Passive downhole heat exchange system and heat exchange method

Abstract

The present invention provides a heat exchange system (100) for exploiting geothermal energy, the heat exchange system comprising a vertical well section (1) extending from the ground to a heat extraction reservoir, the heat exchange system further comprising a downhole heat exchanger (4), and the downhole heat exchanger (4) is arranged in the heat extraction reservoir. The present invention also provides a heat exchange method using the heat exchange system. According to the heat exchange system for exploiting geothermal energy of the present invention and the heat exchange method using the heat exchange system, the problem of tail water recharge is avoided, and the real "heat extraction without water extraction" is realized, and the heat extraction efficiency is high.

Description

Technical Field

[0001] The present invention relates to the technical field of geothermal energy development and utilization, and in particular to a heat exchange system for exploiting geothermal energy and a heat exchange method using the heat exchange system. Background Art

[0002] Heat exchange technology is applied in geothermal energy development and utilization industries, including geothermal heating, cooling, power generation, and the combination of geothermal energy and planting and breeding industries.

[0003] At present, there are two main ways to use geothermal energy by "taking heat instead of water": economic reinjection technology and underground heat exchange technology. However, they have many problems. For example, in order to circulate groundwater, a water outlet well and a water return well are dug, so at least two geothermal vertical wells are required, which is expensive and occupies a large area. In addition, the liquid between the well pipe and the heat reservoir is in a static state as the heat conduction material between the two, with a large thermal resistance and low heat exchange efficiency. Summary of the invention

[0004] The object of the present invention is to at least partially overcome the defects of the prior art and to provide a heat exchange system for exploiting geothermal energy with high heat extraction efficiency.

[0005] The present invention also aims to provide a heat exchange system for exploiting geothermal energy to avoid the problem of tail water reinjection.

[0006] Another object of the present invention is to provide a heat exchange system for exploiting geothermal energy, which occupies a small area, has a high space utilization rate, and has a low well drilling cost.

[0007] Another object of the present invention is to provide a heat exchange method for exploiting geothermal energy.

[0008] To achieve the above purpose or one of the purposes, the technical solution of the present invention is as follows:

[0009] A heat exchange system for exploiting geothermal energy, the heat exchange system comprising a vertical well section extending from the ground to a heat extraction reservoir, the heat exchange system further comprising a downhole heat exchanger, and the downhole heat exchanger is arranged in the heat extraction reservoir.

[0010] According to a preferred embodiment of the present invention, the heat exchange system further comprises a first additional well section and a second additional well section, one end of the first additional well section is connected to the vertical well section at a first position of the vertical well section, the first additional well section is not parallel to the vertical well section, one end of the second additional well section is connected to the other end of the first additional well section, the other end of the second additional well section is directly or indirectly connected to the vertical well section at a second position of the vertical well section through an additional well section, and

[0011] There is a height difference between the first position and the second position, and the downhole heat exchanger is located between the first position and the second position in height.

[0012] According to a preferred embodiment of the present invention, the downhole heat exchanger is arranged in a vertical well section between the first position and the second position.

[0013] According to a preferred embodiment of the present invention, the downhole heat exchanger is arranged in the first additional well section or the second additional well section.

[0014] According to a preferred embodiment of the present invention, the second position is higher than the first position.

[0015] According to a preferred embodiment of the present invention, the other end of the second additional well section is directly connected to the vertical well section, so that the vertical well section, the first additional well section and the second additional well section form a loop.

[0016] According to a preferred embodiment of the present invention, the first additional well section is constructed as a horizontal well section, and the second additional well section is constructed as an inclined well section inclined relative to both the horizontal direction and the vertical direction.

[0017] According to a preferred embodiment of the present invention, the first additional well section extends from the vertical well section, and / or the second additional well section extends from the vertical well section, and

[0018] The first additional well section and the second additional well section are interconnected by a connecting device.

