A medium-deep geothermal geothermal pipe heat exchange well wellhead system and a method of using the same

Abstract

This invention discloses a wellhead system for medium-deep geothermal buried pipe heat exchange wells and its usage method. The system includes an inner pipe and an outer pipe coaxially sleeved together, forming a channel between them. The outer pipe includes a support base pipe and a detachable casing assembly disposed above the support base pipe. A support base pipe side bend is provided on one side of the support base pipe, and an inner pipe core is coaxially connected to the top of the support base pipe. An installation hole is provided on the inner pipe core, communicating with the inner cavity of the support base pipe. A temperature-measuring optical cable passing mechanism is installed within the installation hole. The casing assembly includes an integrally connected casing body and a tray with a central through hole. The lower end of the casing body is connected to the upper end of the support base pipe. The temperature-measuring optical cable, passing through the temperature-measuring optical cable passing mechanism, can exit the wellhead system through an optical cable exit groove on the side wall of the casing body and an optical cable guide groove on the tray. This invention provides a system with high load-bearing capacity, effectively preventing damage to the optical cable during construction.

Description

Technical Field

[0001] This invention relates to the field of geothermal energy development pipelines, specifically to a wellhead system for a medium-deep geothermal buried pipe heat exchange well and its usage method. Background Technology

[0002] As a new mainstream technology for geothermal energy development, medium-deep geothermal energy mainly refers to geothermal resources contained in strata between 200m and 3000m underground. Geothermal temperatures are generally above 50℃, and rock temperatures above 2000m can reach 70℃ and remain stable. Therefore, medium-deep geothermal energy has good heating performance and huge development potential. With technological advancements and improved heat exchange efficiency, high-vacuum metal inner tubes with a thermal conductivity of less than 0.02w / m·K, a pressure resistance greater than 35MPa, and the ability to be used long-term in medium-deep geothermal wells at temperatures above 150℃ are being widely adopted. However, high-vacuum metal inner tubes suspended in geothermal wells are much heavier than commonly used non-metallic insulation pipes such as PE pipes, PE-RT pipes, and PPH pipes, with a total weight exceeding 150 tons. Existing geothermal wellhead devices cannot meet the load-bearing requirements in terms of structural design and material selection. In addition, in order to conduct long-term monitoring and research on the heat exchange efficiency and formation thermal properties of medium-deep geothermal wells, temperature measuring optical cables need to be installed and lowered along the well. However, in the existing technology, most of the relevant components of the wellhead equipment are connected by electric welding. The high temperature generated by the electric welding operation may damage the temperature measuring optical cable. The optical cable is not effectively sealed and fixed in the casing. Under the long-term impact of the heat medium, fatigue damage is easily generated, affecting the service life of the optical cable and the sealing effect and durability at the penetration hole. Moreover, the optical cable is also prone to bending when it is led to the surface, which affects data monitoring.

[0003] In summary, there is an urgent need to develop a geothermal wellhead system that is structurally sound, has high compressive strength, is easy to install on-site, has good sealing performance, can effectively pass through and seal optical cables in the casing, and can meet load-bearing requirements. Summary of the Invention

[0004] In view of the defects and deficiencies in the existing technology, the present invention provides a wellhead system for medium-deep geothermal buried pipe heat exchange wells, so as to solve the technical problems of small load-bearing capacity of geothermal wellhead devices and easy damage due to the lack of sealing and fixing function of monitoring optical cables.

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

[0006] A wellhead system for a medium-deep geothermal buried pipe heat exchange well includes an inner pipe and an outer pipe coaxially sleeved together, with a channel formed between the outer pipe and the inner pipe. The outer pipe includes a support seat pipe and a casing assembly that is detachably connected and disposed above the support seat pipe.

[0007] A side bend of the support tube is provided on one side of the support tube, and an inner tube core is coaxially connected to the top of the support tube. An installation hole is provided on the inner tube core, and the installation hole is connected to the inner cavity of the support tube. A temperature measuring optical cable passing mechanism is installed in the installation hole.

[0008] The casing assembly includes an integrally connected casing body and a tray with a through hole in the center. The lower end of the casing body is connected to the upper end of the support tube. The temperature measuring optical cable passing through the temperature measuring optical cable passage mechanism can pass through the optical cable exit groove opened on the side wall of the casing body and the optical cable guide groove opened on the tray to exit the wellhead system.

