CN110778301B

CN110778301B - High-temperature high-pressure steam secondary fracturing device and method for coal seam drilling

Info

Publication number: CN110778301B
Application number: CN201911004171.0A
Authority: CN
Inventors: 李楠; 孙炜辰; 王笑然; 陈栋
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2019-10-22
Filing date: 2019-10-22
Publication date: 2020-07-14
Anticipated expiration: 2039-10-22
Also published as: CN110778301A

Abstract

The invention discloses a high-temperature high-pressure steam secondary fracturing device and a high-temperature high-pressure steam secondary fracturing method for coal seam drilling. Cleaning the failed drill hole, and sending a hole protecting sleeve, a fracturing steel pipe and a double-path hole packer into the drill hole by using an underground drill; sealing holes by using a double-path hole sealing device before secondary fracturing; after steam is proportioned and pressurized in a three-stage temperature rise mode, high-temperature and high-pressure mixed steam is injected into the fracturing steel pipe to perform secondary fracturing and temperature rise treatment on the coal bed, and the secondary fracturing ending time and the water and gas discharging time are accurately determined according to pressure and temperature real-time monitoring data. The method effectively utilizes a large number of failed drill holes, and greatly improves the coal seam gas extraction efficiency from two aspects of pressure relief, permeability increase and gas desorption promotion by temperature rise.

Description

High-temperature high-pressure steam secondary fracturing device and method for coal seam drilling

Technical Field

The invention relates to a coal seam drilling fracturing device and method, in particular to a coal seam drilling high-temperature high-pressure steam secondary fracturing device and method.

Background

The high gas mine in China accounts for about 70% of the total number of the mines, the coal and gas outburst mine reaches 1192 pairs, and accidents caused by gas account for 27% of the total accidents of the coal mine. And gas (coal bed gas) is a clean energy source. Therefore, the coal mine gas extraction rate is improved and the coal mine gas extraction work intensity is increased from the safety perspective and the energy perspective.

Aiming at the characteristics of large quantity, low extraction efficiency, high cost and the like of the traditional drilling and gas extraction project, various measures are taken in the industry to improve the gas extraction efficiency, wherein the hydraulic fracturing is widely applied due to the advantages of large pressure relief range, simple project implementation, remarkable improvement of the gas extraction efficiency and the like. However, when hydraulic fracturing is adopted, fracturing drill holes are often complicated and changeable due to occurrence of coal rock layers, and in addition, the construction quality of the drill holes cannot be guaranteed, fracturing failure often occurs, the expected fracturing effect cannot be achieved, and at the moment, the fracturing drill holes are often abandoned, so that the use value is lost. In addition, a large number of gas extraction drill holes with very low gas concentration and very low gas flow exist underground, the drill holes lose extraction value, and are usually directly abandoned at present and are not used any more. The existing abandoned fractures and extraction boreholes can also interfere with the fracturing of the peripheral new boreholes, because when the new boreholes around the abandoned boreholes are subjected to hydraulic fracturing, the generated hydraulic fractures can easily penetrate the abandoned boreholes, and the fracturing effect can not be achieved. If the large amount of failure fracturing and gas extraction drill holes are directly abandoned without secondary utilization, the effects of coal seam gas extraction and gas disaster prevention and control are influenced, a large amount of drill holes can be wasted, new drilling engineering quantity is further increased, economic waste is generated, and dangers cannot be completely eliminated. Particularly for a coal seam area extracted by a conventional extraction method, because a large amount of gas existing in an adsorption state still exists in the coal seam due to the lagging of the prior extraction technology, the extraction efficiency of an old drill hole is low so as to be difficult to utilize, a new drill hole is easy to penetrate through the old drill hole, water leakage and gas leakage cannot achieve the fracturing effect, and an effective method for reducing the gas content in the extracted area does not exist at present.

In addition, a great deal of research at home and abroad shows that about 90% of gas in a coal seam exists in an adsorption state, and efficient gas extraction needs to desorb the adsorption gas into free gas firstly. Formation pressure and temperature are two key factors influencing coal bed gas adsorption and desorption, and the coal bed gas desorption is promoted by reducing the pressure and increasing the temperature. However, most of the current hydraulic fracturing or other hydraulic measures mainly promote gas desorption by reducing the pressure of the coal bed, and do not simultaneously realize the large-scale reduction of the pressure of the coal bed and the warming of the coal bed to promote the gas desorption.

The application number of 201811495290.6, named as a device and a method for reinforcing coal bed gas extraction by injecting high-pressure high-temperature steam into a coal bed drilling hole, discloses: the gas injection nozzle device is arranged in a drill hole, and then high-pressure high-temperature water vapor is injected into the drill hole, so that the single-hole gas extraction rate is improved. However, the method or the device disclosed by the patent is not suitable for extracted drill holes broken at the hole opening or shallow part of the drill hole, and cannot perform secondary fracturing on drill holes with fracture failure or drill holes with lost gas extraction value; the steam pressure injected by the method is far beyond the magnitude of fracturing, a large-range fracturing network cannot be generated in a coal bed, and the action range of the coal bed is far smaller than the fracturing influence range. The patent needs to inject a large amount of water vapor into the coal bed, and the coal mine has certain difficulty in producing a large amount of high-temperature and high-pressure water vapor in a short time; in addition, the patent only adopts the water vapor with a single component, and does not reasonably proportion the vapor component from the viewpoint of solving different engineering and implementation problems; meanwhile, the temperature and the pressure of the fracturing steam are formed at one time, and high-temperature and high-pressure mixed steam with different temperatures and pressures cannot be generated according to different requirements. The patent requires new drilling to the coal seam, and because the method has a small range of action on the coal seam and cannot utilize the existing massive failed or abandoned drilling, multiple times of drilling needs to be performed, and the cost of the method is increased. The application range and the practical effect of the patent are greatly limited due to the reasons. Aiming at completely different engineering problems and actual requirements and from completely different angles, the invention innovatively invents drilling hole high-temperature high-pressure mixed steam secondary fracturing equipment and a process method aiming at coal seam fracturing failure or extraction failure. The invention not only avoids the waste of the existing abandoned drilling hole resources, but also promotes the gas desorption effect from two aspects of coal seam fracturing pressure relief and temperature rise, thereby improving the gas extraction efficiency and realizing three purposes. The method has important significance for preventing and treating coal seam gas disasters, improving coal mine safe and efficient production and efficiently developing gas clean energy.

