CN111236907A - Liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring - Google Patents
Liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring Download PDFInfo
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- CN111236907A CN111236907A CN201911325754.3A CN201911325754A CN111236907A CN 111236907 A CN111236907 A CN 111236907A CN 201911325754 A CN201911325754 A CN 201911325754A CN 111236907 A CN111236907 A CN 111236907A
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 248
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 124
- 239000007788 liquid Substances 0.000 title claims abstract description 113
- 238000012544 monitoring process Methods 0.000 title claims abstract description 69
- 230000001965 increasing effect Effects 0.000 title claims abstract description 33
- 230000035699 permeability Effects 0.000 title claims abstract description 30
- 238000000034 method Methods 0.000 title claims abstract description 27
- 230000035939 shock Effects 0.000 title claims abstract description 9
- 239000007789 gas Substances 0.000 claims abstract description 197
- 239000003245 coal Substances 0.000 claims abstract description 69
- 238000005553 drilling Methods 0.000 claims abstract description 25
- 238000012806 monitoring device Methods 0.000 claims abstract description 18
- 238000003860 storage Methods 0.000 claims abstract description 15
- 230000000694 effects Effects 0.000 claims abstract description 9
- 238000001514 detection method Methods 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000005336 cracking Methods 0.000 claims abstract description 5
- 238000000605 extraction Methods 0.000 claims description 43
- 238000002347 injection Methods 0.000 claims description 27
- 239000007924 injection Substances 0.000 claims description 27
- 230000008569 process Effects 0.000 claims description 11
- 239000011435 rock Substances 0.000 claims description 9
- 238000009413 insulation Methods 0.000 claims description 5
- 238000007599 discharging Methods 0.000 claims description 4
- 230000008014 freezing Effects 0.000 claims description 4
- 238000007710 freezing Methods 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- 238000005520 cutting process Methods 0.000 claims description 3
- 238000004172 nitrogen cycle Methods 0.000 claims 1
- 238000001028 reflection method Methods 0.000 claims 1
- 230000008859 change Effects 0.000 abstract description 5
- 238000002309 gasification Methods 0.000 description 8
- 238000010276 construction Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
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Abstract
The invention discloses a liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring, and a video monitoring lens shoots, monitors and obtainsThe size of bubbles generated in liquid nitrogen in the cross-layer drilling hole and the flow rate of the generated bubbles are fed back to the monitoring control center for storage; the quality sensor monitors the mass loss rate of the liquid nitrogen in the cross-layer drilling hole in real time and feeds the mass loss rate back to the monitoring control center for storage; the gas monitoring device detects the gas pressure, the gas flow and the gas temperature in the pressure relief pipe in real time and feeds the gas pressure, the gas flow and the gas temperature back to the monitoring control center for storage; after the primary fracturing is completed, SF is adopted6The gas detector, the sound wave emitter and the sound wave receiver detect the anti-reflection cracking effect, namely the sound wave speed can detect the quantity of cracks generated after anti-reflection, and SF6Gas detection can detect the connectivity of the resulting fractures to each other. The coal body is fractured by the cold impact of liquid nitrogen, the expansion pressure of phase change gas and the frost heaving pressure of water in the fracture through monitoring data, and the permeability increasing effect can be effectively monitored.
Description
Technical Field
The invention relates to a coal seam permeability increasing method, in particular to a liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring.
