Gravel discharge shaft structure of heat exchange pool of geothermal well

Abstract

The utility model belongs to the technical field of geothermal power generation, and particularly relates to a ground temperature well heat exchange pool gravel discharge shaft structure which comprises a drill hole drilled from the ground surface to a dry hot rock stratum, a heat exchange pool with the diameter larger than that of the drill hole is arranged at the bottom of the drill hole, an outer sleeve is fixed in the drill hole, and an inner sleeve is arranged in the outer sleeve in a penetrating mode. A first annulus is formed between the outer sleeve and the inner sleeve; a drill rod is arranged in the inner sleeve in a penetrating mode, and a second annulus is formed between the drill rod and the inner sleeve. The other end of the drill rod extends into the heat exchange pool and is fixedly connected with a telescopic stirring drill bit; the telescopic stirring drill bit comprises a sleeve and a center pipe which are nested with each other, the upper end of the sleeve is fixed to the drill rod, the lower end of the sleeve is open, the center pipe can be inserted into the sleeve in a downward telescopic mode, a plurality of sets of fin plates are evenly arranged on the periphery of the outer side of the sleeve, and each set of fin plates comprises a first fin plate and a second fin plate. According to the utility model, broken stones at the bottom or the edge of the heat exchange pool can be efficiently flushed out.

Description

Technical Field

[0001] This utility model belongs to the field of geothermal power generation technology, specifically relating to a well structure for discharging gravel from a geothermal well heat exchange pool. Background Technology

[0002] Currently, common applications of geothermal energy development include hot spring bathing, medical treatment, heating, building agricultural greenhouses, aquaculture, and grain drying. With increasing demand for electricity, people are starting to use geothermal energy for power generation. However, traditional geothermal energy utilization requires pumps to extract underground hot water to the surface, a process that itself consumes energy. Therefore, traditional geothermal energy power generation typically involves heating water with geothermal energy and using steam turbines to generate electricity; it is difficult to use water turbines to generate electricity from geothermal energy.

[0003] To address this, the applicant has developed an ultra-deep well hydroelectric power generation method utilizing the density difference between hot and cold water in geothermal energy (Publication No. CN119353141A). This method involves drilling a well several kilometers deep, heating artificially injected cold water through underground hot dry rock layers, and using the density difference between the hot and cold water to generate water flow power (head difference), thereby driving the generator unit and achieving efficient energy conversion. In this process, the underground hot dry rock layers, as the core area of ​​heat exchange, play a crucial role in transferring heat, and their contact surface with the water directly affects the efficiency and stability of the entire power generation system. However, the geothermal energy extraction wells in the hot dry rock layers are very deep. If the wells are drilled directly into the hot dry rock layers for heat exchange, the water storage space at the bottom of the hot dry rock layers is relatively small, resulting in insufficient heat in the return water of the extraction wells and reducing the efficiency of the entire power generation system.

[0004] To address this, the applicant employed bottom-hole blasting to construct an underground heat exchange pool for deep geothermal well power generation, increasing the water storage space at the bottom of the geothermal well and thus expanding the contact area between the water and the dry, hot rock. However, after bottom-hole blasting, numerous small stones with a diameter of approximately 2 cm are generated at the bottom of the well. These stones need to be flushed out using a drilling rig, but using only high-pressure water jets is inefficient, and stones located at the bottom or edge of the heat exchange pool are difficult to flush out. Utility Model Content

[0005] The purpose of this utility model is to provide a well shaft structure for discharging gravel from the heat exchange pool of a geothermal well, which can efficiently flush out gravel from the bottom or edge of the heat exchange pool.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by this utility model is as follows:

[0007] A geothermal well structure with a crushed stone discharge wellbore includes a borehole drilled from the surface to a dry, hot rock layer. The bottom of the borehole is a heat exchange pool with a diameter larger than the borehole diameter. An outer sleeve is fixed inside the borehole, and an inner sleeve is inserted inside the outer sleeve, forming a first annulus between the outer sleeve and the inner sleeve. A drill rod is inserted inside the inner sleeve, forming a second annulus between the drill rod and the inner sleeve. One end of the drill rod at the surface is used to connect to a drilling rig, and the other end of the drill rod extends into the heat exchange pool and is fixedly connected to a telescopic stirring drill bit. The telescopic stirring drill bit can be inserted into the heat exchange pool from the inner sleeve and then extended.

[0008] Furthermore, the diameter of the borehole is 600-1000mm, and the depth of the borehole is 3000-10000 meters.

