A medium-deep geothermal single well underground heating system with a pressure regulating device

Abstract

The present invention belongs to the technical field of development and utilization of geothermal energy resources, and discloses a medium-deep geothermal single well underground heating system with a pressure regulating device. A vacuum insulation steel pipe is arranged in the geothermal well wall, and an annular cavity is formed between the vacuum insulation steel pipe and the geothermal well wall. A pressure regulating device is arranged in the annular cavity. A low-temperature liquid working medium is arranged in the annular cavity, and the low-temperature liquid working medium flows into the geothermal medium through the pressure regulating device and forms a high-temperature vapor working medium. The vacuum insulation steel pipe is used to enter the high-temperature vapor working medium, and the high-temperature vapor working medium is converted into a low-temperature liquid working medium through a ground heat utilization unit by absorbing heat and refluxes to the annular cavity. The present invention can increase the temperature of hot water at the outlet of the geothermal well while ensuring the heat extraction power, thereby improving the diversity of geothermal resource utilization. In addition, a pressure regulating device is added to the system, which can reduce the system pump work and improve the economy of the system. At the same time, dynamic regulation of the system can be realized, ensuring the matching of high heat extraction power, outlet temperature and optimal heat extraction flow.

Description

Technical Field

[0001] The invention belongs to the technical field of development and utilization of geothermal energy resources, and in particular relates to a medium-deep geothermal single well underground heating system with a pressure regulating device. Background Art

[0002] The existing development and utilization technologies of medium-deep geothermal resources can be mainly divided into two forms: open single-well heat extraction system and closed single-well heat extraction system. The closed single-well heat extraction system mainly refers to the absence of mass exchange between the heat extraction medium and the geothermal fluid, and the heat is extracted from the geothermal reservoir by heat conduction. The heat extraction power is low. Its application forms mainly include buried pipe type, coaxial sleeve type, single U-tube type, gravity heat pipe type, etc. The buried pipe type and coaxial sleeve type heat extraction technologies are relatively mature and have more field applications. The gravity heat pipe heat exchange technology is less used on site and has technical bottlenecks. The open single-well heat extraction system refers to the geothermal well wall being open, and the geothermal water circulates in the wellbore and the aquifer. The forced convection heat exchange between the heat extraction medium and the geothermal water can be achieved through the downhole heat exchanger, which effectively improves the heat extraction efficiency. However, due to the influence of water extraction policies, the development of the open single-well heat extraction system has been greatly restricted. At the same time, the existing geothermal resource exploitation technologies all use water as the heat exchange medium, and there is also the problem of low heat exchange efficiency.

[0003] Based on a closed single-well heat extraction system, the present invention proposes a geothermal single-well underground heating system with a pressure regulating device. It uses phase change of non-aqueous working fluid to extract heat, which can produce a higher working fluid temperature while keeping the heat extraction rate basically the same, and can be more flexibly invested in different utilization modes and scenarios such as power generation, refrigeration and heating. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a medium-deep geothermal single well underground heating system with a pressure regulating device to solve the problems in the prior art. The technical solution adopted by the present invention is:

[0005] A medium-deep geothermal single well underground heating system with a pressure regulating device, comprising: a geothermal well wall, a vacuum insulation steel pipe, a pressure regulating device and a ground heat utilization unit;

[0006] The vacuum insulation steel pipe is arranged in the geothermal well wall, an annular cavity is formed between the vacuum insulation steel pipe and the geothermal well wall, and the pressure regulating device is arranged in the annular cavity; the bottom of the vacuum insulation steel pipe and the bottom of the pressure regulating device are geothermal medium;

[0007] A low-temperature liquid working medium is arranged in the annular cavity, and the low-temperature liquid working medium flows into the geothermal medium through the pressure regulating device and forms a high-temperature vapor working medium. The vacuum insulated steel pipe is used for the high-temperature vapor working medium to enter. The high-temperature vapor working medium absorbs heat through the ground heat utilization unit and is converted into a low-temperature liquid working medium and flows back to the annular cavity.

