Heat exchange device for geothermal well

Abstract

The invention belongs to the technical field of geothermal development, and particularly relates to a heat exchange device for a geothermal well. The heat exchange device for the geothermal well comprises a shaft part, a heat collector and an electric submersible pump. Under the action of the electric submersible pump, heat in the stratum is continuously transmitted to low-temperature water which circularly flows through the interior of the heat collector by taking the stratum water as a carrier, and the low-temperature water absorbs the heat, converts the heat into high-temperature water and flows out of the heat collector for subsequent utilization of geothermal energy. According to the heat exchange device for the geothermal well, through the design, the heat exchange efficiency between low-temperature water in the heat collector and circularly flowing formation water is improved to a great extent, and the heat exchange device has a good application prospect in the field.

Description

Technical Field

[0001] The invention belongs to the technical field of geothermal development, and in particular relates to a heat exchange device for a geothermal well. Background Art

[0002] In the existing technology, in geothermal development wells that adopt the "extracting heat but not water" exploitation method, since the formation water after heat exchange can only be replenished by weak seepage and natural convection, the formation water heating has the disadvantages of long time and fast temperature decay, which greatly affects the heat extraction efficiency of geothermal development and makes it difficult for the exploited geothermal wells to generate a high level of economic benefits. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a heat exchange device for a geothermal well.

[0004] The heat exchange device for geothermal wells comprises:

[0005] The shaft portion includes a main shaft arranged longitudinally, and an upper branch shaft and a lower branch shaft both connected to the side wall of the main shaft, wherein the upper branch shaft and the lower branch shaft are constructed as a non-enclosed structure;

[0006] A heat collector is disposed inside the main wellbore and the upper branch wellbore and is configured to absorb heat from formation water in the wellbore to heat low-temperature water circulating through the heat collector; and

[0007] An electric submersible pump is disposed in the main wellbore between the upper branch wellbore and the lower branch wellbore, and the electric submersible pump is configured to allow formation water to circulate in the upper branch wellbore, the formation, and the lower branch wellbore.

[0008] Among them, the heat exchange device for geothermal wells is constructed so that under the action of the electric submersible pump, the heat in the formation is continuously transferred to the low-temperature water circulating through the inside of the heat collector using the formation water as a carrier. The low-temperature water absorbs the heat and is converted into high-temperature water and flows out of the heat collector for subsequent utilization of geothermal energy.

[0009] As an extension of the above technical solution, the present invention also provides the following embodiments:

[0010] The heat exchanger includes an outer tube with closed ends and an inner tube arranged inside the outer tube and open at both ends, wherein low-temperature water flows along the annular space between the outer tube and the inner tube, and high-temperature water flows along the inner space of the inner tube.

[0011] The outer tube and the inner tube are configured as concentric tubes.

[0012] A plurality of first circulation holes are provided on the side wall and the bottom end surface of the upper branch wellbore.

[0013] The first circulation hole is located on the portion of the upper branch wellbore that is behind the tail end of the heat extractor.

[0014] A plurality of second circulation holes are provided on the side wall and the bottom end surface of the lower branch wellbore.

[0015] The second circulation holes are distributed throughout the side wall of the lower branch wellbore in the axial direction.

[0016] The upper branch wellbore has a downwardly inclined angle in a direction gradually away from the main wellbore.

[0017] A first packer is provided between the heat extractor and the main wellbore.

[0018] A second packer is arranged between the electric submersible pump and the main wellbore.

[0019] The advantages of the present invention compared to the prior art are:

[0020] Through the design of the wellbore, heat collector and electric submersible pump, the formation water can be circulated at a high speed between the wellbore and the formation. On the one hand, the circulating formation water can achieve full contact with the formation to quickly replenish heat, ensuring that the formation water in the wellbore is maintained at a high temperature. On the other hand, the formation water has a fast flow speed when flowing through the outer wall of the heat collector, and the convective heat transfer coefficient is large, thereby achieving the effect of enhanced heat exchange. The technical solution according to the present invention improves the heat extraction efficiency of geothermal development as a whole, and can produce good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a heat exchange device for a geothermal well according to the present invention.

[0022] All drawings in the present invention are schematic diagrams for illustrating structures and principles, and are not necessarily drawn according to actual sizes and proportions.

