High-efficiency long-service-life direct-connection-thread central thermal insulation pipe for medium-deep geothermal well

Abstract

The utility model discloses a high-efficiency long-service-life direct-connection-thread central thermal insulation pipe for a middle-deep geothermal well, which comprises an outer pipe and an inner pipe which are concentrically sleeved, and the two ends of the inner pipe are welded on the outer pipe; the radial outer side of one end of the outer pipe is thickened to form an outer thickened part, trapezoidal internal threads are arranged on the inner wall of the outer thickened part, the radial inner side of the other end of the outer pipe is thickened to form an inner thickened part, and trapezoidal external threads matched with the trapezoidal internal threads are arranged on the outer wall of the inner thickened part. And the inner thickened part of one outer pipe is in threaded connection with the outer thickened part of the other outer pipe to form an air-tight seal special buckle to finish the connection of the thermal insulation pipe, so that the pipe column is formed. The utility model discloses can reduce the well drilling diameter, reduce the pipe column down-hole resistance, improve the down-hole efficiency, strengthen the intensity and sealing performance of threaded connection simultaneously, thereby effectively prolonging the service life of pipe column.

Description

Technical Field

[0001] This utility model belongs to the field of thermal insulation pipe manufacturing technology, specifically relating to a high-efficiency, long-life, straight-threaded central thermal insulation pipe for medium-deep geothermal wells. Background Technology

[0002] In geothermal applications, due to the limited length of insulated pipes, each pipe needs to be connected via couplings. However, these couplings, acting as significant thermal bridges, become critical points for heat loss. Furthermore, the larger outer diameter of the couplings not only increases resistance during well running and the risk of wellbore enlargement but also raises investment costs. Simultaneously, they exacerbate the vortex effect and flow resistance within the pipe. More importantly, the abrupt change in pipe diameter within the coupling easily creates high-speed cyclones, accelerating localized corrosion rates and making it prone to perforation failure, resulting in substantial economic losses. Utility Model Content

[0003] This invention aims to provide a high-efficiency, long-life, straight-threaded central insulation pipe for medium-deep geothermal wells, which can reduce the drilling diameter, lower the resistance of the tubing string, improve the running-in efficiency, and enhance the strength and sealing performance of the threaded connection, thereby effectively extending the service life of the tubing string.

[0004] To achieve the above objectives, this utility model provides the following technical solution:

[0005] A high-efficiency, long-life, straight-threaded central insulation pipe for medium-deep geothermal wells includes an outer pipe and an inner pipe concentrically arranged, with both ends of the inner pipe welded to the outer pipe. One end of the outer pipe is thickened radially to form an outer thickened portion, and a trapezoidal internal thread is provided on the inner wall of the outer thickened portion. The other end of the outer pipe is thickened radially to form an inner thickened portion, and a trapezoidal external thread matching the trapezoidal internal thread is provided on the outer wall of the inner thickened portion. The inner thickened portions of one outer pipe and the outer thickened portions of the other outer pipe are connected by threads to form an airtight special thread to complete the insulation pipe connection and form a pipe string.

[0006] Furthermore, a sealing interface is provided at the welded ends of the outer and inner tubes, so that the two different insulation tubes can be tightly connected at the end faces through the sealing interface.

[0007] Furthermore, a sealing ring is provided between the sealing interfaces 4 of the two different insulation pipes.

[0008] Furthermore, the diameter of the trapezoidal internal thread gradually decreases from the opening inwards.

[0009] Furthermore, the trapezoidal internal thread has a pitch of 8-10 threads per inch and a taper of 1:16.

[0010] Furthermore, a sealing interface is provided at the transition joint between the outer thickened portion of one of the outer tubes and the inner thickened portion of the other outer tube.

[0011] Furthermore, the height of the thickened portion of the outer tube is slightly greater than the wall thickness of the outer tube.

[0012] Furthermore, the thickness of the outer thickening portion and the inner thickening portion is greater than 5mm, and the thickness length is greater than 100mm.

[0013] Furthermore, metal sealing shoulders are provided on both the inner wall of the outer thickening portion and the outer wall of the inner thickening portion.

[0014] Furthermore, an insulation layer is provided between the outer tube and the inner tube.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] This invention eliminates the need for couplings during insulated pipe connection by setting trapezoidal internal and external threads at both ends of the outer pipe, significantly reducing the number of threads and improving the efficiency of downhole operations. Furthermore, the smaller outer diameter of the pipe wall avoids the impact of larger pipe diameters, reducing the difficulty of drilling operations. In addition, the entire tubing string has no obvious heat dissipation points, greatly improving the insulation effect. The trapezoidal internal and external threads of the two different insulated pipes connect to form a special gas-tight thread with a machined surface seal, significantly enhancing the airtightness of the tubular structure, ensuring smoother fluid flow within the tubing string, and extending its service life.

[0017] Furthermore, this invention ensures a tight fit and precise connection between the two insulation pipes by setting sealing interfaces at both ends, thereby guaranteeing the airtightness and insulation performance of the pipeline. A sealing ring is placed between the two sealing interfaces to ensure the pipe-to-pipe connection is sealed, preventing liquid from corroding the threads from the inside, protecting the threads, and extending their lifespan. Simultaneously, both the outer and inner thickened portions are equipped with metal sealing shoulders, which cooperate with the sealing ring structure to prevent one sealing surface from failing due to excessive interference fit stress on the other, ensuring reliable sealing on both sealing surfaces. Attached Figure Description

[0018] Figure 1 This is a cross-sectional structural diagram of the present invention;

[0019] Figure 2 This is a cross-sectional structural diagram of the connection between the two insulation pipes of this utility model.

