A groundwater recharge system and method suitable for alpine permafrost regions

Abstract

The application discloses a kind of underground water recharge systems and methods suitable for high-cold permafrost regions, relate to underground water recharge technical field, the system includes: underground water recharge well system and gas collection exhaust system;Gas collection exhaust system includes: vertical well;Underground water recharge well system includes: recharge well;Recharge well penetrates permafrost layer into unsaturated layer and aquifer;The bottom of vertical well communicates with unsaturated layer and penetrates permafrost layer, seasonally frozen ground layer to the ground upwards.The application can make air in unsaturated layer quickly exhaust along with underground water recharge process by setting underground water recharge well system and gas collection exhaust system, significantly improve the recharge efficiency of underground water, fundamentally solve the recharge difficulty, recharge efficiency attenuation problem.

Description

Technical Field

[0001] This invention relates to the field of groundwater recharge technology, specifically to a groundwater recharge system and method suitable for high-altitude permafrost regions. Background Technology

[0002] Groundwater recharge is one of the important methods for groundwater remediation. In high-altitude permafrost regions, groundwater is extracted for domestic and industrial use, but over-extraction leads to a continuous decline in the groundwater level, forming a drawdown cone and inducing geological disasters such as land subsidence. Well-injection recharge is necessary to quickly restore the groundwater level and reserves, achieving sustainable utilization of regional groundwater resources. However, when extracting groundwater from aquifers below the permafrost layer, the groundwater level continues to drop below the permafrost floor, forming an unsaturated layer of a certain thickness below the permafrost and above the aquifer. As water is injected into the aquifer, the groundwater level rises, and the sealing effect of the permafrost compresses the air in the unsaturated zone. With continued recharge, the pressure of the unsaturated air increases, making it increasingly difficult for recharged water to enter the aquifer, or requiring greater pressure to force the water in, thus slowing down the injection efficiency. The traditional method involves pressurizing the injection well to replenish groundwater and overcome the resistance created by compressed air in the unsaturated layer. However, this method suffers from significant energy loss, high cost, and low efficiency. Furthermore, excessive injection pressure can lead to wellbore damage and alterations in aquifer structure. Summary of the Invention

[0003] This invention provides a groundwater recharge system and method suitable for high-altitude permafrost regions, which solves the problem that the rise in unsaturated gas phase pressure during groundwater recharge in high-altitude permafrost regions creates a backing effect, leading to reduced groundwater recharge efficiency and excessive energy loss.

[0004] This invention provides a groundwater recharge system suitable for high-altitude permafrost regions, comprising: a groundwater recharge well system and a gas collection and exhaust system; the gas collection and exhaust system comprises: a vertical well; the groundwater recharge well system comprises: a recharge well; The recharge well penetrates the seasonally frozen soil layer and the permanent frozen soil layer from the surface to enter the unsaturated layer and the aquifer. The bottom of the vertical well is connected to the unsaturated layer and extends upward through the permafrost layer and seasonal permafrost layer to the surface.

[0005] Optionally, the distance between the vertical well and the recharge well is the radius R of influence of the unsaturated reticulum pressure rise caused by the recharged groundwater within the designed recharge time. 设计 30%-40%; Where: R 设计The radius of influence of groundwater recharge during the design recharge period causing an increase in unsaturated layer gas pressure; t 设计 For the recharge design time; k a P0 is the effective gas permeability; P0 is the gas pressure in the unsaturated layer at the start of reinjection, μ a The viscosity of the gas in the unsaturated layer is denoted by ρ; the porosity of the unsaturated layer is denoted by ρ; the thickness of the unsaturated layer at the start of reinjection is denoted by H0; the reinjection flow rate of the reinjection well is denoted by Q; and the flow rate of P is denoted by P. a This is the minimum detectable pressure when the groundwater level rises during reinjection, causing the gas in the unsaturated layer to increase.

[0006] Optionally, the gas collection and exhaust system further includes: a horizontal well; the horizontal well is located in the unsaturated layer, communicates with the lower end of the vertical well, and is arranged horizontally from the lower end of the vertical well toward the reinjection well.

