CN113914839A - Fishbone-like drilling low-temperature liquid nitrogen freeze-thaw cycle permeability-increasing coal seam gas extraction method - Google Patents
Fishbone-like drilling low-temperature liquid nitrogen freeze-thaw cycle permeability-increasing coal seam gas extraction method Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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 DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices, or the like
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/20—Displacing by water
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/30—Specific pattern of wells, e.g. optimizing the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimizing the spacing of wells comprising at least one inclined or horizontal well
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
- E21B7/046—Directional drilling horizontal drilling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/20—Driving or forcing casings or pipes into boreholes, e.g. sinking; Simultaneously drilling and casing boreholes
Abstract
The invention discloses a fishbone-like drilling low-temperature liquid nitrogen freeze-thaw cycle permeability-increasing coal seam gas extraction method. Firstly, constructing a main drilling hole in an air inlet lane (or an air return lane or a low-position lane or a high-position lane), arranging fishbone-shaped branch drilling holes on two sides of the main drilling hole along the horizontal direction of a coal seam after a drill bit reaches a preset target position of the coal seam, and forming coal seam gas extraction drilling holes on two sides of the branch drilling holes. Injecting water into the coal bed by a drill hole, injecting low-temperature liquid nitrogen after the injected water seeps about 3 hours in the coal body, quickly freezing the water in the coal bed, stopping injecting nitrogen when the average temperature of the permeability-increasing area of the coal body is reduced to below-4 ℃, and extracting coal bed gas after the coal body naturally melts for 3-5 hours. The coal bed is cracked and anti-reflection under the combined action of the liquid phase-to-solid phase expansion force, the liquid nitrogen gasification expansion force and other forces when being subjected to water, so that macroscopic cracks and microscopic cracks are promoted to be expanded and communicated, and a coal bed gas extraction crack network is formed. The method disclosed by the invention combines the freeze-thaw erosion phenomenon with the coal bed gas extraction, and obviously improves the coal bed gas extraction efficiency.
Description
The technical field is as follows:
the invention relates to a method for extracting coal seam gas, in particular to a fishbone-like drilling low-temperature liquid nitrogen freeze-thaw cycle permeability-increasing coal seam gas extraction method.
Background art:
the high gas mine and the mine with gas outburst danger in China account for about 30 percent of the total amount of the mine in China, and the high occurrence of serious and extra-large malignant gas accidents is not fundamentally solved, which seriously hinders the smooth operation of the safe production work of the coal mine in China in the future. Meanwhile, coal bed gas is an important resource, and the exploitation and utilization of the coal bed gas become necessary requirements for the development of modern coal enterprises. At present, gas extraction is one of the most effective ways for solving and utilizing gas disasters, coal seams in China are mostly high-gas low-permeability coal seams, the difficulty of gas extraction is high, the problems of low gas extraction concentration and small gas extraction amount are solved, the problem is always the serious problem in treating the gas disasters, at present, methods such as hydraulic fracturing, hydraulic slotting, presplitting blasting and the like are mostly adopted to increase the gas permeability of the coal seams, but the permeability of coal bodies is smaller and smaller along with the increase of mining depth, the cracking and permeability-increasing range of a conventional coal seam permeability-increasing and gas-extracting method is small, and the coal bodies cannot form a large-range gas extraction fracture network, so that the gas extraction rate is low, and the gas treatment effect is not ideal.
The freeze thawing phenomenon is a common physical geological action and phenomenon in nature, and particularly occurs in object structures with large temperature difference changes, such as roads and buildings in Qinghai-Tibet plateau and northern area. The freeze-thaw erosion is the phenomenon that the whole soil body or rock is cracked due to the fact that the cracks are enlarged and increased along with the expansion of the volume of moisture in soil and parent substance pores or rock cracks when the moisture is frozen, the corrosion resistance stability of the soil body or rock is greatly reduced after the crack is ablated, and rock and soil move downwards along a slope under the action of gravity. The alternating occurrence of freezing and thawing of the moisture contained on the surface and inside the structure is known as a freeze-thaw cycle. Repeated freeze-thaw cycles cause severe damage to the object structure.
