Deep geothermal energy exploration and production single well structure adopting pipe-in-pipe structure

Abstract

The utility model relates to a deep geothermal heat energy exploration and production single well structure adopting a pipe-in-pipe structure, which solves the problems that the traditional geothermal heat energy exploration and production does not utilize much geothermal heat energy of an underground dry and hot rock stratum, and a multi-well heat production structure is generally adopted. The structure comprises a vertically downward exploring well, a casing pipe is arranged on the well wall of the exploring well, a central pipe is arranged in the center of the casing pipe, a heat preservation layer is arranged on the pipe wall of the central pipe, a cold water injection channel is formed between the inner wall of the casing pipe and the outer wall of the central pipe, a hot water ascending channel is formed in the central pipe, and the bottom end of the exploring well is drilled to a dry hot rock stratum. And cracks are formed in the hot dry rock stratum at the bottom end of the exploring well. According to the utility model, pipe-in-pipe single well heat collection is adopted, open type heat collection is adopted at the well bottom, and cracks are artificially manufactured at the dry-hot rock stratum at the bottom end of the exploring and producing well, so that the heat exchange efficiency is improved, the efficient development and utilization of deep geothermal resources are realized, and the stability and sustainability of the underground environment are kept at the same time.

Description

Technical Field

[0001] This utility model belongs to the field of drilling engineering and relates to a deep geothermal energy exploration and production well, and in particular to a single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure. Background Technology

[0002] Geothermal energy is a type of energy originating from within the Earth. Humans have utilized it for a long time, for example, through hot spring bathing, medical purposes, heating, building greenhouses, aquaculture, and drying grains. The most traditional method of using geothermal energy is to explore shallow geothermal layers and extract the groundwater heated by these layers. Low-temperature geothermal energy is widely distributed and is a clean, renewable energy source. Traditional geothermal energy exploration and extraction typically targets high-temperature groundwater, while the utilization of geothermal energy from deep, dry, hot rock layers is limited and lacks effective methods. Furthermore, traditional geothermal energy exploration and extraction often employs multi-well structures, resulting in high costs. Utility Model Content

[0003] The purpose of this invention is to address the problem that traditional geothermal energy exploration and extraction methods do not fully utilize the geothermal energy of deep underground dry hot rock layers and typically employ multi-well extraction structures. This invention provides a single-well structure for deep geothermal energy exploration and extraction that uses a pipe-in-pipe structure and an open-type bottom end structure to improve heat exchange efficiency and effectively explore and extract deep geothermal energy from underground dry hot rock layers.

[0004] The technical solution adopted by this utility model to solve its technical problem is: a single-well structure for deep geothermal energy exploration and extraction using a pipe-in-pipe structure, including a vertically downward-opening exploration and extraction well, wherein a casing for reinforcement is set in the upper part of the well wall of the exploration and extraction well, the casing depth is 70-90% of the exploration and extraction well depth, a central pipe is set in the center of the casing, the wall of the central pipe is provided with a heat insulation layer, a cold water injection channel is formed between the inner wall of the casing and the outer wall of the central pipe, and a hot water rising channel is formed inside the central pipe, the bottom end of the exploration and extraction well is drilled to a dry hot rock layer, and the exploration and extraction well has cracks in a section of the dry hot rock layer below the casing.

[0005] This is a single-well structure. Water is injected externally into the central pipe, while hot water is extracted internally. The central pipe is insulated to reduce heat loss. In this device, the casing protects the wellbore. Due to the large drilling depth of this structure, the lower part of the exploration / production well penetrates deep into the rock strata. The casing reinforces and protects the more porous sections of the upper rock strata. During the fracturing process, the upper part of the exploration / production well is protected by the casing, preventing crack formation; cracks only appear in the lower section of the exploration / production well where there is no casing. The bottom of the central pipe has an open structure. Cracks are artificially created at the lower end of the exploration / production well in the dry, hot rock strata to improve heat exchange efficiency. Room-temperature water is pumped into the well from the surface through a cold water injection channel. It flows through the network of artificially created cracks, absorbing heat from the dry, hot rock and heating up. Subsequently, the hot water, due to its lower density, rises rapidly to the surface along the hot water rising channel inside the central pipe, completing the heat extraction process. This cycle repeats itself, enabling the efficient development and utilization of deep geothermal resources while maintaining the stability and sustainability of the underground environment.

