CN117189115A - Coal seam anti-reflection device and method for variable-temperature jet flow of coal seam with low permeability in coal mine - Google Patents
Coal seam anti-reflection device and method for variable-temperature jet flow of coal seam with low permeability in coal mine Download PDFInfo
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Abstract
The application belongs to the technical field of coal seam anti-reflection in underground coal mine drilling, and provides a coal seam anti-reflection device and an anti-reflection method for variable-temperature jet flow of a coal seam with low permeability in the coal mine, wherein the device comprises a jet nozzle arranged at an outlet of a high-pressure water pipe, an inlet of the high-pressure water pipe is connected with a high-pressure water pump, and the high-pressure water pump is connected with a rapid heater; the jet flow spray head is also connected with a liquid nitrogen generator through a vacuum heat insulation pipe, the inlet end of the liquid nitrogen generator is connected with the nitrogen generator, the outlet end of the liquid nitrogen generator is connected with the inlet end of a liquid nitrogen storage tank, the outlet of the liquid nitrogen storage tank is connected with a liquid nitrogen tank group, the outlet end of the liquid nitrogen tank group is connected with a low-temperature pump, and the outlet of the low-temperature pump is led into the jet flow spray head through the vacuum heat insulation pipe; the device effectively increases the size of the cracks of the drilled holes, so that the permeability of the coal seam is increased, and the gas yield is improved. Meanwhile, the liquid nitrogen production device is adopted to directly produce liquid nitrogen, so that the cost is low and the liquid nitrogen can be reused. The method is simple and convenient to operate, can effectively solve the loss of liquid nitrogen in the transportation process, improves the effect of the liquid nitrogen on the coal body, and improves the permeability improvement effect of the coal bed.
Description
Technical Field
The application belongs to the technical field of coal seam anti-reflection in underground coal mine drilling, and particularly relates to a coal seam anti-reflection device and an anti-reflection method for variable-temperature jet flow of a coal seam with low permeability in the underground coal mine.
Background
The geological conditions and structural characteristics of different coal beds have large differences, and the occurrence characteristics of the coal bed gas are controlled by various geological factors such as construction conditions, hydrologic conditions, coal bed burial depth, coal reservoir pressure, coal bed thickness and the like, so that the gas distribution is extremely complex. The conventional drilling gas extraction mode at present is poor in effect, the extraction period is long, and the underground exploitation progress is influenced. The measures for mining the protective layer are limited by the occurrence condition of the coal seam and face great limitation. In this context, a series of hydraulically powered measures have been developed, such as hydraulic punching, hydraulic slotting, hydraulic slitting, etc. However, as the mining depth increases, coal seams continuously emerge under complex conditions such as low permeability, high gas pressure, high ground stress and the like, single hydrodynamic permeability-increasing measures and permeability-increasing effects face the subsequent debilitation condition as well, and a set of efficient underground coal seam permeability-increasing method is needed to improve the gas extraction rate aiming at the existing low permeability coal seam.
The hydraulic punching is one of the methods commonly used in gas exploitation at present, the coal body around the hole wall is destroyed by high-pressure water jet, small-sized protrusions are induced in the drill hole, the space generated by flushing the coal body by water jet is utilized, so that the stress of the coal body is released, the permeability of the coal bed is improved, the yield of gas is improved, but the complexity of the coal bed is gradually increased along with the deepening of the exploitation depth, the exploitation effect of single-factor hydraulic punching measures is affected, and the subsequent requirements are difficult to continue to be met, so that the existing hydraulic punching measures are required to be improved, and the punching effect is jointly improved through the interaction of multiple factors.
Disclosure of Invention
Aiming at the problems, the application provides the coal seam anti-reflection device and the coal seam anti-reflection method for the variable-temperature jet flow of the coal seam with low permeability in the coal mine. Meanwhile, the liquid nitrogen production device is adopted to directly produce liquid nitrogen, so that the cost is low and the liquid nitrogen can be reused. The vacuum heat insulation pipeline can be adopted in the transportation process of liquid nitrogen, so that the loss of the liquid nitrogen in the transportation process is reduced, and the effect of the liquid nitrogen in the punching process is improved. The method is simple and convenient to operate, can effectively solve the loss of liquid nitrogen in the transportation process, improves the effect of the liquid nitrogen on the coal body, and improves the permeability improvement effect of the coal bed.