Under normal pressure, the temperature of liquid nitrogen can reach-196 ℃, the expansion rate of the liquid nitrogen is 696 times when the liquid nitrogen is gasified into pure nitrogen at 21 ℃, huge air pressure can be generated in a limited space, the latent heat of gasification of the liquid low-temperature medium is 5.56kJ/mol and 5.34kJ/mol respectively, and a large amount of ambient heat can be absorbed during gasification. The liquid nitrogen has the advantages of simple preparation, wide raw material source and the like, and can be used as an efficient refrigerating and anti-reflection medium in the coal freeze-thaw cycle.
The invention content is as follows:
aiming at the defects of the existing gas extraction technology, a more efficient coal seam permeability-increasing gas extraction method is provided.
In order to achieve the purpose, the invention adopts the following technical scheme: a fishbone-like drilling liquid nitrogen circulating freeze-thawing permeability-increasing coal seam gas extraction method promotes the crack development and development of a low-permeability coal seam and communicates a gas extraction crack network through liquid nitrogen circulating freeze-thawing permeability increasing, so that the gas extraction of the low-permeability coal seam is effectively improved. The method comprises the following specific steps:
the method includes the steps that a main drilling hole is constructed in an air inlet roadway or an air return roadway of a coal mining layer along the direction of a coal seam bedding, a low-position roadway or a high-position roadway, two branch drilling holes are constructed on two sides of the main drilling hole by a drilling machine along the horizontal direction of the coal seam by taking the main drilling hole as a symmetry axis according to the thickness of the coal seam, and secondary branch drilling holes in a fishbone-like shape are constructed on two sides of the two branch drilling holes;
secondly, after the drill withdrawal, low-temperature-resistant steel pipes are arranged in the main drill hole and the branch drill holes, floral tubes are arranged in the secondary branch drill holes, the floral tubes are connected with the low-temperature-resistant steel pipes, and the front parts of the floral tubes are sealed; the low temperature resistant steel pipe is provided with a pressure measuring port, and the pressure measuring port is connected with a pressure gauge;
thirdly, injecting a sealing material into the gap between the low-temperature-resistant steel pipe and the main drilling hole through a grouting pump, and performing grouting and hole sealing;
four temperature measuring holes are symmetrically constructed on two sides of the two fishbone-shaped branch drill holes, and four temperature measuring holes are constructed in total. The distance L from the centers of the four temperature measuring holes to the center of the fishbone-shaped branch drill hole is about 40m, the area between the four temperature measuring holes is a coal seam fracturing and permeability increasing area, a temperature sensor is arranged in each temperature measuring hole, the temperature sensor is led out through a lead and connected with a digital display type temperature meter arranged outside an orifice, and the hole sealing treatment is carried out on the inlet section of each temperature measuring hole;
fifthly, installing a water injection device in the low-temperature circulating freeze-thawing equipment group arranged in the air inlet/return roadway, wherein one end of the water injection device is connected with a mine water source, the other end of the water injection device is connected with a low-temperature-resistant steel pipe, a high-pressure pump is installed on the water injection device, a water injection valve is opened to inject water into the low-temperature-resistant steel pipe, the injected water enters from the two fishbone-shaped branch drill holes through the diversion of the low-temperature-resistant steel pipe, permeates and is retained in coal, and continuously seeps into smaller coal seam cracks;
sixthly, after injected water seeps in the coal body for about 3 hours, connecting a low-temperature-resistant steel pipe in a main drilling hole with a liquid nitrogen tank wagon arranged in a low-temperature circulating freeze thawing equipment set, connecting the liquid nitrogen tank wagon with a liquid nitrogen valve, filling liquid nitrogen into the low-temperature-resistant steel pipe in the main drilling hole, monitoring the temperature of the coal bed through a temperature measuring hole, judging that a coal bed cracking permeability-increasing area is in a better freezing state when the temperature in a drilling temperature measuring area is lower than-4 ℃, closing the liquid nitrogen valve to stop injecting nitrogen, naturally melting the coal body for 3-5 hours, and completing one phase change cracking freeze thawing cycle;
the low-temperature-resistant steel pipe is connected with the high-pressure steady-flow gas storage chamber, the gas storage chamber is pressurized by a booster pump, and a high-pressure gas source can be input into the low-temperature-resistant steel pipe by opening a high-pressure gas valve of the gas storage chamber, so that the aim of dredging the pipeline is fulfilled;
arranging construction gas extraction drill holes on two sides of the two fishbone-shaped branch drill holes, namely a coal seam cracking and permeability-increasing area between the four temperature measuring holes, and extracting gas from the coal seam;
in the self-supporting gas extraction process, according to the change of the gas extraction effect, water injection and liquid nitrogen injection operations can be repeated for multiple times, namely multiple phase change cracking freeze-thaw cycles, and the coal body reaches the stress fatigue limit of the coal body in the multiple freeze-thaw cycles to form a fracture network, so that the extraction effect is greatly improved.