Disclosure of Invention

The invention aims to provide a high-temperature and high-pressure steam secondary fracturing device and method for coal seam drilling, which can effectively utilize abandoned drilling holes after primary extraction again to perform secondary fracturing on a coal seam so as to perform secondary extraction on a coal seam area extracted once and improve the extraction rate of gas.

In order to achieve the purpose, the high-temperature high-pressure steam secondary fracturing device for coal seam drilling comprises a high-temperature high-pressure steam proportioning device, a three-stage heating and pressurizing system, a pipeline for secondary fracturing and a monitoring assembly;

the high-temperature high-pressure steam proportioning device comprises an air storage tank for storing air, a protective gas storage tank for storing protective gas, a high-temperature high-pressure steam boiler for converting water into high-temperature pressurized water steam, a tank A for preserving and proportioning the air, the protective gas and the high-temperature pressurized water steam, and a tank B for receiving the tank A and mixing and preserving the heat; the tank A is communicated with the tank B; an output pipe for outputting the mixed gas is arranged on the tank B, and an output valve for controlling the opening and the closing is arranged on the output pipe; the tank A and the tank B are respectively provided with a tank heating device, a tank pressure sensor and a tank temperature sensor;

the air chamber A, the air chamber B and the air chamber C have the volume ratio of α: β: gamma, wherein α takes the value of 85-90, β takes the value of 1-3, and gamma takes the value of 8-15;

the three-stage heating and pressurizing system for heating and pressurizing the mixed gas is provided with an air inlet and an air outlet, the air inlet is connected with the output pipe, the output pipe is communicated with a circulating water path for pressure relief, and the circulating water path is provided with a pressure relief valve;

the secondary fracturing pipeline comprises a plurality of sections of head-to-tail movably connected hole-protecting sleeves, a plurality of sections of movably connected fracturing steel pipes and roadway internal connecting steel pipes; a hole-protecting sleeve matched with the hole-protecting sleeve is provided with a two-way hole packer for sealing an annular space between the hole-protecting sleeve and the wall of the drilled hole, and the two-way hole packer matched with the hole-protecting sleeve is connected with a hand pump A arranged outside the drilled hole; the hole-protecting sleeve is provided with fracturing holes for gas circulation, and the fracturing holes are positioned in an interval from the hole-protecting sleeve to the bottom of a drilling hole of a double-path hole packer; the fracturing steel pipe is positioned in the hole-protecting sleeve and is matched with the fracturing steel pipe to be provided with a fracturing steel pipe matched double-path hole packer for sealing an annular space between the fracturing steel pipe and the hole-protecting sleeve, the fracturing steel pipe matched double-path hole packer is connected with a hand pump B arranged outside a drilled hole, and a fracturing hole for gas circulation is also arranged on the fracturing steel pipe between the fracturing steel pipe matched double-path hole packer and a zone at the bottom of the drilled hole; the fracturing steel pipe is also provided with fracturing holes for gas circulation, and the fracturing holes are positioned in an interval from the matched double-path hole packer of the fracturing steel pipe to the bottom of the drilling hole; the fracturing steel pipe is connected with the gas outlet of the three-stage heating and pressurizing system through the in-roadway connecting steel pipe and is provided with a fracturing valve for controlling the connection to be opened and closed;

the monitoring assembly comprises pressure sensors arranged on the outer wall of the fractured steel pipe in the interval from the hole opening of the drill hole to the hole bottom, positions close to the hole bottom and the hole opening, temperature sensors arranged on the outer wall of the fractured steel pipe at intervals of 5-10 m, and a data analysis terminal for data acquisition and processing; the pressure sensor and the temperature sensor are both connected to a data analysis terminal outside the borehole.

Further, tertiary intensification charging system includes three group's intensification supercharging devices that end to end links to each other in proper order, and every group intensification supercharging device is including being located the intensification device before its connecting line, being located the booster pump behind its connecting line.

Preferably, one group of temperature and pressure raising devices positioned between the front and rear groups of temperature and pressure raising devices is positioned at the midpoint of the front and rear groups of temperature and pressure raising devices.

Further, the air chamber A, the air chamber B and the air chamber C are connected into a connecting steel pipe through air ducts, and then communicated with the tank B through the connecting steel pipe; and an axial flow fan for accelerating gas mixing is arranged in the connecting steel pipe.

Preferably, the high-temperature high-pressure steam proportioning device, the three-stage heating and pressurizing system and the outer surface of the connecting steel pipe in the roadway are all provided with heat insulation layers.

Furthermore, the tank A is provided with two steel baffles which can be controlled by a knob, and the baffle divides the tank A into three air chambers, namely an air chamber A, an air chamber B and an air chamber C.

Preferably, the hole-protecting sleeve matched double-path hole packer and the fracturing steel pipe matched double-path hole packer are respectively tubular structures which are matched and connected with the hole-protecting sleeve and the fracturing steel pipe, and hole sealing can be carried out in an outer diameter expansion mode through pressurization of the hole-protecting sleeve and the fracturing steel pipe by a hand pump A and a hand pump B.

The invention discloses a high-temperature high-pressure steam secondary fracturing method for coal seam drilling, which comprises the following steps of:

a. selecting a failed fracturing drill hole or a failed extraction drill hole, and after ensuring that no pipeline is left in the drill hole, using a tunnel drilling machine to perform hole sweeping and hole cleaning on the drill hole;

b. connecting the hole protecting sleeves end to end, installing a hole protecting sleeve matched double-path hole packer for sealing an annular space between the hole protecting sleeve and the wall of a drilled hole on the hole protecting sleeve, clamping and feeding the hole protecting sleeve into the drilled hole by adopting a gallery drilling machine, and connecting the hole protecting sleeve matched double-path hole packer with a hand pump A outside the drilled hole;

c. connecting the fractured steel pipe with the pressure sensor and the temperature sensor arranged on the outer wall end to end, installing a two-way hole packer matched with the fractured steel pipe for sealing the annular space between the fractured steel pipe and the hole protecting sleeve on the fractured steel pipe, and then sending the fractured steel pipe into the hole protecting sleeve; the fracturing steel pipe is matched with a double-path hole packer which is connected with a hand pump B outside the hole; synchronously, pressure sensors are arranged at the positions, close to the hole bottom and the hole opening, of the outer wall of the fractured steel pipe;

d. the last section of the fracturing steel pipe at the hole opening of the drill hole is sequentially connected with the three-stage heating and pressurizing system and the high-temperature high-pressure steam proportioning device, a fracturing valve is arranged on a connecting steel pipe in a lane for connecting the fracturing steel pipe with the three-stage heating and pressurizing system, a circulating water path is communicated with an output pipe for connecting the three-stage heating and pressurizing system and the high-temperature high-pressure steam proportioning device, and a pressure relief valve is arranged on the circulating water path;

