Counterweight-free stainless steel inner sleeve for geothermal well
By using counterweightless stainless steel structure in the inner casing of geothermal wells, the problem of counterweight of PE pipes is solved, and the application of low-cost, heat-resistant and pressure-resistant inner casing is achieved, reducing construction difficulty and cost.
Patent Information
- Application Number
- CN202422118796.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-08-05
- Estimated Expiration
- 2034-08-30
AI Technical Summary
The use of PE pipes in the casing of existing geothermal wells requires counterweight, which makes it difficult and costly to go down the well, and the PE pipe material has a high buoyancy, which increases the construction complexity and economic burden.
The counterweightless stainless steel inner casing structure is adopted. By connecting multiple stainless steel pipes at the bottom of the PE pipe, the weight of the stainless steel pipe is used instead of the counterweight, and the connection is combined with flexible and rigid joints, the smooth down-hole and down-hole use of stainless steel pipes is achieved.
It reduces the cost of counterweight structure, shortens the total height of the well wall pipe, reduces the risk of getting stuck, reduces the construction difficulty, and the heat resistance and pressure resistance of stainless steel pipes meet the needs of geothermal wells.
Smart Images
Figure CN223191857U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of geothermal wells, in particular to a non-counterweight stainless steel inner casing for geothermal wells. Background Art
[0002] As a renewable energy source, geothermal energy boasts advantages such as widespread distribution, low cost, ease of extraction, cleanliness, and direct utilization. Promoting its utilization is an effective measure for resource conservation and environmental protection, and a path to sustainable development for human society. Currently, geothermal energy utilization technology is continuously evolving, becoming a preferred option for building heating and cooling. Current geothermal technology involves drilling into the rock and soil layers, typically 2,000 to 3,000 meters underground. An inner casing is inserted into the geothermal well pipe. Through a heat exchanger, cold water enters the well pipe, absorbing the underground heat. The water then flows upward from the bottom of the insulating inner casing, channeling the underground heat to the heat exchanger, where it is used to heat the building.
[0003] At present, the inner casing of geothermal wells mainly adopts PE pipe, such as PETT and continuous glass fiber tape reinforced PE composite pipe, which has certain flexibility, heat resistance and pressure resistance. However, this type of PE pipe still has the following defects: First, the material of this type of PE pipe has a certain buoyancy. Its total length is basically the same as the length of the well wall, which needs to reach 2000m to 3000m. In order to ensure smooth lowering of the pipe, it is necessary to add a counterweight 700 at the bottom of the PE pipe. The counterweight 700 is first lowered into the well to pull the PE pipe downward and smoothly lower it into the well. After the water is turned on, the counterweight 700 also needs to overcome the buoyancy of the PE pipe itself to prevent the PE pipe from floating upward. Therefore, the counterweight 700 generally needs to reach more than 1 t. The counterweight 700 is generally made of stainless steel iron blocks. Figure 5 This type of counterweight has a certain length, which increases the difficulty of going down the well and getting stuck, and the counterweight is also expensive. 2. Currently, for high-temperature areas underground, continuous glass fiber reinforced PE composite pipes are generally used. This composite pipe has good pressure and high temperature resistance. Generally, a composite pipe of about 300m is used in the high-temperature area at the bottom of the well to better achieve underground heat exchange. However, the cost of this type of glass fiber PEPE pipe is high, reaching 180 yuan per meter, which is relatively high. Utility Model Content
[0004] The technical problem to be solved by the utility model is to provide a low-cost counterweight-free stainless steel inner casing for geothermal wells which can replace the counterweight.
[0005] In order to solve the above technical problems, the technical solution of the present invention is: a non-counterweight stainless steel inner casing for geothermal wells, including a PE pipe placed in the geothermal well pipe wall, the bottom end of the PE pipe is connected with a non-counterweight inner casing that can also serve as a counterweight, the non-counterweight inner casing includes multiple stainless steel pipes connected end to end, the stainless steel pipe at the top is connected to the bottom end of the PE pipe by a rigid coupling, and the two adjacent stainless steel pipes are connected by a flexible coupling, the flexible coupling includes two first coupling bodies, the two first coupling bodies are threadedly connected to the corresponding stainless steel pipes, a flexible pipe is connected between the two first coupling bodies, the bottom end of the stainless steel pipe at the bottom end is provided with a conical well plug, and a plurality of water inlet holes are also arranged on the bottom end pipe wall of the stainless steel pipe at the bottom end, and the water inlet holes connect the outside and the inside of the stainless steel pipe; the wall thickness of the stainless steel pipe is 3mm-5mm, and the sum of the lengths of all stainless steel pipes is 200m-300m.