[0009] Furthermore, the outer casing is fixedly installed at a position 70-80% of the borehole depth from the surface to the bottom of the well.

[0010] Furthermore, the telescopic stirring drill bit includes nested sleeves and a central tube. The upper end of the sleeve is fixed to the drill rod, and the lower end of the sleeve is open. The central tube is inserted into the sleeve and can extend downwards. Several sets of fins are evenly arranged around the outer circumference of the sleeve. Each set of fins includes a first fin and a second fin. The upper end of the first fin is hinged to the upper end of the sleeve, the lower end of the first fin is hinged to the upper end of the second fin, and the lower end of the second fin is hinged to the lower end of the central tube. In the initial state, the upper end of the sleeve is fixed to the drill rod, and the central tube extends to its maximum position, keeping the first and second fins vertical. This allows the telescopic stirring drill bit to descend to the bottom along the inner sleeve. When the lower end of the central tube reaches the bottom of the borehole, the drill rod continues to descend. At this time, the sleeve and the central tube retract relatively, and the first and second fins fold outwards. When cold water needs to be injected into the first annulus, and the hot water in the heat exchange tank carries the gravel upwards, the drilling rig can be started at the same time to rotate the drill rod. The drill rod then drives the first fin and the first fin to rotate, creating agitation in the heat exchange tank, which causes the gravel in the heat exchange tank to float, making it easier to carry all the gravel out.

[0011] Furthermore, the sides of the first and second fins facing the direction of rotation, as well as the outer surfaces of the first and second fins, are provided with a plurality of grinding teeth. This technical solution provides grinding teeth on the first and second fins, which, during the rotation and stirring process of the telescopic mixing drill bit, can grind larger stones into smaller pieces, facilitating the removal of blasted stones from the ground surface.

[0012] Furthermore, a fixed disk is provided at the bottom end of the central tube, and a rotating disk is provided below the fixed disk. A wear-resistant block is provided on the bottom surface of the rotating disk. Specifically, the rotating disk is bolted to the bottom axis of the central tube, and the fixed disk is fixed by the rotating disk. This arrangement facilitates the rotation of the sleeve, the first fin, and the first fin plate.

[0013] Furthermore, the upper end of the sleeve is provided with a connector for connecting to the drill pipe, and the end of the connector is provided with an external thread, the connector being threadedly connected to the drill pipe. In this technical solution, the connector and the external thread on the connector facilitate the detachable connection between the sleeve and the drill pipe.

[0014] Furthermore, the inner wall of the sleeve and the outer wall of the central tube are fitted with a sealed piston type, and the sleeve and the central tube are hydraulically driven, with the sleeve being a hydraulic cylinder and the central tube being a piston.

[0015] The utility model adopting the above technical solution has the following advantages:

[0016] 1. When the wellbore structure of this utility model needs to flush out blasted gravel, the telescopic stirring drill bit is first inserted into the hollow inner casing using the drill rod. In the initial state, the upper end of the sleeve is fixed to the drill rod, and the central tube extends to its maximum position, keeping the first and second fins vertical. This allows the telescopic stirring drill bit to descend to the bottom along the inside of the inner casing. When the lower end of the central tube reaches the bottom of the borehole, the drill rod continues to descend, at which point the sleeve and central tube relatively retract, and the first and second fins fold outwards. When it is necessary to inject cold water into the first annulus, and the hot water in the heat exchange tank carries the gravel upwards, the drilling rig can be started simultaneously to rotate the drill rod. The drill rod then drives the first and second fins to rotate, creating agitation in the heat exchange tank, causing the gravel in the heat exchange tank to float, making it easier to carry all the gravel out, thus increasing efficiency.

[0017] 2. This utility model is equipped with grinding teeth on the first and second fins. During the rotation and stirring process of the telescopic stirring drill bit, larger stones can be ground into smaller pieces, making it easier to flush the blasted stones out of the ground. Attached Figure Description

[0018] This utility model can be further illustrated by the non-limiting embodiments given in the accompanying drawings;

[0019] Figure 1 This is a schematic diagram of an embodiment of the gravel discharge wellbore structure for a geothermal well heat exchange tank according to this utility model;

[0020] Figure 2 for Figure 1 Schematic diagram of the telescopic mixing drill bit;

[0021] Figure 3 for Figure 2 A bottom view;

[0022] Figure 4 for Figure 2 A schematic diagram of the cross-sectional structure.