e. the hand pump A and the hand pump B are used for respectively pressurizing the hole-protecting sleeve matched double-path hole packer and the fracturing steel pipe matched double-path hole packer so as to seal an annular space between the hole-protecting sleeve and the hole wall of the failure fracturing drill hole and an annular space between the fracturing steel pipe and the hole-protecting sleeve, the airtightness of each component is tested, and if the airtightness is poor, the hole-protecting sleeve matched double-path hole packer and the fracturing steel pipe matched double-path hole packer are adjusted, so that each component has good airtightness;

f. the mixture gas is proportioned by a high-temperature high-pressure steam proportioning device according to the following proportion: 85% -90% of air, 8% -15% of water vapor and 1% -3% of protective gas; then inputting the mixed gas into a three-stage heating and pressurizing system formed by three groups of heating and pressurizing devices which are sequentially connected end to end;

g. the mixed gas sequentially passes through three groups of heating and pressurizing devices, so that the output temperature of the mixed gas is increased progressively at 150 ℃, 200 ℃ and 250 ℃ and is increased progressively at the pressure of 25MPa, 35MPa and 50 MPa; finally forming high-temperature high-pressure mixed steam with the pressure of more than 45Mpa and the temperature of more than 200 ℃ and less than 300 ℃; after the components are ensured to be normal and the pressure release valves are in a closed state, the output valves on the output pipes of the high-temperature high-pressure steam proportioning devices are opened, and high-temperature high-pressure mixed steam is injected into the coal seam through the fracturing steel pipes for fracturing;

h. continuously feeding high-temperature and high-pressure mixed steam into the pipe, stopping or reducing the boosting function of the heating and boosting device after monitoring values of the two pressure sensors displayed in real time by the data analysis terminal are reduced to a set low-pressure heat injection threshold value, continuously conveying the high-temperature mixed steam with the pressure smaller than the set low-pressure heat injection threshold value into the drill hole for 2-5 hours, ensuring that the coal bed in a secondary fracturing range is fully heated, and then closing each component;

i. measuring that the temperature monitored by all temperature sensors is reduced to 30 ℃ and stabilized below 30 ℃ for 30 minutes through a data analysis terminal, opening a fracturing valve and a pressure relief valve to discharge water, exhaust and relieve pressure after an output valve is in a closed state, and closing the fracturing valve and the pressure relief valve when the discharge and exhaust flow is close to 0;

j. after the drainage and the exhaust are finished, sequentially decompressing the two-way hole packer matched with the fracturing steel pipe and the two-way hole packer matched with the hole-protecting sleeve, and taking out the hole-protecting sleeve, the fracturing steel pipe, the two-way hole packer matched with the fracturing steel pipe and the two-way hole packer matched with the hole-protecting sleeve after complete decompression; and then, the gas extraction pipe is sent into the drill hole, and hole sealing extraction is carried out again.

Furthermore, the double-path hole packer matched with the fractured steel pipe is arranged at the position close to the drill hole opening by about 8m, and the double-path hole packer matched with the hole protection sleeve is arranged at the position close to the drill hole bottom by about 10 m.

Preferably, the components and the proportion of the protective gas are as follows: 20% of nitrogen and 80% of carbon dioxide.

Has the advantages that: the coal seam drilling high-temperature high-pressure steam secondary fracturing device and the method can reuse the widely-existing failed coal seam fracturing drilling and coal seam extraction drilling losing extraction value under the coal mine for secondary fracturing utilization, so that the drilling utilization efficiency is greatly improved, and the drilling engineering quantity is reduced; and moreover, the influence of fracturing on the blank zone and the gas extraction blank zone can be effectively avoided, and the safe and efficient coal mining is ensured. And aiming at the coal seam area which is formed because the extraction efficiency of the old drilled hole is low or the old drilled hole is difficult to utilize due to the laggard of the prior extraction technology and the fracturing effect cannot be achieved because the new drilled hole is easy to penetrate through the old drilled hole, the invention can carry out secondary fracturing on the old drilled hole, thereby improving the extraction rate of the coal seam area.

High-temperature high-pressure mixed steam (air, water vapor and protective gas) mixed according to a certain proportion is adopted for secondary fracturing, so that the pressure of the high-temperature high-pressure mixed steam injected by secondary fracturing of coal seam drilling can reach 45Mpa, and the temperature is between 200 and 300 ℃. Therefore, the problem that the temperature of a prepared water steam boiler is too high and a fire disaster is easily caused in the underground coal mine environment while the pressure is difficult to reach the pressure required by the fracturing of more than 40Mpa by adopting the steam only is solved. The high-temperature and high-pressure mixed steam can fracture a coal bed to generate a crack network in the coal bed, so that the pressure relief and permeability increase effects are achieved; meanwhile, high-temperature and high-pressure mixed steam enters a fracturing fracture network, so that the temperature of the coal bed in a fracturing range can be increased, and the desorption speed of gas adsorbed in the coal bed is greatly accelerated; in addition, the coal body can generate thermal expansion cracks to a certain degree after being heated, so that the fluidity of coal seam gas is further improved, and the gas extraction efficiency is improved. The air, the water vapor and the protective gas (the mixed gas of the nitrogen and the carbon dioxide) have wide sources, are easy to obtain and have low cost; through setting up reasonable mixed steam temperature range to add vapor and protective gas and can ensure that the coal seam in the secondary fracturing scope is not by the gas oxidation of injecticing and is sent out a fire.

On the fracturing steel pipe in the drilling, the position that is close to the hole bottom and closes on the drill way all sets up pressure sensor, and pressure sensor can the vapor pressure of real-time supervision hole bottom and drill way department, and data analysis terminal can show the vapor pressure curve in hole bottom and drill way in real time. The three-stage heating and pressurizing system can be flexibly adjusted or stopped according to the change of the steam pressure, so that blind fracturing and long-time ineffective fracturing are effectively avoided. Through the radial temperature cloud picture of drilling that data analysis terminal shows in real time, can master the steam temperature in the drilling scope, can help judging fracturing degree and appraising the fracturing scope, can correctly grasp the exhaust drainage time after the secondary fracturing again, prevent that high temperature aqueous vapor from scalding the operation personnel.

