Coal bed methane well steam reinjection energy increasing system

Abstract

The application discloses a coal bed gas well steam reinjection energy increasing system and relates to the technical field of coal bed mining. The system comprises a rack, a combustion heat supply mechanism arranged on the rack, a flue gas outlet of the combustion heat supply mechanism connected with a high-temperature vaporization mechanism and a bypass flue through a flue gas distribution box, and outlets of the high-temperature vaporization mechanism and the bypass flue connected with a low-temperature distillation mechanism through a temperature regulating and mixing box. After being pretreated, return flow enters the low-temperature distillation mechanism to form a falling liquid film. Distillation steam generated after defoaming, condensation, fine treatment and online water quality detection is used to form injection steam under controlled pressure, which is then injected into a coal bed gas well to be energized through an injection mechanism. The system realizes operation decoupling between continuous return flow treatment and intermittent steam injection of the coal bed gas well through step-by-step utilization of flue gas temperature, physical isolation of the return flow side and the high-pressure vaporization side, and cooperation of the bypass flue and the clean water buffer tank.

Description

Technical Field

[0001] This invention relates to the field of coal seam mining technology, specifically a steam reinjection and energy enhancement system for coalbed methane wells. Background Technology

[0002] During fracturing and depressurization processes, coalbed methane wells generate a certain amount of flowback fluid. This flowback fluid typically contains coal powder, fracturing proppant, inorganic salts, and residual fracturing fluid additives. It must be stored, transported, and centrally treated before it can be discharged or reused. In some newly built well sites, because the coalbed methane gathering and transportation network has not yet been built or put into operation, the coalbed methane produced by the new wells cannot be promptly utilized by the gathering and transportation system. The flowback fluid also needs to be transported off-site by tanker trucks, resulting in both insufficient utilization of coalbed methane resources and high costs for transporting and treating the flowback fluid. At the same time, adjacent older wells often experience a decline in gas production due to factors such as decreased formation pressure, weakened coalbed methane desorption power, and fluid accumulation in the wellbore. Therefore, under the premise of meeting the requirements of wellbore integrity and reservoir adaptability, it is necessary to inject steam back into older wells to supplement heat and pressure energy and improve their production conditions. However, existing well sites lack a synergistic system that can simultaneously utilize coalbed methane from new wells, treat flowback fluid, and achieve steam reinjection and energy enhancement in older wells.

[0003] In existing technologies, flowback fluid treatment devices, gas heating devices, and coalbed methane well steam injection devices are usually set up separately, lacking a synergistic utilization system suitable for new coalbed methane, flowback fluid, and old wells in the same well site. If the saline flowback fluid is directly sent into the high-temperature and high-pressure vaporization equipment, the coal powder, inorganic salts, and residual additives in the flowback fluid are prone to deposit in the vaporization pipeline, causing scaling, corrosion, or blockage, and there is a risk that pollutants will enter the target coal seam with the steam. If the flowback fluid is first converted into low-pressure steam and then pressurized by the compression equipment, the large volume of steam requires a large, complex, and energy-intensive steam compression device. In addition, existing heating methods usually fail to utilize the combustion flue gas in stages according to the different heat levels required for high-pressure vaporization and flowback fluid distillation, and the continuous operation mode of flowback fluid treatment is difficult to coordinate with the intermittent operation mode of steam injection in old wells. Summary of the Invention

[0004] The purpose of this invention is to provide a steam reinjection system for coalbed methane wells to address the problems in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A steam reinjection enhancement system for coalbed methane wells includes a frame and a combustion and heating mechanism. The combustion and heating mechanism is mounted on the frame. The flue gas outlet of the combustion and heating mechanism is connected to a flue gas distribution box. A high-temperature vaporization mechanism is connected to one side of the flue gas distribution box, and a bypass flue is connected to the other side of the flue gas distribution box in parallel with the high-temperature vaporization mechanism. The outlets of the high-temperature vaporization mechanism and the bypass flue are connected to a temperature regulating mixing box. The flue gas outlet of the temperature regulating mixing box is connected to a low-temperature distillation mechanism. The inlet end of the low-temperature distillation mechanism is connected to a return liquid pretreatment mechanism. The steam outlet of the low-temperature distillation mechanism is connected to a steam purification and condensation mechanism. The qualified condensate outlet of the steam purification and condensation mechanism is connected to a clean water buffer tank. The unqualified condensate outlet of the steam purification and condensation mechanism is connected to the return liquid pretreatment mechanism. The outlet end of the clean water buffer tank is connected to a pressurized vaporization mechanism. The outlet end of the pressurized vaporization mechanism is connected to a high-pressure vaporization coil installed inside the high-temperature vaporization mechanism. The steam outlet of the high-pressure vaporization coil is connected to a steam injection mechanism.