[0007] Optionally, the gas collection and exhaust system includes two sets of vertical wells and two sets of horizontal wells; each set of vertical wells and horizontal wells forms a right angle; the two sets of vertical wells and horizontal wells are respectively at right angles. Shape and right angle The symmetrical distribution is located on both sides of the recharge well.

[0008] Optionally, the gas collection and exhaust system further includes: a permafrost heating and melting device and a micro-negative pressure control device; The permafrost heating and melting device is used to control the temperature inside the vertical well. The micro-negative pressure control device is used to control the negative pressure inside the vertical well.

[0009] Optionally, the permafrost heating and melting device includes: a self-regulating electric mixing cable, a solar panel, and a temperature sensor; the self-regulating electric mixing cable is installed at the bottom of the vertical well; the solar panel is installed on the ground surface and connected to the self-regulating electric mixing cable by wires to provide power; the temperature sensor is installed in the pipe section above the vertical well; when the temperature measured by the temperature sensor is lower than a first temperature, the permafrost heating and melting device starts heating. The micro-negative pressure control device includes a vacuum pump and a pressure sensor. The vacuum pump is installed at the top of the vertical well, and the pressure sensor is installed at the bottom of the vertical well.

[0010] Optionally, the pressure sensor includes a first pressure sensor and a second pressure sensor, wherein the first pressure sensor is installed at the bottom of the vertical well and the second pressure sensor is installed at the end of the horizontal well and away from the vertical well.

[0011] Optionally, the vertical well is provided with a double-layer pipe, which includes an outer pipe and an inner pipe; an insulation layer is provided between the inner pipe and the outer pipe. The horizontal well is located at the top of the unsaturated layer, and its length does not exceed the distance between the vertical well and the reinjection well. It is made of porous material. The horizontal well has a double-layer pipe, with a filter layer filling between the outer pipe and the inner pipe. Both the outer pipe and the inner pipe are water filter pipes. The outer pipe is wrapped with a filter screen.

[0012] Optionally, the groundwater recharge well system may also include a pressurization device and a pressure sensor; The portion of the recharge well from the surface to the lower boundary of the permafrost layer is a solid pipe, while the portion from the lower boundary of the permafrost layer to the aquifer is a filter pipe.

[0013] The present invention also provides a groundwater recharge method suitable for high-altitude permafrost regions, comprising: applying the groundwater recharge system suitable for high-altitude permafrost regions; The method includes: reinjecting groundwater into the aquifer through a groundwater reinjection well system, and expelling air from the unsaturated layer through a gas collection and exhaust system during the groundwater reinjection process.

[0014] The beneficial effects of the present invention are as follows: The present invention provides a groundwater recharge system and method suitable for high-altitude permafrost regions. By setting up a groundwater recharge well system and an air collection and exhaust system, air in the unsaturated layer can be quickly discharged during the groundwater recharge process, which significantly improves the groundwater recharge efficiency and fundamentally solves the problems of difficult recharge and reduced recharge efficiency mentioned above. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a groundwater recharge system suitable for high-altitude permafrost regions, provided in Embodiment 2 of the present invention.

[0016] Figure 2 This is a schematic diagram of the exhaust gas collection system of a groundwater recharge system suitable for high-altitude permafrost regions, provided in Embodiment 2 of the present invention.

[0017] Figure label: 1-Recharge well, 2-Vertical well, 3-Seasonally frozen soil layer, 4-Permafrost layer, 5-Unsaturated layer, 6-Aquifer, 7-Gas movement direction, 8-Recharge water movement direction, 9-Micro negative pressure control device, 10-Upper boundary of permafrost layer, 11-Lower boundary of permafrost layer, 12-Aquifer water level line, 13-Horizontal well, 14-Well cap, 15-Wellhead gas seal device, 16-Temperature sensor, 17-Vertical well inner pipe, 18-Insulation layer, 19-Self-regulating heating cable, 20-Vertical well outer pipe, 21-First gas pressure sensor, 22-Horizontal well pores, 23-Horizontal well outer pipe, 24-Horizontal well inner pipe, 25-Filter layer, 26-Second pressure sensor. Detailed Implementation

[0018] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Example 1

[0019] This embodiment provides a groundwater recharge system and method suitable for high-altitude permafrost regions, including: a groundwater recharge well system and a gas collection and venting system; the gas collection and venting system includes: a vertical well; the groundwater recharge well system includes: a recharge well; Recharge wells penetrate from the surface through the seasonally frozen soil layer and the permanent frozen soil layer to enter the unsaturated layer and aquifer; The bottom of the vertical well is connected to the unsaturated layer and extends upwards through the permafrost layer and seasonal permafrost layer to the surface.

