CN114046148B - Liquid CO 2 Method for improving coal seam water injection effect by fracturing and permeability increasing - Google Patents
Liquid CO 2 Method for improving coal seam water injection effect by fracturing and permeability increasing Download PDFInfo
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- CN114046148B CN114046148B CN202111325256.6A CN202111325256A CN114046148B CN 114046148 B CN114046148 B CN 114046148B CN 202111325256 A CN202111325256 A CN 202111325256A CN 114046148 B CN114046148 B CN 114046148B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C37/00—Other methods or devices for dislodging with or without loading
- E21C37/06—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole
- E21C37/14—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole by compressed air; by gas blast; by gasifying liquids
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C37/00—Other methods or devices for dislodging with or without loading
- E21C37/06—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole
- E21C37/12—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole by injecting into the borehole a liquid, either initially at high pressure or subsequently subjected to high pressure, e.g. by pulses, by explosive cartridges acting on the liquid
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
- E21F17/18—Special adaptations of signalling or alarm devices
Abstract
The invention discloses liquid CO 2 The method for improving the coal seam water injection effect by (liquid carbon) fracturing and permeability increasing comprises the following steps: the method comprises the steps of constructing a water injection main drill hole and a plurality of branch drill holes on the advance working face by using a drilling machine, injecting liquid carbon at dynamic pressure, constructing coal rock strain-fracture-temperature monitoring drill holes around the drill holes, monitoring the development condition of a pore fracture network in a fracturing and infiltration increasing area in real time, and connecting a water injection pipeline to perform multi-channel dynamic and static pressure water injection after the liquid carbon injection is finished. Under the multiple actions of liquid carbon low-temperature freezing, phase change self-pressurization and the like, the crack development and communication and pore evolution development of the coal bed are promoted, and a large-range communicated pore crack network is formed, so that the coal bed injectability and wettability are effectively improved, the coal bed water injection and dust reduction efficiency is favorably improved, the coal bed stress concentration can be reduced, the coal bed impact tendency and the coal and gas outburst danger can be effectively relieved, and the method has wide applicability in the fields of mine dust prevention and dynamic disaster prevention.
Description
Technical Field
The invention relates to a coal seam fracturing and permeability increasing method, in particular to liquid CO 2 A method for improving the coal seam water injection effect by fracturing and permeability increasing.
Background
The coal seam water injection technology has obvious effects in the aspects of dust prevention and suppression, rock burst prevention, gas outburst danger reduction and the like of mines, and is one of important precautionary disaster prevention measures in coal safety production. Along with the increasing of coal mining depth in various regions of China, the deterioration degree of coal is increased, gas pressure and ground stress are continuously enhanced, the permeability of a coal seam is reduced, the difficulty of water injection is also increased, the traditional water injection mode is difficult to realize uniform and full water injection on the coal seam, and higher requirements are provided for improving the water injection effect of the coal seam in new situations.
Most of water injection materials used in the mine production field are water-based solutions, the scale of water consumption is large, the working environment is seriously polluted, the popularization and the application of the technology in arid water-deficient and ecological environment-fragile areas are greatly limited, and the wetting effect required by disaster prevention is often difficult to fully achieve due to the insufficient self physicochemical properties of the conventional water-based solutions. In order to comply with the development trend of the coal industry in China under the carbon neutralization background, liquid CO is explored 2 The novel fracturing and permeability increasing technology based on the method fully exerts the advantages of low-temperature harmlessness, mild fracturing and the like, reduces mine dust pollution, relieves coal seam rock burst and gas outburst danger and obviously improves CO on the basis of effectively improving the permeability of the mined coal seam and improving the wetting effect of the coal seam 2 The utilization rate is reduced, the emission pressure of greenhouse gases is reduced, the large-scale centralized clean and efficient production and utilization of coal based on the advanced permeation-increasing technology are realized, the economic benefit is obvious, and the application prospect is wide.
