Small-caliber central thermal insulation pipe for middle-deep geothermal well

Abstract

The utility model discloses a small-caliber central thermal insulation pipe for a medium-deep geothermal well, which comprises an inner pipe and an outer pipe, two ends of the inner pipe and the outer pipe are annularly connected to form a sealed cavity, a thermal insulation layer wrapping the inner pipe is arranged in the sealed cavity, the thermal insulation layer is of a layered structure, a BOPET (biaxially oriented polyethylene terephthalate) film is used as a base material, and a layer of aluminum film is electroplated on the BOPET film. The BOPET film base material is combined with the electroplated aluminum film, so that the reflection performance of the heat preservation layer is enhanced, outward heat transfer of internal heat is effectively blocked, the light weight and high strength of the heat preservation layer are guaranteed, and the heat preservation layer is compact and flat in structure and convenient to wrap. Due to the design of the strip-shaped ribs, the strength of a coating object is improved, deformation or damage of the heat preservation layer in long-time use is prevented, meanwhile, the strip-shaped ribs can serve as coating datum lines, axis alignment during coating is guaranteed, dislocation of the heat preservation layer at the connector is reduced, flatness is guaranteed, the heat reflectivity and the heat preservation effect are improved, and accurate positioning of constructors is facilitated; the construction efficiency is improved.

Description

Technical Field

[0001] This utility model belongs to the field of central insulation pipes, specifically relating to a small-diameter central insulation pipe for medium-deep geothermal wells. Background Technology

[0002] Small-diameter geothermal central insulated pipes typically refer to central pipes for geothermal wells with an outer diameter ≤100mm. These pipes are used in geothermal well downhole tubing to transport underground heat sources from deep underground to the surface, and are commonly used in geothermal resource development and oil extraction. Traditionally, small-diameter insulated pipes are produced using a one-step process, where the steel pipe and outer protective pipe are coaxially fixed, and polyurethane foam is injected in the middle for one-time molding. This process offers high production efficiency.

[0003] However, small-diameter pipes have a small outer diameter, and the insulation layer is usually thin (e.g., the insulation layer thickness of DN100 pipes is mostly 30-50mm), resulting in lower thermal resistance. Furthermore, if polyurethane foam (temperature resistance ≤120℃) is used to transport geothermal fluids or steam above 120℃, the foam will gradually carbonize and shrink, causing the insulation layer to detach from the inner pipe, forming an "air layer" and drastically increasing heat loss. At the same time, small-diameter pipes have dense joints, requiring section-by-section treatment of the insulation layer during welding or heat fusion connections, leading to high labor costs and difficulty in ensuring a proper seal. Utility Model Content

[0004] To overcome the shortcomings of the existing technology, the purpose of this utility model is to provide a small-diameter central insulation pipe for medium-deep geothermal wells, which solves the problems of high heat loss, limited applicable temperature, difficult manufacturing, and inconvenient installation of existing small-diameter central insulation pipes.

[0005] This utility model is achieved through the following technical solution:

[0006] A small-diameter central insulation pipe for medium-deep geothermal wells includes an inner pipe and an outer pipe. The two ends of the inner pipe and the outer pipe are connected in annular shape to form a sealed cavity. An insulation layer is provided inside the sealed cavity to wrap the inner pipe. The insulation layer has a layered structure and uses BOPET film as the substrate. An aluminum film is electroplated on the BOPET film.

[0007] Furthermore, the insulation layer has a cuboid structure, with strip ribs set on its two long sides.

[0008] Furthermore, the strip ribs are sewn onto the two long sides of the insulation layer with fine thread made of inorganic material.

[0009] Furthermore, multiple cable ties are provided on the aluminum film of the insulation layer.

[0010] Furthermore, the cable tie axis is perpendicular to the axis of the insulation layer, and the cable ties are spaced 0.8-1.2 meters apart.

[0011] Furthermore, the inner and outer tubes are concentric carbon steel pipes, with the outer tube being longer than the inner tube and the outer diameter of the inner tube being smaller than the inner diameter of the outer tube. The inner and outer tubes are annularly welded at both ends to form a sealed cavity, which is then vacuumed.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0013] The combination of BOPET film substrate and electroplated aluminum film in this invention not only enhances the reflective properties of the insulation layer and effectively blocks the transfer of internal heat to the outside, but also ensures the lightweight and high strength of the insulation layer. Moreover, the structure is compact, flat, and easy to cover.

[0014] The design of the strip reinforcement in this utility model not only increases the strength of the covering material and prevents deformation or damage of the insulation layer during long-term use, but also serves as a baseline for the covering, ensuring axial alignment during covering, reducing misalignment of the insulation layer at the interface, ensuring flatness, improving heat reflectivity and insulation effect, facilitating accurate positioning by construction personnel, and improving construction efficiency.

[0015] The design of this utility model cable tie facilitates construction and bundling, and improves work efficiency. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of the insulation layer structure of this utility model.

[0018] Figure 3 This is a schematic diagram of a practical cable tie.

[0019] In the diagram, 1-inner tube; 2-outer tube; 3-insulation layer; 3-1-BOPET film; 3-2-aluminum film; 4-rib; 5-cable tie. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. The description is for explanation and not limitation of the present invention.

[0021] A small-diameter centrally insulated pipe for medium-deep geothermal wells includes an inner pipe 1 and an outer pipe 2, with the two ends of the inner pipe 1 and outer pipe 2 connected in a ring to form a sealed cavity. An insulation layer 3, which wraps around the inner pipe, is disposed within the sealed cavity. The insulation layer 3 has a layered structure and uses a BOPET film 3-1 as the substrate, with an aluminum film 3-2 electroplated on the BOPET film. The insulation layer 3 uses BOPET as the substrate and is pre-plated with a high-reflectivity aluminum film, resulting in good material toughness, excellent heat reflection, and convenient and simple construction.