[0009] The present invention also has the following technical features:

[0010] Specifically, the temperature measuring optical cable passing mechanism includes a ferrule connector body, a ferrule assembly, and a clamping nut. The ferrule connector body has a first central through hole and a first external thread on the upper outer wall of the ferrule connector body. The clamping nut has a second central through hole and a first internal thread on the inner wall of the clamping nut. The first internal thread and the first external thread can be connected in a mating manner.

[0011] The sleeve assembly includes a first sleeve with a third central through hole and a second sleeve with a fourth central through hole;

[0012] The first ferrule has a first conical surface on its outer wall, and the ferrule connector body has a second conical surface on its upper inner wall. The first conical surface and the second conical surface are connected by compression fitting. The first ferrule has a third conical surface on its inner wall, and the second ferrule has a fourth conical surface on its outer wall. The third conical surface and the fourth conical surface are connected by compression fitting.

[0013] The first central through hole, the second central through hole, and the first central through hole and the second central through hole are connected to form the passage for the temperature measuring optical cable 0.

[0014] Furthermore, the lower end of the ferrule connector body is provided with a tapered section, which can be sealed to the upper end of the mounting hole.

[0015] Furthermore, a limiting groove is formed in the upper part of the inner wall of the inner tube core, and a first sealing gasket is provided in the limiting groove.

[0016] Furthermore, the inner tube core includes an integrally connected cylindrical section and a conical section. A fifth conical surface is provided on the inner wall of the upper end of the support tube, and a sixth conical surface is provided on the outer wall of the conical section. The fifth conical surface and the sixth conical surface are connected by extrusion fitting.

[0017] Furthermore, a second sealing gasket is provided between the cylindrical section and the upper end face of the support tube, and the second sealing gasket is embedded in a sealing groove opened on the top surface of the support tube.

[0018] Furthermore, the mounting hole is inclined; a support conversion joint is connected below the support base tube.

[0019] Furthermore, it also includes a heat medium conveying pipe that can be detachably connected to the inner pipe. The heat medium conveying pipe includes a straight pipe section and a bent pipe section. The bottom end of the straight pipe section is connected to the inner pipe by means of a pipe clamp. The bent pipe section extends outward from the side wall of the straight pipe section. The straight pipe section and the bent pipe section are connected through a connecting port.

[0020] Furthermore, the casing assembly also includes a sealing plate, which together with the casing body and the tray forms a sealed chamber, and the optical cable exit slot outlet and the optical cable guide slot inlet are both located within the sealed chamber.

[0021] This invention also protects a method for using a wellhead system for a medium-deep geothermal buried pipe heat exchange well. This method, implemented using the aforementioned medium-deep geothermal buried pipe heat exchange well wellhead system, includes the following steps:

[0022] Step 1: After the sunken geothermal well chamber is constructed, connect the support conversion joint to the geothermal well outer casing, then connect the support base pipe to the support conversion joint, and then connect the casing assembly used to lower and install the inner pipe string to the upper end of the support base pipe.

[0023] Step 2: The temperature measuring optical cable is lowered and installed into the outer casing of the geothermal well along with the inner tube. The inner tube core is fitted onto the last inner tube, and the temperature measuring optical cable passes through the installation hole. The last inner tube is lowered and installed, and the inner tube core is coaxially installed on the support base tube. The inner tube string is suspended above the inner tube core by means of the pipe clamp.

[0024] Step 3: Remove the casing assembly and connect and install the heat transfer pipe at the upper end of the inner pipe;

[0025] Step 4: Insert the temperature-sensing optical cable through the temperature-sensing optical cable via the ferrule connector body, ferrule assembly, and clamping nut. The ferrule connector body is connected to the mounting hole via a tapered pipe thread. Press the ferrule assembly into the tapered contact surface of the ferrule connector body, and tighten the clamping nut to achieve a fixed seal of the temperature-sensing optical cable on the wellhead device.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (1) Through structural and material optimization, the system of the present invention ensures that the wellhead device can withstand the weight of the inner tube made of metal material of more than 150T. By setting the side bend of the support seat pipe on the side wall of the support seat pipe, the flow resistance of the high heat medium is small, which reduces the lateral scouring of the heat medium on the heat insulation core pipe set in the support seat pipe. It can effectively reduce the injection resistance and disturbance to the heat insulation core pipe. By setting the temperature measuring optical cable passing mechanism, it is ensured that the optical cable can be smoothly led out in the wellhead device and sealed reliably, ensuring that the heat medium will not leak due to the use of the optical cable during the heat medium circulation process. Through the structural design of the casing assembly, the optical cable clamped in the temperature measuring optical cable passing mechanism is led out of the system without heat medium leakage. By replacing the support conversion joint of different specifications, the same specification of wellhead device can be used in geothermal wells with different specifications of outer casing pipes, which is more versatile and lower in cost.