The application is realized by the following technical scheme: the coal seam permeability-increasing device comprises a jet nozzle arranged at the outlet of a high-pressure water pipe, wherein the inlet of the high-pressure water pipe is connected with a high-pressure water pump, and the high-pressure water pump is connected with a rapid heater; the jet flow spray head is also connected with a liquid nitrogen generator through a vacuum heat insulation pipe, the inlet end of the liquid nitrogen generator is connected with the nitrogen generator, the outlet end of the liquid nitrogen generator is connected with the inlet end of a liquid nitrogen storage tank, the outlet of the liquid nitrogen storage tank is connected with a liquid nitrogen tank group, the outlet end of the liquid nitrogen tank group is connected with a low-temperature pump, and the outlet of the low-temperature pump is led into the jet flow spray head through the vacuum heat insulation pipe;
the rapid heater, the high-pressure water pump, the low-temperature pump, the liquid nitrogen storage tank, the liquid nitrogen generator and the nitrogen generator are respectively connected with the PLC control system;
the outer wall of the vacuum heat insulation pipe (2) is provided with a pressure sensor for monitoring the pressure condition in the drilled hole.
And the outlet end of the high-pressure water pump is provided with a water injection valve, and the outlet end of the low-temperature pump is provided with a nitrogen injection valve.
The jet nozzle is arranged in the coal seam; a sealing plug is arranged between the end parts of the high-pressure water pipe and the vacuum heat-insulating pipeline and the coal bed; the jet nozzle is connected with the high-pressure water pipe and the vacuum heat insulation pipeline by flanges respectively.
The pressure range of the liquid nitrogen tank set (11) is 0.6-2.8MPA; the minimum pressure of the liquid nitrogen tank is 0.6-0.7MPA, and the pressure difference of the liquid nitrogen tank is set to be 0.5 times or 1 time of the initial pressure.
The depth of the jet nozzle entering the coal seam is 1-2m, so that coal seam permeability improvement is performed; and continuing to perform variable-temperature jet flow anti-reflection at a distance of 1.5-6.5 m.
The method for permeability improvement by adopting the coal seam permeability-improving device for coal seam variable-temperature jet flow of the coal mine underground hypotonic coal seam comprises the following steps:
(1) Determining construction process parameters of hydraulic drilling and monitoring drilling according to underground coal seam occurrence conditions, physical parameters, working pressure of water jet equipment and site requirements, wherein the hydraulic drilling size is 80-170mm, and the monitoring drilling size is 42-75mm; the monitoring drill holes are respectively arranged in a mode of being parallel or perpendicular to the hydraulic drill holes, and a hole distribution mode of 1 hydraulic drill hole and 6 or 7 monitoring drill holes is adopted; the hole distribution intervals of the monitoring drilling holes and the hydraulic drilling holes are respectively as follows: l (L) 1 One monitoring well of =1.2-1.6 m, L 2 1-2, L of=2.0-2.2m monitoring holes 3 2, L of=2.6-3.00 m monitoring wells 4 2 monitoring wells =3.2-3.6 m;
(2) Selecting a high-pressure water jet nozzle with the size of 1.8-2.6mm according to the mechanical parameters of the coal seam and the requirements of field application, controlling the water jet pressure to be 80-120MPa, and controlling the water temperature to be 0-90 ℃;
(3) The method comprises the steps of utilizing 80-120MPa high-pressure water jet to impact a coal bed in a drilled hole, utilizing the water jet to impact at a high speed to break the coal bed to form a punched hole, setting a waterproof range finder on the central position of a drill rod near a connecting spray head to transmit back a punching area parameter and guaranteeing the water jet punching effect, and properly adjusting the water jet impact parameter according to punching data transmitted by the range finder aiming at the conditions of containing gangue or weak surfaces in the coal bed and the like, so that a large-range uniform damage area is formed in the hole;
(4) Using a spiral drill rod to move the cinder and residual water in the hole to the outside of the hole, and respectively carrying out secondary separation and recycling on the cinder and the residual water in the well;