[0008] Furthermore, the ground heat utilization unit includes a cascade utilization part and a direct utilization part; the cascade utilization part and the direct utilization part are used to produce heat exchange for the high-temperature vapor working medium and transfer the heat to the heat user; the cascade utilization part and the direct utilization part work together or independently.

[0009] Furthermore, the cascade utilization part includes a steam turbine, a generator, a compressor, a condenser, a working fluid storage tank and a secondary circulation pump;

[0010] The top of the vacuum insulated steel pipe is connected to the steam turbine, the steam turbine is connected to the generator, the exhaust end of the steam turbine is connected to the compressor, the output end of the compressor is connected to the condenser, the drainage end of the condenser is connected to the working fluid storage tank, and the working fluid storage tank is connected to the annular cavity through a working fluid pump; the heat exchange end of the condenser is connected to the heat user through the secondary circulation pump and the first heat exchange circulation water.

[0011] Furthermore, it also includes an air-oil separator and a throttle valve; the output end of the compressor is connected to the condenser through the air-oil separator and the throttle valve in sequence; the oil discharge end of the air-oil separator is connected to the oil collecting tank.

[0012] Furthermore, the direct utilization part includes a heat exchanger and a primary circulation pump; the top of the vacuum insulation steel pipe is connected to the input end of the heat exchanger, and the output end of the heat exchanger is connected to the working fluid storage tank; the heat exchange end of the heat exchanger is connected to the heat user through the primary circulation pump and the second heat exchange circulation water pipe;

[0013] The heat exchanger and the steam turbine are connected in parallel to the top of the vacuum insulation steel pipe, and the flow direction of the high-temperature steam working medium is controlled by a valve.

[0014] Further, the pressure regulating device comprises a movable sealing gasket, a compressible spring and a device body;

[0015] The device body and the movable sealing gasket are annular and are arranged around the vacuum insulation steel pipe. The device body is fixedly connected to the movable sealing gasket through the compressible spring. The movable sealing gasket is located above the device body. The device body and the movable sealing gasket are arranged at intervals. A gap is set between the device body and the geothermal well wall.

[0016] When the movable sealing gasket is not in contact with the device body, the low-temperature liquid working medium in the annular cavity flows downward into the geothermal medium through the gap between the device body and the movable sealing gasket and the gap between the device body and the geothermal well wall;

[0017] When the movable sealing gasket contacts the device body, the gap between the device body and the movable sealing gasket is closed, and the low-temperature liquid working medium flows downward into the geothermal medium through the gap between the device body and the geothermal well wall.

[0018] Furthermore, it also includes an oil pump, an oil return pipeline and an oil sump;

[0019] The oil collecting tank is arranged in the device body, and the oil collecting tank is connected to the oil collecting tank through the oil return pipeline and the oil pump.

[0020] Furthermore, a pressure sensor is arranged on the movable sealing gasket.

[0021] The present invention has the following beneficial effects:

[0022] (1) Compared with the traditional medium-deep geothermal single well heat extraction system, the medium-deep geothermal single well underground heating system with a pressure regulating device proposed by the present invention innovatively adopts organic working fluids, carbon dioxide, etc. as heat exchange working fluids to directly exchange heat with the formation. While ensuring the heat exchange capacity, the outlet temperature of the geothermal well is further improved, and the application scope of the single geothermal well is broadened, so that it can be used in power generation, heating, refrigeration and other fields at the same time;

[0023] (2) The medium-deep geothermal single well underground heating system with a pressure regulating device proposed in the present invention innovatively proposes to install a pressure regulating device inside the geothermal well. The device can adjust the flow rate of the working fluid flowing into the bottom of the well for heat exchange according to the pressure difference between the liquid working fluid and the vapor working fluid in the geothermal well, thereby ensuring that the heat exchange working fluid can fully absorb heat and improving the overall heating efficiency of the system. At the same time, an oil collecting tank is designed at the bottom of the pressure regulating device to reduce the risk of compressor lubricating oil entering the geothermal well.