[0007] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0008] In one alternative: the frame is a rectangular frame formed by welding steel profiles, and a fireproof partition is provided on the frame, which divides the frame into a combustion zone, a return liquid treatment zone, and a high-pressure steam injection zone. The gas inlet of the combustion heating mechanism is connected to a gas conditioning mechanism, which includes a gas-liquid separator, a coalescing filter, a desulfurization and pressure stabilizing tank, and a shut-off valve assembly connected in sequence along the gas flow direction.

[0009] In one alternative: the combustion heating mechanism includes a burner and a combustion chamber connected to the burner. The combustion chamber is a horizontal cylindrical shape, and the inner wall of the combustion chamber is provided with a fire-resistant and heat-insulating layer. The flue gas distribution box is connected to the end of the combustion chamber away from the burner. The shut-off valve group includes two quick-shut-off valves spaced apart along the gas flow direction, and a venting branch is provided between the two quick-shut-off valves.

[0010] In one alternative: the high-temperature vaporization mechanism includes a horizontally arranged high-temperature vaporization cylinder, with a flame-insulating guide cylinder coaxially arranged inside the high-temperature vaporization cylinder, and the high-pressure vaporization coil spirally surrounding the outside of the flame-insulating guide cylinder, with flue gas flow gaps left between the high-pressure vaporization coil and the flame-insulating guide cylinder, as well as between the high-pressure vaporization coil and the inner wall of the high-temperature vaporization cylinder.

[0011] In one alternative embodiment: the low-temperature distillation mechanism includes a vertically arranged distillation cylinder, an annular flue gas jacket coaxially sleeved on the outer side of the distillation cylinder, the lower part of the annular flue gas jacket communicating with a temperature-regulating mixing chamber, and an exhaust pipe connected to the upper part of the annular flue gas jacket. A spiral smoke guide plate extending around the outer wall of the distillation cylinder is provided inside the annular flue gas jacket. A liquid distribution ring is provided at the upper inner end of the distillation cylinder, with distribution holes spaced circumferentially towards the inner wall of the distillation cylinder on the distribution ring. A scraper shaft is provided axially inside the distillation cylinder, with multiple scraper supports spaced axially on the scraper shaft. Each scraper support has an elastic scraper blade at its outer end, the outer edge of which elastically fits against the inner wall of the distillation cylinder. A conical concentrate collection tank is provided at the bottom of the distillation cylinder, and the concentrate collection tank is connected to a concentrate storage tank via a concentrate discharge valve.

[0012] In one alternative: the backflow pretreatment mechanism includes a cyclone separator, a self-cleaning filter and a raw liquid buffer tank connected in sequence along the flow direction of the backflow liquid. The outlet end of the raw liquid buffer tank is connected to the distribution ring through a raw liquid circulation pump. The steam outlet at the top of the distillation cylinder is connected to a vacuum pipeline, and a vacuum pump is installed on the vacuum pipeline.

[0013] In one alternative embodiment: the steam purification and condensation mechanism includes a demister, a raw liquid preheating condenser, a condensate refiner, an online water quality detector, and a three-way switching valve connected sequentially along the direction of distilled steam flow. The raw liquid preheating condenser has a steam channel and a raw liquid channel that are isolated from each other. The steam channel is connected between the demister and the condensate refiner. The raw liquid channel is connected between the raw liquid buffer tank and the liquid distribution ring. The two outlets of the three-way switching valve are respectively connected to the purified water buffer tank and the raw liquid buffer tank.

[0014] In one alternative embodiment: the pressurized vaporization mechanism includes a high-pressure plunger pump and a high-pressure vapor-water separator. The inlet of the high-pressure plunger pump is connected to a purified water buffer tank, the outlet of the high-pressure plunger pump is connected to the inlet of the high-pressure vaporization coil, the outlet of the high-pressure vaporization coil is connected to the high-pressure vapor-water separator, the liquid phase outlet of the high-pressure vapor-water separator is connected to a pressure-reducing flash tank, and the discharge end of the pressure-reducing flash tank is connected to the purified water buffer tank.