(5) Partial sectional hole sealing is carried out on the water jet punching area by utilizing the sectional temperature-resistant pressure-resistant hole sealing device, normal-temperature nitrogen is injected into the hole sealing area, and the injection pressure P of the normal-temperature nitrogen is controlled Normal nitrogen =nP Gas burner Wherein P is Gas burner For the gas pressure in the coal seam, n is the pressure coefficient, n=4-7, and injection is utilizedWater is endowed in the normal-temperature nitrogen extrusion coal seam, the water can enter the deep part of the coal seam, and meanwhile, a channel is provided for liquid nitrogen to enter the coal seam; injecting low-temperature liquid nitrogen after normal-temperature nitrogen injection is completed, and controlling injection quantity Q of low-temperature liquid nitrogen Liquid nitrogen =1.3-1.7πD i 2 4, wherein D i The broken diameter of the local drilling hole formed by the water jet impact before the ith nitrogen injection is provided by a range finder on the drill rod; meanwhile, an automatic pressure relief valve is reserved on the sectional hole sealing device, and partial pressure relief is carried out when the high pressure generated by liquid nitrogen gasification reaches a preset range;
(6) The freezing temperature of the water medium is often lower than the freezing temperature of pure water under the influence of partial inorganic salt components in the underground stratum water medium, so that the freezing capacity of the coal bed is basically lost when the temperature in the segmented hole sealing area is increased to the range of-7 ℃ to-13 ℃, and the liquid nitrogen treatment is completed;
the high-temperature high-pressure water jet with the pressure of 90-130MPa is used for impacting the area again, and a larger damage area is formed on the frozen drilling coal bed again;
(7) Repeating the steps (5) and (6), respectively and sequentially injecting normal-temperature nitrogen and low-temperature liquid nitrogen into the area again, and repeatedly impacting the area by using high-temperature water jet flows with different pressures and temperatures;
the water jet impingement is: the flow rate of water is 1-2.5 m/min, and the injection time is 5-35min; the first time is high-temperature water jet with the pressure of 80-120MPa, the second time is high-temperature water jet with the temperature of 75-85 ℃ and the pressure of 10-20MPa higher than the first time, and the water temperature in the high-temperature high-pressure water jet is decreased by 5-20 ℃ each time, so that the pressure is kept constant; the amount of low-temperature liquid nitrogen injected each time is gradually decreased by 10-30 percent; the flow rate of the liquid nitrogen at the beginning is 1.5-3.5 m/min, and the injection time is 10-30min; the temperature of the liquid nitrogen is controlled between-200 and-205 DEG C
Compared with the prior art, the method has the advantages that the high-temperature water jet and the liquid nitrogen are jointly acted on the coal bed, and compared with the water jet which is singly acted on the coal bed, the method can cause better coal bed crushing effect, plays a better anti-reflection effect and increases the yield of gas; meanwhile, the liquid nitrogen is not easy to be influenced by the coal bed temperature to cause gasification in the long-distance conveying process, and the final anti-reflection effect is influenced.
Liquid nitrogen acts on coal seams to have three main effects. Firstly, the cooling effect of the liquid nitrogen enables the coal bed to generate thermal stress; secondly, after punching by high-temperature water jet, residual water in the hole enters into the coal seam fracture, and water can be quickly frozen after liquid nitrogen is injected, so that the coal seam is frozen; thirdly, the liquid nitrogen is converted from liquid phase to gas phase and the volume of the liquid nitrogen is rapidly expanded. The three effects act on the coal seam together to expand the coal seam cracks and improve the gas yield.
The water jet and the liquid nitrogen alternately act on the coal seam, so that the permeability-increasing effect of the coal seam can be improved. Liquid nitrogen can be directly generated through the nitrogen generator and the liquid nitrogen generator, so that the use of canned liquid nitrogen is reduced, the cost is reduced, meanwhile, the loss of liquid nitrogen in the transportation process can be reduced by adopting a vacuum heat insulation pipeline, and the freezing, thermal stress and expansion effect of the liquid nitrogen are improved. The PLC control system is connected with the rapid heater operation panel and used for monitoring the water temperature and the water quantity in the heater; the pressure sensor at the high-pressure water pump is connected with the PLC control system and is used for monitoring the pressure of water jet; the nitrogen making machine and the liquid nitrogen generator operation panel are connected with a PLC control system to monitor the production process of liquid nitrogen; the liquid nitrogen storage tank is connected with the PLC control system and is used for monitoring the reserve and pressure conditions of liquid nitrogen; the pressure sensor at the low-temperature pump is connected with the PLC control system and monitors the internal pressure of the transportation pipeline in real time.
