Gas combined extraction system and process

Abstract

The invention discloses a gas combined extraction system and process, and relates to the technical field of gas extraction, the gas combined extraction system comprises a foam fracturing system, a blasting gasification system, an extraction system, a detection unit and a control system, the extraction point of the extraction system and the blasting point of the blasting gasification system are located on the upper coal seam and the lower coal seam on the two sides of the middle coal seam, the extraction system is operated in situ after the blasting gasification system is withdrawn out of the drill hole, and detection units are arranged on the foam fracturing system, the blasting gasification system and the extraction system. The foam fracturing system, the blasting gasification system, the extraction system and the detection unit are all in communication connection with the control system. According to the method, a favorable pressure unloading zone is formed on the upper coal seam and the lower coal seam through blasting operation, and the unloading zone can remarkably improve the air permeability of the middle coal seam and enable gas to escape more easily, so that the gas extraction efficiency is effectively improved, and the risk of gas outburst is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gas extraction, and in particular to a gas combined extraction system and process. Background Art

[0002] Gas outburst is a special term for disasters. It refers to a geological disaster caused by the increase in mining depth and gas content in coal seams. Under the action of ground stress and the gravitational force of gas release, the weak coal seams break through the resistance line and release a large amount of gas and coal instantly. In the process of coalbed methane mining, gas outburst is a problem that cannot be ignored, especially in coal seams with high gas content. This problem is particularly prominent.

[0003] Traditional gas control methods, such as pre-extraction of gas and water injection to reduce pressure, can reduce gas content and outburst risks to a certain extent, but these methods are often difficult to implement and the results are not satisfactory when faced with complex and changeable geological conditions. Especially in some coal seams with hard strata and complex structures, traditional control methods often cannot achieve the expected results. Therefore, a new gas extraction system and process are urgently needed to solve this problem. Summary of the invention

[0004] The purpose of the present invention is to provide a gas combined extraction system and process to solve the problems existing in the above-mentioned prior art and optimize the treatment of gas outburst problems.

[0005] To achieve the above object, the present invention provides the following solutions: The present invention provides a gas joint extraction system, comprising a foam fracturing system, an explosive gasification system, an extraction system, a detection unit and a control system. The fracturing pipeline of the foam fracturing system is arranged in a middle coal seam, the extraction point of the extraction system and the blasting point of the explosive gasification system are both located in the upper coal seam and the lower coal seam on both sides of the middle coal seam, the extraction system is operated in situ after the explosive gasification system is withdrawn from the borehole, the foam fracturing system, the explosive gasification system and the extraction system are all provided with the detection unit, and the foam fracturing system, the explosive gasification system, the extraction system and the detection unit are all communicatively connected with the control system.

[0006] Preferably, the foam fracturing system includes a foam generator, a fracturing fluid storage tank, a high-pressure pump and a fracturing pipeline, one end of the foam generator is connected to a water tank and a carbon dioxide storage tank respectively, and the other end is connected to the fracturing fluid storage tank, the fracturing fluid storage tank is connected to the fracturing pipeline through a high-pressure pump, and the fracturing pipeline is L-shaped and has a plurality of fracturing holes evenly spaced along the axial direction at the end.

[0007] Preferably, a mixer is connected to the fracturing fluid storage tank, and the mixer is connected to the foam generator and the proppant reservoir respectively. The proppant reservoir stores proppant, and the proppant includes resin-coated sand, quartz sand, walnut shells, glass beads, plastic balls or expanded clay.

[0008] Preferably, the flow meter and the valve of the detection unit are sequentially arranged on the outlet pipe of the high-pressure pump, and a pressure sensor is arranged on the fracturing pipeline, and the pressure sensor is located inside the innermost fracturing hole of the fracturing pipeline.

[0009] Preferably, the aperture of the fracturing hole is 50 mm-100 mm; the outlet flow rate of the high-pressure pump is 150 L / min-250 L / min, and the outlet pressure of the fracturing pipeline is 10 MPa-15 MPa.

