Coaxial heat exchange type medium-deep layer geothermal energy heat-extraction non-water-extraction underground heat exchange device

Abstract

The invention provides a coaxial heat exchange type medium-deep layer geothermal energy heat extraction non-water-extraction underground heat exchange device, and mainly relates to the technical field of geothermal exploitation. A coaxial heat exchange type medium-deep layer geothermal energy heat extraction non-water-extraction underground heat exchange device comprises a connecting pipe, instrument installation pipes are fixedly arranged on the two sides of the connecting pipe, an upper suspension is arranged on the upper portion of the connecting pipe, a lower suspension is arranged at the bottom of the connecting pipe, a well pipe is installed in the connecting pipe, an outer pipe is arranged in the well pipe, an inner pipe is arranged in the outer pipe, and the inner pipe is connected with the instrument installation pipes. The inner pipe is communicated with the lower portion of the outer pipe, and the outer pipe penetrates through the top of the connecting pipe and is fixedly connected with an outer pipe hanger. According to the geothermal well heating system, the problems that recharge is incomplete and a recharge well is prone to being blocked, the geological environment is damaged to disturb the stratum, a pump needs to be lifted and lowered during maintenance, and the pump falls due to water level lowering during long-term operation in geothermal well heating can be effectively solved by adopting the geothermal energy single-well heat taking and water taking-free underground heat exchange technology on the premise that heating is met.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of geothermal exploitation, and specifically, it is a downhole heat exchange device for extracting heat without extracting water in medium and deep geothermal energy with coaxial heat exchange. Background Art

[0002] With the global emphasis on environmental protection and sustainable development, the energy structure is gradually transforming towards clean energy. Geothermal energy, as a clean and renewable energy, especially medium and deep geothermal energy, has the characteristics of rich content, relatively low cost, and wide distribution, with high utilization value and an increasingly important position in the energy structure.

[0003] Currently, geothermal well heating usually involves two wells, one for extraction and one for injection. Mining permits and water intake permits need to be obtained before extraction construction can be carried out. During the heat exchange process, geothermal water needs to be pumped out from underground and recharged into the injection well. However, the recharge rate is about 90%, and the recharge is incomplete, which can lead to problems such as damage to the geological environment and formation disturbance. When pumping water from the extraction well, a small amount of sand will be brought to the ground along with the geothermal water. The water extraction process may not only cause pipeline blockage, increase the maintenance cost and difficulty of equipment, reduce the service life of the equipment, but also have a certain negative impact on land subsidence.

[0004] In addition, in the prior art, the following problems also exist in the operation process of the geothermal well heating system: 1. High equipment maintenance cost: At the start and end of the heating season, the pump pipes and submersible pumps need to be frequently lifted and lowered. During operation, if the pump does not operate or the cable leaks electricity, the pump needs to be lifted for repair, which affects the heating effect and may even cause the pump to drop or burn. 2. Complicated procedures: A water intake permit needs to be obtained, and the procedures are complex and time-consuming. 3. Geological environment problems: Extracting and recharging groundwater may cause geological environment disturbance and trigger geological problems such as land subsidence. Summary of the Invention

[0005] To solve the deficiencies of the prior art, the present invention provides a downhole heat exchange device for extracting heat without extracting water in medium and deep geothermal energy with coaxial heat exchange. This device can address the problems existing in geothermal well heating, such as "incomplete recharge and easy blockage of the injection well", "damage to the geological environment and formation disturbance", and "need to lift and lower the pump for maintenance and pump drop due to long-term operation and water level decline". On the premise of meeting heating requirements, the downhole heat exchange technology of extracting heat without extracting water from a single geothermal well is adopted to effectively avoid the occurrence of the above problems.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: Coaxial heat exchange medium-deep geothermal energy heat extraction without water extraction downhole heat exchange device, including a connecting pipe, on both sides of the connecting pipe are fixedly provided with instrument installation pipes, on the upper part of the connecting pipe is provided with an upper suspension, at the bottom of the connecting pipe is provided with a lower suspension, inside the connecting pipe is installed a well pipe, inside the well pipe is provided with an outer pipe, inside the outer pipe is provided with an inner pipe, the lower part of the inner pipe is communicated with the outer pipe, the outer pipe penetrates through the top of the connecting pipe and is fixedly connected with an outer pipe suspension, at the top of the inner pipe is provided with a well source side working medium outlet, on one side of the upper part of the well pipe is provided with a well source side working medium inlet, and the bottom of the well pipe is of an open structure.

