Wellhead system of middle-deep layer geothermal buried pipe heat exchange well and using method of wellhead system

Abstract

The middle-deep layer geothermal buried pipe heat exchange well wellhead system comprises an inner pipe and an outer pipe which are coaxially arranged in a sleeved mode, a channel is formed between the outer pipe and the inner pipe, and the outer pipe comprises a supporting seat pipe and a pile casing assembly detachably arranged above the supporting seat pipe in a communicating mode; one side of the supporting seat tube is provided with a supporting seat tube side bent tube, the top of the supporting seat tube is coaxially communicated with an inner tube bushing, the inner tube bushing is provided with a mounting hole, the mounting hole is communicated with an inner cavity of the supporting seat tube, and a temperature measuring optical cable penetrating mechanism is arranged in the mounting hole in a penetrating manner; the pile casing assembly comprises a pile casing body and a tray, the pile casing body and the tray are integrally connected, and a through hole is formed in the center of the tray. A temperature measuring optical cable penetrating through the temperature measuring optical cable penetrating mechanism can penetrate out of the wellhead system through an optical cable penetrating-out groove formed in the side wall of the pile casing body and an optical cable guiding groove formed in the tray. The system is large in bearing capacity, and damage to the optical cable in the construction process can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to the field of geothermal energy development pipelines, and in particular to a wellhead system for a mid-deep geothermal buried pipe heat exchange well and a use method thereof. Background Art

[0002] The development and utilization of medium-deep geothermal energy is a new mainstream technology of geothermal energy. Medium-deep geothermal energy mainly refers to the geothermal resources contained in the strata between 200m and 3000m underground. The geothermal temperature is generally above 50℃. The rock temperature above 2000m underground can reach 70℃ and the temperature is stable. Therefore, medium-deep geothermal has a good heating effect and huge development potential. With the advancement of technology and the improvement of heat exchange efficiency, high-vacuum metal inner tubes with thermal conductivity less than 0.02w / m·K, compressive strength greater than 35MPa, and long-term use in medium-deep geothermal wells with a temperature greater than 150℃ are being promoted on a large scale. However, the high-vacuum metal inner tubes suspended and installed in geothermal wells are much heavier than the commonly used non-metallic insulation pipes such as PE pipes, PE-RT pipes, and PPH pipes. The total weight even exceeds 150 tons. The existing wellhead devices of geothermal wells 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 of medium-deep geothermal wells and the thermal properties of the formation, a temperature measuring optical cable must be installed along with the pipe in the entire well. However, in the existing technology, most of the relevant components of the wellhead device are connected by electric welding. The high temperature generated by the electric welding operation may cause damage to the temperature measuring optical cable. The optical cable cannot be effectively sealed and fixed in the casing. Fatigue damage is easily caused under the long-term impact of the heat medium, affecting the service life of the optical cable and the sealing effect and durability of the penetration hole. Moreover, the optical cable is prone to bending when it is led to the ground, affecting data monitoring.

[0003] In summary, there is an urgent need to develop a geothermal wellhead system with a reasonable structure, high compressive strength, simple on-site installation, good sealing performance, the ability to effectively penetrate and seal the optical cable in the casing, and the ability to meet the load-bearing requirements. Summary of the invention

[0004] In view of the defects and shortcomings in the prior art, the present invention provides a wellhead system for a medium-deep geothermal buried pipe heat exchange well to solve the technical problems in the prior art that the wellhead device of the geothermal well has a small load-bearing capacity and is easily damaged due to the lack of sealing and fixing function of the monitoring optical cable.