Disclosure of Invention
The technical problem is as follows: the invention aims to provide liquid CO 2 A method for improving the water injection effect of coal seam by fracturing and permeability enhancement features that low-temp liquid carbon is injected by dynamic pressure and the liquid CO is used in combination with static pressure porous water injection technology 2 Low temperature freezing, high permeability, phase change self-pressurization andthe characteristics of acidification, blockage removal and the like change the internal native structure and physical and mechanical properties of the coal rock, improve the brittleness of the coal rock, promote the continuous expansion and extension of fracture channels and the development and communication of pores, further form a pore fracture network, effectively improve the porosity and permeability of the coal rock, finally obviously improve the injectability and wettability of a coal bed, inhibit the generation of mine dust from a source, and prevent the outburst risk of mining deposit coal and gas and various dynamic disasters caused by stress concentration to a certain extent.
The technical scheme is as follows: liquid CO of the invention 2 The method for improving the coal seam water injection effect by fracturing and permeability enhancement comprises the following steps:
a. constructing the main drilling hole in the area 20-50 m ahead of the working surface along the coal seam inclination angle direction by using a mining geological drilling machine or a rock electric drill, wherein the distance between the position of the drilling hole and the bottom plate is 1.6-2.0 m, and the diameter phi of the main drilling hole is 1 = 80-120 mm, the distance between the main drill holes is 10-25 m, and the length of the drill hole is calculated according to the following formula:
L＝L 1 -S
wherein L is the length of the drilled hole and m; l is 1 Is the working face length, m; s is a parameter which is changed along with the water permeability of the coal bed and the drilling direction, and m is 20m generally taken for the coal bed with weak water permeability.
b. After the main drilling hole reaches the designed depth, 4-6 branch drilling holes are uniformly constructed along the coal seam at 360 degrees by using a horizontal directional drilling machine with the main drilling hole as the center of a circle, and the axial distance of the branch drilling holes is selected within the range of 5-15 m according to the situation;
c. after the drill is withdrawn, laying low-temperature-resistant water injection steel pipes in the main drill hole and the branch drill holes, wherein pressure measuring ports are arranged at the outer outlets of the low-temperature-resistant water injection steel pipes, a pressure sensing device is externally connected to monitor the carbon injection pressure, and the low-temperature-resistant main water injection steel pipes are exposed out of the coal wall by 0.8-1.2 m so as to facilitate the connection of subsequent pipelines;
d. welding a baffle disc with the diameter slightly smaller than the bore diameter of the drill hole at the position 100-150 mm away from the pipe orifice at the front end of a low-temperature resistant main water injection steel pipe, binding cotton yarn and other substances between the baffle disc and the pipe orifice, inserting the low-temperature resistant main water injection steel pipe into the hole through the central position of the baffle disc to fix the water injection pipe and prevent slurry leakage, conveying cement mortar added with a small amount of accelerating agent to the main drill hole by using a mining hole sealing pump, injecting a grouting gap, performing hole sealing operation, wherein the hole sealing length is 10-25 m, ensuring the length to be larger than the length of a coal loosening zone, and preventing a large amount of injected water from seeping;
e. 2 upward-inclination advanced monitoring drill holes are constructed from the air way to the working face extraction direction, the included angle between the drill hole inclination and the working face extraction direction is 5-15 degrees, the sensing optical cable and the water injection drill holes are arranged in a crossed mode, the elevation angle of each monitoring hole is 30-60 degrees, the hole depth is 50-80 m, the control vertical height is larger than 15m, the control horizontal distance is larger than 30m, and after the inclined drilling construction is finished, a hole sealing device is installed at a hole opening. And then, implanting the sensing optical cable into the inclined drill hole by utilizing the PVC pipe fitting, and performing full-hole grouting after the hole opening is closed, so that the sensing optical cable and the surrounding rock are coupled into a whole. After the sensing optical cable and the communication optical cable are in cold connection, the sensing optical cable is overhead along the side wall of the roadway and led to the main roadway to be connected with a BOTDR data acquisition instrument, and after cement grout in the monitoring hole is solidified, the initial strain, the crack distribution and the temperature change condition of the monitoring coal seam can be obtained;
f. the low-temperature resistant water injection steel pipe in the main drilling hole passes through a quick connector, a high-pressure rubber pipe and a low-temperature resistant metal hose and liquid CO arranged in the return air roadway 2 Tank connection, liquid CO 2 Conveying to a coal seam to be mined by a low-temperature liquid booster pump, and arranging a flowmeter at the joint of the quick joint for monitoring liquid CO 2 The delivery flow and the carbon injection flow are taken to be 0.6 to 1.2m 3 H, a pressure gauge, a pressure sensor and a safety valve are arranged above the storage tank to measure the liquid CO in the tank body 2 Monitoring and adjusting the pressure, controlling the pressure in the tank to be 1.6-2.0 MPa and not less than 1.4MPa, and liquid CO 2 The conveying pressure is maintained at the level of 1.2-1.5 times of the coal bed gas pressure, and the conveying pipeline is provided with a one-way valve and a return pipe to prevent liquid CO from being caused by factors such as temperature difference and pressure difference 2 Refluxing;