[0015] In one alternative embodiment: the steam injection mechanism includes a steam injection manifold connected to the steam outlet of a high-pressure steam-water separator, the outlet of the steam injection manifold is connected to an insulated steam transmission pipe, a thermal expansion compensator and a steam injection valve assembly are sequentially arranged on the insulated steam transmission pipe along the steam flow direction, the end of the insulated steam transmission pipe is connected to a downhole insulated steam injection pipe extending into the coalbed methane well, and a thermal recovery packer located above the target coal seam is arranged on the outside of the downhole insulated steam injection pipe.

[0016] In one alternative: a flue gas return pipe is connected between the flue gas outlet of the low-temperature distillation mechanism and the temperature-controlled mixing box. An induced draft fan is installed on the flue gas return pipe. A detection instrument group and a control cabinet are installed on the frame. The detection instrument group includes a flow detector installed at the liquid inlet of the high-pressure vaporization coil, a pressure detector and a temperature detector installed at the outlet of the high-pressure vaporization coil, and a pressure detector and a liquid level detector installed on the distillation cylinder. The control cabinet is electrically connected to the detection instrument group, the flue gas distribution box, the high-pressure plunger pump, the three-way switching valve, and the induced draft fan.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention forms a closed-loop water quality control path through backflow pretreatment, low-temperature distillation, and condensate refining. Coal powder, proppant, inorganic salts, and residual additives in the backflow are separated before entering the high-pressure vaporization coil. Only qualified condensate enters the high-pressure vaporization coil, avoiding scaling, corrosion, and blockage caused by direct vaporization of salt-containing backflow in the high-temperature and high-pressure coil. The demister, condensate refiner, online water quality detector, and three-way switching valve further intercept salt-containing droplets and low-molecular-weight organic matter, reducing the risk of pollutants entering the target coal seam with steam, ensuring the safety of steam injection in old wells and reservoir permeability, while reducing the cost of coil cleaning and replacement maintenance.

[0019] 2. This invention utilizes combustion flue gas to provide a high-temperature heat source for high-pressure condensate by first passing it through a high-temperature vaporization mechanism, and then into a low-temperature distillation mechanism with an annular flue gas jacket. The combustion heat is utilized in stages according to the temperature levels required for high-pressure vaporization and vacuum distillation. The raw liquid preheating condenser preheats the return liquid to be treated with the condensation heat of distilled steam, recovers the latent heat of vaporization, and reduces the heat load of the burner. When the flow rate and calorific value of coalbed methane at the well site meet the requirements, the coalbed methane from new wells that have not yet entered the gathering and transportation network can be converted on-site into the heat required for return liquid treatment and old well heating, reducing the amount of return liquid transported and the treatment cost, improving the utilization rate of coalbed methane resources, and supplementing the thermal and pressure energy of decaying old wells, improving desorption and drainage conditions.

[0020] 3. This invention stores qualified condensate produced by continuous distillation in a purified water buffer tank, enabling continuous operation of low-temperature distillation of the return liquid. The bypass flue bypasses the high-temperature vaporization mechanism during periods when steam injection is stopped, ensuring that no simultaneous steam injection is required when only the return liquid is being treated. The multi-branch steam injection valve group also allows steam to be injected sequentially into different old wells to meet intermittent throughput requirements. The scraper shaft drives the elastic scraper to continuously update the liquid film on the inner wall of the distillation cylinder and scrape off the adhering substances. Combined with vacuum low-temperature distillation, this reduces the risk of rapid scaling and coking. The control cabinet implements interlocks for gas leaks, flameouts, coil water outages, over-temperature and over-pressure, and substandard water quality, ensuring the safety and reliability of the high-pressure steam injection and return liquid treatment process. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the steam injection manifold installation according to the present invention.

[0023] Figure 3 This is a schematic diagram of the upper part of the frame of the present invention.

[0024] Figure 4 This is a schematic diagram of the burner and combustion chamber installation of the present invention.

[0025] Figure 5 This is a schematic diagram of the installation of the thermal recovery packer of the present invention.

[0026] Figure 6 This is a schematic diagram of the installation of the original liquid circulation pump of the present invention.

[0027] Figure 7 This is a schematic diagram of the flame-insulating guide tube and high-pressure vaporization coil structure of the present invention.

[0028] Figure 8 This is a schematic diagram of the installation of the spiral smoke guide plate of the present invention.