[0005] To achieve the above object, the present invention adopts the following technical scheme:

[0006] A wellhead system for a mid-deep geothermal buried pipe heat exchange well, comprising an inner pipe and an outer pipe coaxially sleeved, a channel formed between the outer pipe and the inner pipe, the outer pipe comprising a support seat pipe, and a casing assembly detachably connected and arranged above the support seat pipe;

[0007] A support seat tube side bend is provided on one side of the support seat tube, an inner tube bushing is coaxially connected to the top of the support seat tube, a mounting hole is provided on the inner tube bushing, the mounting hole is connected to the inner cavity of the support seat tube, and a temperature measuring optical cable passing mechanism is passed through the mounting 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 seat tube. The temperature measuring optical cable passed through the temperature measuring optical cable passing mechanism can pass through the wellhead system through the optical cable outlet groove provided on the side wall of the casing body and the optical cable guide groove provided on the tray.

[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 compression nut, wherein a first central through hole is provided in the ferrule connector body, a first external thread is provided on the outer wall of the upper end of the ferrule connector body, a second central through hole is provided in the compression nut, and a first internal thread is provided on the inner wall of the compression nut, and the first internal thread and the first external thread can be matched and connected;

[0011] The ferrule assembly comprises a first ferrule provided with a third central through hole and a second ferrule provided with a fourth central through hole;

[0012] A first conical surface is provided on the outer wall of the first ferrule, a second conical surface is provided on the inner wall of the upper end of the ferrule joint body, the first conical surface and the second conical surface are connected by extrusion fit, a third conical surface is provided on the inner wall of the first ferrule, a fourth conical surface is provided on the outer wall of the second ferrule, the third conical surface and the fourth conical surface are connected by extrusion fit;

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

[0014] Furthermore, a tapered section is provided at the lower end of the ferrule joint body, and the tapered section can be sealingly connected to the upper end of the mounting hole.

[0015] Furthermore, the upper part of the inner wall of the inner tube bushing is concave to form a limiting groove, and a first sealing gasket is arranged in the limiting groove.

[0016] Furthermore, the inner tube bushing includes a cylindrical section and a conical section that are integrally connected, a fifth conical surface is provided on the inner wall of the upper end of the support seat tube, a sixth conical surface is provided on the outer wall of the conical section, and 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 surface of the support seat tube, and the second sealing gasket is embedded in a sealing groove provided on the top surface of the support seat tube.

[0018] Furthermore, the mounting hole is arranged at an angle; and a support conversion joint is connected below the support seat tube.

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

[0020] Furthermore, the protective tube assembly also includes a sealing plate, which is combined with the protective tube body and the tray to form a closed chamber, and the optical cable outlet groove and the optical cable guide groove inlet are both located in the closed chamber.

[0021] The present invention also protects a method for using a wellhead system for a medium-deep geothermal buried pipe heat exchange well. The method is implemented by the wellhead system for a medium-deep geothermal buried pipe heat exchange well, and comprises the following steps:

[0022] Step 1: After the construction of the sunken geothermal well chamber is completed, the support conversion joint is connected to the outer casing of the geothermal well, and then the support seat pipe is connected to the support conversion joint, and then the casing assembly used for lowering and installing the inner pipe string is connected to the upper end of the support seat pipe;

[0023] Step 2: The temperature measuring optical cable is lowered and installed together with the inner tube into the outer casing of the geothermal well. The inner tube bushing is sleeved on 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 bushing is coaxially installed on the support seat tube. The inner tube string is suspended on the inner tube bushing with the help of a pipe clamp.

[0024] Step 3, remove the casing assembly, and connect and install the heat medium delivery pipe on the upper end of the inner tube;

[0025] Step 4: insert the temperature measuring optical cable through-mechanism consisting of the ferrule connector body, the ferrule assembly and the compression nut into the temperature measuring optical cable in sequence, connect the ferrule connector body to the installation hole through the tapered pipe thread, press the ferrule assembly into the tapered contact surface of the ferrule connector body, tighten the compression nut, and realize the fixed seal of the temperature measuring optical cable on the wellhead device.