g. in the carbon injection process, after coal rock strain-fracture-temperature monitoring drilling monitoring and BOTDR data acquisition and analysis display, the booster pump and the stop valve are closed when the coal body cracking degree of the coal bed to be mined reaches a preset effect, and liquid CO is stopped 2 Injecting, namely, after the coal seam naturally returns to the temperature for a certain time, connecting a water injection pipeline to perform dynamic and static pressure water injection operation;
h. in the water injection process, the water increment is inspected by sampling the construction inspection holes around the water injection hole, and the water increment of the coal sample is taken as the judgment standard of the effective wetting radius by 2.0 percent or more, so that the water injection work of one period is completed.
Has the advantages that: the invention innovatively converts liquid CO 2 The fracturing and permeability increasing process is combined with the coal bed static pressure water injection process, and liquid CO is injected into the coal bed through all levels of drill holes in the early stage of the engineering 2 The original structure and mechanical properties of the coal rock mass are continuously changed by utilizing the properties of low temperature, high expansibility, high latent heat of vaporization and the like, the macroscopic fracture expansion and the development communication of microscopic fractures in the coal mass are promoted, and dynamic and static pressure water injection operation is carried out at the later stage of engineering, so that water is continuously diffused in a fracture network and fully contacted with the surface of the coal rock mass, thereby effectively wetting the coal mass and achieving the purpose of reducing dust generation from the source. The method can greatly shorten the water injection period of the coal seam difficult to inject water, remarkably improve the water content and the wetting range of the coal seam, play a role in inhibiting dust from being generated from a source, effectively increase the air permeability of the coal seam, reduce the structural strength of coal rocks, improve the gas extraction efficiency, and reduce the outburst danger of coal and gas and the threat brought by various coal mine dynamic disasters to a certain extent. And has the following advantages:
liquid CO 2 The latent heat of vaporization of the coal is 25.25KJ/mol, the injected liquid carbon absorbs a large amount of ambient heat in the vaporization phase change process, the coal rock body shrinks under the ultralow temperature action of the liquid carbon, temperature stress is generated in the coal body, when the temperature stress exceeds the tensile strength of the coal rock body, the coal rock is broken and destroyed, and the cracks are continuously developed and extended to form a communication network;
liquid CO 2 Excellent expansion performance, and every 1kg of liquid CO under the standard condition 2 507L of gas can be obtained after complete vaporization, an expansion force with compression or stretching effect on the coal body is generated in the vaporization phase change process of the gas, and when the expansion force is gradually increased to exceed the compressive strength of the coal body, the coal body is damaged and microcracks are generated, so that the porosity and the permeability of the coal body are improved;
liquid CO 2 The surface tension coefficient is 3.4dyne/cm, which is far lower than 72dyne/cm of water at room temperature, so that the liquid carbon has better penetration effect on the solid surface than waterThe coal is easy to enter tiny holes and cracks in the coal to play a role; CO 2 2 Dynamic viscosity of 13.67X 10 -6 Pa s is about 1/1000 of water, has good permeability in coal seam cracks and is beneficial to the expansion of crack radius. Coal sample to CO under low pressure 2 、CH 4 The adsorption selectivity coefficient of (2) is 8.5, the adsorption selectivity coefficient of both under high pressure conditions is 5.5 2 After vaporization, the storage space for adsorbing gas in the coal gap can be quickly occupied, so that the storage space is converted into a free state, the gas extraction efficiency is improved, and the outburst risk of coal and gas is reduced; CO 2 2 The acidification effect of the water-soluble clay mineral can dissolve the clay mineral blocked in the coal seam cracks, so that the permeability of the coal seam cracks is increased;
liquid CO compared to liquid nitrogen 2 The temperature of the liquid carbon is high, the requirements on liquid storage and conveying devices and construction conditions are relatively low, the liquid carbon has the advantage of mild cracking, and rapid seepage and leakage of injected water caused by excessive cracking are avoided; the relatively high temperature can save the time for the temperature return of the coal seam, and when the conditions allow, on the basis of the low-temperature liquid carbon induced cracking and permeability increasing in the former stage, a static pressure water injection system can be selected for carrying out coal seam water injection in the later stage, so that the water injection energy consumption and the cost are reduced;
compared with the traditional electrical sensor, the distributed optical fiber sensing technology has the advantages of continuous measurement, strong electromagnetic interference resistance, corrosion resistance, light weight and small volume, has the advantages of simple single-end measurement structure, long transmission distance, capability of simultaneously measuring temperature and strain and the like, and can realize the real-time monitoring of the pore fracture structure and the temperature change of the coal-rock mass.
