Geothermal recharge well control device

Abstract

A geothermal recharge well control device comprises an outer supporting pipe arranged in a pipe well and an inner water return pipe arranged in the outer supporting pipe. A first gravel layer is filled between the inner wall of the tube well and the outer supporting tube, and a second gravel layer is filled between the outer supporting tube and the inner water return tube; an exchange pipe connected with the outer supporting pipe is arranged at the crack opening. Through a double-layer filtering structure formed by the water return pipe in the outer supporting pipe and connection between the exchange pipe and the crack, a circulation loop of water in the crack is controlled, and the circulation speed of the water in the crack is increased; moreover, the filtering radius is increased, the filtering capacity and the water yield are improved, and the device has the advantages of good economical efficiency and high practicability.

Description

Technical Field

[0001] The utility model belongs to the technical field of geothermal recovery, and particularly relates to a control device for a geothermal reinjection well. Background Art

[0002] As a clean and renewable energy source, geothermal resources have received increasing attention. During the heat recovery process, first, the whole rock needs to be fractured to generate cracks, and then chemical agents are used to further transform the generated cracks. The injected cold water is added to the pipe well and exchanges heat with the rock and soil layers. The hot water after heat exchange is transported to the equipment or area to be heated through the return pipe. However, at present, the connectivity between the cracks mainly depends on the natural gaps for mutual circulation, and it is difficult to control the reinjection volume.

[0003] The prior art, such as the document with the authorization publication number CN218759840U, discloses a directional branch well system for medium-deep geothermal reinjection wells, including a soft soil layer and a rock and soil layer. The soft soil layer and the rock and soil layer are provided with pipe wells, including a return pipe and several branch pipes; the return pipe is installed inside the pipe well, and the lower end of the return pipe is placed in the rock and soil layer: several cracks are fractured in the rock and soil layer, and the cracks are connected to the pipe well: the heads and tails of the cracks are connected by branch pipes.

[0004] The working principle of the above structure is as follows: cold water is added to the pipe well, and part of the cold water flows into the first crack through the uppermost branch pipe, then flows through the branch pipe to the next crack, and finally flows out from the gap opening of the bottom crack through the branch pipe to complete the heat exchange between the cold water and the rock and soil. Finally, it is sucked in from the lower end of the return pipe to avoid stagnant water in the crack and increase the water body flow in the crack.

[0005] However, the device still has the following problems: on the basis of setting the branch pipes and the plugging layer, most of the heat exchange water bodies flowing through the cracks need to be sucked in from the bottom of the return pipe, the flow rate of the water body is slow, and the lower pipe body is prone to blockage. Summary of the Utility Model

[0006] Aiming at the above problems, the purpose of the utility model is to provide a control device for a geothermal reinjection well. Through the double-layer filtering structure composed of the return pipe inside the outer support pipe and the connection between the exchange pipe and the crack, the circulation circuit of the water body in the crack is controlled, and the flow rate of the water body in the crack is increased; moreover, the filtering radius is increased, the filtering volume and the water output are improved, and it has the advantages of good economy and strong practicability.

[0007] In order to achieve the above purpose, the technical solution of the utility model is as follows:

[0008] A geothermal reinjection well control device includes an outer support pipe arranged in a pipe well and an inner return water pipe arranged in the outer support pipe; a first gravel layer is filled between the inner wall of the pipe well and the outer support pipe, and a second gravel layer is filled between the outer support pipe and the inner return water pipe; an exchange pipe connected to the outer support pipe is arranged at the crack opening.

[0009] As a further preference of the present utility model, the exchange pipe includes a pipe body with one end connected to the crack opening and the other end inserted into the outer support pipe and connected to the second gravel layer, two support ring plates arranged at both ends of the pipe body, and a plurality of support rods arranged between the two support ring plates and distributed circumferentially along the pipe body.

[0010] As a further preference of the present utility model, the exchange pipe further includes openings arranged on the pipe wall of the pipe body; further, the openings are bridge-shaped holes.