According to the application, by combining high-temperature water jet and low-temperature liquid nitrogen, alternating treatment is performed on the coal bed in the drill hole, and the coal bed is impacted by the high-pressure water jet, so that the coal body around the drill hole is damaged and damaged, and primary cracks and secondary cracks in the coal bed are developed. Through injecting normal temperature nitrogen gas of certain pressure into the water jet punching area, the existing moisture can be driven to enter the deep part of the coal seam, a channel is provided for liquid nitrogen to invade the coal seam, and the liquid nitrogen treatment range and effect are increased. And then injecting low-temperature liquid nitrogen, forming thermal stress on the coal bed around the drill hole by using the low-temperature liquid nitrogen, and simultaneously performing frost heaving action on the ice wedge formed by freezing the water medium in the coal bed and expansion force of liquid nitrogen phase change, so that the coal bed hole cracks in the drill hole are further expanded under the combined action of multiple acting forces. And then the area is impacted by the high-temperature water jet again, and a large-range damage area is formed on the frozen drilling coal seam again by utilizing the impact load action of the high-temperature high-pressure water jet. Simultaneously, under the action of high-temperature water, the low-temperature coal matrix is caused to thermally crack, so that thermal damage is formed, and the cracks of the coal bed holes in the drilled holes are further developed. And repeatedly completing the combined treatment of the high-temperature water jet and the low-temperature nitrogen, and under the combined alternate circulation treatment of the high-temperature water jet and the low-temperature liquid nitrogen, the coal structure in the drill hole is deteriorated, the damage area is increased, the primary and secondary cracks are developed, the cracks are communicated with each other, and a channel is provided for gas migration, so that the permeability increasing effect of the coal seam of the drill hole is improved.
Drawings
FIG. 1 is a schematic diagram of a through-the-layer borehole and the development of a coal seam fracture;
FIG. 2 is a schematic illustration of a bedding borehole and the development of a coal seam fracture;
FIG. 3 is a schematic diagram of a hydraulic borehole and monitoring borehole arrangement; in the figure: a is parallel arrangement of monitoring holes; b is a parallel arrangement sectional view; c is that the monitoring holes are vertically arranged;
FIG. 4 is a flow chart of a method for enhancing permeability of a coal seam in a borehole;
in the figure: 1-jet nozzle; 2-vacuum insulated pipe; 3-plugging; 4-a nitrogen making machine; a 5-liquid nitrogen generator; 6-a liquid nitrogen storage tank; 7-a cryopump; 8-a PLC control system; 9-a high-pressure water pump; 10-a rapid heater; 11-liquid nitrogen tank group; 12-a high-pressure water pipe; 13-flange connection; 14-coal seam.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments; all other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, the disclosure of which is incorporated herein by reference as is commonly understood by reference.
Those skilled in the art will recognize that equivalents of the specific embodiments described, as well as those known by routine experimentation, are intended to be encompassed within the present application. The experimental methods in the following examples are conventional methods unless otherwise specified.
Example 1: the coal seam permeability-increasing device for the variable-temperature jet flow of the coal seam with low permeability in the coal mine comprises a jet flow nozzle arranged at the outlet of a high-pressure water pipe, wherein the inlet of the high-pressure water pipe is connected with a high-pressure water pump, and the high-pressure water pump is connected with a rapid heater; the jet flow spray head is also connected with a liquid nitrogen generator through a vacuum heat insulation pipe, the inlet end of the liquid nitrogen generator is connected with the nitrogen generator, the outlet end of the liquid nitrogen generator is connected with the inlet end of a liquid nitrogen storage tank, the outlet of the liquid nitrogen storage tank is connected with a liquid nitrogen tank group, the outlet end of the liquid nitrogen tank group is connected with a low-temperature pump, and the outlet of the low-temperature pump is led into the jet flow spray head through the vacuum heat insulation pipe; the rapid heater, the high-pressure water pump, the low-temperature pump, the liquid nitrogen storage tank, the liquid nitrogen generator and the nitrogen generator are respectively connected with the PLC control system.
The outlet of the nitrogen generator is connected with the liquid nitrogen generator, a jet medium is provided for liquid nitrogen jet equipment, the outlet of the liquid nitrogen generator is connected with the inlet of the liquid nitrogen storage tank, liquid nitrogen flows through the vacuum insulation pipeline through the low-temperature pump to reach the jet spray head, the internal pressure of each tank of the liquid nitrogen tank set is different, and the liquid nitrogen tank set provides different internal pressures to realize the multi-stage low-temperature fracturing effect.
In order to facilitate the liquid nitrogen to act on the inside of the water jet punching hole so as to enhance the permeability of the coal seam and improve the gas yield, a sealing device is required to be used for sealing holes, and sealing operation is required to be carried out. In order to help to realize the automatic control process, the nitrogen generator control system further comprises a PLC control system, wherein the PLC control system is connected with the rapid heater, the high-pressure water pump, the low-temperature pump, the liquid nitrogen generator and the nitrogen generator.