[0023] The symbols for the main components are explained below:

[0024] 1. Heat exchange tank; 2. Outer sleeve; 3. Inner sleeve; 4. First annulus; 5. Drill rod; 6. Second annulus; 7. Drilling rig; 8. Telescopic mixing drill bit; 9. Formation; 801. Sleeve; 802. Central tube; 803. First fin; 804. Second fin; 805. Grinding teeth; 806. Fixed disc; 807. Rotating disc; 808. Wear-resistant block; 809. Joint; 810. External thread; 811. Bolt. Detailed Implementation

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that similar or identical parts are referred to by the same reference numerals in the drawings or description. Implementations not shown or described in the drawings are forms known to those skilled in the art. Furthermore, directional terms mentioned in the embodiments, such as "up," "down," "top," "bottom," "left," "right," "front," and "back," are only for reference to the directions in the drawings and are not intended to limit the scope of protection of the present invention.

[0026] The geothermal well heat exchange pool with gravel discharge wellbore structure in this embodiment, such as... Figure 1 As shown, the system includes a borehole drilled from the surface to the dry hot rock layer. The borehole is obtained by drilling rig 7 from the surface downwards to the dry hot rock layer. The bottom of the borehole is a heat exchange pool 1 with a diameter larger than the borehole diameter. The heat exchange pool 1 is obtained by blasting with explosives sent to the bottom of the well. An outer casing 2 is fixed inside the borehole by cement cementing. An inner casing 3 is inserted inside the outer casing 2. The inner and outer surfaces of the inner casing 3 can be coated with heat insulation paint. The upper end of the inner casing 3 is generally fixed and suspended inside the outer casing 2 by a tool. A first annulus 4 is formed between the outer casing 2 and the inner casing 3. A drill rod 5 is inserted inside the inner casing 3. A second annulus 6 is formed between the drill rod 5 and the inner casing 3. One end of the drill rod 5 at the surface is used to connect to the drilling rig 7. The other end of the drill rod 5 extends into the heat exchange pool 1 and is fixedly connected to a telescopic stirring drill bit 8. The telescopic stirring drill bit 8 can be inserted into the heat exchange pool 1 from the inner casing 3 and then extended.

[0027] In actual drilling, the diameter of the borehole is 600-1000mm and the depth is 3000-10000 meters. The outer casing 2 can be fixed at 70-80% of the depth from the surface to the bottom of the well. In this embodiment, the diameter of the borehole is 600mm and the depth is 5000 meters. The outer casing 2 is cemented to a depth of 4000 meters from the surface to the bottom of the well.

[0028] like Figures 2-4 As shown, the telescopic stirring drill bit 8 of this embodiment includes a sleeve 801 and a central tube 802 nested together. The upper end of the sleeve 801 is provided with a connector 809 for connecting to the drill rod 5. The end of the connector 809 is provided with an external thread 810. The connector 809 is threadedly connected to the drill rod 5. The lower end of the sleeve 801 is open, and the central tube 802 can be inserted into the sleeve 801 in a downward telescopic manner. Several sets of fins are evenly arranged around the outer circumference of the sleeve 801. Each set of fins includes a first fin 803 and a second fin 804. The upper end of the first fin 803 is hinged to the upper end of the sleeve 801, the lower end of the first fin 803 is hinged to the upper end of the second fin 804, and the lower end of the second fin 804 is hinged to the lower end of the central tube 802.

[0029] The sides of the first fin 803 and the second fin 804 facing the direction of rotation, as well as the outer surfaces of the first fin 803 and the second fin 804, are provided with a plurality of grinding teeth 805. A fixed disk 806 is provided at the bottom end of the central tube 802, and a rotating disk 807 is provided below the fixed disk 806. Wear-resistant blocks 808 are provided on the bottom surface of the rotating disk 807. Specifically, the rotating disk 807 is pressed into the center of the bottom surface of the central tube 802 by bolts 811, and the fixed disk 806 is pressed and fixed by the rotating disk 807. The inner wall of the sleeve 801 and the outer wall of the central tube 802 are fitted with a sealed piston type. The sleeve 801 and the central tube 802 are hydraulically driven, with the sleeve 801 being a hydraulic cylinder and the central tube 802 being a piston.

[0030] When the blasted rock fragments need to be flushed out, the telescopic stirring drill bit 8 is first inserted into the hollow inner casing 3 using the drill rod 5. In the initial state, the upper end of the sleeve 801 is fixed to the drill rod 5, and the central tube 802 extends to the maximum position, keeping the first fin 803 and the second fin 804 in a vertical state. In this way, the telescopic stirring drill bit 8 can be lowered to the bottom along the inside of the inner casing 3.