Drawings
FIG. 1 is liquid CO 2 Schematic diagram of dynamic pressure infiltration increasing method;
FIG. 2 is a schematic view of the main bore grouting sealing method in FIG. 1;
FIG. 3 is a schematic view of a branch bore distribution of FIG. 1;
FIG. 4 is a schematic diagram of a strain-fracture-temperature monitoring method for a coal seam in a permeability-increasing area.
In the figure: 1 coal seam to be mined2-pressure sensor, 3-pressure measuring port, 4-flowmeter, 5-main water injection pipeline, 6-flow divider, 7-branch pipeline stop valve, 8-main pipeline stop valve, 9-water injection pressure gauge, 10-quick connector, 11-flowmeter, 12-water filter, 13-water injection permeation-increasing area, 14-grouting gap, 15-branch drilling hole, 16-strain-crack-temperature monitoring drilling hole, 17-high-pressure rubber pipe, 18-low-temperature-resistant water injection steel pipe, 19-main drilling hole, 20-gear disc, 21-drilling gap, 22-hole sealing slurry, 23-special hole sealing device for detection hole, 24-sensing optical cable, 25-BOTDR data acquisition instrument, 26-pressure gauge, 27-pressure sensor, 28-safety valve, 29-liquid CO 2 The device comprises a storage tank, 30 parts of a one-way valve, 31 parts of a booster pump, 32 parts of a carbon injection flow meter, 33 parts of a stop valve, 34 parts of a low-temperature resistant metal hose, 35 parts of a coal rock body and 36 parts of a communication optical cable.
Detailed Description
A ZDY120S coal mine hydraulic drilling machine is used at the position 40 meters ahead of the stope face along the dip angle direction of the coal seam, and the construction aperture phi is applied to the coal seam 1 to be mined 1 The method is characterized in that the method comprises the following steps of =110mm initial drilling, the position of a hole is 1.6m away from a bottom plate, a machine body is fixed on a coal baffle of a mining face conveyor, an emulsion pump station is used as a power source, the operation is carried out in a full hydraulic mode, and the length of the drilling hole is determined to be 120m according to the length of a mining face, the water permeability of a coal seam, the drilling direction and other conditions;
the average distance between the drill holes is 15m, and 18 water injection drill holes are arranged in total. After the main drilling hole 19 reaches the designed depth, 6 branch drilling holes 15 are uniformly distributed along the coal seam at 360 degrees by using a KHYD-140 type horizontal directional drilling machine by taking the main drilling hole 19 as the center of a circle, the axial distance between the branch drilling holes 15 is 10m, and the fracturing and moistening area 13 is completely covered as far as possible;
after the drilling is withdrawn, a low-temperature-resistant water injection steel pipe 18 is laid in the main drilling hole 19 and the branch drilling hole 15, a pressure measuring port 3 is arranged at an external outlet of the low-temperature-resistant water injection steel pipe 18, a CPT-20SD3 ultralow-temperature liquid carbon pressure sensor 2 is externally connected to monitor the water injection pressure, and the water injection pipe is exposed out of the coal wall by 0.8m and is convenient for the connection of subsequent pipelines;
welding a baffle disc 20 with the diameter slightly smaller than the bore diameter of the drill hole at the position 150mm away from the pipe orifice at the front end of a low-temperature-resistant water injection steel pipe 18, inserting the low-temperature-resistant water injection pipe 18 into the hole through the central position of the baffle disc 20 to fix the water injection pipe and prevent slurry leakage, conveying cement mortar added with a small amount of accelerating agent to a main drill hole 19 by using a BFK-10/2.4 type mining hole sealing pump, injecting a grouting gap 14, performing hole sealing operation, and taking the length of a grouting hole sealing section to be 25m to ensure that the length is larger than the length of a coal loosening zone so as to prevent a large amount of injected water from seeping;
2 pitching advance monitoring drill holes 16 are constructed from the air way to the working face extraction direction, the included angle between the drilling tendency and the working face extraction direction is 15 degrees, the sensing optical cable 24 and the water injection drill holes are arranged in a crossed mode, the elevation angle of each monitoring hole is 45 degrees, the hole depth is 60 meters, the control vertical height is 30 meters, the control horizontal distance is 45 meters, and after the construction of the inclined drill holes is finished, the hole sealing device 23 is installed at a hole opening. Then, the sensing optical cable 24 is implanted into the inclined drill hole through a PVC pipe, and full-hole grouting is performed after the hole opening is closed, so that the sensing optical cable 24 and the coal rock mass 35 are coupled into a whole. After the sensing optical cable 24 and the communication optical cable 36 are in cold connection, the sensing optical cable is overhead along the side wall of the roadway and led to the main roadway to be connected with the BOTDR data acquisition instrument 25, and after cement grout in the monitoring hole is solidified, the initial strain, the crack distribution and the temperature change condition of the monitored coal seam can be obtained.