[0006] As a preferred technical solution, the flexible pipe is a PE pipe.
[0007] As a preferred technical solution, one end of the first coupling body is provided with a first threaded end, and the other end of the first coupling body is provided with a first press-fit end, the outer surface of the first threaded end is provided with a first external thread threadedly connected to the stainless steel pipe, the first press-fit end is provided with a first press-fit ring groove, the end of the flexible tube is inserted into the first press-fit ring groove, and the outer surface of the first press-fit end is rolled with a first extrusion groove that is concave inward and presses the outer surface of the flexible tube.
[0008] As a preferred technical solution, the rigid coupling includes a second coupling body, one end of the second coupling body is provided with a second threaded end, the other end of the second coupling body is provided with a second press-fit end, the outer surface of the second threaded end is provided with a second external thread threadedly connected to the stainless steel pipe, the second press-fit end is provided with a second press-fit ring groove, the end of the PE pipe is inserted into the second press-fit ring groove, and the outer surface of the second press-fit end is rolled with a second extrusion groove that is concave inward and presses the outer surface of the PE pipe.
[0009] As an optimal technical solution, the conical well plug is a solid stainless steel plug inside, the top of the stainless steel plug is threadedly connected to the stainless steel pipe at the bottom, the stainless steel plug and the stainless steel pipe are welded at the fitting seam, and the bottom end of the stainless steel plug is a conical structure that is convenient for going down the well.
[0010] Due to the adoption of the above technical scheme, the beneficial effects of the present invention are as follows: the inner casing structure of the present invention is composed of the original PE pipe and the stainless steel pipe in the prior art, the stainless steel pipe is arranged at the bottom end of the PE pipe, and is used to replace a certain length of the original PE pipe, and the inner casing is placed as a whole in the well wall pipe, wherein the stainless steel pipe is close to the bottom end of the well wall pipe. Due to the large weight of the stainless steel pipe itself, it can replace the counterweight structure in the prior art, so the counterweight structure can be cancelled. After the counterweight structure is cancelled, the original concentrated counterweight is redistributed evenly, which not only reduces the cost of the counterweight structure, but also no longer requires a reserved space for the placement of the counterweight structure in the well wall pipe, which can shorten the total height of the well wall pipe, and the inner casing without counterweight can also reduce the possibility of jamming when it comes out of the well; the stainless steel pipe itself has good heat resistance and pressure resistance, and uses flexible couplings to increase the micro-deformation of the stainless steel pipe, which can completely replace the PE pipe for application in geothermal wells. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.
[0012] Figure 1 It is a structural schematic diagram of an embodiment of the utility model;
[0013] Figure 2 It is a schematic diagram of a flexible coupling according to an embodiment of the present utility model;
[0014] Figure 3 Schematic diagram of a rigid coupling according to an embodiment of the present invention;
[0015] Figure 4 This is a schematic diagram of the stainless steel tube at the bottom end of an embodiment of the present utility model;
[0016] Figure 5 is a schematic diagram of background technology;
[0017] In the figure: 100-PE pipe; 200-stainless steel pipe; 300-rigid coupling; 301-second coupling body; 302-second threaded end; 303-second press-fit end; 304-second press-fit ring groove; 305-second extrusion groove; 400-flexible coupling; 401-first coupling body; 402-flexible pipe; 403-first threaded end; 404-first press-fit end; 405-first press-fit ring groove; 406-first extrusion groove; 500-conical well plug; 501-stainless steel plug; 502-conical structure; 600-water inlet hole; 700-counterweight. DETAILED DESCRIPTION
[0018] The present invention is further described below with reference to the accompanying drawings and examples. In the detailed description that follows, certain exemplary embodiments of the present invention are described by way of illustration only. It goes without saying that those skilled in the art will recognize that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and description are illustrative in nature and are not intended to limit the scope of the claims.