[0010] Preferably, the blasting gasification system includes a microencapsulation device, an injection pump, a water tank, a spiral static mixer and a venturi injector. The upper end of the microencapsulation device is respectively connected to a chemical reagent tank and a packaging material tank, and the lower end is connected to the spiral static mixer. The spiral static mixer is connected to a plurality of the injection pumps. The upper coal seam and the lower coal seam are provided with a plurality of boreholes at equal intervals and staggered therein. Steel cylinders are provided in the boreholes. Each of the injection pumps is connected to the venturi injector through a blasting tube.

[0011] Preferably, the chemical reagent tanks include a hydrogen peroxide solution tank and a potassium perchlorate solution tank; the spacing between the drill holes is 2m-5m; the plate heat exchanger of the microencapsulation equipment is provided with a temperature sensor of the detection unit, and the temperature sensor is connected to a temperature controller; each of the injection pumps is provided with a pressure sensor of the detection unit, and the injection pressure of the injection pump is 5MPa-10MPa.

[0012] Preferably, the extraction system includes an extraction pump, a separator and a gas storage tank, one end of the separator is connected to the gas storage tank, and the other end is connected to a plurality of the extraction pumps, each of the extraction pumps corresponds to one of the boreholes, and the extraction pump passes through the borehole through an extraction pipe; a sampling port, a flow meter of the detection unit and a gas concentration sensor are provided on the outlet pipe of the extraction pump.

[0013] The present invention discloses a gas joint extraction process, which specifically includes the following steps according to the above-mentioned gas joint extraction system: S1, start the foam fracturing system, continuously inject foam fracturing fluid, and as the pressure gradually increases until it reaches the breaking point of the coal seam, the coal seam will crack and form cracks, and further increase the flow rate of the foam fracturing fluid until the flow meter and pressure sensor values ​​are stable, and then gradually add proppant to the foam fracturing fluid. When the flow rate and pressure of the fracturing pipeline reach a stable state and the opening degree of the fracturing gap remains at a predetermined standard, stop adding proppant; S2, start the blasting gasification system, use the microencapsulation equipment to atomize the dissolved chemical reagent solution into tiny droplets through the spray head, and make microcapsules, start the injection pump, adjust the injection pressure of the injection pump to 5MPa-10MPa, and inject the microcapsule mixture into the coal seam by pressure injection. After the injection pressure of the microencapsulation equipment is stable and the values ​​of the pressure sensor and the flow meter are stable, the injection pump stops injecting. After the injection is completed, the geothermal energy is used to catalyze the reaction of hydrogen peroxide and potassium perchlorate to produce a large amount of oxygen, increase the pressure in the coal seam, and cause the coal seam to rupture; S3, install the extraction system. When the gas concentration reaches more than 20% and the gas flow is stable, and the pressure standard of the negative pressure extraction system is met, the extraction standard is reached, and the extraction pump of the extraction system is turned on to extract the coalbed methane under negative pressure. The coalbed methane is transported to the gas storage tank through the separator.

[0014] Preferably, in step S2, the operating temperature of the microencapsulation equipment is controlled at 15°C-20°C, and the pressure at various locations is monitored in real time; in step S3, the coalbed methane is sampled before entering the separator, and the gas sample is analyzed.