[0020] Preferably, the distance between the vertical well and the recharge well is the radius R of influence of the unsaturated layer gas pressure rise caused by the recharged groundwater within the designed recharge time. 设计 30%-40%; Where: R 设计 The radius of influence of groundwater recharge during the design recharge period causing an increase in unsaturated layer gas pressure; t 设计 For the recharge design time; k a P0 is the effective gas permeability; P0 is the gas pressure in the unsaturated layer at the start of reinjection, μ a The viscosity of the gas in the unsaturated layer is denoted by ρ; the porosity of the unsaturated layer is denoted by ρ; the thickness of the unsaturated layer at the start of reinjection is denoted by H0; the reinjection flow rate of the reinjection well is denoted by Q; and the flow rate of P is denoted by P. a This is the minimum detectable pressure when the groundwater level rises during reinjection, causing the gas in the unsaturated layer to increase.

[0021] During reinjection, when the groundwater level rises and causes the gas level in the unsaturated layer to increase, the limit of gas fluctuation amplitude that existing mature sensors suitable for field gas pressure can effectively monitor is generally 100 Pa, i.e., P. a A value of 100 Pa is typically used. That is, when the increase in gas pressure in the unsaturated layer is less than 100 Pa, existing mature gas pressure sensors that can be used for field monitoring cannot effectively detect it. Therefore, it can be considered that when the increase in gas pressure in the unsaturated layer is less than 100 Pa, the rise in groundwater level has no effect on gas pressure.

[0022] Preferably, the gas gathering and exhaust system further includes: a horizontal well; the horizontal well is located in the unsaturated layer, communicates with the lower end of the vertical well, and is arranged horizontally from the lower end of the vertical well toward the reinjection well.

[0023] Preferably, the gas collection and exhaust system includes two sets of vertical wells and two sets of horizontal wells; each set of vertical wells and horizontal wells forms a right angle; the two sets of vertical wells and horizontal wells are respectively at right angles. Shape and right angle The symmetrical distribution is located on both sides of the recharge well.

[0024] Preferably, the gas collection and exhaust system further includes: a permafrost heating and melting device and a micro-negative pressure control device; The permafrost heating and melting device is used to control the temperature inside vertical wells; The micro-negative pressure control device is used to control the negative pressure inside a vertical well.

[0025] Preferably, the permafrost heating and melting device includes: a self-regulating electric mixing cable, a solar panel, and a temperature sensor; the self-regulating electric mixing cable is installed at the bottom of the vertical well; the solar panel is installed on the ground surface and connected to the self-regulating electric mixing cable by wires to provide power; the temperature sensor is installed in the pipe section above the vertical well; when the temperature measured by the temperature sensor is lower than a first temperature, the permafrost heating and melting device starts heating. The micro-negative pressure control device includes a vacuum pump and a pressure sensor. The vacuum pump is installed at the top of the vertical well, and the pressure sensor is installed at the bottom of the vertical well.

[0026] Preferably, the pressure sensor includes a first pressure sensor and a second pressure sensor, wherein the first pressure sensor is installed at the bottom of the vertical well and the second pressure sensor is installed at the end of the horizontal well and away from the vertical well.

[0027] Preferably, the vertical well is provided with a double-layer pipe, which includes an outer pipe and an inner pipe; an insulation layer is provided between the inner pipe and the outer pipe. The horizontal well is located at the top of the unsaturated layer, and its length does not exceed the distance between the vertical well and the reinjection well. It is made of porous material. The horizontal well has a double-layer pipe. The outer pipe and the inner pipe of the horizontal well are filled with a filter layer. Both the outer pipe and the inner pipe of the horizontal well are water filter pipes. The outer pipe of the horizontal well is wrapped with a filter screen.