[0023] The specific meanings of the reference numerals in the figures are as follows:

[0024] 1. Wellbore portion; 11. Main wellbore; 12. Upper branch wellbore; 121. First circulation hole; 13. Lower branch wellbore; 131. Second circulation hole; 2. Heat extractor; 21. Outer pipe; 22. Inner pipe; 3. Submersible electric pump; 4. First packer; 5. Second packer; 100. Heat exchange device for geothermal well. DETAILED DESCRIPTION

[0025] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0026] Figure 1 1 is a schematic diagram of the structure of a heat exchange device 100 for a geothermal well according to the present invention. As shown in the figure, the heat exchange device 100 for a geothermal well according to the present invention includes a wellbore 1, a heat collector 2 and an electric submersible pump 3. The wellbore 1 includes a main wellbore 11, an upper branch wellbore 12 and a lower branch wellbore 13. The main wellbore 11 is longitudinally arranged in a geothermal well (not shown, the same below), and the upper branch wellbore 12 and the lower branch wellbore 13 are both constructed to be connected to the side wall of the main wellbore 11 and extend outward from the side wall of the main wellbore 11. The upper branch wellbore 12 and the lower branch wellbore 13 are both constructed as non-enclosed structures to facilitate the circulation of formation water, and the upper branch wellbore 12 is located above the lower branch wellbore 13. The heat collector 2 is constructed to absorb the heat of the formation water in the wellbore 1 and heat the low-temperature water circulating through it, and the heat collector 2 is arranged inside the main wellbore 11 and the upper branch wellbore 12. The electric submersible pump 3 is arranged in the main wellbore 11 between the upper branch wellbore 12 and the lower branch wellbore 13. And the heat exchange device 100 for geothermal well is configured such that, under the action of the electric submersible pump 3, the heat in the formation is continuously transferred to the low-temperature water circulating through the heat collector 2 with the formation water as the carrier, and the low-temperature water absorbs the heat and turns into high-temperature water and flows out of the heat collector 2 for the subsequent utilization of geothermal energy.

[0027] During specific operation, under the action of the electric submersible pump 3, the heat in the formation is continuously transferred to the low-temperature water circulating through the heat exchanger 2 with the formation water as the carrier. The low-temperature water absorbs the heat and turns into high-temperature water and flows out of the heat exchanger 2 for subsequent utilization of geothermal energy.

[0028] According to the heat exchange device 100 for geothermal wells of the present invention, through the design of the wellbore 1, the heat collector 2 and the electric submersible pump 3, the formation water can be circulated at a high speed between the wellbore 1 and the formation. On the one hand, the circulating formation water can achieve full contact with the formation to quickly replenish heat, ensuring that the formation water in the wellbore 1 is maintained at a high temperature. On the other hand, the formation water has a fast flow speed when flowing through the outer wall of the heat collector 2, and the convective heat transfer coefficient is large, thereby achieving the effect of enhanced heat exchange. The heat exchange device 100 for geothermal wells of the present invention improves the heat extraction efficiency of geothermal development as a whole, and can produce good economic benefits.

[0029] like Figure 1As shown, in one embodiment of the present invention, the heat collector 2 includes an outer tube 21 with closed ends and an inner tube 22 disposed inside the outer tube 21 and open at both ends. During specific operation, low-temperature water injected from the outside flows along the annular space between the outer tube 21 and the inner tube 22. After the low-temperature water absorbs the heat from the formation water, it is converted into high-temperature water. The high-temperature water enters the interior of the inner tube 22 at the ends of the outer tube 21 and the inner tube 22, and flows along the internal space of the inner tube 22 to the external device for subsequent utilization of geothermal energy. Through this design, the heat collector 2 realizes the function of absorbing heat in the process of contact with the formation water, thereby converting low-temperature water into high-temperature water, realizing the collection of geothermal energy, and enabling the subsequent utilization of geothermal energy to proceed smoothly.

[0030] Furthermore, in a preferred embodiment of the present invention, the outer tube 21 and the inner tube 22 are constructed as concentric tubes. With this design, the annular space between the outer tube 21 and the inner tube 22 has a uniform width in the circumferential direction, so that the low-temperature water in the annular space between the outer tube 21 and the inner tube 22 is also in a uniformly distributed state, and the absorption of heat in the formation water by the low-temperature water is also uniform, thereby avoiding the waste of heat caused by uneven absorption of heat on the one hand, and on the other hand, if the temperature of the liquid inside the heat collector 2 is often in an uneven state, it will have a certain adverse effect on the structural stability of the heat collector 2. By setting the outer tube 21 and the inner tube 22 in the form of concentric tubes, the above situation is avoided to a large extent, and the service life of the heat collector 2 is improved.