[0024] (3) The medium-deep geothermal single well underground heating system with a pressure regulating device proposed by the present invention can ensure that the pressure of the heat exchange medium and the critical state of the heat exchange medium match the high-temperature section of the geothermal well, so that the heat exchange medium can be accurately vaporized in the high-temperature section of the geothermal well, further improving the heat absorption power of the heat exchange medium, thereby improving the heat extraction capacity of the system; at the same time, a fin plate is installed on the geothermal well wall below the pressure regulating device, which can further increase the contact area between the heat exchange medium and the high-temperature wall surface, further improving the heat exchange power;

[0025] (4) The medium-deep geothermal single-well underground heating system with a pressure regulating device proposed in the present invention can not only reduce the extended flow resistance of the non-water heat-extracting working fluid, reduce the system pump work, and improve the economy of the system, but also prevent the non-water heat-extracting working fluid from accumulating due to state changes in the underground, ensuring that the working fluid can fully exchange heat in the underground, further improving the heat extraction power of the system. At the same time, a one-way valve is installed on the heat exchange working fluid output channel to ensure that the high-temperature heat-extracting working fluid does not flow back during the operation of the system, thereby ensuring the safe operation of the system.

[0026] (5) The medium-deep geothermal single-well underground heating system with a pressure regulating device proposed by the present invention can dynamically adjust the flow rate of the working fluid according to the pressure data monitored by the pressure sensor, thereby achieving the matching of high heating power, outlet temperature and optimal heat flow rate;

[0027] (6) The medium-deep geothermal single well underground heating system with a pressure regulating device proposed by the present invention realizes the multi-level utilization of geothermal resources in view of the conditions of geothermal wells, and can be used for cogeneration of heat and power as well as independent heating, thus improving the scope of application of the system;

[0028] (7) The medium-deep geothermal single-well underground heating system with a pressure regulating device proposed in the present invention is equipped with a compressor and its supporting oil return system on the cascade utilization circuit, which improves the utilization efficiency of geothermal energy and solves the problem of compressor damage caused by insufficient lubricating oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 Schematic diagram of the pressure regulating device when it is not working;

[0031] Figure 3 Schematic diagram of the pressure regulating device when it is working;

[0032] Figure 4 Top view of the pressure regulating device;

[0033] Figure 5 Traffic control flow chart;

[0034] In the figure: 1 geothermal well wall, 2 vacuum insulation steel pipe, 3 pressure regulating device, 3-1 movable sealing gasket, 3-2 compressible spring, 3-3 device body, 3-4 return oil pipeline, 3-5 oil collecting tank, 4 fin plate, 5 check valve, 6 steam turbine, 7 generator, 8 compressor, 9 gas-oil separator, 10 throttle valve, 11 oil collecting tank, 12 oil pump, 13 condenser, 14 secondary circulation pump, 15 heat user, 16 primary circulation pump, 17 heat exchanger, 18 pressure sensor, 19 working fluid pump, 20 working fluid storage tank. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention Figure 1-Figure 5 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0036] In order to solve the technical problems existing in the existing medium-deep geothermal resource exploitation process, the present invention proposes a medium-deep geothermal single-well underground heating system with a pressure regulating device and its application. The invention can increase the hot water temperature at the outlet of the geothermal well while ensuring the heating power, thereby improving the diversity of geothermal resource utilization; in addition, a pressure regulating device is added to the system to reduce the system pump work and improve the economy of the system; at the same time, the system can be dynamically controlled to ensure the matching of high heating power, outlet temperature and optimal heat flow.