[0028] Preferably, the groundwater recharge well system also includes a pressurization device and a pressure sensor; The portion of the recharge well from the surface to the lower boundary of the permafrost layer is a solid pipe, while the portion from the lower boundary of the permafrost layer to the aquifer is a filter pipe.

[0029] This embodiment provides a groundwater recharge system and method suitable for high-altitude permafrost regions, applied to the aforementioned groundwater recharge system suitable for high-altitude permafrost regions; the method includes: recharging groundwater into the aquifer through a groundwater recharge well system, and discharging air from the unsaturated layer through an air collection and exhaust system during the groundwater recharge process.

[0030] This embodiment provides a groundwater recharge system and method suitable for high-altitude permafrost regions. By setting up a groundwater recharge well system and an air collection and exhaust system, air in the unsaturated layer can be quickly discharged during the groundwater recharge process, significantly improving the groundwater recharge efficiency and fundamentally solving the problems of difficult recharge and reduced recharge efficiency mentioned above. Example 2

[0031] This embodiment provides a groundwater recharge system suitable for high-altitude permafrost regions, such as... Figure 1 and Figure 2 As shown, it includes a groundwater recharge well system and a gas collection and exhaust system; The groundwater recharge system includes a recharge well 1; it may also include a pressurization device and a pressure sensor. The recharge well 1 penetrates the seasonally frozen soil layer 3 from the surface, penetrates the permafrost layer 4 (from the upper boundary 10 of the permafrost layer to the lower boundary 11 of the permafrost layer), and enters the unsaturated layer 5 and the aquifer 6. The pressurization device can be a pressurized water pump capable of providing a pressure of 1 standard atmosphere to improve water injection efficiency. The recharge well 1 has a diameter of 500-600 mm and is made of PPR (Polypropylene-Random). The portion of the well wall from the surface to the lower boundary 11 of the permafrost layer is a solid pipe; the portion from the lower boundary 11 of the permafrost layer to a certain depth (not less than 2 m) of the aquifer 6 is a filter pipe with a pore size of 10 mm and a porosity of not less than 20%. The recharge well 1 injects water from the surface into the aquifer under gravity or pressurization conditions, and the direction of water movement is as follows: Figure 1 As shown in label 8.

[0032] The gas collection and exhaust system includes: a vertical well 2, a horizontal well 13, a permafrost heating and melting device, and a micro-negative pressure control device 9. The bottom of the vertical well 2 is connected to the horizontal end of the horizontal well 13, and extends upwards through the permafrost layer 4 and the seasonally frozen layer 3 to the surface. The horizontal well 13 is located below the lower boundary 11 of the permafrost layer, specifically at the top of the unsaturated layer 5, facilitating gas escape from the unsaturated layer 5. Gas from the unsaturated layer 5 can freely enter the vertical well 2 from the horizontal gas collection well 13.

[0033] Specifically, the radius R of influence of groundwater recharge in recharge well 1 causing an increase in unsaturated layer gas pressure is... 设计 Within the designated area, two sets of vertical wells 2 and two sets of horizontal wells 13 are installed, with the two sets of vertical wells 2 and the two sets of horizontal wells 13 forming right angles. Shape and right angle The vertical well 2 is symmetrically distributed on both sides of the recharge well 1, and the distance between the vertical well 2 and the recharge well 1 is the radius R of the influence of the recharged groundwater causing the unsaturated layer gas pressure to rise. 设计 30%-40% of this amount allows for rapid release of air pressure generated in the unsaturated layer during water injection. Formula (1): R 设计 The radius of influence of groundwater recharge during the design recharge period causing an increase in unsaturated layer gas pressure; t 设计 For the recharge design time; k a P0 is the effective gas permeability, and P0 is the gas pressure in the unsaturated layer at the start of reinjection, which is equal to the atmospheric pressure at the surface of the reinjection well; μ a Where is the viscosity of the gas in the unsaturated layer; n is the porosity of the unsaturated layer; H0 is the thickness of the unsaturated layer at the start of reinjection; Q is the reinjection flow rate of the reinjection well; and P... a When groundwater levels rise during reinjection, causing gas levels to rise in the unsaturated layer, the limit of gas fluctuation amplitude that existing mature sensors suitable for field gas pressure monitoring can effectively monitor is generally taken as 100 Pa. That is, when the gas pressure rise in the unsaturated layer is less than 100 Pa, existing mature gas pressure sensors suitable for field monitoring cannot effectively monitor it, and it is considered that the rise in groundwater level has no effect on gas pressure.