[0028] (2) The inner tube filler in the system of the present invention, through the sealing structure of the upper and lower end faces, allows the insulation tube string to be directly coaxially aligned and automatically pressed and sealed on the wellhead device, avoiding damage to the temperature measuring optical cable caused by the high temperature of the electric welding connection. The present invention has a simple structure, is easy to use, and is worth promoting. Attached Figure Description

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

[0030] Figure 2 This is a partial structural diagram of the present invention;

[0031] Figure 3 This is a schematic diagram of the inner tube core-filling structure of the present invention;

[0032] Figure 4 This is a schematic diagram of the temperature-measuring optical cable crossing mechanism of the present invention;

[0033] Figure 5 This is a schematic diagram of the protective sleeve structure of the present invention.

[0034] Meaning of reference numerals in the attached diagram:

[0035] 1-Supporting tube, 2-Inner tube filler, 3-Temperature measuring optical cable crossing mechanism, 4-Supporting conversion joint, 5-Supporting tube side bend, 6-First sealing gasket, 7-Second sealing gasket, 8-Inner tube, 9-Casing, 10-Temperature measuring optical cable, 11-Heat medium conveying pipe, 12-Geothermal well outer casing, 13-Pipe clamp; 21-Mounting hole, 22-Cylindrical section, 23-Conical section; 31-Compression fitting body, 32-Compression fitting assembly, 33-Compression nut; 91-Casing body, 92-Pattern, 93-Sealing plate; 111-Straight pipe section, 112-Bend pipe section, 321-First compression fitting, 322-Second compression fitting. Detailed Implementation

[0036] It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0037] It should be noted that, unless otherwise specified, all parts used in this invention are commercially available. The system provided by this invention is suitable for submerged installation operations at geothermal wellheads.

[0038] The terms "upper," "lower," "front," "rear," "top," and "bottom," etc., used in this invention to indicate orientation or positional relationships are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "Inner" and "outer" refer to the inner and outer contours of the corresponding components, and should not be construed as limitations on the invention. In this invention, "front" and "rear" are as follows... Figure 1 As shown in the description.

[0039] Furthermore, the terms "first," "second," and other ordinal numbers are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0040] In this invention, unless otherwise stated, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] Example 1

[0042] Following the above technical solutions, such as Figure 1 As shown, this embodiment provides a wellhead system for a medium-deep geothermal buried pipe heat exchange well, including an inner pipe 8 and an outer pipe coaxially sleeved together, forming a channel between the outer pipe and the inner pipe 8. The outer pipe is characterized by including a support pipe 1 and a detachably connected casing assembly 9 disposed above the support pipe 1. The side bend of the support pipe 8 serves as a heat medium channel, minimizing lateral scouring of the inner pipe 8 within the support pipe 1, effectively reducing injection resistance and disturbance to the inner pipe. In this embodiment, the support pipe 1 is a low-alloy high-strength steel pipe with a special-shaped tee.

[0043] A side bend 5 is provided on one side of the support tube 1, and an inner tube filler 2 is coaxially connected to the top of the support tube 1. An installation hole 21 is provided on the inner tube filler 2, which communicates with the inner cavity of the support tube 1. A temperature-measuring optical cable passing mechanism 3 passes through the installation hole 21. The inner tube filler 2 is made of low-alloy high-strength steel and mainly serves for load-bearing, positioning, and fixing. The entire inner tube string installed in the support tube 1 needs to be suspended from the inner tube filler 2 using pipe clamps.

[0044] The casing assembly 9 includes an integrally connected casing body 91 and a tray 92 with a central through hole. The lower end of the casing body 91 is connected to the upper end of the support tube 1. The temperature-measuring optical cable 10, which passes through the temperature-measuring optical cable passing mechanism 3, can pass through the wellhead system via the optical cable exit groove on the side wall of the casing body 91 and the optical cable guide groove on the tray 92. Both the optical cable exit groove and the optical cable guide groove are oblique holes, used for positioning protection and cable lead-out, to prevent the optical cable from being damaged by the lifting clamps used to lift and suspend the inner tube during the lowering and installation process.