15-20 secondary branch drill holes with the same angle and the length of 30-50m are arranged on the two fishbone-shaped drill holes constructed along the horizontal direction of the coal seam, and 5-10 m perforated pipes are arranged in the secondary branch drill holes. In the process of filling liquid nitrogen, when the pressure of the liquid nitrogen in the low-temperature-resistant steel pipe exceeds 8MPa, the liquid nitrogen valve is closed, and when the pressure is lower than 2MPa, the liquid nitrogen valve is opened to continuously fill the liquid nitrogen. The real-time detection and control of the running condition and implementation of technical equipment are realized through the field workstation, the monitoring instrument and the sensor, and the acquisition, display, processing and analysis of engineering data are realized.
Has the advantages that:
according to the invention, a freeze-thaw erosion phenomenon and circulating freeze-thaw are innovatively applied to coal body fracturing and permeability increasing extracted gas, and a bionic technology is adopted, namely, drill holes are arranged in a fishbone shape to guide medium water to permeate into coal bodies, liquid nitrogen is used as a refrigerating medium, and nitrogen expands 696 times during gasification, so that on one hand, the expansion effect effectively accelerates the migration of water in coal body macroscopic cracks and increases the moisture content in microscopic pores, and the freeze-thaw cycle has a larger permeability increasing area; on the other hand, the liquid nitrogen gasification expansion force and the water phase transformation frost heaving force and the flowing osmotic pressure act together to promote the development and communication of macroscopic cracks and microscopic cracks in the coal body, so that the freeze thawing efficiency is high.
And has the following advantages:
(1) in the circulating freeze thawing process, a liquid medium in a coal body generates a 'freezing-expanding-melting-freezing' circulating process, a coal layer reaches a fatigue and stress limit under alternating stress, and under the combined action of frost heaving force of water phase change, expansion force of liquid nitrogen vaporization and liquid flowing osmotic pressure in the melting process, macroscopic cracks are promoted to develop and communicate and pores are promoted to develop and develop in a micro-opening mode, so that a gas extraction crack network is formed, the pressure of the coal layer can be effectively unloaded, and the air permeability of the coal layer is increased;
(2) the single-hole gas extraction amount and concentration of the coal seam can be effectively improved after the cyclic freeze thawing, and the gas concentration decay time is prolonged;
(3) the medium water is uniformly diffused into the coal bed through the branch drill holes, so that a local high-stress concentration area of the coal bed can be effectively eliminated after freeze thawing, migration of locally accumulated gas is promoted, the coal and gas outburst potential accumulated in the coal bed is released, and the coal and gas outburst elimination effect is good;
the method effectively solves the problems of low gas extraction efficiency, long extraction period and small influence range of the extraction drill hole of the high-gas low-permeability coal seam, and has wide practicability.