[0034] Specifically, each set of horizontal wells 13 and vertical wells 2 constitutes a right-angled gas collection-exhaust well. The horizontal wells 13 and vertical wells 2 are connected by flanges. The horizontal wells 13 are arranged horizontally from the lower end of the vertical wells 2 towards the reinjection well 1. The two sets of horizontal wells 13 and the two sets of vertical wells 2 form a right angle symmetrical about the reinjection well 1. Shape and right angle Two sets of gas collection and exhaust wells of the type.

[0035] Vertical well 2 primarily vents air from the unsaturated layer 5 to the surface, reducing the gas pressure in the unsaturated layer and providing favorable conditions for water injection into reinjection well 1. The walls of vertical well 2 are made of stainless steel, with a diameter of 15-20 cm. It features double-layered inner and outer pipes: an inner vertical well pipe 17 and an outer vertical well pipe 20. An insulation layer 18 is installed between the inner and outer pipes, working in conjunction with a permafrost heating and melting device to prevent freezing and ensure efficient venting.

[0036] Horizontal well 13 primarily serves as a gas collection point. It has a diameter of 20cm and a length of 20-50m, not exceeding the distance between vertical well 2 and reinjection well 1. Horizontal well 13 is made of porous stainless steel with 1mm pores. Circular well holes are located throughout the well wall to facilitate gas collection.

[0037] Specifically, the horizontal well 13 includes an outer pipe 23 and an inner pipe 24. The outer pipe 23 is wrapped with a 20-mesh stainless steel filter to prevent particles from the unsaturated layer from entering. A filter layer 25 is filled between the outer pipe 23 and the inner pipe 24 to prevent fine particles from being carried into the horizontal well 13 when gas escapes from the unsaturated layer 5. The horizontal well 13 has horizontal well pores 22. Both the outer pipe 23 and the inner pipe 24 are water filter pipes with a porosity of not less than 25%. A second pressure sensor 26 is installed at the end of the horizontal well 13, at the position furthest from the vertical well 2, to monitor the dynamic changes in pressure within the horizontal well 13.

[0038] When groundwater is replenished into aquifer 6 through reinjection well 1, the water level 12 of aquifer 6 continuously rises, driving out or compressing the gas in unsaturated layer 5. This causes the gas in unsaturated layer 5 to enter horizontal well 13. The compressed air can escape through the permeable porous horizontal well 13 and be discharged from exhaust well 2 (the gas movement direction is as follows). Figure 1 As shown in marker 7, this maintains a low gas pressure in the unsaturated layer 5, reducing or eliminating the supporting effect of gas in the unsaturated layer and significantly improving groundwater recharge efficiency. This solves the problem of increased air pressure in the unsaturated layer formed by water injection inhibiting recharge water from entering the aquifer.

[0039] The permafrost heating and melting device includes a self-regulating electric heating tape 19, a solar panel, and a temperature sensor 16. It is used to prevent the vertical well from accumulating ice on the inner wall and blocking the exhaust gas during long-term operation. When high-moisture-content gas escapes from the unsaturated layer 5 from the vertical well 2, its temperature drops as it passes through the lower-temperature permafrost layer 4, even reaching freezing point, and gradually icing onto the inner wall of the well. A self-regulating electric heating tape 19 can be installed within a certain range at the bottom of the vertical well 2 (from the bottom of the permafrost layer 4 to the surface, with a length not exceeding 20% ​​of the permafrost layer). This range heats the gas escaping from the unsaturated layer, ensuring that the temperature of the gas escaping from the vertical well is above 0°C but does not exceed 6°C (the temperature of the gas at the surface outlet of the vertical well). The self-regulating electric mixing cable 19 is installed at the bottom of the vertical well in a built-in manner; the solar panel is installed on the ground surface and is connected to the self-regulating electric mixing cable 19 by wires to provide power; the temperature sensor 16 is installed in the upper pipe section of the vertical well 2. When the measured temperature is lower than the first temperature of 0℃, the permafrost layer heating and melting device is automatically activated to heat and maintain the temperature inside the well and avoid blockage and freezing problems.