Background
The coal bed with high gas content in the coal mine in China accounts for 50% -70%, the coal bed pressure and the gas pressure are continuously increased along with the continuous increase of the mining depth, the gas problem is serious day by day, and gas explosion and gas outburst become difficult problems to be solved urgently in mine safety production. Coal beds in China are mostly high-gas low-permeability coal beds, and the existing methods such as hydraulic fracturing, hydraulic slotting, presplitting blasting and the like are not enough to overcome the problems of high gas adsorption and low gas permeability of the coal beds, so that the existing gas extraction has low concentration, small extraction amount and unsatisfactory extraction effect. At present, the mode of liquid nitrogen injection well is widely concerned about the multiple action mechanisms of cold impact, phase change gas expansion force and water ice phase change frost heaving force. However, in practical tests, the existing liquid nitrogen well injection method and patent have the following significant problems: because the liquid nitrogen has a severe gasification problem in the well injection process, the volume of the liquid nitrogen has an expansion rate of 696 times after the liquid nitrogen is gasified and expanded to 21 ℃ pure nitrogen, which means that at the initial stage of the liquid nitrogen well injection, when the liquid nitrogen does not flow to the coal position, the drill hole is filled with the heated and gasified nitrogen and the air pressure continuously rises, the air pressure in the drill hole quickly reaches dozens of MPa, the liquid nitrogen causes the effective pressure and flow rate which can be provided by the well injection pump not to be high due to the poor stability of the liquid nitrogen, the difference is more than 10 times compared with the gas expansion pressure generated in the drill hole, finally the liquid nitrogen cannot be injected into the drill hole rapidly in large quantity, the liquid nitrogen can be injected into the drill hole only with extremely small flow, but the advantage of the permeability increase of the liquid nitrogen cannot be exerted (namely, the impact force of the volume expansion when the liquid nitrogen is gasified and the freezing effect of the coal due, the impact force of rapid expansion differential is lost); meanwhile, the time required for increasing the permeability of the coal seam is greatly increased, and the permeability increasing effect cannot be ensured.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a liquid nitrogen circulating cold impact permeability-increasing method based on multi-parameter monitoring, which can ensure that liquid nitrogen can be quickly and continuously injected into a through-layer drill hole through monitoring data, and can simultaneously crack coal bodies by utilizing the cold impact of the liquid nitrogen, the expansion pressure of phase change gas and the frost heaving pressure of water in cracks and effectively monitor the permeability-increasing effect.
In order to achieve the purpose, the invention adopts the technical scheme that: a liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring comprises the following specific steps:
A. drilling a layer-through borehole in the roadway, wherein the borehole penetrates through the rock stratum and extends into the coal seam;
B. hydraulic seam cutting equipment is adopted to stretch into the cross drilling hole to reach the coal seam, and a plurality of disc-shaped cracks are cut at equal intervals in the coal seam along the direction vertical to the cross drilling hole by taking the cross drilling hole as the center;
C. one end of a liquid nitrogen injection pipe and one end of a pressure relief pipe extend into the cross-layer drill hole to reach the coal seam, and a video monitoring lens with a light source is installed at one end of the liquid nitrogen injection pipe; then, sealing the rock stratum section of the cross-layer drilled hole, arranging a quality sensor at the section, closest to the sealed hole, of the cross-layer drilled hole, and respectively connecting the other end of the pressure relief pipe with two gas pipelines through a tee joint; a safety valve and a spherical valve are respectively arranged on the two gas pipelines; a gas monitoring device is arranged on the pressure relief pipe; the video monitoring lens, the quality sensor and the gas monitoring device are all connected with the monitoring control center; the gas monitoring device consists of a temperature sensor, a gas pressure meter and a gas flowmeter;
D. connecting the other end of the liquid nitrogen injection pipe with a liquid nitrogen pump, starting the liquid nitrogen pump, opening a spherical valve, and simultaneously opening a video monitoring lens, a quality sensor and a gas monitoring device; liquid nitrogen is injected into the cross-layer drill hole through the liquid nitrogen injection pipe and enters each disc-shaped crack, the liquid nitrogen is gasified to absorb heat so as to quickly reduce the temperature of the coal body, and the water in the coal body is frozen and expanded to apply freezing expansion force to the coal body to crack; meanwhile, the gasified nitrogen rapidly expands in volume to apply gas expansion force to the coal body to crack, the air pressure in the through-layer drill hole is rapidly increased, and the nitrogen is discharged out of the through-layer drill hole from a gas pipeline where the spherical valve is located through the pressure relief pipe, so that the air pressure in the through-layer drill hole is reduced, and the liquid nitrogen can be continuously injected; the video monitoring lens shoots and monitors the size of bubbles generated in the liquid nitrogen in the through-layer drilling hole