[0022] Furthermore, the design of this insulation pipe also considers the special environment of geothermal wells, such as the presence of high temperature, high pressure, and corrosive media. Therefore, the inner pipe 1 and outer pipe 2 are made of carbon steel, which has excellent high temperature resistance, high pressure resistance, and corrosion resistance, ensuring the long-term stable operation of the insulation pipe in harsh environments. At the same time, the strength and rigidity of the carbon steel pipe provide solid support for the insulation layer, preventing deformation or damage at high temperatures. In addition, the annular welds at both ends of the inner and outer pipes form a sealed cavity, effectively preventing the media in the geothermal well from penetrating into the insulation layer, thus ensuring the durability of the insulation effect. The outer pipe 2 is longer than the inner pipe 1, and the outer diameter of the inner pipe 1 is smaller than the inner diameter of the outer pipe 2. The annular welds at both ends of the inner pipe 1 and outer pipe 2 form a sealed cavity, which is then vacuum-sealed.

[0023] Furthermore, the insulation layer 3 has a cuboid structure, with strip ribs 4 set on its two long sides. These strip ribs 4 are sewn onto the two long sides of the insulation layer 3 with fine, inorganic thread. In the three-layer composite structure of the central insulation pipe, the insulation layer 3 is prone to eccentricity or deformation due to external forces (such as compression or vibration) during transportation and installation, leading to increased heat loss and even corrosion of the working pipe. The strip ribs 4 are evenly distributed along the circumference of the insulation layer and fixed to the outer wall of the working pipe or the inner wall of the protective layer, forming a "positioning skeleton" to ensure that the insulation layer 3 is always wrapped around the center of the inner pipe 1, avoiding eccentricity. The strip ribs 4 act as "rigid supports," improving the circumferential stiffness of the insulation layer 3 and reducing the following problems:

[0024] (1) External load impact: When buried, resist radial compression caused by soil backfill or ground vehicle load.

[0025] (2) Thermal expansion and contraction stress: When the inner tube 1 expands due to heating, the strip rib 4 restricts the displacement of the insulation layer 3 to prevent the outer tube 2 from cracking due to excessive deformation.

[0026] (3) At the same time, the strip 4 can be used as a "baseline" during installation to ensure that the axes are aligned when multiple insulation pipes are connected, and to reduce the misalignment of the insulation layer at the interface.

[0027] Furthermore, multiple cable ties 5 are provided on the aluminum film 3-2 of the insulation layer 3. The cable ties 5 pass around the strip rib 4 and the insulation layer 3 and are tightly attached to the surface of the insulation layer 3. The axis of the cable ties 5 is perpendicular to the axis of the insulation layer 3, and the cable ties 5 are spaced 0.8-1.2 meters apart, preferably 1 meter apart.

[0028] The installation process of this utility model is as follows:

[0029] Step 1: Sew the strip ribs 4 to the two long sides of the insulation layer 3 with fine thread made of inorganic material;

[0030] Step 2: Lay the insulation layer, wrap the insulation layer 3 around the inner tube 1, and wrap the cable tie 5 around the strip rib 4 and the insulation layer 3, and tighten it tightly against the surface of the insulation layer 3.

[0031] Step 3: Evacuate the inner tube 1 and outer tube 2 under vacuum and weld the two ends together in a ring. The vacuum heating temperature should not exceed 200℃, and the vacuum should reach 10℃. -1 After Pa, the heating time is less than 1 hour, and a vacuum layer is formed between the outer tube 2 and the insulation layer.

Claims

1. A small-diameter centrally insulated pipe for medium-deep geothermal wells, characterized in that, It includes an inner tube (1) and an outer tube (2). The two ends of the inner tube (1) and the outer tube (2) are connected in an annular shape to form a sealed cavity. An insulation layer (3) is provided inside the sealed cavity to wrap the inner tube. The insulation layer (3) has a layered structure and uses BOPET film (3-1) as the substrate. An aluminum film (3-2) is electroplated on the BOPET film.

2. The small-diameter centrally insulated pipe for medium-deep geothermal wells according to claim 1, characterized in that, The insulation layer (3) has a cuboid structure, and strip ribs (4) are provided on the two long sides of the insulation layer (3).

3. A small-diameter centrally insulated pipe for medium-deep geothermal wells according to claim 2, characterized in that, The strip ribs (4) are sewn onto the two long sides of the insulation layer (3) with fine thread, which is made of inorganic material.

4. A small-diameter centrally insulated pipe for medium-deep geothermal wells according to claim 1, characterized in that, Multiple cable ties (5) are provided on the aluminum film (3-2) of the insulation layer (3).

5. A small-diameter centrally insulated pipe for medium-deep geothermal wells according to claim 4, characterized in that, The cable ties (5) are perpendicular to the axis of the insulation layer (3), and the cable ties (5) are spaced 0.8-1.2 meters apart.

6. A small-diameter centrally insulated pipe for medium-deep geothermal wells according to claim 1, characterized in that, The inner tube (1) and the outer tube (2) are concentric carbon steel pipes. The length of the outer tube (2) is greater than that of the inner tube (1), and the outer diameter of the inner tube (1) is smaller than that of the outer tube (2). The inner tube (1) and the outer tube (2) are circumferentially welded at both ends to form a sealed cavity, and the sealed cavity is vacuumed.

Images