The low temperature resistant water injection steel pipe 18 in the main drilling hole 19 passes through the quick connector 10, the high pressure rubber pipe 17, the low temperature resistant metal hose 34 and the liquid CO arranged in the return air tunnel 2 Reservoir 29 connected, liquid CO 2 The low-temperature liquid is conveyed to a coal seam 1 to be mined through a DWB100-1200/100 type low-temperature liquid booster pump 31, a flow divider 6 is arranged at the joint of a main water injection pipeline and each low-temperature resistant water injection steel pipe 18 to realize low-temperature liquid carbon multi-channel injection, the water injection pressure and the water injection flow of each drill hole are dynamically regulated through a pressure sensing device 2, a main pipeline stop valve 8 and a branch pipeline stop valve 7, a flow meter 11 is arranged at the joint of a quick joint 10 to monitor liquid CO 2 The delivery flow and the carbon injection flow are measured to be 0.8m 3 A pressure gauge 26, a pressure sensor 27 and DA21F-40P type liquid CO are arranged above the storage tank 2 Safety valve 28 for liquid CO in tank 2 Monitoring and adjusting the pressure, controlling the pressure in the tank to be 1.6-2.0 MPa and not less than 1.4MPa, and liquid CO 2 The conveying pressure is maintained at the level of 1.2-1.5 times of the coal bed gas pressure, and the conveying pipeline is provided with a one-way valve 30 to prevent factors such as temperature difference and pressure differenceResulting in liquid CO 2 Refluxing;
in the liquid carbon filling process, if the pressure of the conveying pipeline is monitored to exceed 4MPa, the opening degree of the low-temperature liquid booster pump 31 is adjusted to control the pipeline pressure within the bearable range of the device. Injected liquid CO 2 The heat of the surrounding environment is absorbed rapidly, on one hand, the coal seam self-vaporizing and expanding is realized, on the other hand, the moisture in the coal seam is frozen, so that the volume of the coal seam is increased continuously, the original structure and the physical and mechanical properties in the coal rock are changed continuously under the actions of low-temperature liquid carbon frost-expansion force and vaporizing and expanding, the fracture channels are expanded and extended continuously, the macroscopic fractures and the microscopic fractures are communicated with each other to form a fracture network, and the porosity of the coal seam is improved greatly, so that the permeability of the coal seam is improved effectively;
in the carbon injection process, the low-temperature liquid booster pump 31 is closed and the liquid CO stops when the development degree of the coal body fracture of the coal bed to be mined reaches an expected range through data acquired and analyzed by the strain-fracture-temperature monitoring drill 16 and the BOTDR data acquisition instrument 25 2 Injecting, namely, after the coal seam naturally returns to the temperature and reaches a preset temperature through monitoring of the monitoring drill holes, accessing a water injection system to perform dynamic and static pressure water injection operation;
in the water injection process, injected water is solidified and expanded and a water injection channel is continuously widened under the condition of a frozen coal bed environment formed by low-temperature liquid carbon, after the water is cooled and melted, the water enters holes and cracks in each level in a coal body through various motion modes such as permeation, capillary and diffusion, on one hand, the space and the width of the permeation channel are continuously expanded in the whole water injection process, water is sent to each position in the coal body, and on the other hand, the water is slowly absorbed through the capillary action of micro-pores. And constructing, inspecting holes around the water injection holes, sampling, inspecting the moisture increment, and finishing a period of water injection work by taking the moisture increment of the coal sample of 2.0% or more as a judgment standard of an effective wetting radius.