The method for permeability improvement by adopting the coal seam permeability-improving device for coal mine underground hypotonic coal seam variable-temperature jet flow comprises the following steps:
(1) And determining construction process parameters of hydraulic drilling and monitoring drilling according to underground coal seam occurrence conditions, physical parameters and working pressure of water jet equipment, reasonably arranging drilling positions, intervals and the like, and avoiding gas extraction blank areas or gas extraction overlapping areas in the later period. Typically, the hydraulic borehole size may be 80-170mm and the monitor borehole size may be 42-75mm. And determining that the monitoring drilling holes are respectively arranged in a parallel or vertical hydraulic drilling mode according to the actual condition of the site and the construction difficulty of the monitoring holes. Due to the influences of underground construction disturbance and rock burst, the phenomena of hole collapse, hole blocking and the like of the monitoring holes are main problems faced in the later period, so that the anti-reflection effect of the later period coal bed and the evaluation of the effective extraction radius are influenced.
Thus, a hole pattern of 1 hydraulically drilled hole plus 6 or 7 monitor drilled holes is used. Considering the actual anti-reflection radius of the underground coal seam hydraulization measure, the distances between the drilling monitoring holes and the hydraulization drilling hole distribution holes are respectively L 1 One monitoring well of =1.2-1.6 m, L 2 1-2, L of=2.0-2.2m monitoring holes 3 2, L of=2.6-3.00 m monitoring wells 4 The arrangement mode of the monitoring holes is shown in fig. 1, only one monitoring hole is needed for short-distance monitoring, even if the hole collapse problem occurs, the subsequent monitoring holes can still provide effective monitoring data, and the two long-distance monitoring holes are arranged to ensure that the effective anti-reflection radius of the coal seam can be effectively measured in the later stage.
(2) Selecting a high-pressure water jet nozzle with the size of 1.8-2.6mm according to the mechanical parameters of the coal seam and the requirements of field application, controlling the water jet pressure to be 80-120MPa, and controlling the water temperature to be 0-90 ℃;
(3) And (3) performing water jet drilling operation, starting a rapid heater to heat through a PLC control system, rapidly lifting the water temperature to a specified temperature, opening a valve switch of the rapid heater, starting a high-pressure water pump, pressurizing water flow through the high-pressure water pump, enabling the water flow to reach a jet nozzle through a vacuum heat insulation pipe, forming high-speed water jet at the jet nozzle to impact a coal bed, crushing the coal bed by utilizing the high-speed impact of the water jet, and finally forming a drill hole of a certain scale.
The method comprises the steps of utilizing 80-120MPa high-pressure water jet to impact a coal bed in a drilled hole, utilizing the water jet to impact at a high speed to break the coal bed to form a punched hole, setting a waterproof range finder to transmit back a punching area parameter and guaranteeing a water jet punching effect at the middle position on a drill rod near a connecting nozzle, and properly adjusting the water jet impact parameter according to punching data transmitted back by the range finder aiming at the conditions of containing gangue or weak surfaces in the coal bed, so as to form a large-range uniform damage area in the hole;
in the first water jet punching, water is not required to be heated, and water jet impact is directly used for forming punching, so that the subsequent injection of liquid nitrogen is facilitated.
(4) The coal cinder and part of residual water in the hole are moved outside the hole by using a spiral drill rod, the coal cinder and the residual water are respectively separated and recycled, the separated coal cinder enters a coal bunker, and the residual water can be used for secondary use through a mine water treatment device in the pit;
(5) In order to ensure the local low-temperature treatment effect of the coal seam in the drilled hole, the water jet punching area is subjected to local sectional hole sealing by utilizing a sectional temperature-resistant pressure-resistant hole sealing device, normal-temperature nitrogen is firstly injected into the hole sealing area by utilizing a nitrogen injection pipe, water enters the deep coal seam by utilizing the pressure of the normal-temperature nitrogen, and meanwhile, a channel can be provided for low-temperature liquid nitrogen to enter the coal seam, so that the low-temperature treatment range and effect are improved, and the injection pressure P of the normal-temperature nitrogen is controlled Normal nitrogen =nP Gas burner Wherein P is Gas burner For the gas pressure in the coal seam, n is the pressure coefficient, and n=4-7.