[0007] A heat preservation layer is provided outside the inner pipe, a counterweight is provided at the bottom of the inner pipe, and a screen pipe is provided at the lower part of the inner pipe.

[0008] A pressure gauge and a thermometer are installed on the instrument installation pipe, and the instrument installation pipe is arranged on the side of the well pipe between the upper suspension and the lower suspension.

[0009] A settlement monitoring point is provided on the instrument installation pipe.

[0010] A wellhead cover plate is installed at the top of the well pipe, and the top of the inner pipe penetrates through the wellhead cover plate.

[0011] An injection nitrogen port is provided on one side of the well pipe, and the injection nitrogen port is arranged on the side of the well pipe between the upper suspension and the lower suspension.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. Cost saving: This device can transform and reuse abandoned geothermal wells, revitalizing the existing assets of abandoned geothermal wells. Before the transformation, the pump pipe and submersible pump need to be lifted and lowered at the beginning and end of the heating season. During the heating period, if the pump does not operate or the cable leaks electricity, the pump needs to be lifted for repair, affecting the heating effect. Even the phenomenon of pump dropping and pump burning may occur. After the transformation, there is no need to install the pump pipe and submersible pump, and it only relies on a small-power circulation pump to operate, and the operation cost is only 1 / 3 of the original power.

[0013] 2. Simplified procedures: Using this technology does not extract groundwater, and there is no need to apply for a water intake permit, solving the problem of inconvenient handling of water intake permits.

[0014] 3. Environmental protection advantages: Using the coaxial heat exchange technology, no geothermal water is extracted and no recharging is required, avoiding problems such as tail water discharge and recharging; at the same time, it will not disturb the geothermal energy and will not cause geological environment problems such as ground settlement.

[0015] 4. Improved stability: By setting a counterweight at the bottom of the inner pipe and injecting nitrogen through the injection nitrogen port on the side of the well pipe to prevent corrosion and other measures, the stability and service life of the device downhole are improved. Description of the drawings

[0016] Figure 1 is the external structure schematic diagram of the present invention; Figure 2 It is a schematic diagram of the internal structure of the present invention; Figure 3 It is a schematic diagram of the inner tube structure of the present invention; Figure 4 It is a schematic diagram of the application principle of the present invention.

[0017] Reference numerals shown in the drawings: 1. Well source side working medium outlet; 2. Wellhead cover plate; 3. Well source side working medium inlet; 4. Outer tube suspension; 5. Upper suspension; 6. Settlement monitoring point; 7. Instrument installation pipe; 8. Nitrogen injection port; 9. Lower suspension; 10. Well tube; 11. Outer tube; 12. Inner tube; 20. Connecting pipe; 120. Thermal insulation layer; 121. Counterweight; 122. Screen pipe. Specific embodiments

[0018] In combination with the drawings and specific embodiments, the present invention will be further described. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by this application.

[0019] Combined with the attached Figures 1 - 4 , the coaxial heat exchange medium-depth geothermal energy heat extraction without water extraction downhole heat exchange device includes a connecting pipe 20. Instrument installation pipes 7 are fixedly arranged on both sides of the connecting pipe 20. An upper suspension 5 is arranged on the upper part of the connecting pipe 20. A lower suspension 9 is arranged at the bottom of the connecting pipe 20. A well tube 10 is installed in the connecting pipe 20. An outer tube 11 is arranged in the well tube 10. An inner tube 12 is arranged in the outer tube 11. The lower part of the inner tube 12 communicates with the outer tube 11. The outer tube 11 penetrates through the top of the connecting pipe 20 and is fixedly connected with an outer tube suspension 4. A well source side working medium outlet 1 is arranged at the top of the inner tube 12. A well source side working medium inlet 3 is arranged on one side of the upper part of the well tube 10. The bottom of the well tube 10 is an open structure.