[0019] like Figure 1 and Figure 2 As shown, a non-counterweight stainless steel inner casing for a geothermal well includes a PE pipe 100 placed in the wall of the geothermal well pipe, the bottom end of the PE pipe 100 is connected to a non-counterweight inner casing that can also serve as a counterweight, the non-counterweight inner casing includes a plurality of stainless steel pipes 200 connected end to end, the stainless steel pipe 200 at the top is connected to the bottom end of the PE pipe 100 by a rigid coupling 300, and two adjacent stainless steel pipes 200 are connected by a flexible coupling 400, the flexible coupling 400 includes two first coupling bodies 401, the two first coupling bodies 401 are threadedly connected to the corresponding stainless steel pipes 200, and a flexible pipe 402 is connected between the two first coupling bodies 401, the bottom end of the stainless steel pipe 200 at the bottom end is provided with a tapered well plug 500, and a plurality of water inlet holes 600 are also arranged on the bottom end pipe wall of the stainless steel pipe 200 at the bottom end, and the water inlet holes 600 communicate with the outside and inside of the stainless steel pipe 200. Since the original PE pipe 100 itself has a certain degree of flexibility, a rigid coupling 300 can be used to connect the stainless steel pipe 200 and the PE pipe 100. In order to ensure that the stainless steel pipe 200 can be smoothly lowered into the well, a flexible coupling 400 is used to connect the stainless steel pipes 200. The flexible coupling 400 allows the stainless steel pipe 200 to better adapt to the well wall angle. At the same time, a conical well plug 500 is used at the bottom end of the stainless steel pipe 200 to seal the bottom end of the stainless steel pipe 200, and the conical structure is used to guide the stainless steel pipe 200 to move downward smoothly. When in use, cold water enters the deep wall of the geothermal well through the outside of the inner casing, absorbs the underground high-temperature heat, and then enters the interior of the inner casing through the water inlet 600 at the bottom, flows upward, and guides the underground high-temperature heat to the heat exchanger, which heats the building through the heat exchanger.
[0020] In the existing technology, PE pipes are mainly used for geothermal wells of 2500m-3000m. In order to ensure the smooth installation and use of the inner casing, a counterweight needs to be connected at the bottom. Therefore, the utility model provides a new stainless steel inner casing, which can eliminate the original counterweight and has the characteristics of reasonable design and low cost.
[0021] The inner casing structure of the utility model is composed of the original PE pipe and the stainless steel pipe in the prior art. The stainless steel pipe is arranged at the bottom end of the PE pipe to replace a certain length of the original PE pipe. The inner casing is placed in the well wall pipe as a whole, wherein the stainless steel pipe is close to the bottom end of the well wall pipe. Since the stainless steel pipe has a large weight, it can replace the counterweight structure in the prior art, so the counterweight structure can be cancelled. After the counterweight structure is cancelled, not only the cost of the counterweight structure is reduced, but also the well wall pipe no longer needs to reserve a space for placing the counterweight structure, which can shorten the total height of the well wall pipe, and the inner casing without counterweight can also reduce the possibility of jamming when it comes out of the well; the stainless steel pipe itself has good heat resistance and pressure resistance, and uses a flexible coupling to increase the micro-deformation of the stainless steel pipe, which can completely replace the PE pipe for application in geothermal wells.
[0022] In the existing technology, for a 2500m geothermal well, the high-temperature zone at the bottom of the inner casing generally uses about 300m of continuous glass fiber tape reinforced PE composite pipe, and the rest can use ordinary PE pipe 100. This continuous glass fiber tape reinforced PE composite pipe has good heat resistance and pressure resistance, but due to the high cost of this composite pipe, its use is limited, and this composite pipe also needs to be equipped with a counterweight at the bottom before it can be used.
[0023] In this embodiment, a stainless steel pipe 200 can be used to replace the original continuous glass fiber tape reinforced PE composite pipe at the bottom of the geothermal well. Different sizes can be replaced according to the wall thickness of the stainless steel pipe 200.
