A double-walled heat-insulated water intake pipe for the upper return section of a geothermal well

Abstract

The invention discloses a double-walled insulated water intake pipe for the return section of a geothermal well, which relates to the field of geothermal development technology, and comprises an outer pipe and an inner pipe arranged inside the outer pipe, wherein an inner insulation layer is fixedly attached to the inner wall of the inner pipe, an outer insulation layer is fixedly attached to the outer wall of the inner pipe, and a gap exists between the outer surface of the outer insulation layer and the inner wall of the outer pipe. The double-walled insulated water intake pipe for the return section of a geothermal well provided by the invention can improve the heat insulation performance of the pipe and reduce the heat loss when hot water is transported upward in the pipe.

Description

Technical Field

[0001] The invention relates to the technical field of geothermal development, and in particular to a double-walled heat-insulating water intake pipe used for a return section of a geothermal well. Background Art

[0002] Geothermal energy is a new type of clean, environmentally friendly and renewable energy. Actively developing and utilizing geothermal energy has important practical significance and long-term strategic significance for alleviating energy resource pressure, achieving non-fossil energy goals, promoting the revolution in energy production and consumption, and promoting the construction of ecological civilization.

[0003] At present, the main way to utilize medium and deep geothermal energy is the pumping groundwater system. The pumping groundwater system circulates heat through drilling production wells and reinjection wells. There are many limitations in its use. For example, it requires that the geothermal development and utilization area has relatively rich underground hot water resources; in some porous heat storage areas, the effect of geothermal tail water reinjection has always been unsatisfactory. The tiny impurities in the reinjection water may block the gaps in the rock formations of the geothermal wells, resulting in the inability to reinject, which is a major factor restricting the development and utilization of geothermal resources by the pumping groundwater system; if there is no reinjection, it will lead to a drop in groundwater levels, subsidence of the surface, and salinization of the soil; in urban areas with dense buildings, the location of the drilling well is also an important factor restricting geothermal development. Based on the shortcomings of the pumping groundwater system, the development of a new geothermal development model has become a necessary way to promote the utilization of geothermal energy.

[0004] The closed heat extraction system for single well injection and extraction of geothermal wells only needs to drill a geothermal well, cement the well, connect the water extraction pipeline and lower it into the predetermined position of the geothermal well, and inject the circulating medium (cold water) through the annulus between the water extraction pipeline and the geothermal well. After the circulating medium (cold water) reaches the predetermined position, it extracts heat from the geothermal reservoir and heats up, then enters the inner pipe of the water extraction pipeline and returns to the ground heat exchanger, thus truly realizing the heat extraction without water extraction for geothermal development, and has low requirements for geothermal resources, and does not have the problem of tail water re-injection blocking the formation, and has broad market application prospects. Since the reinjected medium is injected from the annulus between the pipeline and the borehole, and the injected temperature is room temperature, and the extracted geothermal water is output from the center of the pipeline, if a conventional hot water extraction pipe is used, there is only a layer of pipe wall between the hot water in the pipe and the cold water outside the pipe, thereby reducing the temperature of the water in the pipe, so a new double-layer heat extraction and insulation pipe is needed to reduce the heat loss of the water after heat exchange after it is taken from the underground reservoir to the ground. Summary of the invention

[0005] The purpose of the present invention is to provide a double-walled insulated water intake pipe for the return section of a geothermal well to solve the problems existing in the above-mentioned prior art, improve the thermal insulation performance of the pipeline, and reduce the heat loss when hot water is transported upward in the pipeline.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a double-walled insulated water intake pipe for the return section of a geothermal well, comprising an outer pipe and an inner pipe arranged inside the outer pipe, an inner insulation layer is fixedly attached to the inner wall of the inner pipe, an outer insulation layer is fixedly attached to the outer wall of the inner pipe, and a gap exists between the outer surface of the outer insulation layer and the inner wall of the outer pipe.

[0008] Preferably, it further comprises an upper heat-insulating sleeve and a lower heat-insulating sleeve, wherein the upper heat-insulating sleeve and the lower heat-insulating sleeve are respectively sleeved on the upper and lower ends of the inner tube and both abut against the inner wall of the outer tube.

[0009] Preferably, the inner tube comprises a tube body, a male sealing sleeve and a female sealing sleeve, and both ends of the tube body are respectively sealed and fixedly connected to the male sealing sleeve and the female sealing sleeve. For two adjacent inner tubes, the male sealing sleeve of one inner tube can be sealed and inserted into the female sealing sleeve of the other inner tube, the upper heat-insulating sleeve is arranged outside the male sealing sleeve, and the lower heat-insulating sleeve is arranged outside the female sealing sleeve.