[0020] In the diagram: 1-Outer tube; 2-Inner tube; 3-Special gas-tight buckle; 4-Sealing interface; 5-Sealing ring. Detailed Implementation

[0021] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown in this embodiment, a high-efficiency, long-life, straight-threaded, central insulation pipe for medium-deep geothermal wells includes an outer pipe 1 and an inner pipe 2 concentrically mounted. Both ends of the inner pipe 2 are welded to the outer pipe 1, and an insulation layer is provided between the outer pipe 1 and the inner pipe 2. One end of the outer pipe 1 is thickened radially to form an outer thickened portion. The height of the outer thickened portion is slightly greater than the wall thickness of the outer pipe. A trapezoidal internal thread is provided on the inner wall of the outer thickened portion. The diameter of the trapezoidal internal thread gradually decreases from the opening inwards, with a pitch of 8-10 threads per inch and a taper of 1:16. The outer thickened portion increases the wall thickness of the outer pipe 1, giving it higher strength and rigidity at the connection point. This effectively withstands larger mechanical loads, pressures, or external impacts, reducing the risk of deformation under high pressure or strong force. The trapezoidal thread typically has a larger contact surface, enabling it to withstand higher torque and tensile force, thus ensuring the strength and stability of the connection. At the other end of the outer tube 1, an inner thickened section is formed by radial thickening. A trapezoidal external thread matching the trapezoidal internal thread is provided on the outer wall of the inner thickened section. The thickness of both the outer and inner thickened sections is greater than 5mm, and the thickening length is greater than 100mm. Metal sealing shoulders are provided on both the inner and outer walls of the outer and inner thickened sections. These metal sealing shoulders are angled, used to position the upper thread, control the upper thread torque, improve the thread's anti-sticking ability, ensure a good seal, prevent external liquid corrosion of the thread, and extend the lifespan of the thread and the insulation pipe. In geothermal applications, they can also absorb deformation caused by thermal stress. Simultaneously, in conjunction with the sealing ring structure, they prevent one sealing surface from being overloaded due to interference fit, thus avoiding the failure of the other sealing surface and ensuring reliable sealing on both sealing surfaces.

[0023] When multiple insulation pipes are connected in a direct connection mode, such as Figure 2As shown, the inner thickened portion of one outer tube 1 is connected to the outer thickened portion of another outer tube 1 via threads to form a special gas-tight coupling 3 with a machined surface seal. This precise thread fit forms a tubing string, achieving a tight connection between the two tubes. This design eliminates the need for couplings, significantly reducing the number of threads and improving the efficiency of downhole operations. Furthermore, the smaller outer diameter of the tube wall avoids the impact of larger diameter tubes, reducing the difficulty of drilling operations. In addition, the entire tubing string has no obvious heat dissipation points, greatly improving the insulation effect. Sealing interfaces 4 are set at the welded ends of the outer tube 1 and inner tube 2. The two different insulated tubes achieve a tight fit between their end faces through these sealing interfaces, forming a precise joint. A sealing ring 5 is placed between the sealing interfaces 4 of the two different insulated tubes to ensure the airtightness and insulation performance of the pipeline. The sealing ring 5 is made of high-temperature resistant fluororubber with a "T"-shaped cross-section, ensuring the sealing of the pipe-to-pipe connection, preventing liquid from corroding the threads from the inside, protecting the threads, and extending service life. A sealing interface 4 is provided at the transition joint between the outer thickened part of one outer tube 1 and the inner thickened part of the other outer tube 1 to ensure the airtightness or liquid tightness of the connection part, prevent leakage of the internal medium (gas or liquid) during operation, and thus ensure the safety, stability and environmental friendliness of the system.

Claims

1. A high-efficiency, long-life, straight-threaded central insulation pipe for medium-deep geothermal wells, characterized in that, The system includes an outer tube (1) and an inner tube (2) that are concentrically fitted together. The two ends of the inner tube (2) are welded to the outer tube (1). One end of the outer tube (1) is thickened on its radial outer side to form an outer thickened part. A trapezoidal internal thread is provided on the inner wall of the outer thickened part. The other end of the outer tube (1) is thickened on its radial inner side to form an inner thickened part. A trapezoidal external thread matching the trapezoidal internal thread is provided on the outer wall of the inner thickened part. The inner thickened part of one outer tube (1) is connected to the outer thickened part of the other outer tube (1) by thread to form a special gas-tight buckle (3) to complete the connection of the insulation pipe and form a pipe column.

2. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, A sealing interface (4) is provided at the welding points of the outer tube (1) and the inner tube (2) so that the two different insulation tubes can be connected and tightly fitted through the sealing interface (4).

3. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 2, characterized in that, A sealing ring (5) is provided between the sealing interfaces (4) of the two different insulation pipes.

4. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, The diameter of the trapezoidal internal thread gradually decreases from the opening inwards.

5. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 4, characterized in that, The trapezoidal internal thread has a pitch of 8-10 threads per inch and a taper of 1:

16.

6. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, A sealing interface (4) is provided at the transition joint between the outer thickening portion of one of the outer tubes (1) and the inner thickening portion of the other outer tube (1).

7. The high-efficiency, long-life, straight-threaded, central insulation pipe for medium-deep geothermal wells according to claim 1, characterized in that, The height of the thickened portion of the outer tube (1) is slightly greater than the wall thickness of the outer tube (1).

8. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, The thickness of the outer and inner thickened portions is greater than 5 mm, and the length of the thickened portion is greater than 100 mm.

9. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, Metal sealing shoulders are provided on both the inner wall of the outer thickening portion and the outer wall of the inner thickening portion.

10. The high-efficiency, long-life, straight-threaded, medium-deep geothermal well central insulation pipe according to claim 1, characterized in that, An insulation layer is provided between the outer tube (1) and the inner tube (2).

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