Before fracturing, a hole-protecting sleeve matched double-path hole packer and a fracturing steel pipe matched double-path hole packer are used for injecting pressure, and after the two double-path hole packers are opened and expanded, 2 annular spaces between the hole-protecting sleeve and a drilled hole and between the hole-protecting sleeve and the fracturing steel pipe are sealed, so that the annular space between the hole-protecting sleeve and the drilled hole is not required to be subjected to cement injection sealing with complex and fussy process; after the fracturing engineering is finished, the two matched double-path hole packers can be subjected to pressure relief and then the hole protecting sleeve, the fracturing steel pipe and the matched double-path hole packers are taken out, so that the fracturing pipeline can be recycled, and the economic cost and the time cost of fracturing are greatly reduced.

The three-stage heating and pressurizing system can realize three-stage adjustable heating and pressurizing of high-temperature and high-pressure steam, so that the generated high-temperature and high-pressure mixed steam meets the construction requirements, and meanwhile, the temperature and the pressure of the high-temperature and high-pressure steam can be adjusted in real time as required. Meanwhile, the temperature and the pressure of the steam in the pipeline are guaranteed to be kept, and the danger brought to operating personnel and devices in a roadway due to the fact that the steam pressure and the temperature are greatly increased in a short time is avoided.

Compared with the reference documents in the background art, the invention discloses a high-temperature high-pressure steam secondary fracturing device and method for coal mine underground coal seam drilling, which mainly utilize coal seam drilling holes which fail in primary fracturing or lose gas extraction value to perform high-temperature high-pressure steam secondary fracturing. The method effectively utilizes a great amount of abandoned drill holes in the underground coal mine, avoids a great amount of waste of the drill holes, and greatly reduces the new drilling engineering quantity. Meanwhile, the high-temperature high-pressure steam is adopted for drilling and secondary fracturing, so that a fracturing fracture network structure can be formed in a coal seam, and the formation pressure of an extraction area is effectively reduced; the high-temperature steam adopted by the invention can also increase the temperature of the coal bed in the range of the crack network, thereby promoting the desorption of the adsorbed gas into the free gas and further improving the gas extraction efficiency. In conclusion, the invention not only avoids the waste of the existing drilling resources, but also promotes the gas desorption effect from two aspects of coal seam fracturing pressure relief and temperature rise, thereby improving the gas extraction efficiency and realizing three purposes with one goal. The method has important significance for preventing and treating coal seam gas disasters, improving coal mine safety and high-efficiency production and gas clean energy efficient extraction and development.

Drawings

Fig. 1 is a schematic diagram of a coal seam drilling high-temperature high-pressure steam secondary fracturing device and method.

FIG. 2 is a schematic diagram of the construction in a coal seam drilling hole high-temperature high-pressure steam secondary fracturing drilling hole.

FIG. 3 is a schematic view of a high temperature and high pressure steam proportioning device.

Fig. 4 is a schematic diagram of a secondary fracturing pipeline and its monitoring components.

FIG. 5 is a graph showing a steam pressure curve of a data analysis terminal in secondary fracturing construction.

In the figure: 1-coal bed; 2-a floor roadway; 3-failure fracturing the borehole; 4-hole protecting sleeve; 5-fracturing the steel pipe; 6, extracting and drilling in failure; 7-a two-way hole packer matched with the fracturing steel pipe; 8-a hole-protecting sleeve is matched with a two-way hole packer; 9-a temperature sensor; 10-a pressure sensor; 11-fracturing the hole; 12-a cable; 13-a data analysis terminal; 14-connecting steel pipes in the lane; 15-a fracturing valve; 16-three-stage heating and pressurizing system; 17-a booster pump; 18-a temperature raising device; 19-a pressure relief valve; 20-high temperature high pressure steam proportioning device; 21-a circulating water tank; 22-a circulating water circuit; 23-a blower fan; 24-an air reservoir; 25-a pressure pump; 26-protective gas storage tank; 27-high temperature high pressure steam boiler; 28-air supply valve; 29-adjusting knob; 30-a baffle plate; 31-in-can warming device; 32-a base; a 33-A tank; 34-B tank; 35-air chamber; 36-an airway tube; 37-connecting steel pipes; 38-a fan; 39-a canister pressure sensor; 40-in-can temperature sensor; 41-an output valve; 42-an output pipe; 43-bottom of hole pressure curve; 44-orifice pressure curve; 45-low pressure heat injection threshold; 46-hand pump A; 47-hand pump B.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1 to 4, the high-temperature and high-pressure steam secondary fracturing device for coal seam drilling provided by the invention comprises a high-temperature and high-pressure steam proportioning device 20, a three-stage heating and pressurizing system 16, a pipeline for secondary fracturing and a monitoring assembly;

the high-temperature high-pressure steam proportioning device 20 comprises an air storage tank 24 for storing air, and the air storage tank 24 can be pressurized by a blower 23 for supplying air; a protective gas storage tank 26 for storing protective gas, a high-temperature and high-pressure steam boiler 27 for converting water into high-temperature pressurized water vapor, an A tank 33 for preserving heat and proportioning air, protective gas and high-temperature pressurized water vapor, and a B tank 34 for receiving the A tank 33 and mixing and preserving heat; the A tank 33 and the B tank 34 are communicated, and the A tank 33 and the B tank 34 are both fixed on the base 32; an output pipe 42 for outputting mixed gas is arranged on the B tank 34, and an output valve 41 for controlling the opening and the closing is arranged on the output pipe 42; the tank A33 and the tank B34 are internally provided with an in-tank heating device 31, an in-tank pressure sensor 39 and an in-tank temperature sensor 40;

as shown in FIG. 3, three air chambers 35 are arranged in the tank A33, namely, the air chamber A is communicated with the air storage tank 24, the air chamber B is communicated with the protective air storage tank 26, the air chamber C is communicated with the high-temperature high-pressure steam boiler 27, air supply valves 28 are arranged between the three air chambers 35 and the air storage tank 24, the protective air storage tank 26 and the high-temperature high-pressure steam boiler 27 respectively to control the communication and disconnection, a pressure pump 25 can be further arranged on a connecting pipeline of the air storage tank 24 communicated with the air chamber A to supply air to the air chamber A through the pressure pump 25, the volume ratio of the air chamber A, the air chamber B and the air chamber C is α: β: gamma, wherein α takes values of 85-90, β takes values of 1-3, and gamma takes values.

As a design scheme of three air chambers 35, the A tank 33 is provided with two steel baffles 30 the positions of which can be controlled by a knob, the baffles 30 divide the A tank 33 into three air chambers of an air chamber A, an air chamber B and an air chamber C, and the position of the steel baffles 30 is moved by adjusting the knob 29 to change the volume ratio of the air chambers A, B and C, so that the optimal mixed gas ratio is selected.