[0019] According to a preferred embodiment of the present invention, the heat exchange system also includes an inlet pipe, an outlet pipe and an uphole heat exchanger, one end of the inlet pipe is connected to the downhole heat exchanger, the other end of the inlet pipe is connected to the uphole heat exchanger, one end of the outlet pipe is connected to the downhole heat exchanger, and the other end of the outlet pipe is connected to the uphole heat exchanger; the inlet pipe, the outlet pipe, the downhole heat exchanger and the uphole heat exchanger constitute a closed circulation loop to transfer the heat from the downhole heat exchanger to the user-side heating circuit through the uphole heat exchanger.

[0020] According to another aspect of the present invention, a heat exchange method is provided, wherein the heat exchange method adopts the heat exchange system for exploiting geothermal energy described in the above embodiment.

[0021] According to the heat exchange system for exploiting geothermal energy and the heat exchange method using the heat exchange system of the present invention, by adopting a downhole heat exchanger, it is possible to realize the utilization of geothermal energy by "extracting heat without extracting water", without the need for tail water reinjection, thus avoiding the problem of tail water reinjection; further, in addition to the vertical well section, the heat exchange system also includes a first additional well section (for example, a horizontal well section) and a second additional well section (for example, an inclined well section), so that the vertical well section, the horizontal well section and the inclined well section form a loop, and the downhole heat exchanger is arranged in the loop. Due to the temperature difference between the heat exchanger and the location far away from the heat exchanger in the loop, the temperature of the vertical well section at the heat exchanger decreases and the water density increases, while the temperature of the vertical well section at the location far away from the heat exchanger is relatively large and the water density is relatively small, so that a natural circulation flow of the water medium in the loop can be formed. With the help of the natural circulation flow of the medium, the geothermal energy in the heat reservoir can be more efficiently exploited. Therefore, the heat exchange system for exploiting geothermal energy and the heat exchange method using the heat exchange system of the present invention have high heat extraction efficiency.

[0022] In addition, the heat exchange system for exploiting geothermal energy of the present invention only requires one vertical geothermal well, which occupies a small area, has high space utilization rate and low well drilling cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a heat exchange system for exploiting geothermal energy according to an embodiment of the present invention; and

[0024] Figure 2 Schematic diagram of an exemplary downhole heat exchanger according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Exemplary embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements. In addition, in the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the disclosed embodiments. However, it is apparent that one or more embodiments may also be implemented without these specific details. In other cases, known structures and devices are embodied in a schematic manner to simplify the accompanying drawings.

[0026] The present invention aims to propose a new downhole heat exchange technology with high heat output power, good economy and good environmental protection effect, which can completely solve the problem of difficult tail water reinjection and improve the economic feasibility of geothermal energy utilization.

[0027] According to the general concept of the present invention, there is provided a heat exchange system for exploiting geothermal energy, the heat exchange system comprising a vertical well section extending from the ground to a heat extraction reservoir, the heat exchange system further comprising a downhole heat exchanger, and the downhole heat exchanger is arranged in the heat extraction reservoir. Further, the heat exchange system further comprises a first additional well section and a second additional well section, one end of the first additional well section is connected to the vertical well section at a first position of the vertical well section, the first additional well section is not parallel to the vertical well section, one end of the second additional well section is connected to the other end of the first additional well section, the other end of the second additional well section is directly or indirectly connected to the vertical well section at a second position of the vertical well section through an additional well section, and there is a height difference between the first position and the second position, and the downhole heat exchanger is located between the first position and the second position in height.

[0028] According to the heat exchange system for exploiting geothermal energy and the heat exchange method using the heat exchange system of the present invention, by adopting a downhole heat exchanger, it is possible to realize the utilization of geothermal energy by "extracting heat without extracting water", without the need for tail water reinjection, thus avoiding the problem of tail water reinjection; further, in addition to the vertical well section, the heat exchange system also includes a first additional well section (for example, a horizontal well section) and a second additional well section (for example, an inclined well section), so that the vertical well section, the horizontal well section and the inclined well section form a loop, and the downhole heat exchanger is arranged in the loop. Due to the temperature difference between the heat exchanger and the location far away from the heat exchanger in the loop, the temperature of the vertical well section at the heat exchanger decreases and the water density increases, while the temperature of the vertical well section at the location far away from the heat exchanger is relatively large and the water density is relatively small, so that a natural circulation flow of the water medium in the loop can be formed. With the help of the natural circulation flow of the medium, the geothermal energy in the heat reservoir can be more efficiently exploited. Therefore, the heat exchange system for exploiting geothermal energy and the heat exchange method using the heat exchange system of the present invention have high heat extraction efficiency.