[0029] Figure 9 This is a schematic diagram of the internal structure of the distillation cylinder of the present invention.

[0030] Figure 10 This is a schematic diagram of the system of the present invention.

[0031] Figure Labels and Annotations: 11 Frame, 12 Fireproof Baffle, 13 Gas-Liquid Separator, 14 Coalescing Filter, 15 Desulfurization and Pressure Stabilizing Tank, 16 Shut-off Valve Assembly, 17 Burner, 18 Combustion Chamber, 19 Flue Gas Distribution Box, 20 High-Temperature Vaporization Tube, 21 Flame Insulation Guide Tube, 22 High-Pressure Vaporization Coil, 23 Bypass Flue, 24 Temperature Control Mixing Box, 25 Distillation Tube, 26 Annular Flue Gas Jacket, 27 Spiral Smoke Guide Plate, 28 Cyclone Sand Desander, 29 Self-Cleaning Filter, 30 Raw Material Buffer Tank, 31 Raw Material Circulation Pump, 32 Liquid Distribution Ring, 33 Scraper Shaft, 34 Scraper Support, 35 Spring 36. Scraper blade, 37. Concentrate collection tank, 38. Concentrate discharge valve, 39. Concentrate storage tank, 40. Demister, 41. Raw material preheating condenser, 42. Vacuum pump, 43. Condensate refiner, 44. Online water quality detector, 45. Three-way switching valve, 46. Clean water buffer tank, 47. High-pressure plunger pump, 48. High-pressure steam-water separator, 49. Pressure-reducing flash tank, 50. Steam injection manifold, 51. Insulated steam pipe, 52. Thermal expansion compensator, 53. Steam injection valve assembly, 54. Downhole insulated steam injection pipe, 55. Thermal recovery packer, 56. Flue gas return pipe, 57. Exhaust stack, 58. Control cabinet. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Example 1

[0034] In one embodiment, such as Figures 1-10 As shown, a steam reinjection energy enhancement system for coalbed methane wells is installed on a frame 11. The frame 11 is a rectangular frame formed by welding steel sections. The bottom of the frame is provided with lifting holes and fixing seats that can be connected to transport vehicles or well site foundations. Fireproof partitions 12 are vertically installed on the frame 11, separating the gas combustion zone from the return fluid treatment zone and the high-pressure steam injection zone. The combustion zone is equipped with a gas conditioning mechanism and a combustion heating mechanism. The return fluid treatment zone is equipped with a return fluid pretreatment mechanism, a low-temperature distillation mechanism, and a steam purification and condensation mechanism. The high-pressure steam injection zone is equipped with a clean water buffer tank 45, a pressurization vaporization mechanism, and a steam injection mechanism.

[0035] The inlet of the gas conditioning unit is connected to the gas outlet of the newly commissioned coalbed methane well via a gas pipeline. The coalbed methane from the new well first enters the gas-liquid separator 13. The gas-liquid separator 13 is a vertical cylindrical tank with a liquid collection section and a liquid discharge port at the bottom. Free water and larger coal dust in the coalbed methane fall into the liquid collection section under the action of gravity and airflow deflection. The coalbed methane after gas-liquid separation enters the coalescence filter 14. The coalescence filter 14 removes fine droplets and particles. Subsequently, the coalbed methane enters the desulfurization and pressure stabilization tank 15. After pressure stabilization, the coalbed methane enters the burner 17 through the shut-off valve group 16.

[0036] The burner 17 is installed at one end of the combustion chamber 18, and the other end of the combustion chamber 18 is connected to the flue gas distribution box 19. The flue gas distribution box 19 is equipped with a heat-resistant regulating baffle. The regulating baffle changes the ratio of flue gas flow between the high-temperature vaporization mechanism and the bypass flue 23 through the actuator. When the high-pressure vaporization coil 22 in the high-temperature vaporization mechanism is in normal steam injection state, the flue gas mainly flows through the high-temperature vaporization mechanism. When only the return liquid is distilled and the old well is not injected with steam, the flue gas mainly enters the temperature regulating mixing box 24 through the bypass flue 23.

[0037] The flowback fluid enters the hydrocyclone desander 28 from the new well flowback fluid storage unit. Under the action of cyclone, it separates denser particles such as coal powder and proppant. Then it enters the self-cleaning filter 29 to remove the remaining suspended matter. The pretreated flowback fluid enters the closed raw liquid buffer tank 30. The raw liquid buffer tank 30 is not open. Its gas phase space is connected to the well site gas treatment unit through a safety pipeline.