and the flow rate of the generated bubbles in real time and feeds the bubbles back to the monitoring control center for storage, wherein the flow rate of the bubbles is gradually slower and slower along with the gradual gasification of the liquid nitrogen; the quality sensor monitors the mass loss rate of the liquid nitrogen in the cross-layer drill hole in real time and feeds the mass loss rate back to the monitoring control center for storage, the mass loss rate of the liquid nitrogen can indicate the speed of the liquid nitrogen in the cross-layer drill hole entering the fracture, and the mass loss rate can firstly rise and then fall after the liquid nitrogen is injected; the gas monitoring device detects the gas pressure, the gas flow and the gas temperature in the pressure relief pipe in real time and feeds the gas pressure, the gas flow and the gas flow back to the monitoring control center for storage, the gas pressure and the gas flow can be gradually reduced in the continuous gasification process after the liquid nitrogen is injected, the gas temperature can be continuously reduced in the gasification process after the liquid nitrogen is injected, and the temperature can be raised until the liquid nitrogen in the through-layer drill hole is completely gasified;
E. when liquid nitrogen flows out from a gas pipeline where the spherical valve is continuously injected by liquid nitrogen, stopping a liquid nitrogen pump and closing the spherical valve, setting an opening threshold value of a safety valve, continuously gasifying and expanding the liquid nitrogen in a through-layer drill hole, applying gas expansion force to the coal body to crack, opening the safety valve when the gas pressure in the through-layer drill hole exceeds a set opening threshold value, discharging the nitrogen in the through-layer drill hole from the gas pipeline where the safety valve is located to the through-layer drill hole at the moment, so that the gas pressure in the through-layer drill hole is reduced, closing the safety valve when the gas pressure is lower than the set opening threshold value, continuously gasifying and expanding the liquid nitrogen in the through-layer drill hole at the moment, applying gas expansion force to crack the coal body again until the gas pressure in the through-layer drill hole exceeds the set opening threshold value, opening the safety valve to release pressure, repeatedly performing gas expansion force cracking on the coal body for multiple times until the mass loss rate of the real-, The flow rate of the real-time bubbles, the gas flow value and the gas pressure value in the real-time pressure relief pipe are all 50% -80% of the respective peak value, and the received real-time gas temperature value starts to rise; completing a fracturing and permeability increasing process of one-time through-layer drilling;
F. two gas extraction drill holes are drilled in the coal seam on two sides of the cross-layer drill hole, and the two gas extraction drill holes penetrate through each disc-shaped crack; two gas extraction drill holes are respectively provided withAn acoustic transmitter and an acoustic receiver, both provided with an SF6Gas detector, SF6The gas detector, the sound wave transmitter and the sound wave receiver are all connected with the monitoring control center;
①, the monitoring control center controls the sound wave transmitter to transmit sound waves, the sound wave receiver receives the sound waves and feeds the sound waves back to the monitoring control center, so that a detected sound wave speed value is obtained, then the monitoring control center calls a standard sound wave speed value of the non-fractured position of the coal seam, the standard sound wave speed value and the sound wave speed value are compared, if the detected sound wave speed value is less than or equal to 70% of the standard sound wave speed value (because the sound wave speed in the coal seam is greater than the sound wave speed in the air, the detected sound wave speed is smaller, the more cracks are formed between two gas extraction drill holes), the step ② is carried out, and if the detected sound wave speed value is greater than 70%;
② injecting trace gas SF into the through-hole via the liquid nitrogen injection pipe at a pressure not greater than the threshold opening pressure of the safety valve6Then two SF6Gas detector detects whether SF exists in two gas extraction drill holes in real time6A gas; if two SF6The gas detectors all detect SF6Gas (by detecting SF)6Gas can determine the connectivity of fractures generated after the permeability of a coal body between a cross-layer drill hole and two gas extraction drill holes is increased; if the gas extraction drill holes can be detected, the generated fractures are mutually communicated to form at least one channel, so that the cross-layer drill holes are respectively communicated with the two gas extraction drill holes; that is, the speed of sound wave can detect the number of cracks generated after the permeability is increased, and the SF6Gas detection can detect the connectivity of the fractures generated to each other, then proceed to step ④, otherwise proceed to step ③;
③ repeating steps D and E, completing the fracturing and permeability increasing process of one through-layer drilling, and entering step ①;
④, completing the fracturing effect detection, and performing gas extraction on the coal seam through the two gas extraction drill holes;
G. and D, after the gas extraction of the position is finished, repeating the steps A to F at another position of the roadway at a certain distance, performing the coal bed permeability increasing and the gas extraction of the position, and circulating the steps until the coal bed permeability increasing and the gas extraction of the whole roadway are finished.