[0010] Preferably, an annular groove is provided on the outer peripheral surface of one end of the male sealing sleeve for insertion into the female sealing sleeve, a sealing ring is provided in the annular groove, and the male sealing sleeve and the female sealing sleeve that are plug-connected are sealed and connected via the sealing ring.

[0011] Preferably, a female connecting sleeve and a male connecting sleeve are respectively provided at both ends of the outer tube, and the male connecting sleeve of one of the two adjacent outer tubes can be threadedly connected to the female connecting sleeve of the other outer tube.

[0012] Preferably, an annular limiting protrusion is provided on the outer circumferential surface of the male sealing sleeve, and the annular limiting protrusion includes a bearing portion whose outer circumferential surface is an inverted cone surface, and the inner surface of the outer tube is provided with an inverted cone bearing surface corresponding to the bearing portion, and the upper insulation sleeve includes an insulation bearing portion, and the insulation bearing portion is cooperatively connected between the outer circumferential surface of the bearing portion and the inverted cone bearing surface, and the inner surface and outer surface of the insulation bearing portion are in contact with the outer circumferential surface of the bearing portion and the inverted cone bearing surface respectively.

[0013] Preferably, the upper thermal insulation sleeve also includes a limiting portion fixedly connected to the thermal insulation bearing portion, the inner surface of the limiting portion is provided with a first limiting groove, the first limiting groove is provided with a first limiting retaining ring, the first limiting retaining ring can form a block for the annular limiting protrusion so that the annular limiting protrusion cannot be separated from the upper thermal insulation sleeve upward, the inner surface of the outer tube is provided with a second limiting groove, the second limiting groove is provided with a second limiting retaining ring, the second limiting retaining ring can form a block for the limiting portion so that the upper thermal insulation sleeve cannot be separated from the inverted cone bearing surface upward.

[0014] Preferably, the inner insulation layer is formed by lining the inner tube with a polyethylene tube, and the outer insulation layer is formed by applying a binder to the outer wall of the inner tube and spraying SiO2 aerogel powder.

[0015] Preferably, the upper thermal insulation sleeve and the lower thermal insulation sleeve are both made of polytetrafluoroethylene.

[0016] Preferably, the tube body is a seamless steel tube, the male sealing sleeve and the female sealing sleeve are both made of 35CrMo material, and the tube body is fixedly connected to the male sealing sleeve and the female sealing sleeve by welding.

[0017] Compared with the prior art, the present invention has achieved the following technical effects:

[0018] The double-walled insulated water intake pipe for the return section of a geothermal well provided by the present invention, after the circulating medium undergoes heat exchange in the high-temperature area in the lower middle part of the geothermal well, when it returns to the ground heat exchanger from the central channel of the inner pipe, the provision of the inner insulation layer and the outer insulation layer improves the thermal insulation performance of the inner pipe. Moreover, there is air in the gap between the outer surface of the outer insulation layer and the inner wall of the outer pipe. Air is a poor conductor of heat, which further reduces the heat transfer from the inner pipe to the outer pipe, thereby improving the thermal insulation performance of the pipeline and reducing the heat loss when hot water is transported upward in the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure of a double-walled heat-insulated water intake pipe for the upper return section of a geothermal well provided by the present invention;

[0021] Figure 2 for Figure 1 A partial enlarged schematic diagram of part I of the double-walled insulated water intake pipe used for the return section of a geothermal well;

[0022] Figure 3 A cross-sectional view of an upper heat-insulating sleeve in a double-wall heat-insulating water intake pipe for use in the upper return section of a geothermal well provided by the present invention;

[0023] Figure 4 A cross-sectional view of a lower insulation sleeve in a double-wall insulation water intake pipe for the upper return section of a geothermal well provided by the present invention;

[0024] Figure 5 A schematic diagram of the structure of the double-walled heat-insulated water intake pipes connected to each other for the upper return section of a geothermal well provided by the present invention;

[0025] Figure 6 for Figure 5 A partial enlarged schematic diagram of part II;

[0026] Figure 7 A schematic diagram of the structure of using the double-walled heat-insulating water-intake pipe for the upper return section of a geothermal well provided by the present invention to extract heat from a single geothermal well;