[0029] In addition, the heat exchange system for exploiting geothermal energy of the present invention only requires one vertical geothermal well, which occupies a small area, has high space utilization rate and low well drilling cost.

[0030] Figure 1 Schematic diagram of a heat exchange system for exploiting geothermal energy according to an embodiment of the present invention. Figure 1 Take the overall concept of the present invention in detail with an example. Figure 1As shown, a heat exchange system 100 for exploiting geothermal energy includes a vertical well section 1 extending from the ground to a heat extraction reservoir, wherein the heat extraction reservoir is a rock formation storing geothermal energy, and the rock formation contains an aqueous medium, and the geothermal energy can be utilized by extracting heat from the aqueous medium in the rock formation. The vertical well section 1 is, for example, constructed as a metal casing extending into the ground, and has perforations on the peripheral wall of the metal casing so that the aqueous medium in the rock formation can enter the inside of the metal casing. The non-heat extraction section of the vertical well section should be cemented, for example, cement is poured around the periphery of the vertical well section to fix it relative to the formation; the heat extraction section of the vertical well section can be filled with gravel outside the well pipe, that is, gravel is filled in the gap between the metal casing and the heat extraction reservoir to prevent gravel in the rock formation from entering the metal casing through the perforations, and only allow the aqueous medium to enter the metal casing, thereby playing a filtering role. Preferably, a heat-insulating layer 9 is provided on the portion of the vertical well section 1 between the heat-extracting reservoir and the ground. The heat-insulating layer 9 can be constructed as a heat-insulating casing, such as a cement casing. The heat-insulating layer 9 plays a heat-insulating role to prevent heat from being dissipated in the non-heat-extracting section, so as to improve the heat exchange efficiency of the heat exchange system. Appropriate sealing is performed at the ground or near the liquid level in the vertical well section 1 to isolate it from the outside.

[0031] The heat exchange system is designed to include a downhole heat exchanger 4, and the downhole heat exchanger 4 is arranged in the heat extraction reservoir, such as Figure 1 As shown, the downhole heat exchanger 4 is located in the part of the vertical well section 1 located in the heat extraction reservoir. The heat exchange system also includes an inlet pipe 5, an outlet pipe 6 and an uphole heat exchanger 7. One end of the inlet pipe 5 is connected to the downhole heat exchanger 4, and the other end of the inlet pipe 5 is connected to the uphole heat exchanger 7. One end of the outlet pipe 6 is connected to the downhole heat exchanger 4, and the other end of the outlet pipe 6 is connected to the uphole heat exchanger 7. The inlet pipe 5, the outlet pipe 6, the downhole heat exchanger 4 and the uphole heat exchanger 7 form a closed circulation loop to transfer the heat from the downhole heat exchanger 4 to the user-side heating circuit through the uphole heat exchanger 7. The heat exchange system also includes a pump 8, such as a centrifugal pump, for pumping fluid to the downhole heat exchanger 4. The pump 8 is preferably arranged on the inlet pipe 5. Alternatively, it can also be arranged on the outlet pipe 6.