[0015] Compared with the prior art, the present invention has achieved the following technical effects: The present invention forms a favorable pressure unloading zone in the upper and lower coal seams through blasting operations. This unloading zone can significantly improve the permeability of the middle coal seam, making it easier for gas to escape, thereby effectively improving gas extraction efficiency and significantly reducing the risk of gas outbursts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the connection structure of a fracturing blasting system in an embodiment of the present invention; Figure 2 A schematic diagram of the connection structure of the extraction system in an embodiment of the present invention; Figure 3 It is a schematic diagram of the partial structure of the gas joint extraction system in an embodiment of the present invention; In the figure: 1-ground, 2-rock layer, 3-roof, 4-upper coal seam, 5-middle coal seam, 6-lower coal seam, 7-bottom plate, 8-fracturing pipeline, 9-foam fracturing crack, 10-skip extraction gasification coal seam, 11-extraction pump, 12-gas concentration sensor, 13-pressure sensor, 14-water tank, 15-flow meter, 16-valve, 17-high pressure pump, 18-fracturing fluid storage tank, 19-mixer, 20-proppant storage tank, 21-foam generator, 22-carbon dioxide storage tank, 23-drilling hole, 24-steel cylinder, 25-injection pump, 26-venturi injector, 27-coalbed methane storage tank, 28-pressure monitoring unit, 29-temperature sensor, 30-mixed microcapsule storage tank, 31-temperature controller, 32-plate heat exchanger, 33-spiral static mixer, 34-microencapsulation equipment, 35-hydrogen peroxide solution tank, 36-potassium perchlorate solution tank, 37-coalbed methane analyzer, 38-separator. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The purpose of the present invention is to provide a gas combined extraction system and process to solve the problems existing in the prior art and optimize the treatment of gas outburst problems.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Embodiment 1 like Figures 1 to 3As shown, a gas joint extraction system is provided in this embodiment, including a foam fracturing system, an blasting gasification system, an extraction system, a detection unit and a control system. The fracturing pipeline 8 of the foam fracturing system is arranged in the middle coal seam 5, and the extraction point of the extraction system and the blasting point of the blasting gasification system are both located in the upper coal seam 4 and the lower coal seam 6 on both sides of the middle coal seam 5. The extraction system is operated in situ after the blasting gasification system is withdrawn from the borehole 23. The foam fracturing system, the blasting gasification system and the extraction system are all provided with detection units, and the foam fracturing system, the blasting gasification system, the extraction system and the detection unit are all communicatively connected with the control system. In this embodiment, the middle coal seam 5 is the main area of ​​gas accumulation. By blasting and gasifying both sides of it, the channel can be effectively opened, which helps to accelerate the flow of gas to the extraction point, making the negative pressure effect of the extraction system more significant and improving the extraction efficiency; by arranging the blasting points on the upper coal seam 4 and the lower coal seam 6 on both sides of the middle coal seam 5, the blasting operation can form a pressure unloading zone at these locations. The unloading zone helps to reduce the ground stress of the middle coal seam 5, making the gas in the middle coal seam 5 easier to escape, reducing the risk of gas outburst.

[0022] Specifically, the ground 1 is located at the top of the system, supporting the rock layer 2 and the coal seam structure; the rock layer 2 covers the roof 3 and the coal seam, and constitutes an upper structure that cannot be ignored in the process of coal mining. It provides support for the underground coal seam and affects the mining conditions of the coal seam; the roof 3 is a hard rock layer located above the upper coal seam 4. The roof 3 is usually hard rock, which plays a role in protecting the coal seam and also affects the stability of the coal seam; the bottom plate 7 is located below the coal seam, supporting the coal seam and the entire structure, and is usually a relatively hard rock layer 2. Among them, the roof 3 and the bottom plate 7 are key structural layers, which have an important impact on the stability and pressure conduction of the coal seam. The skip-mining gasified coal seams 10 are evenly arranged in the upper coal seam 4 and the lower coal seam 6.

[0023] As an optional solution, the foam fracturing system in this embodiment includes a foam generator 21, a fracturing fluid storage tank 18, a high-pressure pump 17 and a fracturing pipeline 8. One end of the foam generator 21 is connected to the water tank 14 and the carbon dioxide gas storage tank 22 respectively, and the other end is connected to the fracturing fluid storage tank 18. The fracturing fluid storage tank 18 is connected to the fracturing pipeline 8 through the high-pressure pump 17. The fracturing pipeline 8 is L-shaped and has a plurality of fracturing holes evenly spaced along the axial direction at the end. After the fracturing pipeline 8 is fractured, a plurality of foam fracturing cracks 9 will appear around the fracturing holes. In this embodiment, there is only one horizontal well in the middle coal seam 5, equipped with a fracturing pipeline 8. After the fracturing pipeline 8 is fractured, it does not need to be withdrawn.