[0038] When the system starts, the backflow liquid is first added to the raw liquid buffer tank 30, and the drive motors of the raw liquid circulation pump 31, the scraper shaft 33, the raw liquid preheating condenser 40, and the vacuum pump 41 are started. The raw liquid circulation pump 31 delivers the backflow liquid to the distribution ring 32. The backflow liquid flows downward along the inner wall of the distillation cylinder 25 through the distribution holes. The scraper shaft 33 drives multiple scraper supports 34 and elastic scrapers 35 to rotate. The elastic scrapers 35 spread the backflow liquid into a descending liquid film of relatively uniform thickness and scrape off the deposits on the cylinder wall.

[0039] The burner 17 operates at low load. The flue gas mainly enters the annular flue gas jacket 26 through the bypass flue 23 and the temperature regulating mixing box 24. Under the guidance of the spiral guide plate 27, the flue gas spirals upward around the outer wall of the distillation cylinder 25 and is discharged through the exhaust pipe 57. The return liquid evaporates under the action of negative pressure and wall heating. The unevaporated salt, coal powder, low volatile substances and some fracturing additives are concentrated to the bottom of the distillation cylinder 25.

[0040] The concentrate enters the concentrate collection tank 36. When the liquid level, conductivity, density or viscosity of the concentrate reaches the set discharge conditions, the concentrate discharge valve 37 opens, allowing the concentrate to flow into the concentrate storage tank 38. The concentrate discharge conditions are based on maintaining the concentrate's pumpability and fluidity, and the concentrate cannot be directly evaporated in the distillation cylinder 25.

[0041] The steam generated by the distillation cylinder 25 is discharged from the top and enters the demister 39. The demister 39 intercepts the salt droplets carried in the steam. After demistering, the steam enters the raw liquid preheating condenser 40. The distilled steam is condensed in the steam channel. The return liquid to be treated absorbs heat in the raw liquid channel. The condensate produced by condensation enters the condensate fine processor 42 to remove low molecular weight organic matter that may migrate with the steam.

[0042] When the condensate passes through the online water quality detector 43, the online water quality detector 43 detects the conductivity and organic matter index of the condensate. When the system is just started, the water quality index is unqualified, or the detector is abnormal, the control cabinet 58 controls the three-way switching valve 44 to guide the condensate back to the original liquid buffer tank 30. When the condensate water quality continuously meets the set conditions, the three-way switching valve 44 switches to allow qualified condensate to enter the purified water buffer tank 45.

[0043] Once the condensate stored in the water buffer tank 45 reaches the minimum water volume required for a single steam injection operation, the wellbore integrity test should be performed on the old well to be enhanced. The test should include at least the wellhead rated pressure, the remaining strength of the casing and tubing, the cementing quality, the temperature resistance of the packer, the target coal seam fracturing pressure, and the water-sensitive compatibility of the condensate and the coal sample. The steam injection pressure, temperature, and single-cycle steam injection volume cannot be determined directly without completing the above tests.

[0044] After confirming that the wellbore meets the steam injection conditions, the high-pressure plunger pump 46 is started. The high-pressure plunger pump 46 draws liquid condensate from the clean water buffer tank 45 and delivers the condensate to the high-pressure vaporization coil 22. When the detection instrument group detects that the liquid inlet flow rate of the high-pressure vaporization coil 22 has reached the minimum safe flow rate, the control cabinet 58 controls the flue gas distribution box 19 to gradually increase the amount of flue gas entering the high-temperature vaporization mechanism, while correspondingly reducing the amount of flue gas in the bypass flue 23.

[0045] After the high-temperature flue gas enters the high-temperature vaporization cylinder 20, it flows around the high-pressure vaporization coil 22 under the guidance of the flame-insulating guide tube 21. The high-pressure plunger pump 46 has already put the condensate into a high-pressure liquid state. The condensate absorbs heat in the high-pressure vaporization coil 22 and gradually forms a steam-water mixture. After the steam-water mixture enters the high-pressure steam-water separator 47, the steam enters the steam injection manifold 49 from the upper steam outlet, and the separated liquid enters the pressure-reducing flash tank 48 from the bottom and returns to the clean water buffer tank 45 after pressure reduction.

