform a cyclic hydraulic fracturing again.
[0091] (e) Repeat the operation until the packer 6 is retreated to a depth of 15 m from the orifice of the fractured borehole for the last cyclic hydraulic fracturing.
[0092] (f) Withdraw the packer 6 to complete the retreated segmented hydraulic fracturing.
[0093] As shown in FIG. 7, the packer includes a front expansion hose hole-sealer 6-1 and a rear expansion hose hole-sealer 6-2. The front expansion hose hole-sealer 6-1 and the rear expansion hose hole-sealer 6-2 are spaced apart in the borehole. A connecting pipe 6-3 and a high-pressure thin hose 17 are disposed between the front and rear hose hole-sealers. The front hose hole-sealer includes a first hydraulic quick connector 6-4, a first fixed sleeve 6-5, a first sliding sleeve 6-6, a first metal pipe 6-7, and a first hole-sealer cavity 6-14. One end of the first metal pipe 6-7 passes through the first sliding sleeve 6-6 and is connected to the first hydraulic quick connector 6-4, and the other end passes through the first sliding sleeve 6-6. The rear hose hole-sealer includes a second hydraulic quick connector 6-8, a third hydraulic quick connector 6-9, a threaded connector 6-16, a second sliding sleeve 6-13, a second fixed sleeve
6-10, a second metal pipe 6-11, and a second hole-sealer cavity 6-15. One end of the second metal pipe 6-11 passes through the second fixed sleeve 6-10 and is connected to the second hydraulic quick connector 6-8, and the other end is connected to the second sliding sleeve 6-13. The first hydraulic quick connector 6-4 is connected to the second hydraulic quick connector 6-8 through the connecting pipe 6-3. One end of the high-pressure thin hose 17 passes through the first fixed sleeve 6-5 and is connected to the front expansion hose hole-sealer 6-1, and the other end sequentially passes through the second fixed sleeve 6-10, the second hole-sealer cavity 6-15, the second sliding sleeve 6-13 and the threaded connector 6-16 and is connected to an outer hand pump 18. When the hand pump pressurizes, a capsule hole-sealer expands radially and retracts longitudinally, and the first sliding sleeve 6-6 and the second sliding sleeve 6-13 are freely slidable on the first metal pipe 6-7 and the second metal pipe
6- 11 respectively. The connecting pipe 6-3 is provided with a through hole for releasing high-pressure water to fracture a coal-rock mass.
[0094] After borehole construction is completed, the connecting pipe 6-3 of an appropriate length is selected according to the length of hydraulic fracturing of the construction, the hand pump 18 injects water through the high-pressure thin hose 17 to the front and rear expansion hose hole-sealers for expansion hole sealing, then the hydraulic fracturing pulse pump 7-1 or the hydraulic fracturing high-pressure pump
7- 2 injects high-pressure water into the boreholes through the first metal pipe 6-7 and the second metal pipe 6-11, and the through hole on the connecting pipe 6-3 is used for releasing high-pressure water to fracture a coal-rock mass. The front expansion hose hole-sealer 6-1 and the rear expansion hose hole-sealer 6-2 expand radially and retract longitudinally after water injection, the first sliding sleeve 6-6 and the second sliding sleeve 6-13 freely slide along the first metal pipe 6-7 and the second metal pipe 6-11 respectively, a seal ring is provided between the metal pipe and the sliding sleeve to prevent water from flowing out of the packer, and water is injected until a borehole segment between two expansion hose hole-sealers is fractured completely. The water pressure is removed, and the two hole-sealers return to the state before water injection, and may be directly moved to a next borehole to be hydraulically fractured.