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

[0027] (1) The system of the present invention optimizes the structure and materials to ensure that the wellhead device can withstand the gravity of the inner tube made of metal material above 150T. By arranging the side bend of the support seat tube on the side wall of the support seat tube, the flow resistance of the high heat medium is small, which reduces the lateral scouring of the heat medium on the insulation core tube arranged in the support seat tube, and can effectively reduce the injection resistance and the disturbance to the insulation core tube. By arranging the temperature measuring optical cable crossing mechanism, it is ensured that the optical cable can be smoothly led out of the wellhead device and the sealing is reliable, 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 lead-out system clamped in the temperature measuring optical cable crossing mechanism will not leak heat medium. By replacing the support conversion joints of different specifications, the wellhead device of the same specification can be used in geothermal wells with outer casings of different specifications, which has stronger versatility and lower cost.

[0028] (2) The inner tube bushing in the system of the present invention has a sealing structure on the upper and lower end surfaces, so that the insulation pipe string can be directly coaxially installed on the wellhead device and automatically compressed and sealed, thereby avoiding damage to the temperature measuring optical cable caused by high temperature caused by electric welding connection. The present invention has a simple structure, is easy to use, and is worthy of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0030] Figure 2 It is a schematic diagram of the local structure of the present invention;

[0031] Figure 3 It is a schematic diagram of the inner tube bushing structure of the present invention;

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

[0033] Figure 5 It is a schematic diagram of the casing structure of the present invention.

[0034] Meaning of reference numerals:

[0035] 1-support seat tube, 2-inner tube core, 3-temperature measuring optical cable passing mechanism, 4-support conversion joint, 5-support seat tube side elbow, 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-installation hole, 22-column section, 23-taper section; 31-ferrule joint body, 32-ferrule assembly, 33-pressing nut; 91-casing body, 92-tray, 93-sealing plate; 111-straight pipe section, 112-bend pipe section, 321-first ferrule, 322-second ferrule. DETAILED DESCRIPTION

[0036] It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0037] It should be noted that, unless otherwise specified, the parts used in the present invention are all commercially available. The system provided by the present invention is suitable for the sinking installation operation of a geothermal wellhead.

[0038] The terms "upper", "lower", "front", "back", "top", "bottom" and the like used in the present invention to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific direction, be constructed and operate in a specific direction. "Inside" and "outside" refer to the inside and outside of the contours of the corresponding components, and the above terms cannot be understood as limiting the present invention. The front and back in the present invention are as follows: Figure 1 Description shown.

[0039] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0040] In the present invention, unless otherwise specified, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Example 1

[0042] Following the above technical solution, 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, forming a channel between the outer pipe and the inner pipe 8, and is characterized in that the outer pipe includes a support seat pipe 1, and a casing assembly 9 that is detachably connected and arranged above the support seat pipe 1; the side bend pipe 8 of the support seat pipe serves as a heat medium channel, which has little lateral scouring on the inner pipe 8 arranged in the support seat pipe 1, and can effectively reduce the injection resistance and disturbance to the inner pipe; in this embodiment, the support seat pipe 1 is a special-shaped three-way low-alloy high-strength steel pipe.

[0043] A support seat tube side bend 5 is provided on one side of the support seat tube 1, and an inner tube bushing 2 is coaxially connected to the top of the support seat tube 1. An installation hole 21 is provided on the inner tube bushing 2, which is connected to the inner cavity of the support seat tube 1. A temperature measuring optical cable passing mechanism 3 is passed through the installation hole 21; the inner tube bushing 2 is made of low-alloy high-strength steel and mainly plays the role of bearing, positioning and fixing. The inner tube string set in the support seat tube 1 needs to be suspended on the inner tube bushing 2 with the help of a pipe clamp.

[0044] 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 seat tube 1. The temperature measuring optical cable 10 inserted in the temperature measuring optical cable passing mechanism 3 can pass through the wellhead system through the optical cable passing groove provided on the side wall of the casing body 91 and the optical cable guide groove provided on the tray 92. Both the optical cable passing groove and the optical cable guide groove are inclined holes, which are used for positioning, protecting and leading out the optical cable, so as to prevent the lifting card used for lifting and hanging the inner tube from touching the optical cable and damaging the optical cable during the installation process of the inner tube.