[0045] The casing assembly 9 provides temporary protection and guidance support for the inner pipe and the temperature measuring optical cable 10 that is lowered along with the pipe. During the installation of the geothermal well's metal inner pipe, it ensures that the temperature measuring optical cable 10 is lowered and installed together with the inner pipe 8 without affecting the overall installation progress of the inner pipe 8. After the inner pipe 8 and the temperature measuring optical cable 10 are lowered and installed, the casing assembly 9 can be removed to complete the sinking installation of the geothermal wellhead.

[0046] As a preferred embodiment, the temperature measuring optical cable crossing mechanism 3 includes a ferrule connector body 31, a ferrule assembly 32, and a clamping nut 33. The ferrule connector body 31 has a first central through hole, and the upper outer wall of the ferrule connector body 31 has a first external thread. The clamping nut 33 has a second central through hole, and the inner wall of the clamping nut 33 has a first internal thread. The first internal thread and the first external thread can be connected in a mating manner.

[0047] The sleeve assembly 32 includes a first sleeve 321 with a third central through hole and a second sleeve 322 with a fourth central through hole;

[0048] The outer wall of the first ferrule 321 is provided with a first conical surface, the inner wall of the upper end of the ferrule connector body 31 is provided with a second conical surface, the first conical surface and the second conical surface are connected by compression fitting, the inner wall of the first ferrule 321 is provided with a third conical surface, the outer wall of the second ferrule 322 is provided with a fourth conical surface, the third conical surface and the fourth conical surface are connected by compression fitting.

[0049] The first central through hole, the second central through hole, and the first central through hole and the second central through hole are connected to form the passage for the temperature measuring optical cable 10.

[0050] In a preferred embodiment, the lower end of the ferrule connector body 31 is provided with a tapered section, which can be sealed to the upper end of the mounting hole 21. In this embodiment, the tapered section and the upper end of the mounting hole 21 can achieve a sealed connection through a clearance fit.

[0051] As a preferred embodiment, a limiting groove is formed in the upper part of the inner wall of the inner tube core 2, and a first sealing gasket 6 is provided in the limiting groove. The first sealing gasket 6 is a soft metal sealing gasket that is resistant to high temperature, high pressure and aging.

[0052] As a preferred embodiment, the inner tube core 2 includes an integrally connected cylindrical section 22 and a conical section 23. A fifth conical surface is provided on the inner wall of the upper end of the support tube 1, and a sixth conical surface is provided on the outer wall of the conical section 23. The fifth and sixth conical surfaces are connected by extrusion fitting to achieve a tight fit between the support tube 1 and the inner tube core 2, and to ensure the strength, coaxiality, stability and tightness of the connection between the pipe fittings.

[0053] In a preferred embodiment, a second sealing gasket 7 is provided between the cylindrical section 22 and the upper end face of the support tube 1. The second sealing gasket 7 is embedded in a sealing groove opened on the top surface of the support tube to ensure that the inner tube core 2 and the support tube 1 can be sealed together under the weight of the inner tube string, and that the heat medium does not leak under normal operation of the device. The second sealing gasket 7 is a soft metal sealing gasket that is resistant to high temperature and high pressure and anti-aging.

[0054] In a preferred embodiment, the mounting hole 21 is inclined. The bottom of the support base tube 1 is connected to the support adapter 5 by bolts 4.

[0055] As a preferred embodiment, it also includes a heat medium conveying pipe 11 that can be detachably connected to the inner pipe 8. The heat medium conveying pipe 11 includes a straight pipe section 111 and a bent pipe section 112. The bottom end of the straight pipe section 111 is connected to the inner pipe 8 by means of a pipe clamp 12. The bent pipe section 112 extends outward from the side wall of the straight pipe section 111. The straight pipe section 111 and the bent pipe section 112 are connected through a connecting port.