And then injecting low-temperature liquid nitrogen into the area, storing the liquid nitrogen which is prepared in advance in a liquid nitrogen storage tank through a nitrogen making machine and a liquid nitrogen generator, opening a valve of the liquid nitrogen storage tank when the liquid nitrogen needs to be injected, starting a low-temperature pump through a PLC control system to convey the liquid nitrogen to a jet nozzle through a vacuum heat insulation pipe, and injecting the liquid nitrogen into a hole drilled by a water jet through a drill bit.
Control of the injection quantity Q of liquid nitrogen in consideration of partial liquid nitrogen intrusion into the coal seam Liquid nitrogen =1.3-1.7πD i 2 4, wherein D i The broken diameter of the local drilling formed by the water jet impact before the ith nitrogen injection is mainly provided by a range finder. In order to prevent the risk of liquid nitrogen gasification volume expansion, an automatic pressure relief valve is reserved on the sectional hole sealing device, and partial pressure relief is carried out when the high pressure generated by liquid nitrogen gasification reaches a preset range.
The method is characterized in that the method comprises the steps of carrying out partial cooling and freezing treatment by using low-temperature liquid nitrogen, converting the internally-occurring pore and crack water medium into ice medium in a short time, forming ice wedge frost heaving action on the coal bed, simultaneously, generating thermal stress in the coal bed under a larger temperature gradient due to larger difference of heat transfer coefficients of all parts, and expanding and communicating coal bed pore cracks under the combined action of the pore and crack water medium.
The action of liquid nitrogen on coal seams has three main effects. Firstly, the cooling effect of the liquid nitrogen enables the coal bed to generate thermal stress; secondly, after punching by high-temperature water jet, the cracks in the holes are increased, residual water in the holes enters into the cracks of the coal bed, residual water can be quickly frozen after liquid nitrogen is injected, so that the coal bed is frozen, the frozen part is quickly melted in the holes impacted by the high-temperature water jet, and the cracks of the coal bed are increased due to severe temperature change; thirdly, the liquid nitrogen is converted into gas phase from liquid phase, the gas phase can expand rapidly, and the gas phase volume is far more than the liquid phase physical strength, so that the coal seam crack is increased. The three effects act on the coal seam together, so that the crushing effect of the coal seam can be obviously improved, the number and quantity of the coal seam cracks are greatly increased, the air permeability of the coal seam is improved, and the gas yield is improved.
(6) The freezing temperature of the water medium is often lower than the freezing temperature of pure water under the influence of partial inorganic salt components in the underground stratum water medium, so that the freezing capacity of the coal bed is basically lost when the temperature in the segmented hole sealing area is increased to the range of-7 ℃ to-13 ℃, and the liquid nitrogen treatment is completed; and then the region is impacted by the high-temperature water jet with the pressure of 90-130MPa, and a large-range damage region is formed on the frozen drilling coal seam again by utilizing the impact effect of the high-temperature high-pressure water jet. Simultaneously, under the action of high-temperature water, the low-temperature coal matrix is caused to thermally crack, so that thermal damage is formed, and the cracks of the coal bed holes in the drilled holes are further developed.
(7) Repeating the steps 5-6, injecting low-temperature liquid nitrogen into the area again, and then repeatedly impacting the area by using high-temperature water jet with different pressure. The above process is repeated a plurality of times.
The first time is normal temperature water medium, and the second time is high temperature water jet flow at 75-85 ℃. The temperature of the water jet is gradually decreased, and the pressure of the water jet is gradually increased along with the increase of the damage range. Meanwhile, the pressure of nitrogen injected at normal temperature is controlled to be kept constant every time, and the amount of liquid nitrogen injected is gradually increased according to the increase of the hydraulic punching range. Through the high-pressure water jet impact and the low-temperature liquid nitrogen alternate circulation treatment, the coal body structure is deteriorated, the damage and destruction area is increased, the primary and secondary cracks are developed, and the cracks are communicated with each other, so that the permeability improvement effect of the coal seam is improved. The amount of low-temperature liquid nitrogen injected each time is gradually decreased by 10-30%.
In the device and the control method for coal seam permeability improvement by using variable-temperature jet flow, the development condition of coal seam cracks is judged according to a pressure sensor on the outer wall of a vacuum heat-insulating pipe, and the injection quantity of two media, namely water and liquid nitrogen, is determined through the pressure in a drill hole.