[0024] As an optional solution, in this embodiment, a mixer 19 is connected to the fracturing fluid storage tank 18, and the mixer 19 is respectively connected to the foam generator 21 and the proppant storage tank 20. The proppant storage tank 20 stores proppant, and the proppant includes resin-coated sand, quartz sand, walnut shells, glass beads, plastic balls or expanded clay. The proppant selected in this embodiment is resin-coated sand, whose base material is high-purity natural quartz sand, the resin type is phenolic resin, the resin coating ratio is 7%, and the proppant particle size is selected to be 0.6mm-1.18mm.

[0025] As an optional solution, in this embodiment, the outlet pipe of the high-pressure pump 17 is provided with a flow meter 15 and a valve 16 of a detection unit in sequence, and the fracturing pipeline 8 is provided with a pressure sensor 13, which is located inside the innermost fracturing hole of the fracturing pipeline 8. In this embodiment, each pressure sensor 13 is connected to a pressure monitoring unit 28 (digital display instrument), which can monitor the pressure on the fracturing pipeline 8 in real time.

[0026] As an optional solution, the aperture of the fracturing hole in this embodiment is 50mm-100mm; the outlet flow rate of the high-pressure pump 17 is 150L / min-250L / min, and the outlet pressure of the fracturing pipeline 8 is 10MPa-15MPa. In this embodiment, when the deep coal seam is processed, due to the high gas content, the stress of the deep coal seam is large, and gas outburst is prone to occur, so a higher fracturing pressure is required; when the shallow coal seam is processed, due to the low ground stress of the shallow coal seam, the adopted fracturing pressure can be 12MPa, and the scale of explosive gasification is also small. The main purpose is to increase the gas flow channel in the shallow fracture and optimize the extraction efficiency.

[0027] As an optional solution, the blasting gasification system in this embodiment includes a microencapsulation device 34, an injection pump 25, a spiral static mixer 33 and a venturi injector 26. The upper end of the microencapsulation device 34 is connected to a chemical reagent tank and a packaging material tank respectively, and the lower end is connected to a spiral static mixer 33. The spiral static mixer 33 is connected to a number of injection pumps 25. The upper coal seam 4 and the lower coal seam 6 are staggered with a number of boreholes 23 at equal intervals. Steel cylinders 24 are arranged in the boreholes 23. Each injection pump 25 is connected to the venturi injector 26 through a blasting pipe. The blasting gasification system in this embodiment can not only improve the gas extraction efficiency of the middle coal seam 5, but also improve the efficiency and safety of coal mining. It has higher flexibility and adaptability, is not limited by the formation structure and geological conditions, and can be effectively implemented in various complex coal seam environments. The use of blasting technology to gasify the upper and lower coal seams 6 is an innovative and practical gas control method.

[0028] As an optional solution, the chemical reagent tank in this embodiment includes a hydrogen peroxide solution tank 35 and a potassium perchlorate solution tank 36; hydrogen peroxide and potassium perchlorate are prepared and mixed at a mass ratio of 0.491. A spiral static mixer 33 is used to dissolve hydrogen peroxide and potassium perchlorate in an appropriate solvent and mix them with a packaging material. Then, a microencapsulation device 34 is used to atomize the dissolved hydrogen peroxide and potassium perchlorate solutions into tiny droplets through a spray head, and the solvent is removed by drying to improve the stability of the microcapsules. The spacing of the boreholes 23 is 2m-5m, preferably 3m. A temperature sensor 29 of a detection unit is provided on the plate heat exchanger 32 of the microencapsulation device 34, and the temperature sensor 29 is connected to a thermostat 31. In this embodiment, a plate heat exchanger 32 is provided in the mixed microcapsule storage tank 30, and a temperature sensor 29 is provided in the plate heat exchanger 32. The temperature sensor 29 collects liquid temperature data in real time and transmits it to the temperature controller 31. The temperature controller 31 compares the current temperature value in the plate heat exchanger 32 with the set value. If there is a deviation, the plate heat exchanger 32 is adjusted for flow or power. The plate heat exchanger 32 adjusts the temperature of the liquid in the tank through the medium (cooling or heating), and the cycle is repeated until the temperature is maintained in a constant temperature range of 15°C-20°C. Each injection pump 25 is provided with a pressure sensor 13 of a detection unit, and each pressure sensor 13 is connected to a pressure monitoring unit 28. The injection pressure of the injection pump 25 is 5MPa-10MPa.