As a further improvement of the communication mode between the tank a 33 and the tank B34, as shown in fig. 3, the air chamber a, the air chamber B and the air chamber C are all connected to a connecting steel pipe 37 through an air duct 36, and then the tank B34 is connected through the connecting steel pipe 37; and an axial flow fan 38 for accelerating the mixing of the gases is provided in the connecting steel pipe 37. The fan 38 may be electrically driven or rotated by the flowing air to accelerate the mixing of different gases.

The tank A33, the tank B34, the in-tank heating device 31, the in-tank pressure sensor 39 and the in-tank temperature sensor 40 in the tank can bear high-temperature high-pressure steam with the pressure of 15-20 MPa and the temperature of 200-300 ℃, and the in-tank heating device 31 can keep the temperature of the mixed steam in the tank at 120-150 ℃.

As shown in fig. 1, the three-stage temperature-raising and pressure-increasing system 16 for raising temperature and increasing pressure of the mixed gas has an air inlet and an air outlet, the air inlet is connected with an output pipe 42, the output pipe 42 is communicated with a circulating water path 22 for pressure relief, and the circulating water path 22 is provided with a pressure relief valve 19; as a preferable scheme, the three-stage heating and pressurizing system 16 includes three groups of heating and pressurizing devices connected end to end in sequence, and each group of heating and pressurizing devices includes a heating device 18 located in front of a connecting pipeline thereof and a pressurizing pump 17 located behind the connecting pipeline thereof. And one group of temperature-raising and pressure-boosting devices positioned between the front and rear groups of temperature-raising and pressure-boosting devices is positioned at the midpoint position of the front and rear groups of temperature-raising and pressure-boosting devices. The output temperature of the mixed gas is increased gradually at 150 ℃, 200 ℃ and 250 ℃ and increased gradually at pressures of 25MPa, 35MPa and 50MPa by a temperature increasing device 18 and a booster pump 17; finally, high-temperature high-pressure steam with the pressure of more than 45Mpa and the temperature of more than 200 ℃ and less than 300 ℃ is formed.

Namely, the mixed gas firstly enters a first group of temperature-raising and pressure-increasing devices through a gas inlet, is heated to 150 ℃ by a temperature-raising device 18 and is then pressurized to 25Mpa by a booster pump 17; then the mixture enters a second group of heating and pressurizing devices, the temperature is raised to 200 ℃ by a heating device 18, and then the mixture is pressurized to 35Mpa by a pressurizing pump 17; finally, the mixture enters a third group of heating and pressurizing devices, is heated to 250 ℃ by a heating device 18 and is pressurized to 50Mpa by a pressurizing pump 17; finally, high-temperature high-pressure steam with the pressure of more than 45Mpa and the temperature of more than 200 ℃ and less than 300 ℃ is formed.

The other end of the circulating water path 22 can be connected to the circulating water tank 21, water vapor generated by pressure relief enters the circulating water tank 21 through the circulating water path 22 and is cooled to form water, and the circulating water tank 21 can be supplied with water from the high-temperature high-pressure steam boiler 27, so that the cyclic utilization of the fracturing water is realized.

The pipeline for secondary fracturing comprises a plurality of sections of head-to-tail movably connected hole-protecting sleeves 4, a plurality of sections of movably connected fracturing steel pipes 5 and a roadway internal connecting steel pipe 14; a hole-protecting sleeve matched double-path hole packer 8 used for sealing an annular space between the hole-protecting sleeve 4 and the wall of the drilled hole is arranged in a matched manner with the hole-protecting sleeve 4, and the hole-protecting sleeve matched double-path hole packer 8 is connected with a hand pump A46 arranged outside the drilled hole; a fracturing hole 11 for gas circulation is arranged on the hole-protecting sleeve 4 from the two-way hole packer 8 matched with the hole-protecting sleeve to the hole-protecting sleeve 4 positioned in the hole bottom area of the drilled hole, namely the fracturing hole 11 for gas circulation is arranged on the hole-protecting sleeve 4, and the fracturing hole 11 is positioned in the area from the two-way hole packer 8 matched with the hole-protecting sleeve to the hole bottom of the drilled hole; the fracturing steel pipe 5 is positioned in the hole-protecting sleeve 4, a fracturing steel pipe matched double-path hole packer 7 used for sealing an annular space between the fracturing steel pipe 5 and the hole-protecting sleeve 4 is installed in cooperation with the fracturing steel pipe 5, the fracturing steel pipe matched double-path hole packer 7 is connected with a hand pump B47 arranged outside a drilled hole, fracturing holes 11 used for gas circulation are also arranged from the fracturing steel pipe 7 matched double-path hole packer 7 to the fracturing steel pipe 5 positioned in a hole bottom interval of the drilled hole, namely the fracturing holes 11 used for gas circulation are also arranged on the fracturing steel pipe 5, and the fracturing holes 11 are positioned in an interval from the fracturing steel pipe matched double-path hole packer 7 to the hole bottom of the drilled hole; the fracturing steel pipe 5 is connected with an air outlet of a three-stage heating and pressurizing system 16 through an in-roadway connecting steel pipe 14, and a fracturing valve 15 is arranged to control the connection to be opened and closed; hand pumps a46 and B47 may be arranged in the floor laneway 2;

the hole-protecting sleeve 4, the fracturing steel pipe 5, the double-path hole packer 7 matched with the fracturing steel pipe and the double-path hole packer 8 matched with the hole-protecting sleeve can be clamped and conveyed into the drill hole and the hole-protecting sleeve 4 by using the tunnel drilling machine, so that the operation intensity of workers can be effectively reduced, and the operation efficiency is improved.

As shown in fig. 4, the monitoring assembly comprises pressure sensors 10 arranged on the outer wall of the fractured steel pipe 5 in the interval from the drill hole opening to the hole bottom, near the hole bottom and at the position close to the drill hole opening, temperature sensors 9 arranged on the outer wall of the fractured steel pipe 5 at intervals of 5-10 m, and a data analysis terminal 13 arranged in the bottom plate roadway 2 and used for data acquisition and processing; the pressure sensor 10 and the temperature sensor 9 are both connected to a data analysis terminal 13 outside the borehole.

It should be noted that both the steel tube 14 and the steel tube 5 in the roadway can bear high-temperature and high-pressure steam with pressure greater than 50MPa and temperature greater than 300 ℃ to ensure the safety and reliability of the system during the whole fracturing process. The sensors and the data analysis terminal 13 are connected with each other by high-temperature-resistant cables 12, and the data analysis terminal 13 is ensured to receive signals of each sensor.