[0011] As a further preference of the present utility model, the outer support pipe includes a skeleton ring, a plurality of connecting rods arranged outside the skeleton ring and distributed circumferentially along the skeleton ring, and a plurality of reinforcing connecting rods arranged at intervals inside the skeleton ring and connected to the inner return water pipe.

[0012] As a further preference of the present utility model, the outer support pipe further includes a pipe-shaped filter screen arranged on the inner side of the skeleton ring.

[0013] As a further preference of the present utility model, there are a plurality of skeleton rings, which are concentrically arranged along the direction of the pipe well; each connecting rod is at least used to connect two adjacent skeleton rings.

[0014] As a further preference of the present utility model, in the direction from top to bottom along the pipe well, the distribution spacing of the skeleton rings becomes smaller.

[0015] As a further preference of the present utility model, the inner return water pipe includes a sedimentation pipe arranged at the bottom of the pipe well and a filter pipe arranged at the upper end of the sedimentation pipe and extending to the water-stop layer.

[0016] As a further preference of the present utility model, the particle size of the first gravel layer is larger than that of the second gravel layer.

[0017] As a further preference of the present utility model, each reinforcing connecting rod is distributed radially along the inner return water pipe. Description of the Drawings

[0018] Attached Figure 1 is a schematic cross-sectional structure diagram of the present utility model.

[0019] Attached Figure 2 is a schematic partial structure diagram of the exchange pipe in the present utility model.

[0020] Appendix Figure 3 This is a schematic structural diagram of the exchange pipe of the present utility model from a top-down perspective.

[0021] Appendix Figure 4 This is a schematic structural diagram of the outer support pipe and the inner return water pipe of the present utility model from a top-down perspective.

[0022] Description of the drawings: Pipe well a, crack opening b, water stop layer c;

[0023] Outer support pipe 1, inner return water pipe 2, exchange pipe 3, first gravel layer 11, second gravel layer 12;

[0024] Pipe body 301, support ring plate 302, support rod 303;

[0025] Skeleton ring 101, connecting rod 102, reinforced connecting rod 103, pipe-shaped filter screen 104;

[0026] Precipitation pipe 201, filter pipe 202. Detailed implementation manners

[0027] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "outer", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this utility model is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0028] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and limited, terms such as "set" and "connected" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection: it can be a mechanical connection or an electrical connection: it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0029] A geothermal reinjection well control device provided by the present utility model includes an outer support pipe 1 arranged in a pipe well a and an inner return water pipe 2 arranged inside the outer support pipe 1; a first gravel layer 11 is filled between the inner wall of the pipe well a and the outer support pipe 1, and a second gravel layer 12 is filled between the outer support pipe 1 and the inner return water pipe 2; an exchange pipe 3 connected to the outer support pipe 1 is arranged at the crack opening b.

[0030] In this embodiment, the particle size of the first gravel layer 11 is larger than that of the second gravel layer 12, so as to achieve the effect of double-layer water filtration.

[0031] In this embodiment, the outer support pipe 1 includes a skeleton ring 101, a plurality of connecting rods 102 arranged outside the skeleton ring 101 and distributed circumferentially along the skeleton ring 101, and a plurality of reinforcing connecting rods 103 arranged at intervals inside the skeleton ring 101 and connected to the inner return water pipe 2.

[0032] As a further preference of this embodiment, there are a plurality of skeleton rings 101, which are concentrically arranged along the direction of the well a; each connecting rod 102 is at least used to connect two adjacent skeleton rings 101. Further, each connecting rod 102 is distributed along the direction of the well a and can connect all the skeleton rings. The advantage of such a setting is that the structure is simplified and the installation difficulty of the outer support pipe 1 is reduced.

[0033] As a further preference of this embodiment, in the direction from top to bottom along the well a, the distribution distance of the skeleton rings 101 becomes smaller. The reason for such a setting is that the pressure increases from top to bottom, and the larger distribution density at the lower end can improve the strength of the outer support pipe 1.

[0034] As a further preference of this embodiment, each reinforcing connecting rod 103 is distributed radially along the inner return water pipe 2. Such a setting is beneficial to improving the support strength of the outer support pipe 1 for the inner return water pipe 2.