[0029] As an optional solution, the extraction system in this embodiment includes an extraction pump 11, a separator 38 and a gas storage tank 27. One end of the separator 38 is connected to the gas storage tank 27, and the other end is connected to a plurality of extraction pumps 11. Each extraction pump 11 corresponds to a borehole 23, and the extraction pump 11 passes through the borehole 23 through an extraction pipe; a sampling port, a flow meter 15 of a detection unit and a gas concentration sensor 12 are provided on the air outlet pipe of the extraction pump 11.

[0030] Embodiment 2 This embodiment provides a gas joint extraction process, which specifically includes the following steps according to the above-mentioned gas joint extraction system: S1, start the foam fracturing system, and continue to inject foam fracturing fluid. As the pressure gradually increases until it reaches the rupture point of the coal seam, the coal seam cracks and forms cracks. The flow rate of the foam fracturing fluid is further increased until the values ​​of the flow meter 15 and the pressure sensor 13 are stable. Then, proppant is gradually added to the foam fracturing fluid. When the flow rate and pressure of the fracturing pipeline 8 reach a stable state and the openness of the fracturing gap is maintained at a predetermined standard, stop adding proppant. In this embodiment, the predetermined standards include a crack width of more than 5 mm, a crack length of more than 50 m, a crack closure capacity within the range of 10 MPa to 30 MPa, and a crack conductivity, i.e., a coal seam permeability increase of more than 5 times.

[0031] S2, start the blasting gasification system, use the microencapsulation device 34 to atomize the dissolved chemical reagent solution into tiny droplets through the spray head, and make microcapsules, start the injection pump 25, adjust the injection pressure of the injection pump 25 to 5MPa-10MPa, and inject the microcapsule mixture into the coal seam by pressure injection. After the injection pressure of the microencapsulation device 34 is stable and the values ​​of the pressure sensor 13 and the flow meter 15 are stable, the injection pump 25 stops injecting. After the injection is completed, the geothermal energy is used to catalyze the reaction of hydrogen peroxide and potassium perchlorate: , producing a large amount of oxygen, increasing the pressure in the coal seam and causing the coal seam to rupture; S3, install the extraction system. When the gas concentration reaches more than 20% and the gas flow is stable, and the pressure standard of the negative pressure extraction system is met, the extraction standard is reached, and the extraction pump 11 of the extraction system is turned on to extract the coalbed methane under negative pressure. The coalbed methane is transported to the gas storage tank through the separator 38.

[0032] Preferably, in step S2, the operating temperature of the microencapsulation equipment 34 is controlled at 15°C-20°C, and the pressure at various locations is monitored in real time; in step S3, the coalbed methane is sampled before entering the separator 38, and the gas sample is analyzed.

[0033] Embodiment 3 A coal mine is located in an area with rich deep coal resources. The upper coal seam 4 of the coal mine is 3.0 meters thick, the lower coal seam 6 is 3.5 meters thick, and the coal seam depth is about 1,200 meters.

[0034] First, liquid water and carbon dioxide are transported to the foam generator 21. By adjusting the foam generator 21, a stable foam fracturing fluid is formed. The foam fracturing fluid can effectively penetrate the coal seam under high pressure conditions, generate cracks, and increase the permeability of the coal seam.

[0035] The prepared foam fracturing fluid is injected into the well through a high-pressure pump 17. The coal seam in this example is located at a deeper level and has a higher gas content. The deep coal seam is usually subjected to greater ground stress and is prone to gas outburst. Therefore, in the process of injecting the foam fracturing fluid, a higher fracturing pressure is required to ensure the generation of cracks and maintain the permeability of the coal seam. According to the size of the cracks and the characteristics of the coal seam, the injection pressure is adjusted to 13MPa. This embodiment deals with deep coal seams with a higher gas content. The deep coal seams have greater ground stress and are prone to gas outburst, so a higher fracturing pressure is required. During the injection process, as the fracturing fluid is continuously injected, the pressure gradually increases. When the pressure reaches the rupture point of the coal seam (about 12MPa), the coal seam begins to crack and form cracks. At this time, the flow rate and pressure reach a stable state, and then proppant is gradually added to the foam fracturing fluid to keep the cracks open.