Preferably, in order to prevent the personnel from scalding, the outer surfaces of the high-temperature high-pressure steam proportioning device 20, the three-stage heating and pressurizing system 16 and the roadway connecting steel pipe 14 are all provided with heat insulation layers.

In order to improve the working efficiency, preferably, the hole-protecting sleeve-matching double-path hole packer 8 and the fracturing steel pipe-matching double-path hole packer 7 are respectively tubular structures which are in matched connection with the hole-protecting sleeve 4 and the fracturing steel pipe 5, and hole sealing can be carried out in an outer diameter expansion mode through pressurizing the hole-protecting sleeve and the fracturing steel pipe by a hand pump A46 and a hand pump B47.

The method for secondary fracturing of the coal seam drilling by using the high-temperature and high-pressure steam can be realized by using the device and can also be separated from the device, and is realized by the steps in the method. The method specifically comprises the following steps:

a. as shown in fig. 1 and 2, a failed fracturing borehole 3 in which fracturing fails or a failed extraction borehole 6 in which the value of continuously extracted gas is lost is selected as a secondary fracturing construction hole in a coal seam 1, and the failed fracturing borehole 3 is taken as an example in the embodiment for explanation. And the adjacent fracturing drill holes or extraction drill holes suspend working, so that the construction effect of secondary fracturing is prevented from being influenced. After ensuring that no pipeline is left in the failure fracturing drill hole 3, using an underground drill rig to perform hole sweeping and hole cleaning on the drill hole; the underground drill rig is used for clamping and feeding into a drill hole, so that the operation intensity of workers can be effectively reduced, and the operation efficiency is improved.

b. As shown in fig. 1 and fig. 2, the hole-protecting sleeves 4 are connected end to end, a hole-protecting sleeve matched double-path hole packer 8 for sealing an annular space between the hole-protecting sleeve 4 and the wall of a drilled hole is arranged on the hole-protecting sleeve 4, the hole is clamped and conveyed into the drilled hole by adopting a gallery drilling machine, and the hole-protecting sleeve matched double-path hole packer 8 is connected with a hand pump A46 outside the drilled hole;

c. connecting the fractured steel pipe 5 with the pressure sensor 10 and the temperature sensor 9 arranged on the outer wall end to end, installing a fractured steel pipe matched double-path hole packer 7 for sealing the annular space between the fractured steel pipe 5 and the hole protecting sleeve 4 on the fractured steel pipe 5, and then sending the fractured steel pipe into the hole protecting sleeve 4; the double-path hole packer 7 matched with the fractured steel pipe is connected with a hand pump B47 outside the hole; synchronously, pressure sensors 10 are arranged at the positions, close to the hole bottom and the hole opening, of the outer wall of the fractured steel pipe 5;

the double-path hole packer 7 matched with the fractured steel pipe is arranged at the position close to the drill hole opening by about 8m, and the double-path hole packer 8 matched with the hole protection sleeve is arranged at the position close to the drill hole bottom by about 10 m.

d. The last section of the fracturing steel pipe 5 at the hole opening of the drill hole is sequentially connected with the three-stage heating and pressurizing system 16 and the high-temperature high-pressure steam proportioning device 20, a fracturing valve 15 is arranged on an in-lane connecting steel pipe 14 for connecting the fracturing steel pipe 5 with the three-stage heating and pressurizing system 16, a circulating water path 22 is communicated on an output pipe 42 for connecting the three-stage heating and pressurizing system 16 and the high-temperature high-pressure steam proportioning device 20, and a pressure relief valve 19 is arranged on the circulating water path 22;

e. pressurizing the hole-protecting sleeve matched double-path hole packer 8 and the fracturing steel pipe matched double-path hole packer 7 respectively through a hand pump A46 and a hand pump B47 to seal an annular space between the hole-protecting sleeve 4 and the hole wall of the failure fracturing drill hole 3 and an annular space between the fracturing steel pipe 5 and the hole-protecting sleeve 4, testing the airtightness of each component, and if the airtightness is poor, adjusting the hole-protecting sleeve matched double-path hole packer 8 and the fracturing steel pipe matched double-path hole packer 7 to enable each component to have good airtightness; the two-way hole packer 8 matched with the hole-protecting sleeve and the two-way hole packer 7 matched with the fracturing steel pipe are arranged, so that the annular space between the hole-protecting sleeve 4 and a drill hole is prevented from being sealed by cement injection with complex and fussy process, and the economic cost and the time cost of fracturing are greatly reduced.

f. The mixture gas is proportioned by the high-temperature high-pressure steam proportioning device 20 according to the following proportion: 85% -90% of air, 8% -15% of water vapor and 1% -3% of protective gas; the construction is carried out by air: water vapor: preparing mixed gas according to the proportion of 85:12:3 of the protective gas; the mixed gas is prepared according to the proportion, so that the pressure of high-temperature and high-pressure steam injected by secondary fracturing of coal seam drilling can reach 45Mpa, and meanwhile, the temperature is between 200 and 300 ℃;

the high-temperature high-pressure steam proportioning device 20 comprises a high-temperature high-pressure steam boiler 27, the steam with the temperature of 200 ℃ and the pressure of 12MPa is generated by the boiler, and the heating device 31 in the tank is opened to preheat the tank A33 and the tank B34. Starting a pressure fan 23, and continuously conveying air with pressure into an air storage tank 24; simultaneously, starting a high-temperature high-pressure steam boiler 27 to produce steam with the temperature of 200 ℃ and the pressure of 12 MPa; observing a temperature sensor 40 in the tank, opening an air storage tank 24, a protective gas storage tank 26 and an air supply valve 28 behind a high-temperature and high-pressure steam boiler 27 after the temperature reaches 120 ℃, and opening a pressure pump 25 to inject mixed gas into the tank A33; the mixed gas enters a connecting steel pipe 37 through a gas guide pipe 36, is fully mixed through a fan 38 and then enters a B tank 34, and when the reading of a pressure sensor 39 in the tank reaches 12MPa and a pressure relief valve 19 is ensured to be closed, an output valve 41 is opened to enable the mixed gas to enter an output pipe 42;

the mixed gas is then fed into a three-stage heating and pressurizing system 16 formed by three groups of heating and pressurizing devices connected end to end in sequence through an output pipe 42.