[0032] The working process of the heat exchange system is first introduced below. During the working process, the pump 8 is turned on, and the medium (such as water) in the closed circulation loop composed of the water inlet pipe 5, the water outlet pipe 6, the downhole heat exchanger 4 and the uphole heat exchanger 7 can flow in the closed circulation loop, that is, flow to the downhole heat exchanger 4 through the water inlet pipe 5; the aqueous medium contained in the heat reservoir contains geothermal energy, which has a higher temperature. The aqueous medium passes through the gravel and the perforations on the metal casing into the vertical well section 1, and exchanges heat with the medium flowing in the downhole heat exchanger 4, that is, transfers heat to the downhole heat exchanger. The medium flowing in the heat exchanger 4 increases its temperature; the medium in the closed circulation loop with increased temperature flows to the uphole heat exchanger 7 through the outlet pipe 6, and the uphole heat exchanger 7 is also connected to the user-side heating circuit, so the medium in the closed circulation loop transfers heat to the user-side heating circuit, and at the same time, the temperature of the medium in the closed circulation loop decreases; the medium with decreased temperature is supplied to the downhole heat exchanger 4 again through the pump 8 and the water inlet pipe 5; the heat exchange system works in this reciprocating cycle to continuously exploit geothermal energy.

[0033] The downhole heat exchange technology proposed in the present invention mainly includes a heat reservoir, a geothermal well, a downhole heat exchanger, a downhole heat exchanger water inlet pipe and a downhole heat exchanger water outlet pipe. The heat reservoir to which the present invention belongs is located in the middle and deep layer, that is, 1 km below the ground. The depth or thickness varies according to the specific target application field and the local reservoir temperature.

[0034] Further, the heat exchange system also includes a first additional well section and a second additional well section, one end of the first additional well section is connected to the vertical well section 1 at a first position of the vertical well section 1, the first additional well section is not parallel to the vertical well section 1, one end of the second additional well section is connected to the other end of the first additional well section, the other end of the second additional well section is directly or indirectly connected to the vertical well section 1 at a second position of the vertical well section 1 through an additional well section, and there is a height difference between the first position and the second position, and the downhole heat exchanger 4 is located in height between the first position and the second position.

[0035] Preferably, the downhole heat exchanger 4 is arranged in the vertical well section 1 between the first position and the second position. However, the present invention is not limited thereto, and the downhole heat exchanger 4 may be arranged in the first additional well section or the second additional well section.

[0036] by Figure 1Taking the shown embodiment as an example, the heat exchange system 100 also includes a horizontal well section 2 and an inclined well section 3, one end of the horizontal well section 2 is connected to the vertical well section 1 at the bottom end of the vertical well section 1, the horizontal well section 2 is perpendicular to the vertical well section 1, one end of the inclined well section 3 is connected to the other end of the horizontal well section 2, the other end of the inclined well section 3 is directly connected to the vertical well section 1 at the middle of the vertical well section 1, and the downhole heat exchanger 4 is between the bottom end and the middle of the vertical well section 1.

[0037] It can be seen that the geothermal well to which the present invention belongs includes an ordinary medium-deep geothermal exploitation vertical shaft (vertical well section), and a group of expanded horizontal wells (horizontal well sections) and inclined wells (inclined well sections). The vertical shaft is interconnected with the horizontal well and the inclined well to form a closed loop, providing a place for natural circulation. The outside of the downhole heat exchanger is hot water from the geothermal well heat reservoir. During the operation of the heat exchanger, due to the temperature difference between the heat exchanger and the place far away from the heat exchanger in the closed loop, the temperature of the vertical well section at the heat exchanger drops and the water density increases, while the temperature of the vertical well section far away from the heat exchanger is relatively large, and the water density is relatively small, which drives the hot fluid in the inclined well to move upward, and establishes a natural circulation (such as Figure 1 As shown by the thick arrows in the figure). Under the action of natural circulation flow, the heat exchange coefficient between the hot water in the vertical well section and the downhole heat exchanger, and between the hot water in the vertical well section and the heat extraction reservoir is much greater than the thermal conductivity of the hot water in the vertical well section in a static state, thereby effectively improving the heat extraction efficiency. In addition, the natural circulation path constructed by horizontal wells, inclined wells and vertical wells also increases the heat exchange area between the heat exchange system and the heat extraction reservoir, and the heat exchange area can be further expanded by increasing the number of loops to achieve a long-term and stable supply of heat.

[0038] like Figure 1 As shown, the second position is higher than the first position. In fact, the first position is higher than the second position, and a natural circulation loop can also be formed. Therefore, the present invention does not exclude the technical solution of the first position being higher than the second position, as long as the downhole heat exchanger 4 is arranged between the first position and the second position.