[0037] like Figure 1 As shown, a medium-deep geothermal single well underground heating system with a pressure regulating device comprises: a geothermal well wall 1, a vacuum insulation steel pipe 2, a pressure regulating device 3 and a ground heat utilization unit;

[0038] The vacuum insulated steel pipe 2 is arranged in the geothermal well wall 1, and an annular cavity is formed between the vacuum insulated steel pipe 2 and the geothermal well wall 1, and the pressure regulating device 3 is arranged in the annular cavity; the bottom of the vacuum insulated steel pipe 2 and below the pressure regulating device 3 are geothermal medium; the geothermal medium refers to the rock layer, ground medium, soil, etc. in the geothermal well.

[0039] A low-temperature liquid working medium is arranged in the annular cavity, and the low-temperature liquid working medium flows into the geothermal medium through the pressure regulating device 3 and forms a high-temperature vapor working medium. The vacuum insulated steel pipe 2 is used for the high-temperature vapor working medium to enter. The high-temperature vapor working medium absorbs heat through the ground heat utilization unit and is converted into a low-temperature liquid working medium and flows back to the annular cavity.

[0040] There is a gap between the vacuum insulated steel pipe 2 and the bottom of the geothermal well wall 1. The annular cavity between the geothermal well wall 1 and the vacuum insulated steel pipe 2 is a low-temperature liquid working medium reflux channel, and the inside of the vacuum insulated steel pipe 2 is a high-temperature vapor working medium output channel; the installation position of the pressure regulating device 3 is determined according to the geothermal well temperature conditions and the heat exchange working medium properties.

[0041] Furthermore, the ground heat utilization unit includes a cascade utilization part and a direct utilization part; the cascade utilization part and the direct utilization part are used to produce heat exchange for the high-temperature vapor working medium and transfer the heat to the heat user 15; the cascade utilization part and the direct utilization part work together or independently.

[0042] The cascade utilization part includes a steam turbine 6, a generator 7, a compressor 8, a condenser 13, a working fluid storage tank 20 and a secondary circulation pump 14. The top of the vacuum insulation steel pipe 2 is connected to the steam turbine 6, the steam turbine 6 is connected to the generator 7, the exhaust end of the steam turbine 6 is connected to the compressor 8, the output end of the compressor 8 is connected to the condenser 13, the drainage end of the condenser 13 is connected to the working fluid storage tank 20, and the working fluid storage tank 20 is connected to the annular cavity through the working fluid pump 19; the heat exchange end of the condenser 13 is connected to the heat user 15 through the secondary circulation pump 14 and the first heat exchange circulation water.

[0043] Furthermore, it also includes an air-oil separator 9 and a throttle valve 10; the output end of the compressor 8 is connected to the condenser 13 through the air-oil separator 9 and the throttle valve 10 in turn; the oil discharge end of the air-oil separator 9 is connected to the oil collecting tank 11.

[0044] The cascade utilization part includes a power generation part and a heating part. After the heat exchange, the high-temperature vapor working medium flows into the steam turbine 6 to perform work under the action of the working medium pump 19. The steam turbine 6 drives the generator 7 to complete the power generation process. After the work, the high-temperature vapor working medium is condensed by the condenser 13 to form a low-temperature liquid working medium and enters the working medium storage tank 20. After the low-temperature circulating water in the condenser 13 is heated, it enters the heat user 15 under the action of the secondary circulation pump 14 to complete the heating process.

[0045] The direct utilization part includes a heat exchanger 17 and a primary circulation pump 16; the top of the vacuum insulation steel pipe 2 is connected to the input end of the heat exchanger 17, and the output end of the heat exchanger 17 is connected to the working fluid storage tank 20; the heat exchange end of the heat exchanger 17 is connected to the heat user 15 through the primary circulation pump 16 and the second heat exchange circulation water;

[0046] The heat exchanger 17 and the steam turbine 6 are connected in parallel to the top of the vacuum insulation steel pipe 2, and the flow direction of the high-temperature steam working medium is controlled by a valve.

[0047] The direct utilization part refers to the process in which the high-temperature vapor working medium after heat exchange flows into the heat exchanger 17 under the action of the working medium pump 19 to exchange heat with the low-temperature circulating water, and the heat is taken away by the low-temperature circulating water under the action of the primary circulation pump 16 to provide heating for the heating user 15.