[0036] First, prepare hydrogen peroxide and potassium perchlorate and mix them at a mass ratio of 0.491. Use a spiral static mixer 33 to dissolve hydrogen peroxide and potassium perchlorate in an appropriate solvent and mix them with a packaging material. Then, use a microencapsulation device 34 to atomize the dissolved hydrogen peroxide and potassium perchlorate solution into tiny droplets through a spray head, and remove the solvent after drying to improve the stability of the microcapsules. The temperature of the dried hydrogen peroxide and potassium perchlorate microcapsules is controlled at 15°C-20°C by a temperature controller 31 to inhibit the decomposition of the two.

[0037] The pressure control system is turned on and the injection pressure is adjusted to 8 MPa. Then, the injection pump 25 is turned on to inject the microcapsule mixture into the coal seam by pressure injection. After the injection pressure of the microencapsulation device 34 is stable and the values ​​of the pressure sensor 13 and the flow meter 15 are stable, the injection pump 25 stops injecting. During the injection process, the control system monitors and controls the pressure change during the injection process and keeps it between 5 MPa and 10 MPa. The temperature sensor 29 ensures that the temperature of the hydrogen peroxide microcapsules and potassium perchlorate microcapsules is maintained between 25°C and 50°C to maintain the stability of the microcapsules and keep the reaction rate of hydrogen peroxide and potassium perchlorate low.

[0038] Usually the temperature of the coal seam is between 130℃ and 190℃. After the injection is completed, geothermal energy is used to catalyze the reaction of hydrogen peroxide and potassium perchlorate to produce a large amount of oxygen, which increases the pressure in the coal seam, causing the coal seam to rupture and improve the gasification effect. A large amount of heat is released during the reaction, and the temperature rises significantly, accelerating the reaction rate. The generated water is gasified into water vapor at high temperature, promoting the gasification reaction of the coal seam and converting the coal into usable synthesis gas. During the reaction process, coalbed methane samples are collected, and sampling and detection are carried out through the coalbed methane analyzer 37 to analyze the composition and concentration of the gas samples. The specific quantitative values ​​of the collected coalbed methane samples are as follows: methane 25%, hydrogen 12%, carbon monoxide 28%, and carbon dioxide 35%. Among them, the ratio of carbon monoxide to carbon dioxide is 0.8, indicating that there is an appropriate amount of combustion reaction during the gasification process.

[0039] After the coalbed methane sample reaches the extraction standard, the extraction pump 11 is turned on to extract the coalbed methane under negative pressure. The coalbed methane passes through the separator 38 to remove impurities and is finally transported to the gas storage tank 27.

[0040] Embodiment 4 A coal mine has rich deep coal resources. The upper coal seam 4 of the coal mine is 2.8 meters thick, the lower coal seam 6 is 3.2 meters thick, and the coal seam depth is about 1000 meters.

[0041] First, liquid water and carbon dioxide are transported to the foam generator 21, and a stable foam fracturing fluid is formed by adjusting the foam generator 21. The foam fracturing fluid can effectively penetrate the coal seam under high pressure conditions, generate cracks, and increase the permeability of the coal seam.

[0042] The prepared foam fracturing fluid is injected into the well through a high-pressure pump 17. According to the size of the cracks and the characteristics of the coal seam, the injection pressure range is adjusted to 12 MPa. Since the ground stress of the shallow coal seam is low, the fracturing pressure used is 12 MPa, and the scale of blasting gasification is also small. The main purpose is to increase the gas flow channel in the shallow cracks and optimize the extraction efficiency. During the injection process, with the continuous injection of the fracturing fluid, the pressure gradually increases. When the pressure reaches the rupture point of the coal seam (about 11 MPa), the coal seam begins to crack and form cracks. At this time, the flow rate and pressure reach a stable state, and then proppant is gradually added to the foam fracturing fluid to keep the cracks open.