[0045] The casing assembly 9 can provide temporary protection and guiding support for the inner pipe and the temperature measuring optical cable 10 lowered along with the pipe. During the lowering and installation of the metal inner pipe of the geothermal well, it is ensured that the temperature measuring optical cable 10 is lowered and installed together with the inner pipe 8 without affecting the installation progress of the overall inner pipe 8. After the lowering and installation of the inner pipe 8 and the temperature measuring optical cable 10 are completed, the casing assembly 9 can be removed to complete the sunken installation work of the geothermal wellhead.

[0046] As a preferred solution of this embodiment, the temperature measuring optical cable passing mechanism 3 includes a ferrule connector body 31, a ferrule assembly 32 and a clamping nut 33. The ferrule connector body 31 is provided with a first central through hole, and the outer wall of the upper end of the ferrule connector body 31 is provided with a first external thread. The clamping nut 33 is provided with a second central through hole, and the inner wall of the clamping nut 33 is provided with a first internal thread, and the first internal thread and the first external thread can be matched and connected;

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

[0048] A first conical surface is provided on the outer wall of the first ferrule 321, a second conical surface is provided on the inner wall of the upper end of the ferrule joint body 31, the first conical surface and the second conical surface are connected by extrusion fit, a third conical surface is provided on the inner wall of the first ferrule 321, a fourth conical surface is provided on the outer wall of the second ferrule 322, the third conical surface and the fourth conical surface are connected by extrusion fit;

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

[0050] As a preferred solution of this embodiment, a tapered section is provided at the lower end of the ferrule joint body 31, and the tapered section can be sealed and connected with the upper end of the mounting hole 21. In this embodiment, the tapered section and the upper end of the mounting hole 21 can be sealed and connected by clearance fit.

[0051] As a preferred solution of this embodiment, the upper inner wall of the inner tube bushing 2 is concave to form a limiting groove, in which a first sealing gasket 6 is arranged. The first sealing gasket 6 is a sealing gasket made of soft metal material that is resistant to high temperature, high pressure and aging.

[0052] As a preferred solution of this embodiment, the inner tube bushing 2 includes a cylindrical section 22 and a conical section 23 which are integrally connected. A fifth conical surface is provided on the inner wall of the upper end of the support seat 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 to achieve a close fit between the support seat tube 1 and the inner tube bushing 2, and to ensure the strength, coaxiality, stability and tightness of the pipe connection.

[0053] As a preferred solution of this embodiment, a second sealing gasket 7 is provided between the cylindrical section 22 and the upper end surface of the support seat tube 1. The second sealing gasket 7 is embedded in a sealing groove provided on the top surface of the support seat tube to ensure that the inner tube bushing 2 and the support seat tube 1 can be sealed and connected under the weight of the inner tube string, and the heat medium does not leak when the device is operating normally. The second sealing gasket 7 is a sealing gasket made of soft metal material that is resistant to high temperature, high pressure and aging.

[0054] As a preferred solution of this embodiment, the mounting hole 21 is arranged obliquely. The bottom of the support seat tube 1 is connected to the support conversion joint 5 through a bolt 4 .

[0055] As a preferred solution of this embodiment, it also includes a heat medium conveying pipe 11 that can be detachably connected to the inner pipe 8, and the heat medium conveying pipe 11 includes a straight pipe section 111 and a curved 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, and the curved pipe section 112 extends outward from the side wall of the straight pipe section 111, and the straight pipe section 111 and the curved pipe section 112 are connected through a connecting port.

[0056] The casing assembly 9 also includes a sealing plate 93, which is enclosed with the casing body 91 and the tray 92 to form a closed chamber, and the optical cable outlet and the optical cable guide slot inlet are both located in the closed chamber. That is, the optical cable outlet, the sealed chamber and the optical cable guide slot are connected, and the sealing plate 93 can also play a supporting and protective role for the optical cable. Figure 5 As shown, as a preference, a stepped slope can be provided in the tray 92, and an optical cable guide groove can be provided along the stepped slope. Such a structure is more convenient for wiring and can reduce the bending of the optical cable.