Claims (9)
1. A device for controlling top coal caving property by pulsed hydraulic fracturing, comprising a hydraulic fracturing pump set (7), a high-pressure hose (8), a packer (6), and a high-pressure seal mounting rod (5), an end of the high-pressure seal mounting rod (5) extending to the bottom of a borehole being provided with the packer (6), the other end of the high-pressure seal mounting rod (5) being connected to the hydraulic fracturing pump set (7) through the high-pressure hose (8), and the packer (6) being connected to a hand pump (18) through a high-pressure thin hose (17), wherein the hydraulic fracturing pump set (7) comprises a hydraulic fracturing high-pressure pump (7-2) and a hydraulic fracturing pulse pump (7-1), the high-pressure hose (8) output from the hydraulic fracturing high-pressure pump (7-2) and the high-pressure hose (8) output from the hydraulic fracturing pulse pump (7-1) are connected through a three-way valve (15), a pipeline between the hydraulic fracturing high-pressure pump (7-2) and the three-way valve (15) is provided with a switch valve I (14), a pipeline between the hydraulic fracturing pulse pump and the three-way valve (15) is provided with a switch valve II (13), the other end of the three-way valve (15) is connected to the high-pressure seal mounting rod (5) through the high-pressure hose (8), and the high-pressure hose (8) is connected to the high-pressure seal mounting rod (5) through an adapter (16).
2. The device for controlling top coal caving property by pulsed hydraulic fracturing according to claim 1, wherein a high-pressure hose pipeline between the three-way valve (15) and the adapter (16) is provided with a pressure relief valve (9).
3. The device for controlling top coal caving property by pulsed hydraulic fracturing according to claim 2, wherein a high-pressure hose pipeline between the three-way valve (15) and the pressure relief valve (9) is provided with a hydraulic fracturing measurement and control instrument (10).
4. A method for controlling top coal caving property by pulsed hydraulic fracturing, comprising the following steps:
step 1. constructing oriented long boreholes (19) parallel to each other and perpendicular to a coal wall in a cut coal seam (11), and constructing inclined long boreholes I (4) and inclined long boreholes II (20) parallel to each other and perpendicular to the coal wall in a transport gate road (1) and a return air gate road (12) respectively, the boreholes of the two gate roads being arranged in a staggered manner;
step 2. mounting and debugging a hydraulic fracturing pulse pump (7-1);
step 3. sending a packer (6) to the bottom of the borehole (4), connecting a high-pressure seal mounting rod (5), an adapter (16) and a high-pressure hose (8) sequentially, and connecting the high-pressure hose to the hydraulic fracturing pulse pump (7-1);
step 4. injecting high-pressure water into the packer by using a hand pump (18), so that the packer (6) is expanded for hole sealing;
step 5. opening a switch valve II, starting the hydraulic fracturing pulse pump (7-1) for pulsed hydraulic fracturing, and monitoring the change in a water pressure of fractured boreholes and water seepage in the coal wall of a fractured area by observing a hydraulic fracturing measurement and control instrument (10) mounted in a pipeline in real time during a fracturing process;
step 6. when the hydraulic fracturing measurement and control instrument (10) monitors that the water pressure of the fractured borehole is less than 5 MPa or a duration of sweating of a coal stratum exceeds 5 to 7 min, closing the hydraulic fracturing pulse pump (7-1), opening a pressure relief valve (9), withdrawing the packer (6) to a designed second fracturing position for re-sealing fracturing, and repeating this step until an entire drilling section is fractured; and step 7. taking out the packer (6), mounting the packer to a next borehole, and repeating steps c-f until all the boreholes are fractured.
5. The method for controlling top coal caving property by pulsed hydraulic fracturing according to claim 4, wherein in step 2, a hydraulic fracturing high-pressure pump (7-2) is mounted and debugged while the hydraulic fracturing pulse pump (7-1) is mounted, and the hydraulic fracturing pulse pump (7-1) and the hydraulic fracturing high-pressure pump (7-2) are connected in parallel together by a three-way valve;
in step 5, after the hydraulic fracturing pulse pump (7-1) is used for pulsed hydraulic fracturing for 30 minutes, the hydraulic fracturing pulse pump (7-1) and the switch valve II (13) are closed, then the switch valve I (14) and the hydraulic fracturing high-pressure pump (7-2) are opened, a fracture generated by pulsed hydraulic fracturing is further propagated by large-displacement pumping injection, and a fracture propagation range is increased; and in step 6, when the hydraulic fracturing measurement and control instrument (10) monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, the hydraulic fracturing high-pressure pump (7-2) is closed, the pressure relief valve (9) is opened, the packer (6) is withdrawn to the designed second fracturing position for re-sealing fracturing, and this step is repeated until the entire drilling section is fractured.