[0048] In the present invention, the pressure regulating device 3 comprises a movable sealing gasket 3-1, a compressible spring 3-2 and a device body 3-3;

[0049] The device body 3-3 and the movable sealing gasket 3-1 are annular and are arranged around the vacuum insulation steel pipe 2. The device body 3-3 is fixedly connected to the movable sealing gasket 3-1 through the compressible spring 3-2. The movable sealing gasket 3-1 is located above the device body 3-3. The device body 3-3 and the movable sealing gasket 3-1 are arranged at intervals. A gap is arranged between the device body 3-3 and the geothermal well wall 1.

[0050] Furthermore, it also includes an oil pump 12, an oil return pipeline 3-4 and an oil collecting tank 3-5;

[0051] The oil collecting tank 3 - 5 is arranged in the device body 3 - 3 , and the oil collecting tank 3 - 5 is connected to the oil collecting tank 11 through the oil return pipeline 3 - 4 and the oil pump 12 .

[0052] Furthermore, a pressure sensor 18 is provided on the movable sealing gasket 3-1.

[0053] The inner ring of the device body 3-3 is tightly connected to the vacuum insulation steel pipe 2, the outer ring of the device body 3-3 is close to the geothermal well wall 1 but with a gap, the bottom of the compressible spring 3-2 is connected to the groove of the device body 3-3, the top of the compressible spring 3-2 is connected to the movable sealing gasket 3-1, a number of small holes are opened on the groove of the device body 3-3, the top of the movable sealing gasket 3-1 is connected to the pressure sensor 12, the oil collecting tank 3-5 is below the device body 3-3, when the movable sealing gasket 3-1 of the pressure regulating device 3 is not in contact with the device body 3-3, the gap between the device body 3-3 and the geothermal well wall 1 is low-temperature liquid working The gap between the lower part of the movable sealing gasket 3-1 and the upper part of the device body 3-3 is the main channel for the reflux of the low-temperature liquid working medium. The small holes around the groove of the device body 3-3 are the reflux holes for the low-temperature liquid working medium. When the movable sealing gasket 3-1 of the pressure regulating device 3 contacts the device body 3-3, the gap between the device body 3-3 and the geothermal well wall 1 is the main channel for the reflux of the low-temperature liquid working medium. The fin plate 4 is installed on the inner circle of the geothermal well wall 1 below the pressure regulating device 3. The interval between the fin plates 4 is determined by the circulating flow rate of the working medium and the conditions of the geothermal well. The one-way valve 5 is installed inside the vacuum insulation pipe, and the flow direction is from top to bottom.

[0054] In the present invention, the cascade utilization part and the direct utilization part can be switched freely according to the needs of heat users and work independently; they can also be controlled by pipeline valves to work simultaneously; the proportion of each part can also be adjusted according to the user's needs for heating and power generation; when the lubricating oil in the oil collecting tank 11 is lower than the specified liquid level, the lubricating oil collected at the bottom of the pressure regulating device 3 is sent to the oil collecting tank 11 through the oil pump 12, and is replenished to the compressor 8 for recycling under the action of the pressure in the tank.

[0055] The working process of the present invention is as follows:

[0056] The high-temperature vapor working medium that fully absorbs heat in the geothermal well, under the action of the working medium pump 19, a part of it enters the turbine 6 to do work, and the turbine 6 drives the generator 7 to generate electricity; the high-temperature vapor working medium that has done work in the turbine 6 enters the compressor 8 to further increase the temperature and pressure, and after the lubricating oil of the high-temperature and high-pressure vapor working medium is separated by the gas-oil separator 9, the relatively pure high-temperature and high-pressure vapor working medium is reduced in pressure by the throttle valve 9 and enters the condenser 13 to further release heat, and after heat release, it becomes a low-temperature liquid working medium and flows into the liquid storage tank 20; and the high-temperature circulating water that has absorbed heat in the condenser 13 enters the heat user 15 for heating under the action of the secondary circulation pump 14 to complete the heat release process, and the low-temperature circulating water after heat release returns to the condenser 13 again, and circulates in sequence to complete the cascade utilization process. The other part of the high-temperature vapor working medium directly enters the heat exchanger 17 under the action of the working medium pump 19 to exchange heat with the low-temperature circulating water. After releasing heat, it becomes a low-temperature liquid working medium and enters the liquid storage tank 20. After mixing with the working medium of the cascade utilization part, it flows into the geothermal well again. Similarly, the high-temperature circulating water after absorbing heat in the heat exchanger 17 enters the heat user 15 for heating under the action of the primary circulation pump 16, completing the heat release process. The low-temperature circulating water after releasing heat returns to the heat exchanger 17 again, and circulates in sequence to complete the direct utilization process.

[0057] In addition, after the ground heat utilization unit releases heat, the low-temperature liquid working medium flows out of the liquid storage tank 20, flows into the geothermal well through the low-temperature liquid working medium reflux channel between the geothermal well wall 1 and the vacuum insulated steel pipe 2, and then flows from the low-temperature liquid working medium reflux branch between the pressure regulating device body 3-3 and the geothermal well wall 1 and the low-temperature liquid working medium reflux main channel between the lower part of the movable sealing gasket 3-1 and the upper part of the device body 3-3, flows downward through the low-temperature liquid working medium reflux holes around the groove of the device body 3-3 to perform a heat exchange process; if the reflux flow rate of the low-temperature liquid working medium is large, the pressure value above the pressure regulating device 3 is large, and the movable sealing gasket 3-1 in the device will move downward and contact the device body 3-3, closing the low-temperature liquid working medium reflux main channel between the lower part of the movable sealing gasket 3-1 and the upper part of the device body 3-3, so that the low-temperature liquid working medium can only flow from the low-temperature liquid working medium reflux branch between the device body 3-3 and the geothermal well wall 1 to the The downward flow completes the heat exchange process. At this time, the pressure sensor 12 transmits the monitored data to the working fluid pump. The working fluid pump will reduce the power and reduce the flow rate of the reflux working fluid, so that the main reflux channel of the low-temperature liquid working fluid is opened again, and the heat exchange working fluid flows downward to perform the heat exchange process; in this process, the lubricating oil in the compressor 8 carried by the heat exchange working fluid is deposited in the oil collecting tank 3-5 at the bottom of the pressure regulating device 3 due to its large density. When the lubricating oil in the oil collecting tank 11 is lower than the specified liquid level, the lubricating oil collected at the bottom of the pressure regulating device 3 is sent to the oil collecting tank 11 through the oil pump 12, and is replenished to the compressor 8 for recycling under the action of the pressure in the tank; and the heat exchange working fluid flowing through the pressure regulating device 3, under the action of the fin plate 4 at the bottom thereof, is in large-area and full contact with the wall of the high-temperature geothermal well, further absorbing the formation heat, and the high-temperature gaseous working fluid after absorbing heat flows through the one-way valve 5 and enters the ground heat utilization unit again to release heat, and circulates in sequence.