[0046] Steam sequentially enters the downhole insulated steam injection pipe 53 through the insulated steam transmission pipe 50, the thermal expansion compensator 51, and the steam injection valve group 52, and is then transported to the target coal seam through the downhole insulated steam injection pipe 53. The thermal recovery packer 54 is located above the target coal seam and is used to isolate the casing annulus. When the insulated steam transmission pipe 50 is heated and elongated, the thermal expansion compensator 51 absorbs the thermal displacement through axial deformation or bending deformation, thus avoiding the concentration of thermal stress on the wellhead flange.

[0047] During steam injection, the wellhead pressure must not exceed the lower of the formation allowable injection pressure and the rated pressure of the wellhead, casing, tubing, packer, and steam pipeline, and a safety margin should be reserved. When the cumulative steam injection volume, cumulative heat supply, or wellhead pressure reaches the set value, the control cabinet 58 reduces the load on the burner 17 and gradually switches the flue gas to the bypass flue 23. After the burner 17 is shut down, the high-pressure plunger pump 46 continues to maintain the cooling flow for a short time to reduce the pipe wall temperature of the high-pressure vaporization coil 22, and then stops the high-pressure plunger pump 46.

[0048] After steam injection is completed in the old well, the steam injection valve group 52 is closed and the well enters the simmering stage, so that the steam heat is transferred to the coal seam. After the simmering is completed, controlled drainage is carried out. After the condensate and formation water in the wellbore are discharged, gas production is resumed. At the same time, steam injection and gas production are not carried out continuously in the same old well, so as to reduce the risk of water lock caused by liquid water occupying the coal seam fractures for a long time.

[0049] Example 2

[0050] The system structure of this embodiment is basically the same as that of embodiment 1. The difference is that the steam injection manifold 49 is provided with multiple branch interfaces, each branch interface is provided with an independent steam injection valve group 52, at least one branch is connected to the selected injection well, and other old wells around the injection well are used as production wells.

[0051] The backflow liquid pretreatment unit, the low-temperature distillation unit, and the steam purification and condensation unit operate continuously. The qualified condensate produced is stored in the clean water buffer tank 45. According to the bottom pressure of different injection wells, coal seam connectivity, and steam injection plan, the corresponding branch steam injection valve group 52 is controlled to open, so that the steam generated by the pressurization and vaporization unit enters different injection wells in sequence.

[0052] When all injection wells stop steam injection but the return fluid still needs to be treated, the flue gas distribution box 19 closes or reduces the flue gas passage to the high-temperature vaporization mechanism and opens the bypass flue duct 23, so that the flue gas enters the annular flue gas jacket 26 through the temperature regulating mixing box 24. At this time, the low-temperature distillation mechanism continues to process the return fluid, and the qualified condensate produced is temporarily stored in the clean water buffer tank 45.

[0053] If the bypass flue gas temperature is higher than the allowable inlet temperature of the low-temperature distillation mechanism, the control cabinet 58 starts the induced draft fan 56, so that a portion of the low-temperature flue gas at the outlet of the annular flue gas jacket 26 returns to the temperature regulating mixing box 24 through the flue gas return pipe 55. After the return flue gas is mixed with the bypass flue gas, the flue gas temperature entering the annular flue gas jacket 26 is reduced, thus avoiding excessively high local wall temperature of the distillation cylinder 25.

[0054] The above embodiments disclose a steam reinjection energy enhancement system for coalbed methane wells. When the system is started, the return fluid circulation, scraping film drive, condensation and vacuum system are started first, and then the combustion heating mechanism is started. When a stable return fluid film and condensation conditions are not established, the burner 17 is not allowed to operate at high load.

[0055] When injecting steam, first start the high-pressure plunger pump 46 and confirm that there is a minimum safe flow in the high-pressure vaporization coil 22, then open the high-temperature flue gas passage. When stopping steam injection, first reduce the combustion load and switch the bypass flue 23, then maintain the cooling water flow of the high-pressure vaporization coil 22, and finally stop the high-pressure plunger pump 46.

[0056] Control cabinet 58 shall perform at least the following interlocks:

[0057] In case of gas leak, burner 17 flameout, or insufficient combustion air pressure, shut off shut-off valve group 16;

[0058] When the liquid inlet flow of the high-pressure vaporization coil 22 is insufficient, the high-temperature flue gas passage is closed and the bypass flue 23 is opened;

[0059] When the outlet pressure, outlet temperature, or pipe wall temperature of the high-pressure vaporization coil 22 exceeds the set value, the combustion load is reduced and pressure relief is performed.