Description of the drawings:
FIG. 1 is a schematic diagram of a method for extracting gas by simulating fishbone drilling of a coal seam and performing liquid nitrogen circulating freeze thawing and permeability improvement;
FIG. 2 is a schematic view of a water injection apparatus;
FIG. 3 is a schematic view of a cryogenic liquid nitrogen tanker;
FIG. 4 is a schematic view of a high pressure, steady flow gas receiver;
FIG. 5 is a schematic view of a temperature monitoring borehole;
in the figure: the method comprises the following steps of 1-coal bed, 2-air inlet lane or air return lane, 3-main drilling hole, 4-fishbone-shaped branch drilling hole, 5-low temperature resistant steel pipe, 6-perforated pipe, 7-hole sealing section, 8-water injection device, 9-high pressure pump, 10-water injection valve, 11-quick adapter, 12-low temperature liquid nitrogen tank car, 13-low temperature liquid nitrogen tank car main valve, 14-booster pump, 15-air inlet, 16-high pressure steady flow gas storage chamber, 17-high pressure gas valve, 18-pressure gauge, 19-temperature monitoring drilling hole, 20-temperature sensor, 21-coal bed gas extraction drilling hole, 22-circulating low temperature freeze thawing equipment group, 23-field work station and 24-goaf.
The specific implementation mode is as follows:
the present invention will be described in further detail with reference to the following examples:
as shown in fig. 1-5, for extracting coal seam gas from a coal seam 1 by fish-bone-like drilling liquid nitrogen freeze thawing permeability increase, firstly, constructing a main drilling hole 3 in an air intake and return roadway 2 to a permeability increase coal extraction layer area along the coal seam bedding, a low-position roadway crossing or a high-position roadway crossing, and constructing 2 branch drilling holes 4 with the lengths of 50-80m along the horizontal direction of the coal seam 1 by using a horizontal directional drilling machine by taking the main drilling hole 3 as a symmetry axis and the main drilling hole 3 to reach 2-l0m away from the upper edge of the coal seam 1 according to the thickness of the coal seam 1; constructing secondary branch drill holes in a fishbone-like manner at two sides of each branch drill hole, guiding low-temperature-resistant steel pipes 5 into the main drill hole 3 and the branch drill holes 4 after the drill holes are withdrawn, installing perforated pipes 6 with the length of 3-5m in the secondary branch drill holes, and connecting the perforated pipes 6 with the low-temperature-resistant steel pipes 5 in the branch drill holes, so that the medium water and the liquid nitrogen can be conveniently conveyed in all directions; the low temperature resistant steel pipe 5 is provided with a pressure measuring port which is connected with a high pressure gauge 18; injecting the configured high-pressure drilling hole sealing material slurry into the gap between the low-temperature-resistant steel pipe 5 and the main drilling hole 3 through a grouting pump to implement conventional high-pressure hole sealing, wherein the length H of a grouting hole sealing section 7 is 15-25 m; symmetrically constructing four temperature measuring holes 19 on two sides of the branch drill hole 4, wherein the distance from the centers of the four temperature measuring holes 19 to the center of the branch drill hole 4 is 30-50m, the area between the four temperature measuring holes 19 is a coal seam fracturing permeability-increasing area, a temperature sensor 20 is arranged in each temperature measuring hole 19, and the temperature sensor 20 monitors the temperature in the drill hole temperature measuring area 19 in real time; injecting water into the low-temperature-resistant steel pipe 5 through a water injection device 8, closing a main drilling hole water injection valve 10 after water injection is finished, enabling the injected water to flow into the secondary branch drilling holes 6 through the two fishbone-shaped branch drilling holes 4, enabling the injected water to permeate into the coal bed through the perforated pipes arranged in the secondary branch drilling holes 6, and enabling the injected water to permeate and remain in the coal body and continuously permeate and enter smaller cracks; after water seepage for 2-3h, removing a water injection valve 10, connecting a low-temperature resistant steel pipe 5 with a liquid nitrogen tank car 12, opening a liquid nitrogen valve 13 to pour liquid nitrogen into the low-temperature resistant steel pipe 5, controlling the nitrogen injection pressure to be 2-8MPa, stopping injecting nitrogen when the average temperature of a drilling temperature measuring area 19 is monitored by a temperature sensor 20 to be lower than-4 ℃, naturally melting coal for 2-3h, and completing the freeze-thaw cycle of a phase change cracking unit; in the process of filling liquid nitrogen, when the pressure of the liquid nitrogen in the low-temperature resistant steel pipe 5 exceeds 8MPa, the liquid nitrogen valve 13 is closed, and when the pressure is lower than 2MPa, the liquid nitrogen valve 13 is opened to continuously fill the liquid nitrogen. The low temperature resistant steel pipe is connected with a high pressure steady flow gas storage chamber 16, gas is fed into the gas storage chamber through a gas inlet 15 and