[0024] The wall thickness of the stainless steel pipe 200 is 3 mm to 5 mm, and the total length of all the stainless steel pipes 200 is 200 m to 300 m. The stainless steel pipe 200 uses a φ108mm round pipe, which is closest in size to the φ110mm PE pipe 100 used underground. When the wall thickness of the stainless steel pipe 200 is 3mm, the total length of all the stainless steel pipes 200 is 300m. According to calculations, the weight of all the stainless steel pipes 200 at this time is much greater than 1t, achieving the purpose of counterweight, which is used to overcome buoyancy and realize the smooth lowering of the inner casing into the well; when the wall thickness of the stainless steel is 4mm, the total length of all the stainless steel pipes 200 is 250m. According to calculations, the weight of all the stainless steel pipes 200 at this time is much greater than 1t, which is used to overcome buoyancy and realize the smooth lowering of the inner casing into the well; when the wall thickness of the stainless steel is 5mm, the total length of all the stainless steel pipes 200 is 200mm. According to calculations, the weight of all the stainless steel pipes 200 at this time is much greater than 1t, which is used to overcome buoyancy and realize the smooth lowering of the inner casing into the well. In the existing technology, the φ110mm continuous glass fiber tape reinforced PE composite pipe costs about 180 yuan / meter, while the replacement φ108mm stainless steel pipe 200 costs about 110 yuan / meter. The cost of stainless steel pipe 200 is significantly lower than the original continuous glass fiber tape reinforced PE composite pipe in the existing technology.
[0025] See also Figure 2The flexible coupling 400 includes two first coupling bodies 401, which are threadedly connected to the corresponding stainless steel pipes 200. A flexible pipe 402 is connected between the two first coupling bodies 401. The flexible pipe 402 is a PE pipe 100. The flexible pipe 402 utilizes the flexibility of the PE pipe 100 to connect the stainless steel pipes 200, achieving slight deformation between the stainless steel pipes 200. The PE pipe 100 is made of the same material as the PE pipe 100 of the inner casing, so it can meet the heat resistance and pressure resistance requirements of geothermal wells. The function of the first coupling body 401 is to connect the PE pipe 100 to the stainless steel pipe 200, and then connect the flexible pipe 402 between the two first coupling bodies 401. The flexible connection between the two stainless steel pipes 200 is achieved through the two coupling bodies and the flexible pipe 402, which has the characteristics of reasonable design.
[0026] See also Figure 2 The first coupling body 401 is a stainless steel coupling, and one end of the first coupling body 401 is provided with a first threaded end 403, and the other end of the first coupling body 401 is provided with a first press-fit end 404, and the outer surface of the first threaded end 403 is provided with a first external thread threadedly connected to the stainless steel pipe 200, and the first press-fit end 404 is provided with a first press-fit ring groove 405, and the end of the flexible tube 402 is inserted into the first press-fit ring groove 405, and the outer surface of the first press-fit end 404 is rolled to provide a first extrusion groove 406 that is concave inward and presses the outer surface of the flexible tube 402. The flexible coupling 400 needs to be prefabricated. A length of approximately 15-25 cm can be cut from an existing PE pipe 100 coil. Both ends are ground flat and chamfered. One end of the flexible tube 402 is then fully inserted into the first press-fit annular groove 405 of one of the first coupling bodies 401. A first, inwardly concave extrusion groove 406 is then rolled onto the outer surface of the first press-fit end 404. The first extrusion groove 406 is an annular circumferential groove formed on the outer surface of the first press-fit end 404. This inwardly concave extrusion groove 406 compresses the outer surface of the flexible tube 402, completing the connection between the flexible tube 402 and one of the first coupling bodies 401. The flexible tube 402 is connected to the other first coupling body 401 in the same manner. When connecting the stainless steel pipes 200, the two first coupling bodies 401 are simply threaded together. To ensure connection reliability, further welding may be performed at the mating point.