6. The method for controlling top coal caving property by pulsed hydraulic fracturing according to claim 4 or 5, wherein in step 1, cut boreholes are constructed first, and then the boreholes of the two gate roads are constructed, two-gate road boring being sequentially performed from a direction of cutting to a direction of a main roadway; and a hydraulic fracturing sequence in step 3 to step 6 is the same as a borehole construction sequence, hydraulic fracturing and borehole construction are performed simultaneously and operated in parallel, and if construction speed is to be matched, the boreholes may be constructed in advance.
7. The method for controlling top coal caving property by pulsed hydraulic fracturing according to claim 6, wherein segmented retreated fracturing is employed, the length of segmented fracturing is 10 to 20 m, and the steps are specifically as follows:
(a) starting the hydraulic fracturing pulse pump (7-1) or the hydraulic fracturing high-pressure pump (7-2);
(b) injecting water into one fractured borehole for performing cyclic hydraulic fracturing once;
(c) when the hydraulic fracturing measurement and control instrument (10) monitors that the water pressure of the fractured borehole is less than 5 MPa or the duration of sweating of the coal stratum exceeds 5 to 7 min, closing the hydraulic fracturing pulse pump (7-1) or the hydraulic fracturing high-pressure pump (7-2), and opening the pressure relief valve (9) to complete the cyclic hydraulic fracturing;
(d) then, retreating the packer (6) by 10 to 20 m toward the direction of an orifice of the borehole, and performing cyclic hydraulic fracturing again;
(e) repeating the operation until the packer (6) is retreated to a depth of 15 m from the orifice of the fractured borehole for the last cyclic hydraulic fracturing; and (f) withdrawing the packer (6) to complete the retreated segmented hydraulic fracturing.
8. The method for controlling top coal caving property by pulsed hydraulic fracturing according to claim 7, wherein the hydraulic fracturing pulse pump (7-1) outputs a hydraulic pulse having a pressure range of 0 to 20 MPa and a rated flow rate of 6.7 m3/h.
9. The method for controlling top coal caving property by pulsed hydraulic fracturing according to claim 8, wherein the packer comprises a front expansion hose hole-sealer (6-1) and a rear expansion hose hole-sealer (6-2), the front expansion hose hole-sealer (6-1) and the rear expansion hose hole-sealer (6-2) being spaced apart in the borehole, and a connecting pipe (6-3) and a high-pressure thin hose 17 being disposed between the front and rear hose hole-sealers; the front hose hole-sealer comprises a first hydraulic quick connector (6-4), a first fixed sleeve (6-5), a first sliding sleeve (6-6), a first metal pipe (6-7), and a first hole-sealer cavity (6-14), one end of the first metal pipe (6-7) passing through the first sliding sleeve (6-6) and being connected to the first hydraulic quick connector (6-4), and the other end passing through the first sliding sleeve (6-6); the rear hose hole-sealer comprises a second hydraulic quick connector (6-8), a third hydraulic quick connector (6-9), a threaded connector (6-16), a second sliding sleeve (6-13), a second fixed sleeve (6-10), a second metal pipe (6-11), and a second hole-sealer cavity (6-15), one end of the second metal pipe (6-11) passing through the second fixed sleeve (6-10) and being connected to the second hydraulic quick connector (6-8), and the other end being connected to the second sliding sleeve (6-13); the first hydraulic quick connector (6-4) is connected to the second hydraulic quick connector (6-8) through the connecting pipe (6-3), one end of the high-pressure thin hose (17) passes through the first fixed sleeve (6-5) and is connected to the front expansion hose hole-sealer (6-1), and the other end sequentially passes through the second fixed sleeve (6-10), the second hole-sealer cavity (6-15), the second sliding sleeve (6-13) and the threaded connector (6-16) and is connected to an outer hand pump (18); when the hand pump presses, a capsule hole-sealer expands radially and retracts longitudinally, and the first sliding sleeve (6-6) and the second sliding sleeve (6-13) are freely slidable on the first metal pipe (6-7) and the second metal pipe (6-11) respectively; and the connecting pipe (6-3) is provided with a through hole for releasing high-pressure water to fracture a coal-rock mass.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810398499.4 | 2018-04-28 | ||