Further, the outer surface of the liquid nitrogen injection pipe and the outer surface of the video monitoring lens are wrapped by heat insulation layers. The heat insulation layer is additionally arranged, so that the heat exchange between the liquid nitrogen in the liquid nitrogen injection pipe and the outside can be reduced; meanwhile, the low-temperature isolation protection can be carried out on the video monitoring lens, so that the video monitoring lens is prevented from being damaged due to the low temperature of liquid nitrogen.
Further, the monitoring control center is a computer.
Further, the opening threshold of the safety valve is 30 MPa.
Compared with the prior art, the method comprises the steps of firstly drilling a cross-layer drill hole in a roadway through a rock layer to the coal layer, utilizing hydraulic seam cutting equipment to cut a plurality of cracks perpendicular to the cross-layer drill hole in the cross-layer drill hole at equal intervals, extending a liquid nitrogen injection pipe and a pressure relief pipe into the cross-layer drill hole, sealing a rock layer section of the cross-layer drill hole, respectively connecting the pressure relief pipe outside the cross-layer drill hole with two gas pipelines through tee joints, and respectively installing a safety valve and a spherical valve on the two gas pipelines. The spherical valve performs switch control on the nitrogen discharged when the liquid nitrogen is injected into the cross-layer drill hole, so that the speed of injecting the liquid nitrogen into the cross-layer drill hole can be controlled; the video monitoring lens shoots and monitors the size of bubbles generated in the liquid nitrogen in the cross-layer drilling hole and the flow rate of the generated bubbles in real time and feeds the bubbles back to the monitoring control center for storage; the quality sensor monitors the mass loss rate of the liquid nitrogen in the cross-layer drilling hole in real time and feeds the mass loss rate back to the monitoring control center for storage; the gas monitoring device detects the gas pressure, the gas flow and the gas temperature in the pressure relief pipe in real time and feeds the gas pressure, the gas flow and the gas temperature back to the monitoring control center for storage; and when the spherical valve is closed, setting a threshold value of the safety valve, so that the safety valve controls the pressure in the through-layer drill hole, opening the safety valve when the air pressure in the through-layer drill hole exceeds the threshold value, discharging the nitrogen in the through-layer drill hole for pressure relief, and automatically closing the safety valve after the pressure relief. The method makes full use of the cold impact of liquid nitrogen, the expansion pressure of the phase-change gas and the frost heaving pressure of residual moisture in the cracks to crack the coal body, has wide effective cracking area, and particularly has the expansion pressure of the phase-change gas along with the continuous liquid nitrogenThe gasification and the repeated opening of the safety valve enable the air pressure in the cross-layer drill hole to repeatedly reach the threshold value of the safety valve, so that the coal body can be repeatedly expanded and damaged, and the fracture network of the coal body is enlarged. After one-time fracturing is completed, two gas extraction drill holes are drilled at the periphery, and then SF is adopted6The gas detector, the sound wave emitter and the sound wave receiver detect the anti-reflection cracking effect, namely the sound wave speed can detect the quantity of cracks generated after anti-reflection, and SF6Gas detection can detect the connectivity of the generated fractures; and gas extraction can be carried out when the gas extraction and the gas extraction meet certain conditions. According to the method, the liquid nitrogen can be ensured to be rapidly and continuously injected into the through-layer drill hole through monitoring data, the coal body is cracked by utilizing the cold impact of the liquid nitrogen, the expansion pressure of phase change gas and the frost heaving pressure of water in the crack, and the anti-reflection effect can be effectively monitored; if the reflection reducing work is not met, the reflection reducing work can be carried out again.