[0043] First, hydrogen peroxide and potassium perchlorate are prepared and mixed at a mass ratio of 0.491. Hydrogen peroxide and potassium perchlorate are dissolved in a suitable solvent using a spiral static mixer 33 and mixed with a packaging material. Then, the dissolved hydrogen peroxide and potassium perchlorate solution is atomized into tiny droplets through a spray head using a microencapsulation device 34, and the solvent is removed by drying to improve the stability of the microcapsules.

[0044] The temperature of the dried hydrogen peroxide and potassium perchlorate microcapsules is controlled at 15°C-20°C by the thermostat 31 to inhibit the decomposition of the two. During the injection process, the control system monitors and controls the pressure change during the injection process to maintain it between 5MPa-10MPa. Then, the injection pump 25 is turned on to inject the microcapsule mixture into the coal seam by pressure injection. During the injection process, the temperature sensor 29 ensures that the temperature of the hydrogen peroxide microcapsules and potassium perchlorate microcapsules is maintained between 25°C-50°C.

[0045] Usually the temperature of the coal seam is between 120℃ and 180℃. After the injection is completed, geothermal energy is used to catalyze the reaction of hydrogen peroxide and potassium perchlorate to produce a large amount of oxygen, which increases the pressure in the coal seam, causes the coal seam to rupture, and improves the gasification effect. A large amount of heat is released during the reaction, and the temperature rises significantly, accelerating the reaction rate. The generated water gasifies into water vapor at high temperature, promotes the gasification reaction of the coal seam, and converts the coal into usable synthesis gas. During the reaction, coalbed methane samples are collected and the composition and concentration of the gas samples are analyzed. The specific quantitative values ​​of the collected coalbed methane samples are as follows: 30% methane, 10% hydrogen, 25% carbon monoxide, and 35% carbon dioxide. The ratio of carbon monoxide to carbon dioxide is 0.71, indicating that there is an appropriate amount of oxidation reaction during the gasification process. In this case, it means that the cracks have been successfully expanded and the gas has been fully released.

[0046] After reaching the extraction standard, the extraction pump 11 is turned on to extract the coalbed methane under negative pressure. The coalbed methane passes through the separator 38 to remove impurities and is finally transported to the gas storage tank 27.

[0047] It can be seen from the above embodiments that the ratio of different gases in the gas composition can reflect the crack expansion after fracturing and gasification. For example, the ratio of methane and carbon dioxide can indicate whether the crack has effectively expanded to the area with higher gas content. In the blasting gasification process, the chemical reaction efficiency of hydrogen peroxide and potassium perchlorate can be evaluated by monitoring the ratio of carbon monoxide and carbon dioxide in the gas composition. The temperature and gasification effect in the reaction process are crucial to gas escape.

[0048] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A gas joint extraction system, characterized in that: It includes a foam fracturing system, an explosive gasification system, an extraction system, a detection unit and a control system. The fracturing pipeline of the foam fracturing system is arranged in the middle coal seam. The extraction point of the extraction system and the blasting point of the explosive gasification system are both located in the upper coal seam and the lower coal seam on both sides of the middle coal seam. The extraction system is operated in situ after the explosive gasification system is withdrawn from the borehole. The foam fracturing system, the explosive gasification system and the extraction system are all provided with the detection unit. The foam fracturing system, the explosive gasification system, the extraction system and the detection unit are all communicatively connected with the control system.

2. The gas combined extraction system according to claim 1, characterized in that: The foam fracturing system includes a foam generator, a fracturing fluid storage tank, a high-pressure pump and a fracturing pipeline. One end of the foam generator is connected to a water tank and a carbon dioxide storage tank respectively, and the other end is connected to the fracturing fluid storage tank. The fracturing fluid storage tank is connected to the fracturing pipeline through a high-pressure pump. The fracturing pipeline is L-shaped and has a plurality of fracturing holes evenly distributed at equal intervals along the axial direction at the end.