[0056] The casing assembly 9 also includes a sealing plate 93, which, together with the casing body 91 and the tray 92, forms a sealed chamber. Both the optical cable exit slot outlet and the optical cable guide slot inlet are located within this sealed chamber. That is, the optical cable exit slot outlet, the sealed chamber, and the optical cable guide slot are connected. The sealing plate 93 also provides support and protection for the optical cable. Figure 5 As shown, preferably, a ladder slope can be provided inside the tray 92, and an optical cable guide groove can be provided along the ladder slope. This structure makes wiring easier and can reduce the bending of the optical cable.

[0057] In this embodiment, all pipe fittings are sealed to prevent leakage of the heat medium.

[0058] Example 2

[0059] This embodiment provides a method for using a wellhead system for a medium-deep geothermal buried pipe heat exchange well. This method is implemented using the wellhead system for a medium-deep geothermal buried pipe heat exchange well provided in Embodiment 1, and includes the following steps:

[0060] Step 1: After the sunken geothermal well chamber is constructed, connect the support conversion joint 4 to the geothermal well outer casing 12, then connect the support seat pipe 1 to the support conversion joint 4, and then connect the casing assembly 9 used for lowering and installing the inner pipe string to the upper end of the support seat pipe 1.

[0061] Step 2: The temperature measuring optical cable 10 is lowered and installed into the outer casing 12 of the geothermal well along with the inner tube 8. The inner tube core 2 is fitted onto the last inner tube 8, and the temperature measuring optical cable 10 passes through the installation hole 21. The last inner tube 8 is lowered and installed, and the inner tube core 2 is coaxially installed on the support base tube 1. The inner tube string is suspended above the inner tube core 2 by means of the pipe clamp 13.

[0062] Step 3: Remove the casing assembly 9 and connect and install the heat transfer pipe 11 at the upper end of the inner pipe 8;

[0063] Step 4: The temperature measuring optical cable passing mechanism 3, consisting of the ferrule connector body 31, the ferrule assembly 32, and the clamping nut 33, is sequentially inserted into the temperature measuring optical cable. The ferrule connector body 31 is connected to the mounting hole 21 through a tapered pipe thread. The ferrule assembly 32 is pressed into the tapered contact surface of the ferrule connector body. The clamping nut is tightened to achieve a fixed seal of the temperature measuring optical cable on the wellhead device.

[0064] This invention's system, through its device structure, pipe components made of low-alloy high-strength steel, and sealing gaskets made of soft metal materials, ensures that the wellhead device can withstand the weight of the inner metal pipe exceeding 150 tons through sealed connections between components. By setting a side bend in the support pipe sidewall, it ensures low flow resistance for the high-heat medium, reducing lateral scouring of the insulation core pipe within the support pipe and effectively minimizing injection resistance and disturbance to the insulation core pipe. The temperature-sensing optical cable passage mechanism ensures the optical cable can be smoothly and reliably led out of the wellhead device, preventing leakage during heat medium circulation. The structural design of the casing assembly allows the optical cable, clamped within the temperature-sensing optical cable passage mechanism, to be led out of the system without heat medium leakage. By replacing different specifications of support conversion joints, the same specification of wellhead device can be used in geothermal wells with different specifications of outer casing pipes, resulting in greater versatility and lower cost.