[0040] The micro-negative pressure control device 9 includes a vacuum pump, a power supply, and a pressure sensor. The vacuum pump, installed at the top of the vertical well 2, creates a negative pressure (-20 to -50 hPa) within the vertical well 2, forming a large airflow gradient between the vertical well 2 and the unsaturated layer 5. This accelerates the flow of gas from the unsaturated layer to the vertical well 2, causing air to be extracted from the unsaturated layer 5. This reduces the pressure exerted by the unsaturated layer air on the reinjected groundwater, improving reinjection efficiency. Simultaneously, a first pressure sensor 21 is installed at the bottom of the vertical well 2. The first pressure sensor 21 and a second pressure sensor 26 dynamically monitor the pressure changes in the vertical well 2 and the horizontal well 13, respectively. When the relative pressure value of the second pressure sensor 26 is greater than 30 hPa (when the relative pressure value in the unsaturated layer is less than 30 hPa, the pressure exerted by the gas on the reinjection efficiency can be considered limited and negligible), the vacuum pump is automatically activated to dynamically assess the operating status of the exhaust and gas collection system.

[0041] like Figure 2 As shown, a permafrost heating and melting device is installed inside the permafrost layer 4 section of the vertical well 2, increasing the escape channel for gas from the unsaturated layer. A wellhead airtight device 15 is installed at the top of the vertical well 2, with a well cap 14 on top of the well cap 15. A micro-negative pressure control device 9 is installed on the well cap 14 to keep the horizontal well 13 and the vertical well 2 in a low-pressure or micro-negative-pressure state, further enhancing the escape efficiency of the compressed air in the unsaturated layer. This is used to reduce the gas phase pressure in the unsaturated layer due to the recharge of cold groundwater, and reduce the energy required for water injection in the groundwater recharge well. The micro-negative pressure control device 9, the wellhead airtight device 15, the temperature sensor 16, and the first air pressure sensor 21 are installed in the inner pipe 17 of the vertical well to ensure that a certain negative pressure value is maintained in the vertical well 2 and the horizontal well 13. The micro-negative pressure control device 9 is activated by monitoring the second air pressure sensor 26 to adjust its pumping power to adapt to the gas pressure release requirements in the unsaturated layer 5 under different conditions. The vertical well inner pipe 17 of the vertical well exhaust well 2 and the horizontal well inner pipe 24 of the horizontal well 13 serve as the gas pressure collection and transportation channels for the unsaturated layer 5. In conjunction with the micro-negative pressure control device 9, they collect and discharge the pressurized gas generated in the unsaturated layer 5 due to the recharge of the aquifer 6 by the groundwater recharge well 2. To ensure the efficient operation of the exhaust gas collection system, the permafrost heating and melting device, and the micro-negative pressure control device 9, no circular wellbore is installed inside the vertical inner pipe 17 of the vertical well 2. An insulation layer 18 and a permafrost heating and melting device are installed between the inner and outer walls of the vertical well 2. This solves the problem of high water content gas in the unsaturated layer freezing and blocking the pipes on the inner wall of the vertical well 2 when passing through the permafrost layer during long-term exhaust.

[0042] The working principle of this invention is to recharge groundwater in high-altitude permafrost regions to restore aquifer groundwater and its reserves. Water is injected into the aquifer through recharge wells, while two vertical wells are symmetrically positioned within the radius of influence of these wells. These vertical wells discharge compressed gas from the unsaturated layer above the aquifer caused by water injection and the resulting rise in groundwater level. This lowers the gas pressure in the unsaturated layer, reducing its upward pressure on the aquifer level and facilitating the recharge water's entry into the aquifer. Simultaneously, to increase the energy released by the vertical wells from the unsaturated layer, horizontal wells are installed at their bottom, at the bottom interface of the permafrost layer, allowing more gas to migrate to the vertical wells more quickly. Furthermore, a micro-negative pressure control device is installed at the wellhead of each vertical well. By pumping air, the gas pressure in both the vertical and horizontal wells is kept low or slightly negative, significantly improving the efficiency of water entering the aquifer from the recharge wells. In addition, to prevent the high water content gas in the unsaturated layer from freezing on the inner wall and blocking the vertical exhaust well when passing through the low-temperature permafrost layer in the vertical well during long-term operation, a permafrost heating and melting device is installed at the bottom of the vertical well through the permafrost layer to heat the gas escaping from the unsaturated layer and keep its temperature not lower than 4°C so that it does not freeze.