[0031] like Figure 1 As shown, in one embodiment of the present invention, the upper branch wellbore 12 has a bottom end surface, and a plurality of first circulation holes 121 are provided on the side wall and the bottom end surface of the upper branch wellbore 12. Through this design, the formation water can flow out of the upper branch wellbore 12 through the first circulation holes 121 provided on the upper branch wellbore 12 for circulation. And because the upper branch wellbore 12 has a bottom end surface structure, the formation water can flow out of the upper branch wellbore 12 more slowly, so that the formation water can exchange heat with the heat extractor 2 for a longer time, which is conducive to the full absorption of heat in the formation water, thereby improving the utilization rate of geothermal energy.

[0032] Furthermore, in one embodiment of the present invention, the first circulation holes 121 are all arranged in the upper branch wellbore 12 at the part after the tail end of the heat collector 2. With this design, the formation water with a higher temperature will flow out of the upper branch wellbore 12 through the first circulation holes 121 only after completing the heat exchange with the entire heat collector 2, so that the heat in the formation water can be absorbed by the heat collector 2 to a greater extent, further improving the utilization rate of geothermal energy.

[0033] like Figure 1As shown, in one embodiment of the present invention, the lower branch wellbore 13 has a bottom end surface, and a plurality of second circulation holes 131 are provided on the side wall and the bottom end surface of the lower branch wellbore 13. Through this design, formation water can flow into the lower branch wellbore 13 through the second circulation holes 131 provided on the lower branch wellbore 13 to circulate. On the one hand, the second circulation holes 131 can filter the formation water, thereby preventing larger particles from entering the interior of the wellbore portion 1, thereby causing unnecessary damage to the heat exchange device 100 for the geothermal well. On the other hand, since the lower branch wellbore 13 has a bottom end surface structure, the formation water can flow into the interior of the lower branch wellbore 13 more slowly, so that the formation water can undergo a longer heat exchange process with the heat source in the geothermal reservoir to absorb more heat, thereby improving the efficiency of geothermal energy extraction and the comprehensive utilization rate of geothermal energy.

[0034] Furthermore, in one embodiment of the present invention, the second circulation holes 131 are distributed throughout the sidewall of the lower branch wellbore 13 in the axial direction. With this design, the number of channels through which the formation water that has absorbed heat enters the lower branch wellbore 13 is greatly increased, thereby helping to speed up the circulation of the formation water and improving the efficiency of geothermal energy extraction as a whole. This preferred embodiment can achieve a certain balance between the utilization rate of geothermal energy and the efficiency of geothermal energy extraction.

[0035] like Figure 1 As shown, in one embodiment of the present invention, the upper branch wellbore 12 has a downward tilt angle in the direction gradually away from the main wellbore 11. Through this design, the formation water inside the upper branch wellbore 12 can flow along the upper branch wellbore 12 in the direction gradually away from the main wellbore 11 under the action of gravity, and perform subsequent circulation operations. Through this design, the flow of formation water is facilitated, so that the circulation of formation water can be carried out more smoothly.

[0036] like Figure 1 As shown, in one embodiment of the present invention, the lower branch wellbore 13 has a downward inclination angle in the direction gradually away from the main wellbore 11. Through this design, it is convenient for formation water flowing through the lower formation to flow into the lower branch wellbore 13 to participate in the circulation flow process, thereby facilitating the utilization rate of geothermal energy.

[0037] like Figure 1As shown, in one embodiment of the present invention, a first packer 4 is provided between the heat collector 2 and the main wellbore 11. Through this design, on the one hand, the heat collector 2 is fixed in the main wellbore 11 by the first packer 4, which is conducive to the heat collector 2 to stably perform its function. On the other hand, the first packer 4 blocks the annular space between the heat collector 2 and the main wellbore 11, so that the formation water does not flow into the upper part of the main wellbore 11 which is difficult to participate in the circulation flow of the heat exchange process, but enters the upper branch wellbore 12 as much as possible to participate in the circulation flow of the heat exchange process, thereby avoiding the waste of geothermal energy and improving the utilization rate and mining efficiency of geothermal energy.

[0038] like Figure 1 As shown, in one embodiment of the present invention, a second packer 5 is provided between the electric submersible pump 3 and the main wellbore 11. With this design, the electric submersible pump 3 is fixed inside the main wellbore 11, which is conducive to the stable function of the electric submersible pump 3.