[0031] When the lower end of the central tube 802 reaches the bottom of the borehole, the drill rod 5 continues to descend. At this time, the sleeve 801 and the central tube 802 retract relative to each other, and the first fin 803 and the second fin 804 fold outwards. When it is necessary to inject cold water into the first annulus 4, and the hot water in the heat exchange tank 1 carries the gravel upwards, the drill rig 7 can be started simultaneously to rotate the drill rod 5. The drill rod 5 then drives the first fin 803 to rotate, creating agitation in the heat exchange tank 1, which causes the gravel in the heat exchange tank 1 to float, making it easier to carry all the gravel out, thus increasing efficiency.

[0032] Because the telescopic mixing drill bit 8 in this embodiment is provided with grinding teeth 805 on the first wing plate 803 and the second wing plate 804, during the rotation and mixing process of the telescopic mixing drill bit 8, larger stones can be ground into smaller pieces, making it easier to flush the blasted stones out of the ground.

[0033] It should be noted that this wellbore structure generally does not require pressurization when injecting cold water into the first annulus 4. Tests have shown that this wellbore structure... Figure 1 As indicated by the arrows, cold water is poured in from the first annulus 4. Because the density of cold water is greater than that of hot water, the cold water flows downward along the first annulus 4 and into the heat exchange pool 1. After heat exchange, it flows upward along the second annulus 6. The resulting water flow velocity can generally reach about 1 m / s. Experiments have shown that gravel with a diameter of about 2 cm can be carried from the bottom of the well net at a flow velocity of ≥0.6 m / s.

[0034] The above provides a detailed description of the gravel discharge wellbore structure for a geothermal well heat exchange tank provided by this utility model. The specific embodiments are described only to aid in understanding the method and core concept of this utility model. It should be noted that those skilled in the art can make various improvements and modifications to this utility model without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A wellbore structure for discharging gravel from a heat exchange tank in a geothermal well, characterized in that: The system includes a borehole extending from the Earth's surface to a dry, hot rock layer. The bottom of the borehole is a heat exchange pool with a diameter larger than the borehole diameter. An outer sleeve is fixed inside the borehole, and an inner sleeve passes through the outer sleeve, forming a first annulus between the outer sleeve and the inner sleeve. A drill rod passes through the inner sleeve, forming a second annulus between the drill rod and the inner sleeve. One end of the drill rod at the Earth's surface is used to connect to a drilling rig, and the other end of the drill rod extends into the heat exchange pool and is fixedly connected to a telescopic stirring drill bit. The telescopic stirring drill bit can be inserted into the heat exchange pool from the inner sleeve and then extended.

2. The wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to claim 1, characterized in that: The diameter of the borehole is 600-1000mm, and the depth of the borehole is 3000-10000m.

3. The wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to claim 1, characterized in that: The outer casing is fixed at a position 70-80% of the borehole depth from the surface to the bottom.

4. A wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to any one of claims 1-3, characterized in that: The telescopic stirring drill bit includes nested sleeves and a central tube. The upper end of the sleeve is fixed to the drill rod, and the lower end of the sleeve is open. The central tube is inserted into the sleeve and can extend downwards. Several sets of fins are evenly arranged around the outer circumference of the sleeve. Each set of fins includes a first fin and a second fin. The upper end of the first fin is hinged to the upper end of the sleeve, the lower end of the first fin is hinged to the upper end of the second fin, and the lower end of the second fin is hinged to the lower end of the central tube.

5. The wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to claim 4, characterized in that: The first and second fins are provided with a plurality of grinding teeth on their sides facing the direction of rotation, as well as on their outer sides.

6. The wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to claim 4, characterized in that: A fixed plate is provided at the bottom end of the central tube, a rotating plate is provided below the fixed plate, and a wear-resistant block is provided on the bottom surface of the rotating plate.

7. The wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to claim 4, characterized in that: The upper end of the sleeve is provided with a connector for connecting to the drill pipe, and the end of the connector is provided with an external thread, and the connector is threadedly connected to the drill pipe.

8. A wellbore structure for crushed stone discharge in a geothermal well heat exchange tank according to any one of claims 5-7, characterized in that: The inner wall of the sleeve and the outer wall of the central tube are fitted with a sealed piston type. The sleeve and the central tube are hydraulically driven, the sleeve is a hydraulic cylinder, and the central tube is a piston.

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