Structure for freely extending inner pipe of central thermal insulation pipe of middle-deep geothermal well

Abstract

The utility model discloses a structure for freely extending an inner pipe of a central thermal insulation pipe of a medium-deep geothermal well, which comprises an outer pipe and an inner pipe which are concentrically sleeved, one end of the inner pipe is welded and fixed on the outer pipe, a hold-down ring is arranged on the outer wall of the other end part of the inner pipe, and a gap is reserved between the hold-down ring and the outer pipe; a positioning ring is fixed on the inner wall of the outer pipe at the same end, and a plurality of fluororubber sealing rings are arranged between the positioning ring and the pressing ring; when the temperature changes, one end of the inner pipe drives the pressing ring to expand or contract in the axial direction, when the inner pipe contracts, the sealing ring is pressed through the pressing ring, the sealing ring is limited and restrained by the positioning ring, and it is guaranteed that the contraction amount of the inner pipe is within the designed allowable range. The inner pipe can freely expand with heat and contract with cold along with the temperature change of internal fluid, stress is prevented from being generated between the inner pipe and the outer pipe, meanwhile, the outer pipe is prevented from bending deformation or crack failure due to stress, and therefore the quality accident risk is avoided.

Description

Technical Field

[0001] This utility model belongs to the field of thermal insulation pipe manufacturing technology, specifically relating to a structure in which the inner tube of the central thermal insulation pipe of a medium-deep geothermal well can extend freely. Background Technology

[0002] During the manufacturing process of geothermal insulation pipes, to cope with the thermal stress caused by the temperature difference between the outer and inner pipes in downhole conditions, a large pre-stress is usually applied to the inner pipe before welding the ends of the inner and outer pipes. However, this practice has some disadvantages: due to the large pre-stress, the inconsistent shrinkage of the inner and outer pipes at room temperature can easily cause the outer pipe to bend, affecting product quality and increasing the difficulty of thread processing, resulting in a decrease in yield. In addition, due to different downhole depths, temperatures, and temperature differences between the inner and outer pipes in different pipe sections, the thermal stress distribution in each pipe section is uneven. The pre-stress of the same batch of insulation pipes cannot be adjusted according to different downhole depths, resulting in differences in the load borne by the pipe body and weld points. In severe cases, this may cause fatigue damage, thereby affecting the overall service life and operational reliability of the insulation pipe. Utility Model Content

[0003] This utility model aims to provide a structure for the free extension of the inner tube of the central insulation pipe of a medium-deep geothermal well. This structure ensures that the inner tube can freely expand and contract with the temperature changes of the internal fluid, avoiding stress between the inner and outer tubes. At the same time, it prevents the outer tube from bending, deforming, or cracking due to stress, thereby avoiding the risk of quality accidents.

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

[0005] A structure for the free extension of the inner tube of a central insulation pipe in a medium-deep geothermal well includes a concentrically nested outer tube and an inner tube. One end of the inner tube is welded and fixed to the outer tube. A clamping ring is provided on the outer wall of the other end of the inner tube, and a gap is maintained between the clamping ring and the outer tube. A positioning ring is fixed on the inner wall of the outer tube at the same end. Multiple fluororubber sealing rings are located between the positioning ring and the clamping ring. When the temperature changes, one end of the inner tube drives the clamping ring to expand or contract axially. When the inner tube contracts, the clamping ring compresses the sealing rings, and the sealing rings are constrained by the positioning rings to ensure that the contraction of the inner tube is within the design allowable range.

[0006] Furthermore, the clamping ring is connected to the inner tube by a thread.

[0007] Furthermore, the sealing ring is slightly larger than the gap between the outer tube and the inner tube, and an elastic seal is achieved through an interference fit.

[0008] Furthermore, at one end of the outer tube and the inner tube being welded together, and between the outer tube and the inner tube, a spacer ring is provided as a welding carrier to fix one end of the inner tube to the outer tube.

[0009] Furthermore, a heat insulation layer is provided in the cavity between the outer tube and the inner tube.

[0010] Furthermore, the thermal insulation layer comprises one or more materials selected from aluminum foil, aerogel, and glass fiber.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] This invention fixes one end of the inner tube of the insulation pipe to the outer tube, while the other end can freely expand and contract. This allows the straightness of the insulation pipe to be controlled within 2‰, resulting in high production efficiency and low energy consumption, making it more suitable for downhole operations. Specifically, a clamping ring is installed at the movable end of the inner tube, a positioning ring is placed on the inner wall of the outer tube at the same end, and a sealing ring is installed between the inner and outer tubes to ensure the cavity is sealed and to cut off the heat convection path. When the temperature changes, the movable end of the inner tube drives the clamping ring to expand or contract axially. Simultaneously, when the inner tube contracts, the clamping ring presses against the sealing ring, and the sealing ring is constrained by the positioning ring, ensuring that the contraction of the inner tube is within the design allowable range. This insulation pipe is suitable for operating environments throughout the entire well section at different depths and can be used under different temperature and elongation conditions, effectively avoiding stress concentration. Therefore, it can prevent failure caused by excessive stress, ensuring reliability and durability in complex downhole environments.