[0060] If the vacuum level of the distillation cylinder 25 is insufficient, the liquid level is too high, or the scraper shaft 33 stops rotating, the feed of the backflow liquid should be stopped and the combustion load reduced.

[0061] When the online water quality detector 43 fails to meet the test or malfunctions, the three-way switching valve 44 is kept in the condensate reflux position.

[0062] When the wellhead pressure reaches the upper limit of steam injection, first reduce the flow rate of the high-pressure plunger pump 46, and then close the corresponding steam injection valve group 52.

[0063] When the water buffer tank 45 is at a low level, it is forbidden to start the high-pressure plunger pump 46 to avoid the high-pressure plunger pump 46 sucking in air and the high-pressure vaporization coil 22 cutting off the water supply.

[0064] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A steam reinjection power enhancement system for coalbed methane wells, comprising a frame (11) and a combustion heating mechanism, wherein the flue gas outlet of the combustion heating mechanism is connected to a flue gas distribution box (19), characterized in that, One side of the flue gas distribution box (19) is connected to a high-temperature vaporization mechanism, and the other side of the flue gas distribution box (19) is connected to a bypass flue (23) arranged in parallel with the high-temperature vaporization mechanism. The outlets of the high-temperature vaporization mechanism and the bypass flue (23) are connected to a temperature regulating mixing box (24). The flue gas outlet of the temperature-controlled mixing box (24) is connected to a low-temperature distillation mechanism, the liquid inlet of the low-temperature distillation mechanism is connected to a return liquid pretreatment mechanism, and the steam outlet of the low-temperature distillation mechanism is connected to a steam purification and condensation mechanism. The qualified condensate outlet of the steam purification and condensation mechanism is connected to a clean water buffer tank (45), and the unqualified condensate outlet of the steam purification and condensation mechanism is connected to a return liquid pretreatment mechanism. The outlet of the purified water buffer tank (45) is connected to a pressurized vaporization mechanism. The outlet of the pressurized vaporization mechanism is connected to a high-pressure vaporization coil (22) located inside the high-temperature vaporization mechanism. The steam outlet of the high-pressure vaporization coil (22) is connected to a steam injection mechanism.

2. The steam reinjection system for enhancing the energy supply of a coalbed methane well according to claim 1, characterized in that, The frame (11) is a rectangular frame formed by welding steel sections. A fireproof partition (12) is provided on the frame (11). The fireproof partition (12) divides the frame (11) into a combustion zone, a return liquid treatment zone and a high-pressure steam injection zone. The gas inlet of the combustion heating mechanism is connected to a gas conditioning mechanism. The gas conditioning mechanism includes a gas-liquid separator (13), a coalescing filter (14), a desulfurization pressure stabilizing tank (15) and a shut-off valve group (16) connected in sequence along the gas flow direction.

3. The steam reinjection system for enhancing the energy supply of a coalbed methane well according to claim 2, characterized in that, The combustion heating mechanism includes a burner (17) and a combustion chamber (18) connected to the burner (17). The combustion chamber (18) is a horizontal cylindrical shape. The inner wall of the combustion chamber (18) is provided with a fire-resistant insulation layer. The flue gas distribution box (19) is connected to the end of the combustion chamber (18) away from the burner (17). The shut-off valve group (16) includes two quick shut-off valves spaced apart along the gas flow direction. A venting branch is provided between the two quick shut-off valves.

4. The steam reinjection power enhancement system for coalbed methane wells according to claim 1, characterized in that, The high-temperature vaporization mechanism includes a horizontally arranged high-temperature vaporization cylinder (20), and a flame-insulating guide cylinder (21) is coaxially arranged inside the high-temperature vaporization cylinder (20). The high-pressure vaporization coil (22) is spirally wrapped around the outside of the flame-insulating guide cylinder (21). There are flue gas flow gaps between the high-pressure vaporization coil (22) and the flame-insulating guide cylinder (21) and between the high-pressure vaporization coil (22) and the inner wall of the high-temperature vaporization cylinder (20).