[0065] The above-described implementation process is merely an example to clearly illustrate this application and is not intended to limit the implementation methods. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementation methods here. However, obvious variations or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A wellhead system for a medium-deep geothermal buried pipe heat exchange well, comprising an inner pipe (8) and an outer pipe coaxially sleeved together, wherein a channel is formed between the outer pipe and the inner pipe (8), characterized in that, The outer tube includes a support base tube (1) and a protective sleeve assembly (9) that is detachably connected to the support base tube (1) above it. A side bend (5) is provided on one side of the support tube (1), and an inner tube core (2) is coaxially connected to the top of the support tube (1). An installation hole (21) is provided on the inner tube core (2), and the installation hole (21) is connected to the inner cavity of the support tube (1). A temperature measuring optical cable passing mechanism (3) is installed in the installation hole (21). The casing assembly (9) includes an integrally connected casing body (91) and a tray (92) with a through hole in the center. The lower end of the casing body (91) is connected to the upper end of the support tube (1). The temperature measuring optical cable (10) passing through the temperature measuring optical cable passing mechanism (3) can pass through the optical cable exit groove opened on the side wall of the casing body (91) and the optical cable guide groove opened on the tray (92) to exit the wellhead system. The temperature measuring optical cable crossing mechanism (3) includes a ferrule connector body (31), a ferrule assembly (32), and a clamping nut (33). The ferrule connector body (31) has a first central through hole, and the upper outer wall of the ferrule connector body (31) has a first external thread. The clamping nut (33) has a second central through hole, and the inner wall of the clamping nut (33) has a first internal thread. The first internal thread and the first external thread can be connected in a mating manner. The sleeve assembly (32) includes a first sleeve (321) having a third central through hole and a second sleeve (322) having a fourth central through hole. The outer wall of the first ferrule (321) is provided with a first conical surface, and the inner wall of the upper end of the ferrule connector body (31) is provided with a second conical surface. The first conical surface and the second conical surface are connected by compression fitting. The outer wall of the first ferrule (321) is provided with a third conical surface, and the inner wall of the second ferrule (322) is provided with a fourth conical surface. The third conical surface and the fourth conical surface are connected by compression fitting. The first central through hole, the second central through hole, the third central through hole and the fourth central through hole are connected to form the passage of the temperature measuring optical cable (10); The inner tube core (2) includes a cylindrical section (22) and a conical section (23) that are integrally connected. A fifth conical surface is provided on the inner wall of the upper end of the support tube (1), and a sixth conical surface is provided on the outer wall of the conical section (23). The fifth conical surface and the sixth conical surface are connected by extrusion fitting. The lower end of the ferrule body (31) is provided with a tapered section, which can be sealed with the upper end of the mounting hole (21) by tapered pipe thread. The mounting hole (21) is inclined; a support conversion joint (4) is connected below the support base tube (1); it also includes a heat medium conveying pipe (11) that can be detachably connected to the inner tube (8), the heat medium conveying pipe (11) includes a straight pipe section (111) and a bent pipe section (112), the bottom end of the straight pipe section (111) is connected to the inner tube (8) by means of a pipe clamp (13), the bent pipe section (112) extends outward from the side wall of the straight pipe section (111), and the straight pipe section (111) and the bent pipe section (112) are connected through a connecting port; the casing assembly (9) also includes a sealing plate (93), the sealing plate (93) and the casing body (91) and the tray (92) enclose a sealed chamber, and the optical cable exit groove outlet and the optical cable guide groove inlet are both located in the sealed chamber.

2. The wellhead system for medium-deep geothermal buried pipe heat exchange wells as described in claim 1, characterized in that, The inner wall of the inner tube core (2) is recessed to form a limiting groove, and a first sealing gasket (6) is provided in the limiting groove.

3. The wellhead system for medium-deep geothermal buried pipe heat exchange wells as described in claim 1, characterized in that, A second sealing gasket (7) is provided between the cylindrical section (22) and the upper end face of the support tube (1), and the second sealing gasket (7) is embedded in the sealing groove opened on the top surface of the support tube (1).

4. A method for using a wellhead system for a medium-deep geothermal buried pipe heat exchange well, characterized in that, This method is implemented using the wellhead system of the medium-deep geothermal buried pipe heat exchange well as described in any one of claims 1 to 3, and includes the following steps: Step 1: After the sunken geothermal well chamber is constructed, connect the support conversion joint (4) to the geothermal well outer casing (12), then connect the support seat pipe (1) to the support conversion joint (4), and then connect the casing assembly (9) used to lower and install the inner pipe string to the upper end of the support seat pipe (1). Step 2: The temperature measuring optical cable (10) is lowered and installed into the outer casing (12) of the geothermal well along with the inner tube (8). The inner tube core (2) is fitted onto the last inner tube (8), and the temperature measuring optical cable (10) passes through the installation hole (21). The last inner tube (8) is lowered and installed, and the inner tube core (2) is coaxially installed on the support base tube (1). The inner tube string is suspended above the inner tube core (2) by means of the pipe clamp (13). Step 3: Remove the casing assembly (9) and connect and install the heat transfer pipe (11) at the upper end of the inner pipe (8). Step 4: Insert the temperature measuring optical cable through the temperature measuring optical cable in sequence through the temperature measuring optical cable, which consists of the ferrule connector body (31), the ferrule assembly (32) and the clamping nut (33). The ferrule connector body (31) is connected to the mounting hole (21) through the tapered pipe thread. Press the ferrule assembly (32) into the tapered contact surface of the ferrule connector body and tighten the clamping nut to achieve the fixed sealing of the temperature measuring optical cable on the wellhead device.

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