[0027] See also Figure 3The rigid coupling 300 is a stainless steel coupling, and the rigid coupling 300 includes a second coupling body 301, one end of the second coupling body 301 is provided with a second threaded end 302, and the other end of the second coupling body 301 is provided with a second press-fit end 303, the outer surface of the second threaded end 302 is provided with a second external thread threadedly connected to the stainless steel pipe 200, the second press-fit end 303 is provided with a second press-fit ring groove 304, the end of the PE pipe 100 is inserted into the second press-fit ring groove 304, and the outer surface of the second press-fit end 303 is rolled with a second extrusion groove 305 that is concave inward and presses the outer surface of the PE pipe 100. During connection, first completely insert the end of the PE tube 100 into the second press-fitting annular groove 304, and roll the second extrusion groove 305 that is concave inward on the outer surface of the second press-fitting end 303. The second extrusion groove 305 is an annular circumferential groove provided on the outer surface of the second press-fitting end 303. The second extrusion groove 305 is concave and deformed inward to compress the outer surface of the PE to complete the connection between the PE tube 100 and the rigid coupling 300. Then, the end of the stainless steel tube 200 is threadedly connected to the rigid coupling 300. In order to ensure the reliability of the connection, the two can be further welded at the joint.
[0028] See also Figure 4 The conical well plug 500 is a solid stainless steel plug 501 inside. The top of the stainless steel plug 501 is threadedly connected to the stainless steel pipe 200 at the bottom. The stainless steel plug 501 and the stainless steel pipe 200 are welded at the fitting seam. The bottom end of the stainless steel plug 501 is a conical structure 502 that is convenient for going down the well.
[0029] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements are intended to fall within the scope of the present invention. The scope of protection claimed in this invention is defined by the appended claims and their equivalents.
Claims
1. A non-weighted stainless steel inner casing for a geothermal well, comprising a PE pipe placed inside the wall of the geothermal well, characterized by: The bottom end of the PE pipe is connected to an unweighted inner sleeve that can also serve as a counterweight. The unweighted inner sleeve includes multiple stainless steel pipes connected end to end. The stainless steel pipe at the top is connected to the bottom end of the PE pipe with a rigid coupling. The two adjacent stainless steel pipes are connected with a flexible coupling. The flexible coupling includes two first coupling bodies. The two first coupling bodies are threadedly connected to the corresponding stainless steel pipes. A flexible pipe is connected between the two first coupling bodies. The bottom end of the stainless steel pipe at the bottom end is provided with a conical well plug. The bottom end wall of the stainless steel pipe at the bottom end is also provided with multiple water inlet holes, and the water inlet holes connect the outside and inside of the stainless steel pipe; the wall thickness of the stainless steel pipe is 3mm-5mm, and the sum of the lengths of all stainless steel pipes is 200m-300m.
2. The non-weighted stainless steel inner casing for geothermal wells according to claim 1, characterized in that: The flexible pipe is a PE pipe.
3. The non-weighted stainless steel inner casing for geothermal wells according to claim 1, characterized in that: One end of the first coupling body is provided with a first threaded end, and the other end of the first coupling body is provided with a first press-fit end. The outer surface of the first threaded end is provided with a first external thread threadedly connected to the stainless steel pipe. The first press-fit end is provided with a first press-fit ring groove. The end of the flexible tube is inserted into the first press-fit ring groove. The outer surface of the first press-fit end is rolled to provide a first extrusion groove that is concave inward and presses the outer surface of the flexible tube.
4. The non-weighted stainless steel inner casing for geothermal wells according to claim 1, characterized in that: The rigid coupling includes a second coupling body, one end of the second coupling body is provided with a second threaded end, the other end of the second coupling body is provided with a second press-fit end, the outer surface of the second threaded end is provided with a second external thread threadedly connected to the stainless steel pipe, the second press-fit end is provided with a second press-fit ring groove, the end of the PE pipe is inserted into the second press-fit ring groove, and the outer surface of the second press-fit end is rolled to provide a second extrusion groove that is concave inward and presses the outer surface of the PE pipe.
5. The non-weighted stainless steel inner casing for geothermal wells according to claim 1, characterized in that: The conical well plug is a solid stainless steel plug inside. The top of the stainless steel plug is threadedly connected to the stainless steel pipe at the bottom. The stainless steel plug and the stainless steel pipe are welded at the fitting seam. The bottom end of the stainless steel plug is a conical structure that is convenient for going down the well.