[0020] A thermal insulation layer 120 is arranged outside the inner tube 12. A counterweight 121 is arranged at the bottom of the inner tube 12. A screen pipe 122 is arranged at the lower part of the inner tube 12. The thermal insulation layer can adopt a DN84 PN6.4MPa heat-insulating fiber-reinforced polyethylene pipe or a dn90 SDR11 polyethylene pipe; a flange is arranged at the top of the inner tube 12 for cooperative installation with the wellhead connecting pipeline; the inner tube 12 communicates with the outer tube 11 at the screen pipe 122; the thermal insulation layer 120 is used to prevent direct heat exchange between the water in the outer tube 11 and the inner tube 12, and improve the efficiency of heat extraction from groundwater; the counterweight 121 is used to improve the vertical state of the inner tube and the outer tube in water and improve the working stability.

[0021] A pressure gauge and a thermometer are installed on the instrument installation pipe 7, and the instrument installation pipe 7 is arranged on the side of the well pipe 10 between the upper suspension 5 and the lower suspension 9; the instrument is used to monitor the pressure and temperature of water.

[0022] Settlement monitoring points 6 are provided on the instrument installation pipe 7. The settlement monitoring points 6 are used to obtain the settlement information of the heat exchange device by using settlement monitoring equipment, so as to ensure the use safety and the working stability of the heat exchange device.

[0023] A wellhead cover plate 2 is installed at the top of the well pipe 10, and the top of the inner pipe 12 penetrates through the wellhead cover plate 2.

[0024] A nitrogen injection port 8 is provided on one side of the well pipe 10, and the nitrogen injection port 8 is arranged on the side of the well pipe 10 between the upper suspension 5 and the lower suspension 9. The nitrogen injection port 8 is used to inject nitrogen into the cavity outside the outer pipe 11 above the groundwater in the well pipe 10, which can effectively prevent the oxidation corrosion, rust, etc. of the well pipe 10 and the outer pipe 11.

[0025] The complete heat exchange and heating system used in conjunction with this device further includes a circulation pump, a heat pump unit, and a heating pipeline network; the circulating medium in this heat exchange device is softened water. Under the action of the circulation pump, the softened water enters the outer pipe 11 from the well source side working medium inlet 3, enters the inner pipe 12 through the screen pipe 122, the groundwater enters the gap between the well pipe 10 and the outer pipe 11 through the open end at the bottom of the well pipe 10, and exchanges heat with the water in the outer pipe 11. The water that absorbs the heat of the groundwater enters the circulation pump through the well source side working medium outlet 1 under the action of the circulation pump, and then enters the heat pump unit for re-heat exchange. The heat pump unit fully exchanges the heat in the water to the heating pipeline network through the heat pump; the working principle of the heat pump unit is similar to that of a common air conditioner. There is a heat conduction medium pipeline in the unit system, and a compressor, an evaporator, an expansion valve, and a condenser are provided in the pipeline; the heat is fully transported to the heating pipeline network for use through the heat pump unit. The heating pipeline network is, for example, Figure 4 a pipeline circulation system with a circulation pump attached, and the heating pipeline network is connected to structures such as radiators for heating; the pipeline flowing out of the softening water tank has automatic valve control. When the water pressure in the heating pipeline or the heat exchange pipeline decreases, new softened water is timely replenished to maintain the normal working water pressure.

[0026] Through this heat exchange device, problems such as "incomplete reinjection and easy blockage of the reinjection well" and "pump lifting and lowering are required for maintenance and the water level drops and the pump drops during long-term operation" existing in geothermal well heating can be solved. On the premise of meeting heating, geothermal energy single-well heat extraction without water extraction and downhole heat exchange heat extraction are adopted.