[0013] Furthermore, this utility model uses a spacer ring between the outer tube and the inner tube as a welding carrier to fix one end of the inner tube to the outer tube, and the spacer ring can also be used to maintain the distance between the inner and outer tubes, thus playing the role of supporting the structure. Attached Figure Description

[0014] Figure 1 This is a cross-sectional structural diagram of the present invention.

[0015] In the diagram: 1-Outer tube; 2-Inner tube; 3-Spacer ring; 4-Positioning ring; 5-Pressure ring; 6-Sealing ring. Detailed Implementation

[0016] 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.

[0017] like Figure 1As shown in the figure, the structure of the inner tube of the central insulation pipe of the medium-deep geothermal well described in this embodiment includes an outer tube 1 and an inner tube 2 concentrically nested. A spacer ring 3 is provided at one end of the outer tube 1 and the inner tube 2 and between the outer tube 1 and the inner tube 2. The spacer ring 3 is not only used to maintain the distance between the inner and outer tubes, but also serves as a supporting structure and as a welding carrier to fix one end of the inner tube 2 to the outer tube 1, ensuring that the relative position of one end of the inner and outer tubes remains unchanged. At the other end of the outer tube 1 and the inner tube 2, a positioning ring 4 is fixed on the inner wall of the outer tube 1. There are multiple fluororubber sealing rings 6 between the positioning ring 4 and the clamping ring 5. The outer diameter of the sealing ring 6 is slightly larger than the gap between the outer tube 1 and the inner tube 2. An elastic seal is achieved through an interference fit. The sealing ring 6 seals the cavity between the inner and outer tubes and cuts off the heat convection path. A clamping ring 5 is provided on the outer wall of the end of the inner tube 2. The clamping ring 5 is tightly screwed to the inner tube 2 by threads. A gap is maintained between the clamping ring 5 and the outer tube 1 so that the movable end of the inner tube 2 can drive the clamping ring 5 to expand or contract axially when the temperature changes. At the same time, when the inner tube 2 contracts, the clamping ring 5 clamps the sealing ring 6. The sealing ring 6 is limited and constrained by the positioning ring 4 to ensure that the contraction of the inner tube 2 is within the design allowable range.

[0018] A heat insulation layer is provided in the cavity between the inner and outer tubes, which is composed of at least one or more materials selected from aluminum foil, aerogel and glass fiber.

[0019] Working Principle: When using a structure where the inner tube of a central insulation pipe in a medium-deep geothermal well can freely extend, one end of the inner and outer tubes is welded and fixed, while the other end of the inner tube 2 can expand or contract axially with temperature changes, adapting to deformation caused by thermal expansion and contraction. When the ambient temperature rises, the inner tube 2 of the insulation pipe expands outward axially. Since one end of the insulation pipe is fixed, the expansion of the inner tube 2 will not pull the outer tube 1, causing deformation. Similarly, when the ambient temperature decreases, the contraction of the inner tube 2 will not pull the outer tube 1, causing deformation. Furthermore, after the inner tube 2 contracts to a certain distance, the compression ring 5 tightly adheres to the sealing ring 6, and the sealing ring 6 is limited by the positioning ring 4, ensuring that the contraction of the inner tube 2 is controllable.

Claims

1. A structure for the free elongation of the inner tube of a central insulation pipe in a medium-deep geothermal well, characterized in that, It includes an outer tube (1) and an inner tube (2) that are concentrically fitted together. One end of the inner tube (2) is welded and fixed to the outer tube (1). A clamping ring (5) is provided on the outer wall of the other end of the inner tube (2), and a gap is maintained between the clamping ring (5) and the outer tube (1). A positioning ring (4) is fixed on the inner wall of the outer tube (1) at the same end. Multiple fluororubber sealing rings (6) are provided between the positioning ring (4) and the clamping ring (5). When the temperature changes, one end of the inner tube (2) drives the clamping ring (5) to expand or contract axially. When the inner tube (2) contracts, the clamping ring (5) clamps the sealing ring (6). The sealing ring (6) is limited by the positioning ring (4) to ensure that the amount of contraction of the inner tube (2) is within the design allowable range.

2. The structure of the inner tube of the central insulation pipe of a medium-deep geothermal well with free elongation according to claim 1, characterized in that, The clamping ring (5) is connected to the inner tube (2) by a threaded connection.

3. The structure of the inner tube of the central insulation pipe of a medium-deep geothermal well with free elongation according to claim 1, characterized in that, The outer diameter of the sealing ring (6) is slightly larger than the gap between the outer tube (1) and the inner tube (2), and elastic sealing is achieved through interference fit.

4. The structure of the inner tube of the central insulation pipe of a medium-deep geothermal well with free elongation according to claim 1, characterized in that, At one end of the outer tube (1) and the inner tube (2) are welded, and a spacer ring (3) is set between the outer tube (1) and the inner tube (2) as a welding carrier to fix one end of the inner tube (2) to the outer tube (1).

5. The structure of a freely elongating inner tube of a central insulation pipe in a medium-deep geothermal well according to any one of claims 1-4, characterized in that, A heat insulation layer is provided in the cavity between the outer tube (1) and the inner tube (2).

6. The structure of a freely elongating inner tube of a central insulation pipe in a medium-deep geothermal well according to claim 5, characterized in that, The thermal insulation layer comprises a combination of one or more materials selected from aluminum foil, aerogel, and glass fiber.

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