[0039] In the present invention, the other end of the second additional well section can be directly connected to the vertical well section 1, so that the vertical well section 1, the first additional well section and the second additional well section form a loop. Alternatively, the heat exchange system of the present invention can also include a third additional well section, the other end of the second additional well section is connected to the third additional well section, and then the third additional well section is connected to the vertical well section 1 at the second position of the vertical well section 1. Similarly, it can also include a fourth additional well section, a fifth additional well section, ..., as long as the vertical well section 1 and the additional well sections can form a loop.

[0040] exist Figure 1In the illustrated embodiment, the first additional well section is configured as a horizontal well section 2, and the second additional well section is configured as an inclined well section 3 inclined relative to both the horizontal and vertical directions. Alternatively, the first additional well section is configured as an inclined well section inclined relative to both the horizontal and vertical directions, and the second additional well section is configured as a horizontal well section. Or alternatively, the first additional well section is configured as an inclined well section inclined relative to both the horizontal and vertical directions, and the second additional well section is configured as an inclined well section inclined relative to both the horizontal and vertical directions.

[0041] Preferably, the first additional well section, the second additional well section and the portion of the vertical well section 1 located between the first position and the second position form an isosceles triangle. However, the present invention is not limited thereto, and the first additional well section, the second additional well section and the portion of the vertical well section 1 located between the first position and the second position may form other shapes.

[0042] According to a preferred embodiment of the present invention, the first additional well section extends from the vertical well section 1, and / or the second additional well section extends from the vertical well section 1, and the first additional well section and the second additional well section are interconnected by a connecting device. Alternatively, the first additional well section is connected to the vertical well section 1 by a connecting device, and / or the second additional well section is connected to the vertical well section 1 by a connecting device.

[0043] Advantageously, the angle between the second additional well section and the vertical well section 1 is less than 20 degrees, and the angle between the first additional well section and the vertical well section 1 is greater than the angle between the second additional well section and the vertical well section 1, especially slightly greater than the angle between the second additional well section and the vertical well section 1, and optionally greater than 5 degrees, for example, which is conducive to the formation of the first additional well section and the second additional well section. In a preferred technical solution, the first additional well section and the second additional well section are directly extended from the vertical well section 1, which can be achieved by using the existing branch well technology. The angle between the second additional well section and the vertical well section 1 is kept small, which is conducive to the implementation of the branch well technology, and the angle between the first additional well section and the vertical well section 1 is greater than the angle between the second additional well section and the vertical well section 1, so that the first additional well section and the second additional well section can intersect naturally. By calculation, as long as the first additional well section and the second additional well section reach the expected length respectively, the first additional well section and the second additional well section can intersect, and then the first additional well section and the second additional well section are interconnected by a connecting device such as a bolt.

[0044] Figure 1The natural circulation in the well includes an arrangement of one vertical well, one horizontal well and one inclined well. In practice, a positive umbrella-shaped or inverted umbrella-shaped arrangement composed of one vertical well, multiple horizontal wells and an inclined well also belongs to the scope of the present invention and has better heat output efficiency. In this case, there are multiple first additional well sections, multiple second additional well sections, and the number of first additional well sections is the same as the number of second additional well sections, so that each first additional well section corresponds to one second additional well section. And advantageously, multiple first additional well sections are evenly distributed along the circumference of the vertical well section 1, and multiple second additional well sections are evenly distributed along the circumference of the vertical well section 1.

[0045] Considering the implementation of branch well technology, multiple first additional well sections are located on one side of the vertical well section 1, and multiple second additional well sections are located on one side of the vertical well section 1, that is, forming a half "umbrella" shape. The angle between each second additional well section and the vertical well section 1 is less than 20 degrees, and the angle between each first additional well section and the vertical well section 1 is greater than the angle between each second additional well section and the vertical well section 1, especially slightly greater than the angle between each second additional well section and the vertical well section 1, optionally greater than 5 degrees, for example, so that the arrangement formed is similar to the shape of a folded half "umbrella". It should be noted that the smaller the angle between the second additional well section and the vertical well section 1, the tighter the umbrella is folded.