is pressurized by a booster pump 14, and a high pressure gas source can be input into the low temperature resistant steel pipe by opening a high pressure gas valve 17 of the gas storage chamber, so that the aim of dredging the pipeline is fulfilled. And arranging coal bed gas extraction drill holes 21 in the two sides of the fracturing and permeability increasing area, which are about 20-35m away from the branch drill hole 4, for gas extraction. The field work station 23 is provided with a monitoring instrument, a control valve button and a sensor, thereby realizing real-time detection and control of the running condition of technical equipment and realizing acquisition, display, processing and analysis of engineering data. In the extraction process, according to the change of the gas extraction effect, the times of circulating water injection and liquid nitrogen injection are controlled, and under the multiple fracturing influences of low-temperature fracturing, high-pressure gas fracturing and frost heaving fracturing of liquid nitrogen, effective communication of fracture networks is promoted, and efficient extraction and utilization of coal bed gas are realized.
Claims (5)
1. A fishbone-like drilling liquid nitrogen circulating freeze-thawing permeability-increasing coal seam gas extraction method is used for communicating a gas extraction fracture network through liquid nitrogen circulating freeze-thawing permeability increasing, so that the gas extraction efficiency of a low-permeability coal seam is effectively improved. The method is characterized by comprising the following steps:
(1) constructing a main drilling hole in an air inlet tunnel or an air return tunnel of a stoping coal seam along the direction of a bedding layer, a low-position tunnel or a high-position tunnel of the coal seam, and constructing two branch drilling holes on two sides of the main drilling hole along the horizontal direction of the coal seam by using the main drilling hole as a symmetry axis;
(2) after the drill withdrawal, installing low-temperature-resistant steel pipes in the main drill hole and the branch drill holes, installing perforated pipes in the secondary branch drill holes, connecting the perforated pipes with the low-temperature-resistant steel pipes, and sealing the front parts of the perforated pipes; the low temperature resistant steel pipe is provided with a pressure measuring port, and the pressure measuring port is connected with a pressure gauge;
(3) injecting a sealing material into a gap between the low-temperature-resistant steel pipe and the main drilling hole through a grouting pump, and performing grouting and hole sealing;
(4) two temperature measuring holes are symmetrically constructed on two sides of the two fishbone-shaped branch drill holes, and four temperature measuring holes are constructed in total. The distance L from the centers of the four temperature measuring holes to the center of the fishbone-shaped branch drill hole is about 40m, the area between the four temperature measuring holes is a coal seam fracturing and permeability increasing area, the inlet section of each temperature measuring hole is subjected to hole sealing treatment, a temperature sensor is arranged in each temperature measuring hole, and the temperature sensor is led out through a lead and connected with a digital display type temperature instrument arranged outside the hole opening;
(5) the water injection device is arranged in a low-temperature circulating freeze-thawing equipment group arranged in an air inlet/return roadway, one end of the inlet section hole sealing treatment water injection device of the temperature measuring hole is connected with a mine water source, the other end of the inlet section hole sealing treatment water injection device of the temperature measuring hole is connected with a low-temperature resistant steel pipe, a water injection valve on the water injection device is opened to inject water into the low-temperature resistant steel pipe, the injected water enters from two fishbone-shaped branch drill holes by shunting of the low-temperature resistant steel pipe, permeates and is retained in coal bodies, and continuously permeates and flows into more tiny coal seam fractures;
(6) after the injected water seeps for about 3 hours in the coal body, connecting the low-temperature-resistant steel pipe in the main drilling hole with a liquid nitrogen tank wagon arranged in a low-temperature circulating freeze-thawing equipment set, opening a liquid nitrogen valve, filling liquid nitrogen into the low-temperature-resistant steel pipe in the main drilling hole, monitoring the temperature of the coal bed through a temperature measuring hole, judging that a coal bed cracking permeability-increasing area is in a better freezing state when the temperature in a drilling hole temperature measuring area is lower than-4 ℃, closing the liquid nitrogen valve to stop nitrogen injection, naturally melting the coal body for 3-5 hours, and completing one phase transition cracking freeze-thawing cycle;
(7) and arranging construction gas extraction drill holes on two sides of the two fishbone-shaped branch drill holes, namely a coal seam cracking and permeability-increasing area between the four temperature measuring holes, and extracting gas from the coal seam.