[0027] In the figure: 100-double-wall insulated water intake pipe for the return section of the geothermal well, 1-outer pipe, 2-inner pipe, 3-inner insulation layer, 4-outer insulation layer, 5-upper insulation sleeve, 6-lower insulation sleeve, 7-tube body, 8-male sealing sleeve, 9-female sealing sleeve, 10-annular groove, 11-sealing ring, 12-female connecting sleeve, 13-male connecting sleeve, 14-annular limiting protrusion, 15-bearing part, 16-inverted cone bearing surface, 17-insulation bearing part, 18-limiting part, 19-first limiting groove, 20-first limiting retaining ring, 21-second limiting groove, 22-second limiting retaining ring, 23-water filter pipe, 24-orifice equipment, 25-circulating medium treatment equipment, 26-heat exchanger, 27-pump, 28-user end, 29-annulus, 30-geothermal reservoir, 31-heat exchange section, 32-upper return section. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The purpose of the present invention is to provide a double-walled insulated water intake pipe for the return section of a geothermal well to solve the problems existing in the prior art, improve the thermal insulation performance of the pipe, and reduce the heat loss when hot water is transported upward in the pipe.

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 and Figure 7 As shown, this embodiment provides a double-walled insulated water intake pipe 100 for the return section of a geothermal well, comprising an outer pipe 1 and an inner pipe 2 arranged in the outer pipe 1, an inner insulation layer 3 is fixedly attached to the inner wall of the inner pipe 2, an outer insulation layer 4 is fixedly attached to the outer wall of the inner pipe 2, and there is a gap between the outer surface of the outer insulation layer 4 and the inner wall of the outer pipe 1.

[0032] When in use, after the circulating medium undergoes heat exchange in the high-temperature area in the lower part of the geothermal well, i.e., the geothermal reservoir 30, and then returns to the ground heat exchanger 26 from the central channel of the inner tube 2, the arrangement of the inner insulation layer 3 and the outer insulation layer 4 improves the thermal insulation performance of the inner tube 2. Moreover, the gap between the outer surface of the outer insulation layer 4 and the inner wall of the outer tube 1 (the air in the gap is a poor conductor of heat) further reduces the heat transferred from the inner tube 2 to the outer tube 1, thereby improving the thermal insulation performance of the pipeline and reducing the heat loss when hot water is transported upward in the pipeline.

[0033] like Figure 1-Figure 4 As shown, in this embodiment, an upper heat insulation sleeve 5 and a lower heat insulation sleeve 6 are also included, and the upper heat insulation sleeve 5 and the lower heat insulation sleeve 6 are respectively sleeved on the upper and lower ends of the inner tube 2 and are both in contact with the inner wall of the outer tube 1. The upper heat insulation sleeve 5 and the lower heat insulation sleeve 6 can ensure the radial relative position between the inner tube 2 and the outer tube 1, and prevent the heat transfer caused by the direct contact between the outer heat insulation layer 4 outside the inner tube 2 and the outer tube 1.

[0034] like Figure 1-Figure 2 and Figure 5-Figure 6 As shown, in this embodiment, the inner tube 2 includes a tube body 7, a male sealing sleeve 8 and a female sealing sleeve 9. The two ends of the tube body 7 are respectively sealed and fixedly connected to the male sealing sleeve 8 and the female sealing sleeve 9. For two adjacent inner tubes 2, the male sealing sleeve 8 of one inner tube 2 can be sealed and inserted into the female sealing sleeve 9 of the other inner tube 2. The upper insulation sleeve 5 is sleeved on the outside of the male sealing sleeve 8, and the lower insulation sleeve 6 is sleeved on the outside of the female sealing sleeve 9, which is convenient for disassembly and installation between the inner tubes 2 and can be used multiple times.

[0035] like Figure 1 and Figure 6 As shown, in this embodiment, an annular groove 10 is provided on the outer circumferential surface of one end of the male sealing sleeve 8 for plugging into the female sealing sleeve 9, and a sealing ring 11 is provided in the annular groove 10. The plug-in connected male sealing sleeve 8 and the female sealing sleeve 9 are sealed and connected via the sealing ring 11, wherein two annular grooves 10 are provided, and the two annular grooves 10 are arranged at intervals, and a sealing ring 11 is provided in each annular groove 10, and the sealing ring 11 is an O-ring, which has a better sealing effect.

[0036] like Figure 1 and Figure 6 As shown, in this embodiment, a female connecting sleeve 12 and a male connecting sleeve 13 are respectively provided at both ends of the outer tube 1. For two adjacent outer tubes 1, the male connecting sleeve 13 of one outer tube 1 can be threadedly connected with the female connecting sleeve 12 of the other outer tube 1, which is convenient for connection and disassembly.