[0058] The embodiments described above are only descriptions of the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, and substitutions made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A medium-deep geothermal single well underground heating system with a pressure regulating device, characterized in that: include: Geothermal well wall (1), vacuum insulation steel pipe (2), pressure regulating device (3) and ground heat utilization unit; The vacuum insulation steel pipe (2) is arranged in the geothermal well wall (1), an annular cavity is formed between the vacuum insulation steel pipe (2) and the geothermal well wall (1), and the pressure regulating device (3) is arranged in the annular cavity; the bottom of the vacuum insulation steel pipe (2) and below the pressure regulating device (3) are geothermal medium; A low-temperature liquid working medium is arranged in the annular cavity, and the low-temperature liquid working medium flows into the geothermal medium through the pressure regulating device (3) and forms a high-temperature vapor working medium. The vacuum insulation steel pipe (2) is used to allow the high-temperature vapor working medium to enter. The high-temperature vapor working medium absorbs heat through the ground heat utilization unit and is converted into a low-temperature liquid working medium and flows back into the annular cavity. The pressure regulating device (3) comprises a movable sealing gasket (3-1), a compressible spring (3-2) and a device body (3-3); The device body (3-3) and the movable sealing gasket (3-1) are annular and are arranged around the vacuum insulation steel pipe (2); the device body (3-3) is fixedly connected to the movable sealing gasket (3-1) via the compressible spring (3-2); the movable sealing gasket (3-1) is located above the device body (3-3); the device body (3-3) and the movable sealing gasket (3-1) are arranged at a distance; and a gap is arranged between the device body (3-3) and the geothermal well wall (1); When the movable sealing gasket (3-1) is not in contact with the device body (3-3), the low-temperature liquid working medium in the annular cavity flows downward into the geothermal medium through the gap between the device body (3-3) and the movable sealing gasket (3-1) and the gap between the device body (3-3) and the geothermal well wall (1); When the movable sealing gasket (3-1) contacts the device body (3-3), the gap between the device body (3-3) and the movable sealing gasket (3-1) is closed, and the low-temperature liquid working medium flows downward into the geothermal medium through the gap between the device body (3-3) and the geothermal well wall (1).

2. A medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 1, characterized in that: It also includes an oil pump (12), an oil return pipeline (3-4) and an oil collecting tank (3-5); The oil collecting tank (3-5) is arranged in the device body (3-3), and the oil collecting tank (3-5) is connected to the oil collecting tank (11) through the oil return pipeline (3-4) and the oil pump (12).

3. A medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 1, characterized in that: A pressure sensor (18) is provided on the movable sealing gasket (3-1).

4. A medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 1, characterized in that: The ground heat utilization unit comprises a cascade utilization part and a direct utilization part; the cascade utilization part and the direct utilization part are used to generate heat exchange for the high-temperature vapor working medium and transmit the heat to the heat user (15); the cascade utilization part and the direct utilization part work together or independently.

5. A medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 4, characterized in that: The cascade utilization part includes a steam turbine (6), a generator (7), a compressor (8), a condenser (13), a working fluid storage tank (20) and a secondary circulation pump (14); The top of the vacuum insulation steel pipe (2) is connected to the steam turbine (6), the steam turbine (6) is connected to the generator (7), the exhaust end of the steam turbine (6) is connected to the compressor (8), the output end of the compressor (8) is connected to the condenser (13), the drainage end of the condenser (13) is connected to the working fluid storage tank (20), and the working fluid storage tank (20) is connected to the annular cavity through a working fluid pump (19); the heat exchange end of the condenser (13) is connected to a heat user (15) through a secondary circulation pump (14) and a first heat exchange circulation water connection.

6. A medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 5, characterized in that: It also includes an air-oil separator (9) and a throttle valve (10); the output end of the compressor (8) is connected to the condenser (13) via the air-oil separator (9) and the throttle valve (10) in sequence; and the oil discharge end of the air-oil separator (9) is connected to the oil collecting tank (11).

7. The medium-deep geothermal single well underground heating system with a pressure regulating device according to claim 5, characterized in that: The direct utilization part comprises a heat exchanger (17) and a primary circulation pump (16); the top of the vacuum insulation steel pipe (2) is connected to the input end of the heat exchanger (17), and the output end of the heat exchanger (17) is connected to the working fluid storage tank (20); the heat exchange end of the heat exchanger (17) is connected to the heat user (15) through the primary circulation pump (16) and the second heat exchange circulation water. The heat exchanger (17) and the steam turbine (6) are connected in parallel to the top of the vacuum insulation steel pipe (2), and the flow direction of the high-temperature steam working medium is controlled by a valve.

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