[0046] The downhole heat exchanger described in the present invention may be in the form of a U-tube or a concentric casing. Figure 1 The downhole heat exchanger 4 shown is in the form of a U-tube. The downhole heat exchanger 4 and the corresponding water inlet pipe 5 and water outlet pipe 6 form a U-shape. Together with the uphole pump 8 and the plate-type uphole heat exchanger 7, they form a geothermal energy utilization loop, which is a closed loop.

[0047] Figure 2 FIG. 2 shows a schematic diagram of a concentric casing type downhole heat exchanger according to an embodiment of the present invention. Figure 2 As shown, the downhole heat exchanger includes a central inner tube 41 and an outer tube 42, the central inner tube 41 is arranged at the center of the outer tube 42, a water inlet 44 is provided on the outer peripheral wall of the upper end of the outer tube 42, the lower end of the outer tube 42 is closed, the lower end of the central inner tube 41 is provided with an inlet, and the upper end of the central inner tube 41 is provided with a water outlet 43. The water inlet 44 is connected to the water inlet pipe 5, and the water outlet 43 is connected to the water outlet pipe 6. The downhole heat exchanger of this embodiment has a simple structure and high heat exchange efficiency.

[0048] As mentioned above, a perforation is provided on the vertical well section 1 to facilitate the entry of the aqueous medium in the heat reservoir into the circulation loop. To enhance the aforementioned natural circulation, the perforation on the vertical well section 1 is located at the downhole heat exchanger 4, and a perforation is also provided at a position away from the downhole heat exchanger 4 on the first additional well section or the second additional well section. This arrangement is conducive to increasing the temperature difference between the downhole heat exchanger 4 and the position away from the downhole heat exchanger 4, thereby increasing the density difference of the circulating medium and enhancing the natural circulation.

[0049] Further advantageously, grooves are formed on the inner wall surface of the first additional well section and the inner wall surface of the second additional well section to increase the heat exchange area of ​​the internal and external media of the first additional well section and the second additional well section, enhance heat exchange, and fully improve heat exchange efficiency.

[0050] According to another aspect of the present invention, a heat exchange method is provided, wherein the heat exchange method adopts the heat exchange system 100 for exploiting geothermal energy described in the above embodiment.

[0051] In the heat exchange method, several branches can be added to the additional well section as needed, and the lengths and head and tail heights of different additional well sections are designed according to the resistance distribution principle and can be changed.

[0052] The downhole heat exchange technology of the present invention has the following characteristics:

[0053] 1) Constructing an underground passive natural heat exchange circulation path in the production well improves the heat extraction efficiency without adding additional energy-consuming components.

[0054] 2) The single well structure is adopted, which has high space utilization and reduces the cost of drilling wells.

[0055] 3) The downhole heat exchanger is a single-side circulation with a compact structure. The uphole heat exchange system is simplified and occupies a small area.

[0056] 4) Groundwater is not exploited, and the underground heat exchange system is completely isolated from the surface heat exchange system to avoid environmental pollution.

[0057] 5) The downhole heat exchange system does not require the use of thermal conductors to increase heat exchange efficiency.

[0058] The present invention combines passive technology with downhole heat exchange technology to develop a new and efficient mid-deep geothermal energy passive downhole heat exchange technology. The basic principle of natural circulation driven passive downhole heat exchange technology is to construct a passive natural heat exchange circulation path in the well, transfer the thermal energy of geothermal water to the downhole heat exchanger through natural circulation, and then transfer it to the heat user through the ground heat exchange system.

[0059] The present invention proposes a technology for extracting heat using a downhole heat exchanger and utilizing non-active technology to improve downhole heat exchange efficiency. The technology has the following advantages: (1) The non-active downhole heat exchange technology only extracts underground heat resources and does not extract groundwater, so no heat exchange tail water is generated, which fundamentally avoids the problem of tail water reinjection and realizes absolutely clean geothermal utilization, which has very important social significance and economic value; (2) The use of non-active downhole heat exchange technology does not rely on the amount of underground water resources, and can extract medium and deep geothermal energy with little or even no water, greatly expanding the available medium and deep geothermal resources; (3) The non-active technology can improve the efficiency of downhole heat exchange without adding other equipment, saving cost and space, thereby improving the economic efficiency of geothermal extraction.