Claims (7)
1. Liquid CO 2 The method for improving the coal seam water injection effect by fracturing and permeability enhancement is characterized by comprising the following steps of:
a. a main drilling hole (19) is constructed in the front area of the working face of the coal seam (1) to be mined by using a mining geological drilling machine or a rock electric drill along the direction of the inclination angle of the coal seam, and the drilling length is calculated according to the following formula:
L＝L 1 -S
wherein L is the length of the drilled hole, m; l is a radical of an alcohol 1 Is the working face length, m; s is a parameter which changes along with the permeability of the coal seam and the drilling direction, m, and for the coal seam with weak permeability, 20m is taken as S;
b. when the main drilling hole (19) reaches the designed depth, a horizontal directional drilling machine is used for uniformly constructing a plurality of branch drilling holes (15) along the 360-degree direction of the coal seam by taking the main drilling hole (19) as the center of a circle;
c. after the drilling is withdrawn, laying a low-temperature-resistant water injection steel pipe (18) in the main drilling hole (19) and the branch drilling hole (15), wherein a pressure measuring port (3) is formed in an external outlet of the low-temperature-resistant water injection steel pipe (18), a pressure sensing device (2) is externally connected for pressure monitoring, the low-temperature-resistant water injection steel pipe (18) is exposed out of the coal wall for a proper length so as to facilitate subsequent pipeline connection, and sealing the main drilling hole by adopting a grouting hole sealing method;
d. constructing a strain-crack-temperature monitoring borehole (16) at the midpoint of the connecting line of each adjacent main borehole along a certain inclination angle, and installing a special hole packer (23) at the hole opening after the construction of the inclined borehole is finished; the sensing optical cable (24) is implanted into the inclined drill hole by utilizing a PVC pipe fitting, and full-hole grouting is performed after the hole opening is closed, so that the sensing optical cable (24) and the coal rock body (35) are coupled into a whole; after the sensing optical cable (24) and the communication optical cable (36) are in cold connection, the sensing optical cable is overhead along the side wall of the roadway and is led to a large roadway to be connected with a BOTDR data acquisition instrument (25);
e. a low-temperature resistant water injection steel pipe (18) in a main drilling hole (19) passes through a quick joint (10), a high-pressure rubber pipe (17), a low-temperature resistant metal hose (34) and liquid CO arranged in an air return roadway 2 The storage tank (29) is connected with liquid CO 2 Is conveyed to a coal bed to be mined by a low-temperature liquid booster pump (31), and a flow meter (11) is arranged at the joint of a quick joint (10) for monitoring liquid CO 2 Delivery flow, liquid CO 2 A pressure gauge (26), a pressure sensor (27) and a safety valve (28) are arranged above the storage tank (29) for liquid CO 2 Liquid CO in the storage tank (29) 2 Pressure monitoring and regulating, liquid CO 2 The injection pressure is maintained to be higher than the coal bed gas pressure, the conveying pipeline is provided with a one-way valve (30) to prevent liquid CO from being caused by temperature difference and pressure difference 2 Refluxing;
f. monitoring the coal rock body fracture evolution situation through a coal rock strain-fracture-temperature monitoring drill hole (16), acquiring the initial strain distribution of each sensing optical cable (24) after cement slurry in a monitoring hole is solidified, obtaining the coal rock fracture network expansion development situation through analyzing the strain distribution, change characteristics and optical cable breakpoint positions of the sensing optical cables (24), closing a booster pump (31) and a stop valve (33) after the fracturing is finished, and stopping liquid CO 2 Injecting, namely, after the coal bed naturally returns to the temperature, connecting a water injection pipeline to perform dynamic and static pressure water injection operation;
g. in the water injection process, the water content increment of the coal sample is inspected by constructing and inspecting holes around the water injection hole, and 2.0 percent of the water content increment of the coal sample is used as a judgment standard of effective wetting to finish the water injection work of one period.