Drawings
FIG. 1 is a schematic view of the construction layout of the present invention;
FIG. 2 is a perspective view of the construction layout of the present invention.
In the figure: 1. coal bed, 2, disc-shaped crack, 3, rock stratum, 4, ball valve, 5, safety valve, 6, liquid nitrogen injection pipe, 7, gas extraction hole, 8, cross-layer drilling, 9, pressure relief pipe, 10, video monitoring lens, 11, quality sensor, 12, gas monitoring device, 13, SF6Gas detector, 14, sound wave emitter, 15, sound wave receiver.
Detailed Description
The present invention will be further explained below.
As shown in fig. 1 and fig. 2, the method comprises the following specific steps:
A. drilling a through-layer drill hole 8 in the roadway, wherein the through-layer drill hole penetrates through the rock stratum 3 and extends into the coal seam 1;
B. hydraulic slotting equipment is adopted to stretch into the cross drilling holes 8 to reach the coal seam 1, and a plurality of disc-shaped cracks 2 are cut at equal intervals in the coal seam 1 along the direction vertical to the cross drilling holes 8 by taking the cross drilling holes 8 as the center;
C. one end of a liquid nitrogen injection pipe 6 and one end of a pressure relief pipe 9 extend into the cross-layer drill hole 8 to reach the coal seam 1, and a video monitoring lens 10 with a light source is installed at one end of the liquid nitrogen injection pipe 6; then, sealing the rock stratum section of the cross-layer drill hole 8, arranging a quality sensor 11 at the section, closest to the sealed hole, of the cross-layer drill hole 8, and respectively connecting the other end of the pressure relief pipe 9 with two gas pipelines through a tee joint; a safety valve 5 and a ball valve 4 are respectively arranged on the two gas pipelines; a gas monitoring device 12 is arranged on the pressure relief pipe 9; the video monitoring lens 10, the quality sensor 11 and the gas monitoring device 12 are all connected with a monitoring control center; the gas monitoring device 12 consists of a temperature sensor, a gas pressure gauge and a gas flowmeter;
D. connecting the other end of the liquid nitrogen injection pipe 6 with a liquid nitrogen pump, starting the liquid nitrogen pump, opening the spherical valve 4, and simultaneously opening the video monitoring lens 10, the mass sensor 1 and the gas monitoring device 12; liquid nitrogen is injected into the cross-layer drill holes 8 through the liquid nitrogen injection pipe 6 and enters each disc-shaped crack 2, the liquid nitrogen is gasified to absorb heat so that the temperature of the coal body is rapidly reduced, and the water in the coal body is frozen and expanded to apply freezing expansion force to the coal body to crack; meanwhile, the gasified nitrogen rapidly expands in volume to apply gas expansion force to the coal body to crack, the air pressure in the through-layer drill hole 8 is rapidly increased, and the nitrogen is discharged out of the through-layer drill hole 8 from a gas pipeline where the spherical valve 4 is located through the pressure relief pipe 9, so that the air pressure in the through-layer drill hole 8 is reduced, and liquid nitrogen can be continuously injected; the video monitoring lens 10 shoots and monitors the size of bubbles generated in the liquid nitrogen in the through-hole 8 and the flow rate of the generated bubbles in real time and feeds the size and the flow rate of the generated bubbles back to the monitoring control center for storage, wherein the flow rate of the bubbles is slower and slower along with the gradual gasification of the liquid nitrogen; the quality sensor 11 monitors the mass loss rate of the liquid nitrogen in the cross-layer drill hole 8 in real time and feeds the mass loss rate back to the monitoring control center for storage, the mass loss rate of the liquid nitrogen can indicate the speed of the liquid nitrogen in the cross-layer drill hole 8 entering the fracture, and the mass loss rate tends to rise and then fall firstly after the liquid nitrogen is injected; the gas monitoring device 12 detects the gas pressure, the gas flow and the gas temperature in the pressure relief pipe 9 in real time and feeds the gas pressure, the gas flow and the gas temperature back to the monitoring control center for storage, the gas pressure and the gas flow can be gradually reduced in the continuous gasification process after the liquid nitrogen is injected, the gas temperature can be continuously reduced in the gasification process after the liquid nitrogen is injected, and the temperature can be raised until the liquid nitrogen in the cross-layer drill hole 8 is completely gasified;