[0037] like Figure 2-Figure 3As shown, in this embodiment, an annular limiting protrusion 14 is provided on the outer circumference of the male sealing sleeve 8, and the annular limiting protrusion 14 includes a bearing portion 15 with an inverted conical surface on the outer circumference, and an inverted conical bearing surface 16 corresponding to the bearing portion 15 is provided on the inner surface of the outer tube 1. The upper heat-insulating sleeve 5 includes a heat-insulating bearing portion 17, and the heat-insulating bearing portion 17 is connected between the outer circumference of the bearing portion 15 and the inverted conical bearing surface 16. The inner surface and outer surface of the heat-insulating bearing portion 17 are respectively in contact with the outer circumference of the bearing portion 15 and the inverted conical bearing surface 16. The bearing portion 15 of the inner tube 2 is supported on the inverted conical bearing surface 16 in the outer tube 1 through the heat-insulating bearing portion 17 of the upper heat-insulating sleeve 5, so as to support the inner tube 2.

[0038] like Figure 2-Figure 3 As shown, in this embodiment, the upper insulation sleeve 5 also includes a limiting portion 18 fixedly connected to the insulation bearing portion 17, the inner surface of the limiting portion 18 is provided with a first limiting groove 19, the first limiting groove 19 is provided with a first limiting retaining ring 20, the first limiting retaining ring 20 can form a block for the annular limiting protrusion 14 so that the annular limiting protrusion 14 cannot be separated from the upper insulation sleeve 5 upward, the inner surface of the outer tube 1 is provided with a second limiting groove 21, the second limiting groove 21 is provided with a second limiting retaining ring 22, the second limiting retaining ring 22 can form a block for the limiting portion 18 so that the upper insulation sleeve 5 cannot be separated from the inverted cone bearing surface 16 upward, thereby limiting the inner tube 2 in the outer tube 1, ensuring that the relative positions of the inner tube 2 and the outer tube 1 remain unchanged.

[0039] In this embodiment, the inner insulation layer 3 is formed by lining the inner tube 2 with a polyethylene tube, and the outer insulation layer 4 is formed by applying a binder to the outer wall of the inner tube 2 and spraying SiO2 aerogel powder. The setting of the polyethylene tube not only improves the thermal insulation performance of the inner tube 2, but also has good corrosion resistance when transmitting high-temperature circulating media. Among them, the manufacturing process of the outer insulation layer 4 is: first apply a metal binder to the outer wall of the inner tube 2, and then spray SiO2 aerogel powder onto the metal binder, and then apply the metal binder after the SiO2 aerogel powder completely covers the outer wall of the inner tube, and then spray SiO2 aerogel powder onto the metal binder, and repeat until the predetermined thickness of the SiO2 aerogel is reached.

[0040] In this embodiment, the upper heat-insulating sleeve 5 and the lower heat-insulating sleeve 6 are both made of polytetrafluoroethylene, which has good heat-insulating effect and is resistant to high temperatures.

[0041] In this embodiment, the pipe body 7 is a seamless steel pipe, the male sealing sleeve 8 and the female sealing sleeve 9 are both made of 35CrMo material, and the pipe body 7 is welded and fixedly connected to the male sealing sleeve 8 and the female sealing sleeve 9. Among them, the outer pipe 1 adopts a standard petroleum drill pipe, which has a reliable structure and greatly improves the service life compared with conventional PVC pipes. In addition, compared with conventional PVC pipes that are almost disposable, this water intake pipe can be used for a long time in multiple wells for multiple times.

[0042] like Figure 7 As shown, the present invention is applicable to medium-deep single-well geothermal wells. The water intake pipe column is composed of a plurality of double-walled insulated water intake pipes 100 for the upper return section of the geothermal well connected end to end and a filter pipe 23 (flower pipe) connected to the double-walled insulated water intake pipe 100 for the upper return section of the geothermal well at the lowest end. The upper end of the water intake pipe column is fixed to the wellhead of the geothermal well through the orifice device 24. The length and lowering depth of the filter pipe 23 should be consistent with the regional span of the geothermal reservoir 30 (heat exchange formation of the circulating medium in the geothermal well). The water intake pipe column includes a heat exchange section 31 and an upper return section 32. The heat exchange section 31 is a pipe section composed of the filter pipe 23. The upper return section is a pipe section between the upper end of the filter pipe 23 in the water intake pipe column and the ground. The device is mainly used for the upper return transmission stage of the circulating medium after heating, that is, the upper return section is composed of a plurality of double-walled insulated water intake pipes 100 for the upper return section of the geothermal well. The heat extraction mode is to lower the water intake pipe column to a predetermined position, and inject the circulating medium through the annulus 29 between the water intake pipe column and the well wall under the action of the pump 27 until the high-temperature area (i.e., the heat exchange formation area). After the circulating medium undergoes heat exchange in the high-temperature area in the lower middle part of the geothermal well, the circulating medium enters through the filter pipe 23 and returns from the central channel of the water intake pipe (the central channel of the inner pipe 2) to the ground circulating medium treatment equipment 25, and enters the heat exchanger 26 after being processed by the circulating medium treatment equipment 25. After heat exchange with the user end 28 at the heat exchanger 26, the circulating medium is then transported to the annulus 29 by the pump 27. The circulating medium travel route is: ground-annulus-filter pipe-double-wall insulation water intake pipe-ground. The present invention can ensure that when the heated circulating medium returns through the central channel of the device, the heat transfer is isolated through multiple insulation measures such as the inner pipe, the inner insulation layer, the outer insulation layer, the air in the gap, and the outer pipe, so as to minimize heat loss.