[0039] In one embodiment of the present invention, the outer tube 21 is a corrugated tube with a large surface area, and the inner tube 22 is a round tube with a smooth inner wall. By setting the outer tube 21 as a corrugated tube, the heat exchange area between the low-temperature water inside the heat collector 2 and the formation water inside the upper branch wellbore 12 is increased, thereby improving the heat exchange efficiency. By setting the inner tube 22 as a round tube with a smooth inner wall, the contact area between the high-temperature water inside the inner tube 22 and the low-temperature water in the annular space between the outer tube 21 and the inner tube 22 is reduced as much as possible, thereby avoiding the loss of heat of the high-temperature water as much as possible. In general, the design scheme of this embodiment is conducive to improving the heat exchange efficiency of geothermal energy and reducing unnecessary loss of geothermal energy.

[0040] According to the heat exchange device 100 for geothermal wells of the present invention, through the design of the wellbore 1, the heat collector 2 and the electric submersible pump 3, the formation water can be circulated at a high speed between the wellbore 1 and the formation, so that, on the one hand, the circulating formation water can be fully in contact with the formation to quickly replenish heat, ensuring that the formation water in the wellbore 1 is maintained at a relatively high temperature. On the other hand, the formation water has a fast flow speed when flowing through the outer wall of the heat collector 2, and a large convective heat transfer coefficient, thereby achieving the effect of enhanced heat exchange. The heat exchange device 100 for geothermal wells of the present invention improves the heat extraction efficiency of geothermal energy development as a whole, and can produce good economic benefits.

[0041] In this application, the specific meanings of the terms "upper", "lower", "inner", "outer", "middle", "side" and the like when indicating directions are as follows: Figure 1 The drawing state of the heat exchange device 100 for a geothermal well is used as a reference.

[0042] Finally, it should be noted that although the present invention has been described in detail with reference to the preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A heat exchange device for a geothermal well, comprising: A shaft section (1) comprises a main shaft (11) arranged longitudinally, and an upper branch shaft (12) and a lower branch shaft (13) both of which are connected to the side wall of the main shaft (11), wherein the upper branch shaft (12) and the lower branch shaft (13) are both constructed as non-enclosed structures; A heat collector (2) is arranged inside the main wellbore (11) and the upper branch wellbore (12), and is configured to absorb heat from formation water in the wellbore portion (1) to heat low-temperature water circulating through the heat collector (2); and An electric submersible pump (3) is arranged in the main wellbore (11) at a position between the upper branch wellbore (12) and the lower branch wellbore (13), and the electric submersible pump (3) is configured to allow formation water to circulate in the upper branch wellbore (12), the formation and the lower branch wellbore (13). The heat exchange device for geothermal wells is constructed such that, under the action of the electric submersible pump (3), the heat in the formation is continuously transferred to the low-temperature water circulating through the inside of the heat collector (2) using the formation water as a carrier. The low-temperature water absorbs the heat and is converted into high-temperature water and flows out of the heat collector (2) for subsequent utilization of geothermal energy.

2. The heat exchange device for geothermal well according to claim 1, characterized in that: The heat collector (2) comprises an outer tube (21) with a closed end, and an inner tube (22) arranged inside the outer tube (21) and open at both ends, wherein low-temperature water flows along the annular space between the outer tube (21) and the inner tube (22), and high-temperature water flows along the internal space of the inner tube (22).

3. The heat exchange device for geothermal well according to claim 2, characterized in that: The outer tube (21) and the inner tube (22) are configured as concentric tubes.

4. The heat exchange device for geothermal well according to claim 3, characterized in that: A plurality of first circulation holes (121) are provided on the side wall and the bottom end surface of the upper branch wellbore (12).

5. The heat exchange device for geothermal well according to claim 4, characterized in that: The first circulation hole (121) is located on the portion of the upper branch shaft (12) behind the tail end of the heat extractor (2).

6. The heat exchange device for geothermal well according to claim 5, characterized in that: A plurality of second circulation holes (131) are provided on the side wall and the bottom end surface of the lower branch shaft (13).

7. The heat exchange device for geothermal well according to claim 6, characterized in that: The second circulation holes (131) are distributed throughout the side wall of the lower branch wellbore (13) in the axial direction.

8. The heat exchange device for geothermal well according to any one of claims 1 to 7, characterized in that: The upper branch wellbore (12) has a downwardly inclined angle in a direction gradually moving away from the main wellbore (11).

9. The heat exchange device for geothermal well according to any one of claims 1 to 7, characterized in that: A first packer (4) is provided between the heat extractor (2) and the main wellbore (11).

10. The heat exchange device for geothermal well according to any one of claims 1 to 7, characterized in that: A second packer (5) is provided between the electric submersible pump (3) and the main wellbore (11).

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