[0043] In high-altitude permafrost regions, the use of traditional groundwater recharge wells for groundwater replenishment results in several issues. First, the air in the unsaturated zone beneath the permafrost layer is compressed, and the high-pressure gas exerts a back pressure on the recharged water, making it difficult for the water to penetrate the aquifer and leading to a gradual decrease in recharge efficiency. By installing a groundwater recharge well system and an air collection and degassing system, air in the unsaturated zone can be rapidly expelled during the recharge process, significantly improving groundwater recharge efficiency and fundamentally solving the aforementioned problems of difficult recharge and declining recharge efficiency.

[0044] The innovation of this invention is also reflected in the spatial positioning of horizontal and vertical wells. Firstly, vertical wells should be positioned within the radius R of the influence of groundwater recharge during the designed recharge time, which causes an increase in unsaturated layer gas pressure. 设计 (Calculated by formula (1)) 30% to 40%, its exhaust efficiency is high when the number of vertical wells is limited. Second, the horizontal wells should be set at the top of the unsaturated layer, that is, the boundary between the unsaturated layer and the permafrost layer, which is conducive to the rapid discharge of compressed gas. Third, the gas collection and exhaust system formed by the horizontal wells and the vertical wells is symmetrically distributed with the reinjection well as the center, so that the compressed gas in the unsaturated layer can be quickly dissipated from the gas collection and exhaust system on both sides.

[0045] In addition, the present invention sets up a micro-negative pressure control device in the vertical well to actively extract gas from the unsaturated layer and keep it in a low-pressure or micro-negative pressure state, which greatly eliminates the problem of difficult reinjection water due to the increase in gas pressure in the unsaturated layer caused by water injection. Furthermore, a permafrost heating and melting device is added to the vertical well to greatly avoid the freezing and blockage problem faced by the exhaust in high-altitude permafrost areas.

[0046] This invention patent can significantly improve reinjection efficiency and greatly save energy consumption. When no gas collection and exhaust well system is installed in the unsaturated layer, during groundwater reinjection, the gas phase resistance in the unsaturated layer increases with the rise of the groundwater level. If external pressurization is implemented to reinject groundwater to overcome the supporting effect of gas in the unsaturated layer, the energy consumed will gradually increase.

[0047] The gas collection and exhaust system is used to improve the efficiency of groundwater recharge wells, and can be characterized by formula (2): In the formula: To improve the water injection efficiency of groundwater recharge wells for gas collection and exhaust systems; The unit for setting the water injection flow rate after the gas collection and exhaust system is m³. 3 / s; The water injection flow rate is expressed in meters (m³) when no air collection and exhaust system is installed. 3 / s; The pressure required for water injection when no gas collection and exhaust system is designed, in kPa; Atmospheric pressure, unit: kPa; The pressure required for water injection after designing the gas collection and exhaust system, in kPa.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention 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 the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A groundwater recharge system suitable for high-altitude permafrost regions, characterized in that, include: Groundwater recharge well system and gas collection and exhaust system; The gas collection and exhaust system includes a vertical well; the groundwater recharge system includes a recharge well. The recharge well penetrates the seasonally frozen soil layer and the permanent frozen soil layer from the surface to enter the unsaturated layer and the aquifer. The bottom of the vertical well is connected to the unsaturated layer and extends upward through the permafrost layer and seasonal permafrost layer to the surface.