[0043] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A double-walled insulated water intake pipe for the return section of a geothermal well, characterized in that: It comprises an outer tube and an inner tube arranged in the outer tube, an inner heat insulation layer is fixedly attached to the inner wall of the inner tube, an outer heat insulation layer is fixedly attached to the outer wall of the inner tube, and there is a gap between the outer surface of the outer heat insulation layer and the inner wall of the outer tube; It also includes an upper heat-insulating sleeve, which is arranged on the upper end of the inner tube and abuts against the inner wall of the outer tube; the inner tube includes a tube body and a male sealing sleeve, the upper end of the tube body is sealed and fixedly connected to the male sealing sleeve, and the upper heat-insulating sleeve is arranged outside the male sealing sleeve; An annular limiting protrusion is provided on the outer circumferential surface of the male sealing sleeve, and the annular limiting protrusion includes a bearing portion whose outer circumferential surface is an inverted conical surface, and the inner surface of the outer tube is provided with an inverted conical bearing surface corresponding to the bearing portion, and the upper heat insulation sleeve includes a heat insulation bearing portion, and the heat insulation bearing portion is cooperatively connected between the outer circumferential surface of the bearing portion and the inverted conical bearing surface, and the inner surface and outer surface of the heat insulation bearing portion are in contact with the outer circumferential surface of the bearing portion and the inverted conical bearing surface respectively; The upper thermal insulation sleeve also includes a limiting portion fixedly connected to the thermal insulation bearing portion, the inner surface of the limiting portion is provided with a first limiting groove, the first limiting groove is provided with a first limiting retaining ring, the first limiting retaining ring can form a block for the annular limiting protrusion so that the annular limiting protrusion cannot be separated from the upper thermal insulation sleeve upward, the inner surface of the outer tube is provided with a second limiting groove, the second limiting groove is provided with a second limiting retaining ring, the second limiting retaining ring can form a block for the limiting portion so that the upper thermal insulation sleeve cannot be separated from the inverted cone bearing surface upward.

2. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 1, characterized in that: It also includes a lower heat-insulating sleeve, which is arranged on the lower end of the inner tube and abuts against the inner wall of the outer tube.

3. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 2, characterized in that: The inner tube also includes a female sealing sleeve, and the lower end of the tube body is sealed and fixedly connected to the female sealing sleeve. The male sealing sleeve of one of the two adjacent inner tubes can be sealed and inserted into the female sealing sleeve of the other inner tube, and the lower insulation sleeve is arranged outside the female sealing sleeve.

4. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 3, characterized in that: The outer peripheral surface of one end of the male sealing sleeve for inserting into the female sealing sleeve is provided with an annular groove, and a sealing ring is provided in the annular groove. The male sealing sleeve and the female sealing sleeve that are plug-connected are sealed and connected via the sealing ring.

5. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 1, characterized in that: The two ends of the outer tube are respectively provided with a female connecting sleeve and a male connecting sleeve. The male connecting sleeve of one of the two adjacent outer tubes can be threadedly connected with the female connecting sleeve of the other outer tube.

6. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 1, characterized in that: The inner heat insulation layer is formed by lining the inner tube with a polyethylene tube, and the outer heat insulation layer is formed by applying a binder to the outer wall of the inner tube and spraying SiO2 aerogel powder.

7. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 2, characterized in that: The upper heat-insulating sleeve and the lower heat-insulating sleeve are both made of polytetrafluoroethylene.

8. The double-walled heat-insulated water intake pipe for the upper return section of a geothermal well according to claim 3, characterized in that: The tube body is a seamless steel tube, the male sealing sleeve and the female sealing sleeve are both made of 35CrMo material, and the tube body is fixedly connected to the male sealing sleeve and the female sealing sleeve by welding.

Images