In order to realize an automatic control process, a PLC control system is respectively connected with the rapid heater 10 and the liquid nitrogen storage tank 6 to monitor the internal temperature, pressure and reserve, and meanwhile, the PLC control system can control the heating program of the heater; the PLC control system is respectively connected with pressure sensors at the high-pressure water pump 9 and the low-temperature pump 7 and monitors the pressure of jet media; the PLC control system is connected with a pressure sensor at the outer wall of the vacuum heat insulation pipe 2 in the drill hole, and monitors the pressure condition in the drill hole; the control panels of the nitrogen generator 4 and the liquid nitrogen generator 5 are respectively connected with a PLC control system and used for monitoring parameters such as flow, pressure and the like in the liquid nitrogen manufacturing process, so that normal production can be ensured.
The method realizes that two jet media, namely high-temperature water jet and liquid nitrogen, impact the coal seam together, can effectively improve the permeability-increasing effect of the coal seam and improve the yield of gas. The method is better than single water jet media. Meanwhile, the loss of liquid nitrogen in the transportation process can be effectively avoided by adopting the vacuum heat insulation pipeline, so that the liquid nitrogen can better act on the coal seam.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (7)
1. The utility model provides a coal seam anti-reflection device of colliery hypotonic coal seam alternating temperature efflux in pit which characterized in that: the high-pressure water jet device comprises a jet nozzle (1) arranged at the outlet of a high-pressure water pipe (12), wherein the inlet of the high-pressure water pipe (12) is connected with a high-pressure water pump (9), and the high-pressure water pump (9) is connected with a rapid heater (10);
the jet flow spray head (1) is also connected with the liquid nitrogen generator (5) through the vacuum heat insulation pipe (2), the inlet end of the liquid nitrogen generator (5) is connected with the nitrogen generator (4), the outlet end of the liquid nitrogen generator is connected with the inlet end of the liquid nitrogen storage tank (6), the outlet of the liquid nitrogen storage tank (6) is connected with the liquid nitrogen tank group (11), the outlet end of the liquid nitrogen tank group (11) is connected with the low-temperature pump (7), and the outlet of the low-temperature pump (7) is led into the jet flow spray head (1) through the vacuum heat insulation pipe (2);
the rapid heater (10), the high-pressure water pump (9), the low-temperature pump (7), the liquid nitrogen storage tank (6), the liquid nitrogen generator (5) and the nitrogen generator (4) are respectively connected with the PLC control system (8);
the outer wall of the vacuum heat insulation pipe (2) is provided with a pressure sensor which is connected with a PLC control system.
2. The coal seam permeability increasing device for coal mine underground hypotonic coal seam variable temperature jet flow according to claim 1, wherein the permeability increasing device is characterized in that: and the outlet end of the high-pressure water pump is provided with a water injection valve, and the outlet end of the low-temperature pump is provided with a nitrogen injection valve.
3. The coal seam permeability increasing device for coal mine underground hypotonic coal seam variable temperature jet flow according to claim 1, wherein the permeability increasing device is characterized in that: the jet nozzle (1) is arranged in the coal seam; a sealing plug (3) is arranged between the end parts of the high-pressure water pipe (12) and the vacuum heat-insulating pipe (2) and the coal seam; the jet nozzle (1) is connected with the high-pressure water pipe (12) and the vacuum heat-insulating pipe (2) by flanges respectively.
4. The coal seam permeability increasing device for coal mine underground hypotonic coal seam variable temperature jet flow according to claim 1, wherein the permeability increasing device is characterized in that: the pressure range of the liquid nitrogen tank set (11) is 0.6-2.8MPA; the minimum pressure of the liquid nitrogen tank is 0.6-0.7MPA, and the pressure difference of the liquid nitrogen tank is set to be 0.5 times or 1 time of the initial pressure.
5. The coal seam permeability increasing device for coal mine underground hypotonic coal seam variable temperature jet flow according to claim 1, wherein the permeability increasing device is characterized in that: the depth of the jet nozzle entering the coal seam is 1-2m, so that coal seam permeability improvement is performed; and continuing to perform variable-temperature jet flow anti-reflection at a distance of 1.5-6.5 m.