[0060] The key technical point of the present invention is to construct a natural circulation path underground, realize the natural circulation of geothermal water underground, improve the heat exchange efficiency with the well wall and heat exchanger, and increase the heat exchange area with the reservoir. Through the special well structure, a closed natural circulation path is constructed, which is combined with the heat exchanger to achieve the effect of improving thermal efficiency, diffusing heat exchange area, and increasing heating capacity.

[0061] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of application of the present invention is defined by the appended claims and their equivalents.

[0062] List of reference numerals:

[0063] 100 heat exchange system

[0064] 1 Vertical well section

[0065] 2 horizontal well section

[0066] 3 Inclined well section

[0067] 4 Downhole heat exchanger

[0068] 5 Water inlet pipe

[0069] 6 Water outlet pipe

[0070] 7. Heat exchanger on well

[0071] 8 Pumps

[0072] 9 Insulation layer

[0073] 41 center inner tube

[0074] 42 outer tube

[0075] 43 Water outlet

[0076] 44 Water Inlet

Claims

1. A heat exchange system (100) for extracting geothermal energy, the heat exchange system comprising a vertical well section (1) extending from the ground to a heat extraction reservoir, with perforations on the peripheral wall of the vertical well section, characterized in that: The heat exchange system further comprises a downhole heat exchanger (4), and the downhole heat exchanger (4) is arranged in the heat extraction reservoir. The heat exchange system further comprises a first additional well section and a second additional well section, one end of the first additional well section being connected to the vertical well section (1) at a first position of the vertical well section (1), the first additional well section being not parallel to the vertical well section (1), one end of the second additional well section being connected to the other end of the first additional well section, the other end of the second additional well section being connected to the vertical well section (1) at a second position of the vertical well section (1) directly or indirectly through an additional well section, and There is a height difference between the first position and the second position, and the downhole heat exchanger (4) is located between the first position and the second position in height.

2. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The downhole heat exchanger (4) is arranged in a vertical well section (1) between a first position and a second position.

3. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The downhole heat exchanger (4) is arranged in the first additional well section or the second additional well section.

4. The heat exchange system (100) for exploiting geothermal energy according to any one of claims 1 to 3, characterized in that: The second position is higher than the first position.

5. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The other end of the second additional well section is directly connected to the vertical well section (1), so that the vertical well section (1), the first additional well section and the second additional well section form a loop.

6. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The first additional well section is configured as a horizontal well section (2), and the second additional well section is configured as an inclined well section (3) inclined relative to both the horizontal direction and the vertical direction.

7. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The first additional well section extends from the vertical well section (1), and / or the second additional well section extends from the vertical well section (1), and The first additional well section and the second additional well section are interconnected by a connecting device.

8. The heat exchange system (100) for exploiting geothermal energy according to claim 1, characterized in that: The heat exchange system further comprises a water inlet pipe (5), a water outlet pipe (6) and an uphole heat exchanger (7); one end of the water inlet pipe (5) is in communication with the downhole heat exchanger (4), the other end of the water inlet pipe (5) is in communication with the uphole heat exchanger (7); one end of the water outlet pipe (6) is in communication with the downhole heat exchanger (4), the other end of the water outlet pipe (6) is in communication with the uphole heat exchanger (7); the water inlet pipe (5), the water outlet pipe (6), the downhole heat exchanger (4) and the uphole heat exchanger (7) form a closed circulation loop, so as to transfer the heat from the downhole heat exchanger (4) to the user-side heating circuit through the uphole heat exchanger (7).

9. A heat exchange method, characterized in that: The heat exchange method adopts the heat exchange system (100) for exploiting geothermal energy according to any one of claims 1 to 8.

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