[0057] The pipes in this embodiment are all sealed to prevent leakage of the heat medium.

[0058] Example 2

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

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

[0061] Step 2, the temperature measuring optical cable 10 is lowered and installed together with the inner tube 8 into the outer casing 12 of the geothermal well, the inner tube bushing 2 is sleeved on 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 bushing 2 is coaxially installed on the support seat tube 1, and the inner tube string is suspended on the inner tube bushing 2 by means of the pipe clamp 13;

[0062] Step 3, remove the casing assembly 9, and connect and install the heat medium delivery pipe 11 on the upper end of the inner tube 8;

[0063] Step 4, insert the temperature measuring optical cable passing mechanism 3 composed of the ferrule joint body 31, the ferrule assembly 32 and the clamping nut 33 into the temperature measuring optical cable in sequence, the ferrule joint body 31 is connected to the mounting hole 21 through a tapered pipe thread, the ferrule assembly 32 is pressed into the conical contact surface of the ferrule joint body, and the clamping nut is tightened to achieve fixed sealing of the temperature measuring optical cable on the wellhead device.

[0064] The system of the present invention ensures that the wellhead device can withstand the gravity of the inner tube of the metal material above 150T through the device structure, the pipeline assembly using low-alloy high-strength steel and the sealing gasket made of soft metal material, and the sealing connection between the components. By arranging the side bend of the support seat tube on the side wall of the support seat tube, it is ensured that the flow resistance of the high heat medium is small, and the lateral scouring of the heat medium on the insulation core tube arranged in the support seat tube is reduced, and the injection resistance and the disturbance to the insulation core tube are effectively reduced; by arranging the temperature measuring optical cable crossing mechanism, it is ensured that the optical cable can be smoothly led out of the wellhead device and the sealing is reliable, 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 lead-out system clamped in the temperature measuring optical cable crossing mechanism will not leak the heat medium, and by replacing the support conversion joints of different specifications, the wellhead device of the same specification can be used in the geothermal wells with outer casings of different specifications, which has stronger versatility and lower cost.

[0065] The above implementation process is only an example for clearly explaining the present application, and is not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of this application.

Claims

1. A wellhead system for a mid-deep geothermal buried pipe heat exchange well, comprising an inner pipe (8) and an outer pipe coaxially sleeved, wherein a channel is formed between the outer pipe and the inner pipe (8), characterized in that: The outer tube comprises a support seat tube (1), and a casing assembly (9) which is detachably connected and arranged above the support seat tube (1); A support seat tube side bend (5) is provided on one side of the support seat tube (1); an inner tube bushing (2) is coaxially connected to the top of the support seat tube (1); a mounting hole (21) is provided on the inner tube bushing (2); the mounting hole (21) is connected to the inner cavity of the support seat tube (1); a temperature measuring optical cable passing mechanism (3) is passed through the mounting hole (21); The casing assembly (9) comprises an integrally connected casing body (91) and a tray (92) with a through hole at the center. The lower end of the casing body (91) is connected to the upper end of the support seat tube (1). The temperature measuring optical cable (10) inserted into the temperature measuring optical cable passing mechanism (3) can pass through the optical cable outlet groove provided on the side wall of the casing body (91) and the optical cable guide groove provided on the tray (92) to pass out of the wellhead system.

2. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: The temperature measuring optical cable passing mechanism (3) comprises a ferrule connector body (31), a ferrule assembly (32) and a clamping nut (33); a first central through hole is arranged in the ferrule connector body (31); a first external thread is arranged on the outer wall of the upper end of the ferrule connector body (31); a second central through hole is arranged in the clamping nut (33); and a first internal thread is arranged on the inner wall of the clamping nut (33); the first internal thread and the first external thread can be matched and connected; The ferrule assembly (32) comprises a first ferrule (321) provided with a third central through hole and a second ferrule (322) provided with a fourth central through hole; A first conical surface is provided on the outer wall of the first ferrule (321), a second conical surface is provided on the inner wall of the upper end of the ferrule joint body (31), the first conical surface and the second conical surface are connected by extrusion fit, a third conical surface is provided on the inner wall of the first ferrule (321), a fourth conical surface is provided on the outer wall of the second ferrule (322), and the third conical surface and the fourth conical surface are connected by extrusion fit; The first central through hole, the second central through hole, the first central through hole and the second central through hole are connected to form a passage for the temperature measuring optical cable (10).

3. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 2, characterized in that: The lower end of the ferrule joint body (31) is provided with a tapered section, and the tapered section can be sealed and connected to the upper end of the mounting hole (21) by using a tapered pipe thread.

4. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: The upper part of the inner wall of the inner tube bushing (2) is concave to form a limiting groove, and a first sealing gasket (6) is arranged in the limiting groove.

5. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: The inner tube bushing (2) comprises a cylindrical section (22) and a conical section (23) which are integrally connected, a fifth conical surface is arranged on the inner wall of the upper end of the support seat tube (1), a sixth conical surface is arranged on the outer wall of the conical section (23), and the fifth conical surface and the sixth conical surface are connected by extrusion fitting.

6. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 5, characterized in that: A second sealing gasket (7) is provided between the columnar section (22) and the upper end surface of the support seat tube (1), and the second sealing gasket (7) is embedded in a sealing groove provided on the top surface of the support seat tube (1).

7. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: The mounting hole (21) is arranged obliquely; and a support conversion joint (4) is connected below the support seat tube (1).

8. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: It also comprises a heat medium transport pipe (11) that can be detachably connected to the inner pipe (8), the heat medium transport pipe (11) comprising a straight pipe section (111) and a curved pipe section (112), the bottom end of the straight pipe section (111) being connected to the inner pipe (8) by means of a pipe clamp (12), the curved pipe section (112) extending outward from the side wall of the straight pipe section (111), and the straight pipe section (111) and the curved pipe section (112) being connected via a connecting port.

9. The mid-deep geothermal buried pipe heat exchange well wellhead system according to claim 1, characterized in that: The protective tube assembly (9) further comprises a sealing plate (93), wherein the sealing plate (93), the protective tube body (91) and the tray (92) enclose a closed chamber, and the optical cable outlet groove and the optical cable guide groove inlet are both located in the closed chamber.

10. A method for using a wellhead system of a mid-deep geothermal buried pipe heat exchange well, characterized in that: The method is implemented by the wellhead system of the medium-deep geothermal buried pipe heat exchange well according to any one of claims 1 to 9, and comprises the following steps: Step 1, after the construction of the sunken geothermal well chamber is completed, the support conversion joint (4) is connected to the outer casing (12) of the geothermal well, and then the support seat tube (1) is connected to the support conversion joint (4), and then the casing assembly (9) used for lowering and installing the inner pipe string is connected to the upper end of the support seat tube (1); Step 2, the temperature measuring optical cable (10) is lowered and installed together with the inner tube (8) into the outer casing (12) of the geothermal well, the inner tube core (2) is sleeved on the last inner tube (8), and the temperature measuring optical cable (10) is passed 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 seat tube (1), and the inner tube string is suspended on the inner tube core (2) by means of a pipe clamp (13); Step 3, removing the casing assembly (9), and connecting and installing a heat medium delivery pipe (11) on the upper end of the inner tube (8); Step 4, insert the temperature measuring optical cable through mechanism (3) composed of the ferrule connector body (31), the ferrule assembly (32) and the clamping nut (33) into the temperature measuring optical cable in sequence, 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 conical contact surface of the ferrule connector body, and the clamping nut is tightened to achieve fixed sealing of the temperature measuring optical cable on the wellhead device.

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