E. when liquid nitrogen flows out from a gas pipeline where the spherical valve 4 is continuously injected by liquid nitrogen, stopping a liquid nitrogen pump, closing the spherical valve 4, setting an opening threshold value of the safety valve 5, continuously gasifying and expanding the liquid nitrogen in the through-layer drill hole 8, applying gas expansion force to the coal body to crack, when the gas pressure in the through-layer drill hole 8 exceeds the set opening threshold value, opening the safety valve 5, discharging the nitrogen in the through-layer drill hole 8 out of the through-layer drill hole 8 from the gas pipeline where the safety valve 5 is located, so that the gas pressure in the through-layer drill hole 8 is reduced, closing the safety valve 5 when the gas pressure is lower than the set opening threshold value, continuously gasifying and expanding the liquid nitrogen in the through-layer drill hole 8 at the moment, applying gas expansion force to the coal body again to crack until the gas pressure in the through-layer drill hole 8 exceeds the set opening threshold value, opening and relieving the pressure of the safety valve 5, repeating the cycle, and performing gas, until the mass loss rate of the real-time liquid nitrogen, the flow rate of the real-time bubbles, the gas flow value and the gas pressure value in the real-time pressure relief pipe 9 which are received by the monitoring control center are all 50% -80% of the respective peak value, and the received real-time gas temperature value starts to rise; completing the fracturing and permeability increasing process of the primary through-layer drill hole 8;
F. two gas extraction drill holes 7 are drilled in the coal seam 1 at two sides of the cross-layer drill hole 8, and the two gas extraction drill holes 7 penetrate through each disc-shaped crack 2; the two gas extraction drill holes 7 are respectively provided with an acoustic wave transmitter 14 and an acoustic wave receiver 15, and are both provided with an SF6Gas detector 13, SF6The gas detector 13, the sound wave emitter 14 and the sound wave receiver 15 are all connected with a monitoring control center;
①, the monitoring control center controls the sound wave transmitter 14 to transmit sound waves, the sound wave receiver 15 receives the sound waves and feeds the sound waves back to the monitoring control center, so that a detected sound wave speed value is obtained, then the monitoring control center calls a standard sound wave speed value of the non-fractured position of the coal seam 1, the standard sound wave speed value and the sound wave speed value are compared, if the detected sound wave speed value is less than or equal to 70% of the standard sound wave speed value (because the sound wave speed in the coal seam is greater than the sound wave speed in the air, the detected sound wave speed is smaller, the more cracks are formed between two gas extraction boreholes 7), the step ② is carried out, and if the detected sound wave speed value is greater than 70% of;
② Tracer gas SF is injected into the through-hole 8 through the liquid nitrogen injection pipe 6 at a pressure not greater than the opening threshold of the safety valve 56Then two SF6The gas detector 13 detects whether SF exists in the two gas extraction drill holes 7 in real time6A gas; if two SF6The gas detectors 13 each detect SF6Gas (by detecting SF)6The gas can determine the connectivity of fractures generated after the permeability of the coal body between the cross-layer drill hole 8 and the two gas extraction drill holes 7 is increased; if the gas extraction borehole is detected, the generated fractures are mutually communicated to form at least one channel, so that the cross-cut borehole 8 is respectively communicated with the two gas extraction boreholes 7; that is, the speed of sound wave can detect the number of cracks generated after the permeability is increased, and the SF6Gas detection can detect the connectivity of the fractures generated to each other, then proceed to step ④, otherwise proceed to step ③;
③ repeating steps D and E, completing the fracturing and permeability increasing process of the once through-layer drill hole 8, and entering step ①;
④, completing the fracturing effect detection, and performing gas extraction on the coal seam through the two gas extraction drill holes 7;
G. and D, after the gas extraction of the position is finished, repeating the steps A to F at another position of the roadway at a certain distance, performing the coal bed permeability increasing and the gas extraction of the position, and circulating the steps until the coal bed permeability increasing and the gas extraction of the whole roadway are finished.