g. The mixed gas sequentially passes through three groups of heating and pressurizing devices, so that the output temperature of the mixed gas is increased progressively at 150 ℃, 200 ℃ and 250 ℃ and is increased progressively at the pressure of 25MPa, 35MPa and 50 MPa; finally forming high-temperature high-pressure mixed steam with the pressure of more than 45Mpa and the temperature of more than 200 ℃ and less than 300 ℃; after the components are ensured to be normal and the pressure release valve 19 is in a closed state, the output valve 41 on the output pipe 42 of the high-temperature and high-pressure steam proportioning device 20 is opened, and high-temperature and high-pressure mixed steam is injected into the coal seam 1 through the fracturing steel pipe 5 for fracturing;

h. along with the continuous pressing of high temperature high pressure steam into fracturing steel pipe 5, the crack in coal seam 1 develops gradually, and coal seam 1 temperature rises gradually, and the gas is continuously desorbed. Observing the data analysis terminal 13, after the numerical values of the hole bottom pressure curve 43 and the orifice pressure curve 44 displayed by the data analysis terminal 13 are reduced to a set low-pressure heat injection threshold value 45 (10 MPa in the construction), reducing the pressurization function of the heating and pressurizing device, continuously conveying high-temperature mixed steam into the fractured steel pipe 5 for 3 hours at the pressure not exceeding the low-pressure heat injection threshold value 45 (namely 10MPa), ensuring that the coal bed 1 in the secondary fracturing range is fully heated, and closing each component after continuously conveying for 3 hours.

i. After the temperature monitored by all the temperature sensors 9 is measured to be reduced to 30 ℃ and stabilized below 30 ℃ for 30 minutes through the data analysis terminal 13, the fracturing valve 15 and the pressure relief valve 19 are opened to drain, exhaust and release pressure when the output valve 19 is in a closed state, and the fracturing valve 15 and the pressure relief valve 19 are closed when the drainage and exhaust flow is close to 0;

j. after the drainage and the exhaust are finished, sequentially decompressing a double-path hole packer 7 matched with the fracturing steel pipe and a double-path hole packer 8 matched with the hole-protecting sleeve, and taking out the hole-protecting sleeve 4, the fracturing steel pipe 5, the double-path hole packer 7 matched with the fracturing steel pipe and the double-path hole packer 8 matched with the hole-protecting sleeve after complete decompression; and then, the gas extraction pipe is sent into the drill hole, and hole sealing extraction is carried out again.

Preferably, the components and the proportion of the protective gas are as follows: 20% of nitrogen and 80% of carbon dioxide. The protective gas can effectively prevent coal from being oxidized, and meanwhile, raw materials are easy to obtain and low in cost.

The coal seam drilling high-temperature high-pressure steam secondary fracturing device and the method can reuse the widely-existing failed coal seam fracturing drilling and coal seam extraction drilling losing extraction value under the coal mine for secondary fracturing utilization, so that the drilling utilization efficiency is greatly improved, and the drilling engineering quantity is reduced; and moreover, the influence of fracturing on the blank zone and the gas extraction blank zone can be effectively avoided, and the safe and efficient coal mining is ensured. And aiming at the coal seam area which is formed because the extraction efficiency of the old drilled hole is low or the old drilled hole is difficult to utilize due to the laggard of the prior extraction technology and the fracturing effect cannot be achieved because the new drilled hole is easy to penetrate through the old drilled hole, the invention can carry out secondary fracturing on the old drilled hole, thereby improving the extraction rate of the coal seam area.

High-temperature high-pressure mixed steam (air, water vapor and protective gas) mixed according to a certain proportion is adopted for secondary fracturing, so that the pressure of the high-temperature high-pressure mixed steam injected by secondary fracturing of coal seam drilling can reach 45Mpa, and the temperature is between 200 and 300 ℃. Therefore, the problem that the temperature of a prepared water steam boiler is too high and a fire disaster is easily caused in the underground coal mine environment while the pressure is difficult to reach the pressure required by the fracturing of more than 40Mpa by adopting the steam only is solved. The high-temperature and high-pressure mixed steam can not only fracture the coal seam 1, but also generate a crack network in the coal seam 1, thereby playing a role in relieving pressure and increasing permeability; meanwhile, the high-temperature and high-pressure mixed steam enters a fracturing fracture network, so that the temperature of the coal bed 1 in a fracturing range can be increased, and the desorption speed of gas adsorbed in the coal bed 1 is greatly accelerated; in addition, the coal body can generate thermal expansion cracks to a certain degree after being heated, so that the fluidity of the gas in the coal seam 1 is further improved, and the gas extraction efficiency is improved. The air, the water vapor and the protective gas (the mixed gas of the nitrogen and the carbon dioxide) have wide sources, are easy to obtain and have low cost; through setting up reasonable mixed steam temperature range to add steam and protective gas and can ensure that coal seam 1 in the secondary fracturing scope is not by the gas oxidation of injecticing and is sent out a fire.

On the fracturing steel pipe 5 in the drilling, the position that is close to the hole bottom and is close to the drill way all sets up pressure sensor 10, and pressure sensor 10 can real-time supervision hole bottom and the steam pressure in drill way department, and data analysis terminal 13 can show the steam pressure curve in hole bottom and drill way in real time. The three-stage heating and pressurizing system 16 can be flexibly adjusted or stopped according to the change of the steam pressure, so that blind fracturing and long-time ineffective fracturing are effectively avoided. Through the radial temperature cloud picture of drilling that data analysis terminal 13 shows in real time, can master the steam temperature in the drilling scope, can help judging fracturing degree and appraising the fracturing scope, can correctly grasp the exhaust drainage time after the secondary fracturing again, prevent that high temperature aqueous vapor from scalding the operation personnel.

Before fracturing, a hole-protecting sleeve matched double-path hole packer 8 is started, a fracturing steel pipe matched double-path hole packer 7 is used for injecting pressure, and after the two double-path hole packers are opened and expanded, 2 annular spaces between the hole-protecting sleeve 4 and a drilled hole and between the hole-protecting sleeve 4 and the fracturing steel pipe 5 are sealed, so that the annular space between the hole-protecting sleeve 4 and the drilled hole is not required to be subjected to cement injection sealing with complex and fussy process; after the fracturing engineering is finished, the two matched double-path hole packers can be subjected to pressure relief and then the hole protecting sleeve 4, the fracturing steel pipe 5 and the matched double-path hole packers are taken out, so that the fracturing pipeline can be recycled, and the economic cost and the time cost of fracturing are greatly reduced.