2. Liquid CO according to claim 1 2 The method for improving the coal seam water injection effect by fracturing and permeability enhancement is characterized by comprising the following steps: the liquid CO 2 Injection pressure is not less than 1.4MPa, wherein: 1.2-1.5 times of coal bed gas pressure P w Less than or equal to liquid CO 2 Injection pressure < overburden pressure P y The carbon injection flow is 0.6 to 1.2m 3 /h。
3. Liquid CO according to claim 1 2 The method for improving the coal seam water injection effect by fracturing and permeability increasing is characterized by comprising the following steps: the drilling parameters comprise that the initial drilling is 20-50 m ahead of the working surface, the position of the hole is 1.6-2.0 m away from the bottom plate, and the water injection flow is 0.01-0.027 m 3 Selected in the range of/h, the diameter phi of the main bore (19) 1 The distance of the main drill holes (19) is 10-25 m, the hole sealing length is 10-25 m, and the distance of the branch drill holes (15) is selected within the range of 5-15 m according to the situation.
4. Liquid CO according to claim 1 2 The method for improving the coal seam water injection effect by fracturing and permeability enhancement is characterized by comprising the following steps: the coal rock strain-fracture-temperature monitoring drill hole (16) is a pilot measurement hole, the sensing optical cable (24) and the water injection drill hole are arranged in a crossed mode, and the aperture phi is 2 =20mm water of drilling tendency and wind tunnelThe horizontal included angle is 5-15 degrees, the elevation angle of the monitoring hole is 30-60 degrees, the hole depth is 50-80 m, the control vertical height is more than 15m, and the horizontal distance is more than 30m.
5. Liquid CO according to claim 1 2 The method for improving the coal seam water injection effect by fracturing and permeability increasing is characterized by comprising the following steps: the sensing optical cable (24) is a mechanically reinforced tightly-packed strain sensing optical cable, has good sensing performance, and meets the monitoring requirements of overburden stress change, fracture evolution and temperature change.
6. Liquid CO according to claim 2 2 The method for improving the coal seam water injection effect by fracturing and permeability increasing is characterized by comprising the following steps: according to the grouting hole sealing method, a baffle disc (20) with the diameter slightly smaller than the aperture is welded at the position 100-150 mm away from a pipe orifice in front of a water injection pipe, cotton yarns are bound between the baffle disc (20) and the pipe orifice, a low-temperature-resistant water injection steel pipe (18) is inserted into a main drilling hole (19) through the central position of the baffle disc (20) to fix the water injection pipe and prevent slurry leakage, a grouting pump is started to convey cement mortar added with a small amount of accelerating agent to the drilling hole and inject the cement mortar into a grouting gap (14) to perform hole sealing operation, the low-temperature-resistant water injection steel pipe (18) is exposed out of a coal wall by 0.5-0.8 m, the hole sealing length is larger than the length of a coal loosening zone, and a large amount of injected water is prevented from leaking out.
7. Liquid CO according to claim 2 2 The method for improving the coal seam water injection effect by fracturing and permeability increasing is characterized by comprising the following steps: the safety valve (28) is a pressure control valve, and the booster pump (31) is CO 2 The low-temperature liquid filling pump is characterized in that the quick joint (10) is an open-close type low-temperature-resistant hydraulic quick joint, and when the joint is disconnected, the valve core is automatically closed to prevent leakage.
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| CN114575813B (en) * | 2022-03-05 | 2023-04-21 | 中国矿业大学 | Liquid nitrogen fracturing device, construction method and fracturing system with fracturing device |
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