Further, the outer surface of the liquid nitrogen injection pipe 6 and the outer surface of the video monitoring lens 10 are both wrapped by heat insulation layers. The heat insulation layer is additionally arranged, so that the heat exchange between the liquid nitrogen in the liquid nitrogen injection pipe 6 and the outside can be reduced; meanwhile, the low-temperature isolation protection can be carried out on the video monitoring lens 10, so that the video monitoring lens is prevented from being damaged due to the low temperature of liquid nitrogen.
Further, the monitoring control center is a computer.
Further, the opening threshold of the safety valve 5 is 30 MPa.
Claims (4)
1. A liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring is characterized by comprising the following specific steps:
A. drilling a layer-through borehole in the roadway, wherein the borehole penetrates through the rock stratum and extends into the coal seam;
B. hydraulic seam cutting equipment is adopted to stretch into the cross drilling hole to reach the coal seam, and a plurality of disc-shaped cracks are cut at equal intervals in the coal seam along the direction vertical to the cross drilling hole by taking the cross drilling hole as the center;
C. one end of a liquid nitrogen injection pipe and one end of a pressure relief pipe extend into the cross-layer drill hole to reach the coal seam, and a video monitoring lens with a light source is installed at one end of the liquid nitrogen injection pipe; then, sealing the rock stratum section of the cross-layer drilled hole, arranging a quality sensor at the section, closest to the sealed hole, of the cross-layer drilled hole, and respectively connecting the other end of the pressure relief pipe with two gas pipelines through a tee joint; a safety valve and a spherical valve are respectively arranged on the two gas pipelines; a gas monitoring device is arranged on the pressure relief pipe; the video monitoring lens, the quality sensor and the gas monitoring device are all connected with the monitoring control center; the gas monitoring device consists of a temperature sensor, a gas pressure meter and a gas flowmeter;
D. connecting the other end of the liquid nitrogen injection pipe with a liquid nitrogen pump, starting the liquid nitrogen pump, opening a spherical valve, and simultaneously opening a video monitoring lens, a quality sensor and a gas monitoring device; liquid nitrogen is injected into the cross-layer drill hole through the liquid nitrogen injection pipe and enters each disc-shaped crack, the liquid nitrogen is gasified to absorb heat so as to quickly reduce the temperature of the coal body, and the water in the coal body is frozen and expanded to apply freezing expansion force to the coal body to crack; meanwhile, the gasified nitrogen rapidly expands in volume to apply gas expansion force to the coal body to crack, the air pressure in the through-layer drill hole is rapidly increased, and the nitrogen is discharged out of the through-layer drill hole from a gas pipeline where the spherical valve is located through the pressure relief pipe, so that the air pressure in the through-layer drill hole is reduced, and the liquid nitrogen can be continuously injected; the video monitoring lens shoots and monitors the size of bubbles generated in the liquid nitrogen in the cross-layer drilling hole and the flow rate of the generated bubbles in real time and feeds the bubbles back to the monitoring control center for storage; the quality sensor monitors the mass loss rate of the liquid nitrogen in the cross-layer drilling hole in real time and feeds the mass loss rate back to the monitoring control center for storage; the gas monitoring device detects the gas pressure, the gas flow and the gas temperature in the pressure relief pipe in real time and feeds the gas pressure, the gas flow and the gas temperature back to the monitoring control center for storage;