[0035] As a further preference of this embodiment, the outer support pipe 1 further includes a tubular filter screen 104 arranged on the inner side of the skeleton ring 101. It can be understood that the tubular filter screen 104 can be a tubular body formed by connecting the head and tail of a plate body or a filter screen with filter holes to fit the inner wall of the skeleton ring 101, and the filter holes thereon are smaller than the particle size of the second gravel layer 12, so as to confine the second gravel layer 12 between the outer support pipe 1 and the inner return water pipe 2 and achieve the effect of secondary water filtration.

[0036] It should be noted that the end of the reinforcing connecting rod 103 far from the inner return water pipe 2 is directly fixedly connected to the inner wall of the skeleton ring 101, so the tubular filter screen 104 is provided with mounting holes for the reinforcing connecting rod 103 to pass through.

[0037] In this embodiment, the inner return water pipe 2 includes a sedimentation pipe 201 arranged at the bottom of the well a and a filter pipe 202 arranged at the upper end of the sedimentation pipe 201 and extending to the water stop layer c.

[0038] It can be understood that the filter pipe 202 can adopt any kind of pipe body with the function of filtering water in the prior art, such as a bridge filter, etc., so it will not be elaborated in this embodiment.

[0039] It should be noted that the distance between the pipe well a and the outer support pipe 1, the distance between the outer support pipe 1 and the inner return water pipe 2, and the filling particle sizes of the first gravel layer 11 and the second gravel layer 12 all need to be determined according to the geological conditions of geothermal exploitation. Therefore, except for the relationships described in this embodiment, specific values are not limited.

[0040] In this embodiment, the exchange pipe 3 includes a pipe body 301 with one end connected to the crack opening b and the other end inserted into the outer support pipe 1 and connected to the second gravel layer 12, two support ring plates 302 arranged at both ends of the pipe body 301, and a plurality of support rods 303 arranged between the two support ring plates 302 and distributed circumferentially along the pipe body 301. Among them, the two support ring plates 302 can be further connected to the crack opening b and the connecting rod 102 respectively to improve the structural strength of the exchange pipe 3; the setting of the support rods 303 is mainly used to make the part of the exchange pipe 3 exposed to the gravel be a double-layer structure, improving the compressive capacity of the pipe body. It should be noted that the pipe orifice of the pipe body 301 does not exceed the skeleton ring 101. The purpose of this setting is to avoid interference with the lowering of the skeleton ring 101 by the pipe body 301 when the outer support pipe 1 is placed into the pipe well a after the installation of the exchange pipe 3 is completed.

[0041] In this embodiment, the exchange pipe 3 further includes openings provided on the pipe wall of the pipe body 301; further, the openings are bridge-shaped holes.

[0042] It should be noted that the generation of the crack opening b can be achieved by existing technologies, so it will not be elaborated in this embodiment. After the crack is formed, the exchange pipe 3 can be installed on the crack opening b. Since the outer support pipe 1 is composed of a plurality of connecting rods 102 distributed along the well wall direction of the pipe well a, during the process of the outer support pipe 1 together with the inner return water pipe 2 inside entering the pipe well a, it is only necessary to ensure that the part of the exchange pipe 3 protruding from the well wall of the pipe well a is located in the gap between two connecting rods 102, and it will not interfere with the placement of the pipe body (the outer support pipe 1 and the inner return water pipe 2) into the pipe well. After the pipe body is placed, gravel can be filled to form a filter layer, and the construction of the control device is completed. The exchange pipe 3 provided in this embodiment is used to be installed at the crack opening b of the crack, aiming to form a specific return water path. The main return water path is that the water body in the crack directly enters the second gravel layer 12 through the exchange pipe 3 for filtration, and then reaches the inner return water pipe 2; the secondary return water path is that the water body in the crack flows into the first gravel layer 11 through the openings, then passes through the second gravel layer 12, and finally reaches the inner return water pipe 2. Among them, the setting of the main return water path can shorten the water body circulation path, improve the circulation speed of the water body in the crack, and thus avoid the occurrence of adverse situations such as too slow water body flow velocity or even becoming stagnant water.