6. A method for permeability improvement by using the coal seam permeability-improving device for coal seam variable temperature jet flow of the coal mine underground hypotonic coal seam according to claim 1, which is characterized in that: the method comprises the following steps:
(1) Determining construction process parameters of hydraulic drilling and monitoring drilling according to underground coal seam occurrence conditions, physical parameters, working pressure of water jet equipment and site requirements, wherein the hydraulic drilling size is 80-170mm, and the monitoring drilling size is 42-75mm; the monitoring drill holes are respectively arranged in a mode of being parallel or perpendicular to the hydraulic drill holes, and a hole distribution mode of 1 hydraulic drill hole and 6 or 7 monitoring drill holes is adopted; the hole distribution intervals of the monitoring drilling holes and the hydraulic drilling holes are respectively as follows: l (L) 1 One monitoring well of =1.2-1.6 m, L 2 1-2, L of=2.0-2.2m monitoring holes 3 2, L of=2.6-3.00 m monitoring wells 4 2 monitoring wells =3.2-3.6 m;
(2) Selecting a high-pressure water jet nozzle with the size of 1.8-2.6mm according to the mechanical parameters of the coal seam and the requirements of field application, controlling the water jet pressure to be 80-120MPa, and controlling the water temperature to be 0-90 ℃;
(3) The method comprises the steps of utilizing 80-120MPa high-pressure water jet to impact a coal bed in a drilled hole, heating water is not needed when the water jet is used for punching holes for the first time, controlling the water temperature to be 15-30 ℃, utilizing the high-speed impact of the water jet to crush the coal bed to form punched holes, and meanwhile, setting a waterproof range finder to transmit back punching hole area parameters and guaranteeing the water jet punching effect at the middle position on a drill rod near a connecting spray head, and properly adjusting the water jet impact parameters according to punching data transmitted back by the range finder aiming at the conditions of containing gangue or weak surfaces in the coal bed, so that a large-range uniform damage area is formed in the holes;
(4) Using a spiral drill rod to move the cinder and residual water in the hole to the outside of the hole, and respectively carrying out secondary separation and recycling on the cinder and the residual water in the well;
(5) Partial sectional hole sealing is carried out on the water jet punching area by utilizing the sectional temperature-resistant pressure-resistant hole sealing device, normal-temperature nitrogen is injected into the hole sealing area, and the injection pressure P of the normal-temperature nitrogen is controlled Normal nitrogen =nP Gas burner Wherein P is Gas burner For the gas pressure in the coal seam, n is a pressure coefficient, n=4-7, water is endowed in the coal seam by utilizing the injected normal-temperature nitrogen, the water can enter the deep part of the coal seam, and meanwhile, a channel is provided for liquid nitrogen to enter the coal seam; injecting low-temperature liquid nitrogen after normal-temperature nitrogen injection is completed, and controlling injection quantity Q of low-temperature liquid nitrogen Liquid nitrogen =1.3-1.7πD i 2 4, wherein D i The broken diameter of the local drilling hole formed by the water jet impact before the ith nitrogen injection is provided by a range finder on the drill rod; meanwhile, an automatic pressure relief valve is reserved on the sectional hole sealing device, and partial pressure relief is carried out when the high pressure generated by liquid nitrogen gasification reaches a preset range;
(6) The freezing temperature of the water medium is often lower than the freezing temperature of pure water under the influence of partial inorganic salt components in the underground stratum water medium, so that the freezing capacity of the coal bed is basically lost when the temperature in the segmented hole sealing area is increased to the range of-7 ℃ to-13 ℃, and the liquid nitrogen treatment is completed;
secondly, impacting the area by using a high-temperature high-pressure water jet with the pressure of 90-130MPa, and forming a damage area with a larger range on the frozen drilling coal bed again;
(7) And (3) repeating the steps (5) and (6), sequentially injecting normal-temperature nitrogen and low-temperature liquid nitrogen into the area again, and repeatedly impacting the area by using high-temperature water jet flows with different pressures and temperatures.
7. The method for permeability improvement by using the coal seam permeability-improving device for coal seam temperature-changing jet flow of coal seam under coal mine as claimed in claim 6, wherein the method comprises the following steps: the water jet impingement is: the flow rate of water is 1-2.5 m/min, and the injection time is 5-35min; the first time is high-temperature water jet with the pressure of 80-120MPa, the second time is high-temperature water jet with the temperature of 75-85 ℃ and the pressure of 10-20MPa higher than the first time, and the water temperature in the high-temperature high-pressure water jet is decreased by 5-20 ℃ each time, so that the pressure is kept constant; the amount of low-temperature liquid nitrogen injected each time is gradually decreased by 10-30 percent; the flow rate of the liquid nitrogen at the beginning is 1.5-3.5 m/min, and the injection time is 10-30min; the temperature of the liquid nitrogen is controlled between-200 and-205 ℃.
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