E. when liquid nitrogen flows out from a gas pipeline where the spherical valve is continuously injected by liquid nitrogen, stopping a liquid nitrogen pump and closing the spherical valve, setting an opening threshold value of a safety valve, continuously gasifying and expanding the liquid nitrogen in a through-layer drill hole, applying gas expansion force to the coal body to crack, opening the safety valve when the gas pressure in the through-layer drill hole exceeds a set opening threshold value, discharging the nitrogen in the through-layer drill hole from the gas pipeline where the safety valve is located to the through-layer drill hole at the moment, so that the gas pressure in the through-layer drill hole is reduced, closing the safety valve when the gas pressure is lower than the set opening threshold value, continuously gasifying and expanding the liquid nitrogen in the through-layer drill hole at the moment, applying gas expansion force to crack the coal body again until the gas pressure in the through-layer drill hole exceeds the set opening threshold value, opening the safety valve to release pressure, repeatedly performing gas expansion force cracking on the coal body for multiple times until the mass loss rate of the real-, The flow rate of the real-time bubbles, the gas flow value and the gas pressure value in the real-time pressure relief pipe are all 50% -80% of the respective peak value, and the received real-time gas temperature value starts to rise; completing a fracturing and permeability increasing process of one-time through-layer drilling;
F. two gas extraction drill holes are drilled in the coal seam on two sides of the cross-layer drill hole, and the two gas extraction drill holes penetrate through each disc-shaped crack; the two gas extraction drill holes are respectively provided with a sound wave transmitter and a sound wave receiver and are respectively provided with an SF6Gas detector, SF6The gas detector, the sound wave transmitter and the sound wave receiver are all connected with the monitoring control center;
①, the monitoring control center controls the sound wave transmitter to emit sound waves, the sound wave receiver receives the sound waves and feeds the sound waves back to the monitoring control center, so that a detected sound wave speed value is obtained, then the monitoring control center calls a standard sound wave speed value of the non-fractured position of the coal seam, the standard sound wave speed value and the detected sound wave speed value are compared, if the detected sound wave speed value is less than or equal to 70% of the standard sound wave speed value, the step ② is executed, and if the detected sound wave speed value is greater than 70% of the standard sound wave speed value, the;
② injecting trace gas SF into the through-hole via the liquid nitrogen injection pipe at a pressure not greater than the threshold opening pressure of the safety valve6Then two SF6Gas detector detects whether SF exists in two gas extraction drill holes in real time6A gas; if two SF6The gas detectors all detect SF6Entering step ④ if the gas is not, entering step ③ if the gas is not;
③ repeating steps D and E, completing the fracturing and permeability increasing process of one through-layer drilling, and entering step ①;
④, completing the fracturing effect detection, and performing gas extraction on the coal seam through the two gas extraction drill holes;
G. and D, after the gas extraction of the position is finished, repeating the steps A to F at another position of the roadway at a certain distance, performing the coal bed permeability increasing and the gas extraction of the position, and circulating the steps until the coal bed permeability increasing and the gas extraction of the whole roadway are finished.
2. The liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring according to claim 1, wherein the outer surface of the liquid nitrogen injection pipe and the outer surface of the video monitoring lens are both wrapped with a heat insulation layer.
3. The liquid nitrogen circulating cold shock permeability increasing method based on multi-parameter monitoring according to claim 1, wherein the monitoring control center is a computer.
4. The liquid nitrogen cycle cold shock anti-reflection method based on multi-parameter monitoring according to claim 1, wherein the opening threshold of the safety valve is 30 MPa.
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