The three-stage heating and pressurizing system 16 can realize three-stage adjustable heating and pressurizing of high-temperature and high-pressure steam, so that the generated high-temperature and high-pressure mixed steam meets the construction requirements, and meanwhile, the temperature and the pressure of the high-temperature and high-pressure steam can be adjusted as required. Meanwhile, the temperature and the pressure of the steam in the pipeline are guaranteed to be kept, and the danger brought to operating personnel and devices in a roadway due to the fact that the steam pressure and the temperature are greatly increased in a short time is avoided.

Compared with the reference documents in the background art, the invention discloses a high-temperature high-pressure steam secondary fracturing device and method for coal mine underground coal seam drilling, which mainly utilize coal seam drilling holes which fail in primary fracturing or lose gas extraction value to perform high-temperature high-pressure steam secondary fracturing. The method effectively utilizes a great amount of abandoned drill holes in the underground coal mine, avoids a great amount of waste of the drill holes, and greatly reduces the new drilling engineering quantity. Meanwhile, the high-temperature high-pressure steam is adopted for drilling and secondary fracturing, so that a fracturing fracture network structure can be formed in the coal seam 1, and the formation pressure of an extraction area is effectively reduced; the high-temperature steam adopted by the invention can also heat the coal bed 1 within the range of the crack network, thereby promoting the desorption of the adsorbed gas into the free gas and further improving the gas extraction efficiency. In conclusion, the invention not only avoids the waste of the existing drilling resources, but also promotes the gas desorption effect from two aspects of coal seam fracturing pressure relief and temperature rise, thereby improving the gas extraction efficiency and realizing three purposes with one goal. The method has important significance for preventing and treating coal seam gas disasters, improving coal mine safety and high-efficiency production and gas clean energy efficient extraction and development.

It should be noted that the above description is only an exemplary example of the present invention, and when the construction is performed at different construction sites, the relevant practitioner may also have the ability to modify the construction cases according to the actual situations and construction needs at the construction sites without departing from the spirit and scope of the present invention, and the above cases are illustrative and should not be construed as limiting the scope of the present invention.

Claims

1. A high-temperature high-pressure steam secondary fracturing device for coal seam drilling comprises a high-temperature high-pressure steam proportioning device, a three-stage heating and pressurizing system, a pipeline for secondary fracturing and a monitoring assembly;

the secondary fracturing pipeline comprises a plurality of sections of head-to-tail movably connected hole-protecting sleeves, a plurality of sections of movably connected fracturing steel pipes and roadway internal connecting steel pipes; a hole-protecting sleeve matched with the hole-protecting sleeve is provided with a two-way hole packer for sealing an annular space between the hole-protecting sleeve and the wall of the drilled hole, and the two-way hole packer matched with the hole-protecting sleeve is connected with a hand pump A arranged outside the drilled hole; the hole-protecting sleeve is provided with fracturing holes for gas circulation, and the fracturing holes are positioned in an interval from the hole-protecting sleeve to the bottom of a drilling hole of a double-path hole packer; the fracturing steel pipe is positioned in the hole-protecting sleeve and is provided with a fracturing steel pipe matched double-path hole packer for sealing an annular space between the fracturing steel pipe and the hole-protecting sleeve in a matched manner, the fracturing steel pipe matched double-path hole packer is connected with a hand pump B arranged outside a drilled hole, a fracturing hole for gas circulation is also arranged on the fracturing steel pipe, and the fracturing hole is positioned in an interval from the fracturing steel pipe matched double-path hole packer to the bottom of the drilled hole; the fracturing steel pipe is connected with the gas outlet of the three-stage heating and pressurizing system through the in-roadway connecting steel pipe and is provided with a fracturing valve for controlling the connection to be opened and closed;

2. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of claim 1, characterized in that: the three-stage heating and pressurizing system comprises three groups of heating and pressurizing devices which are sequentially connected end to end, and each group of heating and pressurizing devices comprises a heating device positioned in front of a connecting pipeline of the heating and pressurizing devices and a pressurizing pump positioned behind the connecting pipeline of the heating and pressurizing devices.

3. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of claim 2, characterized in that: and one group of temperature-raising and pressure-boosting devices positioned between the front and rear groups of temperature-raising and pressure-boosting devices is positioned at the midpoint position of the front and rear groups of temperature-raising and pressure-boosting devices.

4. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of any one of claims 1 to 3, characterized in that: the air chamber A, the air chamber B and the air chamber C are connected into a connecting steel pipe through air ducts, and then communicated with the tank B through the connecting steel pipe; and an axial flow fan for accelerating gas mixing is arranged in the connecting steel pipe.

5. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of any one of claims 1 to 3, characterized in that: and the high-temperature high-pressure steam proportioning device, the three-stage heating and pressurizing system and the outer surface of the connecting steel pipe in the roadway are provided with heat insulation layers.

6. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of any one of claims 1 to 3, characterized in that: the tank A is provided with two steel baffles which can be controlled by a knob, and the baffle divides the tank A into three air chambers, namely an air chamber A, an air chamber B and an air chamber C.

7. The coal seam drilling high-temperature high-pressure steam secondary fracturing device of any one of claims 1 to 3, characterized in that: the hole-protecting sleeve pipe matched double-path hole packer and the fracturing steel pipe matched double-path hole packer are respectively tubular structures which are matched and connected with the hole-protecting sleeve pipe and the fracturing steel pipe, and hole sealing can be carried out in an outer diameter expansion mode through pressurizing the hole-protecting sleeve pipe and the fracturing steel pipe by a hand pump A and a hand pump B.

8. A coal seam drilling high-temperature high-pressure steam secondary fracturing method is characterized by comprising the following steps: the method comprises the following steps:

i. after the temperature monitored by all temperature sensors is measured to be reduced to 30 ℃ and stabilized below 30 ℃ for 30 minutes through a data analysis terminal, opening a fracturing valve and a pressure relief valve to discharge water, exhaust and relieve pressure when an output valve is in a closed state, and closing the fracturing valve and the pressure relief valve when the discharge and exhaust flow is close to 0;

9. The method for high-temperature and high-pressure steam secondary fracturing of coal seam drilling according to claim 8, characterized by comprising the following steps: the fracturing steel pipe matched double-path hole packer is arranged at a position close to about 8m of a drill hole opening, and the hole-protecting sleeve matched double-path hole packer is arranged at a position close to about 10m of a drill hole bottom.

10. The method for secondary fracturing of coal seam drilling by high-temperature and high-pressure steam according to claim 8 or 9, characterized by comprising the following steps: the protective gas comprises the following components in percentage by weight: 20% of nitrogen and 80% of carbon dioxide.