2. The method for extracting gas from the fishbone-like drill hole liquid nitrogen circulating freeze-thaw permeability-increasing coal seam according to claim 1, wherein the two fishbone-like sub-branch drill holes are fishbone-like sub-branch drill holes arranged on the branch drill holes, the fishbone sub-branch drill holes are a plurality of drill holes with an angle of 45 degrees and a length of 30-50m, the number of the sub-branch drill holes on the branch drill holes is 15-20, the interval between the sub-branch drill holes is 3-5m, and a perforated pipe with a length of 5-10 m is installed in each sub-branch drill hole. And the branch drill holes and the secondary branch drill holes are constructed along the horizontal direction of the coal seam.
3. The method for extracting gas from the fishbone-like drilling liquid nitrogen circulating freeze-thaw permeability-increasing coal seam according to claim 1, wherein in the process of filling liquid nitrogen, when the pressure of liquid nitrogen in the low-temperature-resistant steel pipe exceeds 8MPa, a liquid nitrogen valve is closed, and when the pressure is lower than 2MPa, the liquid nitrogen valve is opened to continue filling liquid nitrogen.
4. The method for extracting gas from the fishbone-like drilling hole and liquid nitrogen circulating freeze-thaw permeability-increasing coal seam according to claim 1, characterized in that a field workstation is arranged, and a monitoring instrument and a control platform are arranged in the field workstation, so that real-time detection and operation of technical equipment can be realized.
5. The method for extracting gas from the fishbone-like drilling liquid nitrogen circulating freeze-thaw permeability-increasing coal seam according to claim 1, wherein in the gas extraction process, water injection and liquid nitrogen injection operations can be repeated for multiple times according to changes of gas extraction effects, namely multiple phase change cracking freeze-thaw cycles, so that the stress fatigue limit of a coal body is reached, and the extraction effect is greatly improved.
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| CN202010662865.XA CN113914839A (en) | 2020-07-10 | 2020-07-10 | Fishbone-like drilling low-temperature liquid nitrogen freeze-thaw cycle permeability-increasing coal seam gas extraction method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114575813A (en) * | 2022-03-05 | 2022-06-03 | 中国矿业大学 | Liquid nitrogen fracturing device, construction method and fracturing system with fracturing device |
| CN114856512A (en) * | 2022-06-14 | 2022-08-05 | 六盘水师范学院 | Method for extracting gas from salinity crystallization permeability-increasing coal seam |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114575813A (en) * | 2022-03-05 | 2022-06-03 | 中国矿业大学 | Liquid nitrogen fracturing device, construction method and fracturing system with fracturing device |
| CN114856512A (en) * | 2022-06-14 | 2022-08-05 | 六盘水师范学院 | Method for extracting gas from salinity crystallization permeability-increasing coal seam |
| CN114856512B (en) * | 2022-06-14 | 2023-04-18 | 六盘水师范学院 | Method for extracting gas from salinity crystallization permeability-increasing coal seam |
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