5. A steam reinjection system for enhancing the energy supply of a coalbed methane well according to claim 1, characterized in that, The low-temperature distillation mechanism includes a vertically arranged distillation cylinder (25). An annular flue gas jacket (26) is coaxially fitted on the outside of the distillation cylinder (25). The lower part of the annular flue gas jacket (26) is connected to a temperature-controlled mixing box (24). An exhaust pipe (57) is connected to the upper part of the annular flue gas jacket (26). A spiral guide plate (27) extending around the outer wall of the distillation cylinder (25) is provided inside the annular flue gas jacket (26). A liquid distribution ring (32) is provided at the upper end of the inside of the distillation cylinder (25). The liquid distribution ring (32) is provided with circumferentially spaced... The inner wall of the distillation cylinder (25) has a liquid distribution hole. The distillation cylinder (25) is provided with a scraper shaft (33) along its axial direction. Multiple scraper supports (34) are provided on the scraper shaft (33) along the axial direction. Each scraper support (34) is provided with an elastic scraper (35) at its outer end. The outer edge of the elastic scraper (35) is elastically attached to the inner wall of the distillation cylinder (25). The bottom of the distillation cylinder (25) is provided with a conical concentrate collection tank (36). The concentrate collection tank (36) is connected to the concentrate storage tank (38) through a concentrate discharge valve (37).

6. A steam reinjection power enhancement system for coalbed methane wells according to claim 5, characterized in that, The backflow pretreatment mechanism includes a cyclone separator (28), a self-cleaning filter (29), and a raw liquid buffer tank (30) connected in sequence along the backflow flow direction. The outlet of the raw liquid buffer tank (30) is connected to the distribution ring (32) through the raw liquid circulation pump (31). The steam outlet at the top of the distillation cylinder (25) is connected to a vacuum pipeline, and a vacuum pump (41) is installed on the vacuum pipeline.

7. A steam reinjection power enhancement system for coalbed methane wells according to claim 6, characterized in that, The steam purification and condensation mechanism includes a demister (39), a raw liquid preheating condenser (40), a condensate refiner (42), an online water quality detector (43), and a three-way switching valve (44) connected sequentially along the direction of distilled steam flow. The raw liquid preheating condenser (40) has a steam channel and a raw liquid channel that are isolated from each other. The steam channel is connected between the demister (39) and the condensate refiner (42). The raw liquid channel is connected between the raw liquid buffer tank (30) and the liquid distribution ring (32). The two outlets of the three-way switching valve (44) are connected to the purified water buffer tank (45) and the raw liquid buffer tank (30), respectively.

8. A steam reinjection power enhancement system for coalbed methane wells according to claim 7, characterized in that, The pressurized vaporization mechanism includes a high-pressure plunger pump (46) and a high-pressure vapor-water separator (47). The inlet of the high-pressure plunger pump (46) is connected to the purified water buffer tank (45), the outlet of the high-pressure plunger pump (46) is connected to the inlet of the high-pressure vaporization coil (22), the outlet of the high-pressure vaporization coil (22) is connected to the high-pressure vapor-water separator (47), the liquid phase outlet of the high-pressure vapor-water separator (47) is connected to a pressure-reducing flash tank (48), and the outlet of the pressure-reducing flash tank (48) is connected to the purified water buffer tank (45).

9. A steam reinjection power enhancement system for coalbed methane wells according to claim 8, characterized in that, The steam injection mechanism includes a steam injection manifold (49) connected to the steam outlet of a high-pressure steam-water separator (47). The outlet of the steam injection manifold (49) is connected to an insulated steam transmission pipe (50). A thermal expansion compensator (51) and a steam injection valve group (52) are sequentially arranged on the insulated steam transmission pipe (50) along the steam flow direction. The end of the insulated steam transmission pipe (50) is connected to a downhole insulated steam injection pipe (53) extending into the coalbed methane well. A thermal recovery packer (54) located above the target coal seam is arranged on the outside of the downhole insulated steam injection pipe (53).

10. A steam reinjection power enhancement system for coalbed methane wells according to claim 9, characterized in that, A flue gas return pipe (55) is connected between the flue gas outlet of the low-temperature distillation mechanism and the temperature-controlled mixing box (24). An induced draft fan (56) is installed on the flue gas return pipe (55). A detection instrument group and a control cabinet (58) are installed on the frame (11). The detection instrument group includes a flow detector installed at the liquid inlet of the high-pressure vaporization coil (22), a pressure detector and a temperature detector installed at the outlet of the high-pressure vaporization coil (22), and a pressure detector and a liquid level detector installed on the distillation cylinder (25). The control cabinet (58) is electrically connected to the detection instrument group, the flue gas distribution box (19), the high-pressure plunger pump (46), the three-way switching valve (44), and the induced draft fan (56).

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