| CN201810398499.4A CN108678747B (en) | 2018-04-28 | 2018-04-28 | A kind of method and apparatus of pulsed water fracturing control Top coal caving characteristic |
| PCT/CN2018/113600 WO2019205558A1 (en) | 2018-04-28 | 2018-11-02 | Method and device for controlling top coal caving performance by means of pulse hydraulic fracturing |
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| Publication Number | Publication Date |
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| AU2018405437A1 true AU2018405437A1 (en) | 2019-11-14 |
| AU2018405437B2 AU2018405437B2 (en) | 2020-07-16 |
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| AU2018405437A Ceased AU2018405437B2 (en) | 2018-04-28 | 2018-11-02 | Method and device for controlling top coal caving property by pulsed hydraulic fracturing |
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| Country | Link |
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| CN (1) | CN108678747B (en) |
| AU (1) | AU2018405437B2 (en) |
| RU (1) | RU2704997C1 (en) |
| WO (1) | WO2019205558A1 (en) |
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| CN108678747B (en) * | 2018-04-28 | 2019-08-30 | 中国矿业大学 | A kind of method and apparatus of pulsed water fracturing control Top coal caving characteristic |
| CN112709575A (en) * | 2019-10-24 | 2021-04-27 | 西安闪光能源科技有限公司 | Hard thick coal seam top coal caving method based on controllable shock wave pre-splitting |
| CN111255454A (en) * | 2020-01-17 | 2020-06-09 | 天地科技股份有限公司 | Method for directional roof cutting and pressure relief of hard roof of coal mine |
| CN111636872B (en) * | 2020-06-09 | 2021-10-22 | 中煤科工集团重庆研究院有限公司 | Method for increasing caving property of top coal through hydraulic fracturing |
| CN111908301B (en) * | 2020-07-15 | 2021-03-30 | 中南大学 | Underground ore lifting method |
| CN112343570A (en) * | 2020-10-16 | 2021-02-09 | 煤科集团沈阳研究院有限公司 | Coal mine porous hydraulic fracturing system and control method |
| CN113914858B (en) * | 2021-02-07 | 2024-04-12 | 中国矿业大学 | Basic roof and roof coal synchronous pre-cracking design method for shallow-buried double-hard super-thick coal seam |
| CN113006796B (en) * | 2021-04-14 | 2021-11-23 | 中国矿业大学 | Coal and contact symbiotic oil shale fracturing co-production method |
| CN113011048B (en) * | 2021-04-23 | 2022-02-18 | 西南石油大学 | Repeated fracturing simulation method for horizontal well of compact conglomerate reservoir |
| CN113217099B (en) * | 2021-06-08 | 2024-04-05 | 国能神东煤炭集团有限责任公司 | Hydraulic directional top plate cutting device |
| CN114165197B (en) * | 2021-12-09 | 2022-07-05 | 中国矿业大学(北京) | Pressure-relief and permeability-increasing device and method for pulse hydraulic fracturing coal seam |
| CN115217458B (en) * | 2022-05-25 | 2023-11-28 | 中国矿业大学 | Underground fracturing and proppant injection integrated device and construction method |
| CN115749713B (en) * | 2022-10-14 | 2023-06-16 | 中国矿业大学 | Rock stratum variable frequency pulse seam net fracturing method and equipment |
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| SU883509A1 (en) * | 1980-03-24 | 1981-11-23 | Ордена Октябрьской Революции И Ордена Трудового Красного Знамени Институт Горного Дела Им.А.А.Скочинского | Method of conducting hydraulic treatment of coal bed |
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-
2018
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- 2018-11-02 RU RU2019126284A patent/RU2704997C1/en active
- 2018-11-02 WO PCT/CN2018/113600 patent/WO2019205558A1/en active Application Filing
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| CN108678747A (en) | 2018-10-19 |
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| CN108678747B (en) | 2019-08-30 |
| RU2704997C1 (en) | 2019-11-05 |
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