3. The gas combined extraction system according to claim 2, characterized in that: The fracturing fluid storage tank is connected to a mixer, which is connected to the foam generator and the proppant reservoir respectively. The proppant reservoir stores proppant, which includes resin-coated sand, quartz sand, walnut shells, glass beads, plastic balls or ceramsite.

4. The gas combined extraction system according to claim 2, characterized in that: The flow meter and valve of the detection unit are arranged in sequence on the outlet pipe of the high-pressure pump, and a pressure sensor is arranged on the fracturing pipeline. The pressure sensor is located inside the innermost fracturing hole of the fracturing pipeline.

5. The gas combined extraction system according to claim 4, characterized in that: The aperture of the fracturing hole is 50mm-100mm; the outlet flow rate of the high-pressure pump is 150L / min-250L / min, and the outlet pressure of the fracturing pipeline is 10MPa-15MPa.

6. The gas combined extraction system according to claim 1, characterized in that: The blasting gasification system includes a microencapsulation device, an injection pump, a spiral static mixer and a venturi injector. The upper end of the microencapsulation device is respectively connected to a chemical reagent tank and a packaging material tank, and the lower end is connected to the spiral static mixer. The spiral static mixer is connected to a plurality of the injection pumps. The upper coal seam and the lower coal seam are provided with a plurality of boreholes at equal intervals and staggered. Steel cylinders are provided in the boreholes. Each of the injection pumps is connected to the venturi injector through a blasting tube.

7. The gas combined extraction system according to claim 6, characterized in that: The chemical reagent tanks include a hydrogen peroxide solution tank and a potassium perchlorate solution tank; the spacing between the drill holes is 2m-5m; the plate heat exchanger of the microencapsulation equipment is provided with a temperature sensor of the detection unit, and the temperature sensor is connected to a temperature controller; each of the injection pumps is provided with a pressure sensor of the detection unit, and the injection pressure of the injection pump is 5MPa-10MPa.

8. The gas combined extraction system according to claim 1, characterized in that: The extraction system includes an extraction pump, a separator and a gas storage tank. One end of the separator is connected to the gas storage tank, and the other end is connected to a plurality of the extraction pumps. Each extraction pump corresponds to a borehole, and the extraction pump passes through the borehole through an extraction pipe. A sampling port, a flow meter of the detection unit and a gas concentration sensor are provided on the outlet pipe of the extraction pump.

9. A gas joint extraction process, according to the gas joint extraction system according to any one of claims 1 to 8, characterized in that: The specific steps include: S1, start the foam fracturing system, continuously inject foam fracturing fluid, and as the pressure gradually increases until it reaches the breaking point of the coal seam, the coal seam will crack and form cracks, and further increase the flow rate of the foam fracturing fluid until the flow meter and pressure sensor values ​​are stable, and then gradually add proppant to the foam fracturing fluid. When the flow rate and pressure of the fracturing pipeline reach a stable state and the opening degree of the fracturing gap remains at a predetermined standard, stop adding proppant; S2, start the blasting gasification system, use the microencapsulation equipment to atomize the dissolved chemical reagent solution into tiny droplets through the spray head, and make microcapsules, start the injection pump, adjust the injection pressure of the injection pump to 5MPa-10MPa, and inject the microcapsule mixture into the coal seam by pressure injection. After the injection pressure of the microencapsulation equipment is stable and the values ​​of the pressure sensor and the flow meter are stable, the injection pump stops injecting. After the injection is completed, the geothermal energy is used to catalyze the reaction of hydrogen peroxide and potassium perchlorate to produce a large amount of oxygen, increase the pressure in the coal seam, and cause the coal seam to rupture; S3, install the extraction system. When the gas concentration reaches more than 20% and the gas flow is stable, and the pressure standard of the negative pressure extraction system is met, the extraction standard is reached, and the extraction pump of the extraction system is turned on to extract the coalbed methane under negative pressure. The coalbed methane is transported to the gas storage tank through the separator.

10. The gas combined extraction process according to claim 9, characterized in that: In step S2, the operating temperature of the microencapsulation equipment is controlled at 15°C-20°C, and the pressure at various locations is monitored in real time; in step S3, the coalbed methane is sampled before entering the separator, and the gas sample is analyzed.

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