[0043] The construction steps of the geothermal reinjection well control device provided in this embodiment include: after fracturing is completed, install the exchange pipe 3 at the fracture opening b; after all components of the outer support pipe 1 and the inner return water pipe 2 are installed on the ground, place the outer support pipe 1 together with the inner return water pipe 2 into the wellbore a, and the exchange pipe 3 can pass through the gap between the connecting rods 102 and the pipe orifice of the exchange pipe 3 extends into the space between the outer support pipe 1 and the inner return water pipe 2; finally, fill the first gravel layer 11 and the second gravel layer 12.

[0044] The working principle of the geothermal reinjection well control device provided in this embodiment includes: during reinjection, the water body in the wellbore is filtered by the first gravel layer and the second gravel layer respectively, and finally discharged from the return water pipe; most of the water body in the fracture is discharged into the second gravel layer through the exchange pipe, and a small part flows into the first gravel layer through the opening, and finally discharged from the return water pipe.

[0045] The geothermal reinjection well control device provided in this embodiment, compared with the prior art, has the following advantages: First, by setting the exchange pipe, the flow circuit of the water body in the fracture is controlled, and the flow velocity of the fracture water body is increased; Second, the double-layer filtered tubular structure not only improves the filtering effect, but also increases the filtering radius, improving the filtering volume and the water output; Third, the double-layer filtered tubular structure further improves the structural strength and has good compressive resistance, and is suitable for use in medium-depth geothermal reinjection wells.

[0046] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A geothermal recharge well control device, characterized in that: The invention comprises an outer support pipe (1) arranged in a pipe well (a), and an inner return pipe (2) arranged in the outer support pipe (1); a first gravel layer (11) is filled between the inner wall of the pipe well (a) and the outer support pipe (1), and a second gravel layer (12) is filled between the outer support pipe (1) and the inner return pipe (2); and an exchange pipe (3) connected to the outer support pipe (1) is arranged at the crack opening (b).

2. A geothermal recharge well control device according to claim 1, characterized in that: The exchange tube (3) comprises a tube body (301) having one end connected to the crack opening (b) and the other end inserted into the outer support tube (1) and connected to the second gravel layer (12), two support ring plates (302) arranged at both ends of the tube body (301), and a plurality of support rods (303) arranged between the two support ring plates (302) and distributed along the circumference of the tube body (301).

3. A geothermal recharge well control device according to claim 2, characterized in that: The exchange tube (3) further comprises an opening arranged on the tube wall of the tube body (301).

4. A geothermal recharge well control device according to claim 1, characterized in that: The outer support pipe (1) comprises a skeleton ring (101), a plurality of connecting rods (102) arranged outside the skeleton ring (101) and distributed circumferentially along the skeleton ring (101), and a plurality of reinforcing connecting rods (103) arranged at intervals inside the skeleton ring (101) and connected to the inner water return pipe (2).

5. A geothermal recharge well control device according to claim 4, characterized in that: The outer support tube (1) further comprises a tubular filter screen (104) arranged on the inner side of the skeleton ring (101).

6. A geothermal recharge well control device according to claim 4, characterized in that: There are a plurality of skeleton rings (101), which are arranged concentrically along the direction of the pipe well (a); a single connecting rod (102) is used to connect at least two adjacent skeleton rings (101).

7. A geothermal recharge well control device according to claim 6, characterized in that: In the direction from top to bottom along the tube well (a), the distribution spacing of the skeleton rings (101) becomes smaller.

8. A geothermal recharge well control device according to claim 1, characterized in that: The inner water return pipe (2) comprises a sedimentation pipe (201) arranged at the bottom of the pipe well (a), and a water filter pipe (202) arranged at the upper end of the sedimentation pipe (201) and extending to the water stop layer (c).

9. A geothermal recharge well control device according to claim 1, characterized in that: The particle size of the first gravel layer (11) is greater than the particle size of the second gravel layer (12).

10. A geothermal recharge well control device according to claim 3, characterized in that: The opening is a bridge-shaped hole.

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