[0027] The specific steps are as follows: (1) On the basis of the original abandoned geothermal well, the coaxial heat exchange technology is adopted, without extracting geothermal water, without reinjection, without disturbing the geothermal water, without damaging the geological environment, and without causing ground settlement.

[0028] (2) The sampling coaxial heat exchange technology does not require the extraction of geothermal water, so it does not require a submersible pump, avoiding the problems of maintenance of the submersible pump and pump failure.

[0029] (3) In the coaxial heat exchange medium-deep geothermal energy heat extraction without water extraction well heat exchange device heating system, such as Figure 4 .

[0030] ① First, the well-source side circulating working medium enters the heat extraction well through the circulation pump, is heated and then enters the heat pump unit for heat exchange for secondary heating. The cooled well-source side circulating working medium enters the heat extraction well again for circulating heating.

[0031] ② Under the action of the user-side circulation pump, the user-side circulating working medium is heated through heat exchange and the heat pump unit, and then heats the user side; after the heat exchange is completed, it enters the heat pump unit again for circulating heating.

[0032] (4) Basic situation of abandoned wells The well depth of the production well and recharge well is about 1500m. The upper part is a φ273.1mm×8.89mm oil casing, the middle and lower parts are a φ139.7mm×6.98mm oil casing, and the lower part is a filter pipe and a sedimentation pipe. The water intake target layer is generally the Neogene Guantao Formation.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coaxial heat exchange type underground heat exchange device for extracting heat from deep geothermal energy without extracting water, comprising a connecting pipe (20), characterized in that: Instrument installation pipes (7) are fixedly provided on both sides of the connecting pipe (20), an upper suspension (5) is provided on the upper part of the connecting pipe (20), a lower suspension (9) is provided on the bottom of the connecting pipe (20), a well pipe (10) is installed in the connecting pipe (20), an outer pipe (11) is provided in the well pipe (10), an inner pipe (12) is provided in the outer pipe (11), the inner pipe (12) is communicated with the lower part of the outer pipe (11), the outer pipe (11) passes through the top of the connecting pipe (20) and is fixedly connected to the outer pipe suspension (4), a well source side working fluid outlet (1) is provided on the top of the inner pipe (12), a well source side working fluid inlet (3) is provided on one side of the upper part of the well pipe (10), and the bottom of the well pipe (10) is an open structure.

2. The coaxial heat exchange type medium-deep geothermal energy heat extraction without water downhole heat exchange device according to claim 1 is characterized by: The inner tube (12) is provided with a heat-insulating layer (120) on the outside, a counterweight (121) is provided on the bottom of the inner tube (12), and a screen tube (122) is provided on the lower part of the inner tube (12).

3. The coaxial heat exchange type medium-deep geothermal energy heat extraction without water downhole heat exchange device according to claim 1 is characterized by: A pressure gauge and a temperature gauge are installed on the instrument installation pipe (7), and the instrument installation pipe (7) is arranged on the side of the well pipe (10) between the upper suspension (5) and the lower suspension (9).

4. The coaxial heat exchange type underground heat exchange device for extracting heat from deep geothermal energy without taking water according to claim 1 is characterized in that: The instrument installation pipe (7) is provided with a settlement monitoring point (6).

5. The coaxial heat exchange type medium-deep geothermal energy heat extraction without water downhole heat exchange device according to claim 1 is characterized in that: A wellhead cover plate (2) is installed on the top of the well pipe (10), and the top of the inner pipe (12) passes through the wellhead cover plate (2).

6. The coaxial heat exchange type medium-deep geothermal energy heat extraction without water downhole heat exchange device according to claim 1 is characterized by: A nitrogen injection port (8) is provided on one side of the well pipe (10), and the nitrogen injection port (8) is arranged on the side of the well pipe (10) between the upper suspension (5) and the lower suspension (9).

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