2. The groundwater recharge system for high-altitude permafrost regions according to claim 1, characterized in that, The distance between the vertical well and the recharge well is the radius R of the influence of the recharged groundwater causing an increase in unsaturated geogas pressure during the designed recharge period. 设计 30%-40%; Where: R 设计 The radius of influence of groundwater recharge during the design recharge period causing an increase in unsaturated layer gas pressure; t 设计 For the reinjection design time; k a P0 is the effective gas permeability; P0 is the gas pressure in the unsaturated layer at the start of reinjection, μ a The viscosity of the gas in the unsaturated layer is denoted by ρ; the porosity of the unsaturated layer is denoted by η; the thickness of the unsaturated layer at the start of reinjection is denoted by H0; the reinjection flow rate of the reinjection well is denoted by Q; and the flow rate of P is denoted by ρ. a This is the minimum detectable pressure when the groundwater level rises during reinjection, causing the gas in the unsaturated layer to increase.

3. The groundwater recharge system for high-altitude permafrost regions according to claim 1, characterized in that, The gas collection and exhaust system further includes a horizontal well; the horizontal well is located in the unsaturated layer, communicates with the lower end of the vertical well, and is arranged horizontally from the lower end of the vertical well toward the reinjection well.

4. The groundwater recharge system for high-altitude permafrost regions according to claim 3, characterized in that, The gas collection and exhaust system includes two sets of vertical wells and two sets of horizontal wells; each set of vertical wells and horizontal wells forms a right angle; the two sets of vertical wells and horizontal wells are respectively at right angles. Shape and right angle The symmetrical distribution is located on both sides of the recharge well.

5. The groundwater recharge system for high-altitude permafrost regions according to claim 1, characterized in that, The gas collection and exhaust system also includes: a permafrost layer heating and melting device and a micro-negative pressure control device; The permafrost heating and melting device is used to control the temperature inside the vertical well. The micro-negative pressure control device is used to control the negative pressure inside the vertical well.

6. The groundwater recharge system for high-altitude permafrost regions according to claim 5, characterized in that, The permafrost heating and melting device includes: a self-regulating electric mixing cable, a solar panel, and a temperature sensor; the self-regulating electric mixing cable is installed at the bottom of the vertical well; the solar panel is installed on the ground surface and is connected to the self-regulating electric mixing cable by wires to provide power; the temperature sensor is installed in the pipe section above the vertical well; when the temperature measured by the temperature sensor is lower than a first temperature, the permafrost heating and melting device starts heating. The micro-negative pressure control device includes a vacuum pump and a pressure sensor. The vacuum pump is installed at the top of the vertical well, and the pressure sensor is installed at the bottom of the vertical well.

7. The groundwater recharge system for high-altitude permafrost regions according to claim 6, characterized in that, The pressure sensor includes a first pressure sensor and a second pressure sensor. The first pressure sensor is installed at the bottom of the vertical well, and the second pressure sensor is installed at the end of the horizontal well and away from the vertical well.

8. The groundwater recharge system for high-altitude permafrost regions according to claim 3, characterized in that, The vertical well is equipped with a double-layer pipe, which includes an outer vertical well pipe and an inner vertical well pipe; an insulation layer is provided between the inner vertical well pipe and the outer vertical well pipe. The horizontal well is located at the top of the unsaturated layer, and its length does not exceed the distance between the vertical well and the reinjection well. It is made of porous material. The horizontal well has a double-layer pipe, with a filter layer filling between the outer pipe and the inner pipe. Both the outer pipe and the inner pipe are water filter pipes. The outer pipe is wrapped with a filter screen.

9. The groundwater recharge system for high-altitude permafrost regions according to claim 1, characterized in that, Groundwater recharge well systems also include pressurization devices and pressure sensors; The portion of the recharge well from the surface to the lower boundary of the permafrost layer is a solid pipe, while the portion from the lower boundary of the permafrost layer to the aquifer is a filter pipe.

10. A groundwater recharge method suitable for high-altitude permafrost regions, characterized in that, Applied to the groundwater recharge system for high-altitude permafrost regions as described in any one of claims 1-9; The method includes: reinjecting groundwater into the aquifer through a groundwater reinjection well system, and expelling air from the unsaturated layer through a gas collection and exhaust system during the groundwater reinjection process.

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