[0006] Preferably, both the sleeve and the central tube are made of stainless steel.

[0007] Preferably, the insulation layer is an aerogel insulation layer.

[0008] Preferably, the bottom of the central pipe is 0.5-2 meters higher than the bottom of the exploration well.

[0009] Preferably, the inner diameter of the sleeve is 0.8-1.5 meters, and the outer diameter of the central tube does not exceed 60% of the inner diameter of the sleeve.

[0010] Preferably, the depth of the exploration well is 3000-10000 meters.

[0011] Preferably, the cracks in the dry, hot rock layer are artificially formed using a splitting method.

[0012] Preferably, the cracks in the dry hot rock layer are formed using controlled blasting or hydraulic fracturing techniques.

[0013] This utility model adopts a single-well heat extraction method with a pipe-in-pipe structure and an open-type heat extraction system at the bottom of the well. Cracks are artificially created in the dry hot rock layer at the lower section of the exploration well to improve the efficiency of heat exchange, thereby realizing the efficient development and utilization of deep geothermal resources while maintaining the stability and sustainability of the underground environment. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the structure of this utility model.

[0016] Figure 2 This is a schematic diagram of the upper section of the exploration well of this utility model.

[0017] In the diagram: 1. Exploration well, 2. Casing, 3. Central pipe, 4. Insulation layer, 5. Cold water injection channel, 6. Hot water rising channel, 7. Dry hot rock layer, 8. Crack. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0019] Example: A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure, such as... Figure 1 As shown. This device includes a vertically downward-facing exploration well 1, with a depth of 3000-10000 meters. A casing 2 is installed in the upper section of the well wall of the exploration well 1, with a depth of 75% of the depth of the exploration well 1. A central pipe 3 is installed at the center of the casing 2. Both the casing 2 and the central pipe 3 are made of stainless steel. An insulation layer 4, which is an aerogel insulation layer, is installed on the inner or outer wall of the central pipe. A cold water injection channel 5 is formed between the inner wall of the casing 2 and the outer wall of the central pipe 3, and a hot water rising channel 6 is formed inside the central pipe 3. The bottom of the exploration well 1 is drilled to a dry hot rock layer 7. Cracks 8 are present in the dry hot rock layer 7 below the bottom of the casing 2 in the lower section of the exploration well 1. The cracks in the dry hot rock layer are artificially formed using a fracturing method, employing controlled blasting or hydraulic fracturing technology.

[0020] In this example, the inner diameter of the sleeve is 1 meter, and the outer diameter of the central tube is 0.4 meters. The bottom end of the central tube is about 1 meter higher than the bottom end of the sleeve.

[0021] In this example, the drilling configuration involved using a 1-meter diameter drilling rig to drill vertically downwards from the surface to a predetermined depth, forming a vertical wellbore several kilometers deep. During this process, to ensure borehole stability and prevent interference from the surface environment, stainless steel casing of matching diameter was installed for borehole wall protection within 75% of the depth range from the surface to the bottom.

[0022] Downhole layout: After reaching the target depth, a precise sealing and fracturing operation is carried out in a specific area at the bottom of the well (dry hot rock layer). Multiple fractures are artificially created using controlled blasting or hydraulic fracturing technology to expand the heat exchange area and improve the efficiency of heat energy collection.

[0023] Heat exchange system: A 400 mm outer diameter stainless steel central pipe is deployed inside the well, with its bottom located approximately 1 meter above the drilling end. The pipe integrates a high-efficiency aerogel insulation layer, serving as a channel for hot water to rise. The annular space between the outer side of this pipe and the casing is designed as a cold water injection channel, forming a closed-loop circulation system. Based on the natural convection principle of hot water rising and cold water sinking, continuous heat energy exchange is achieved between the deep underground dry hot rock and surface water.

[0024] Working principle: During system operation, ambient temperature water is pumped from the surface into the well through the inlet. It flows through a network of fractures created by artificial splitting, absorbing heat from the dry, hot rock and heating up. Subsequently, the hot water, due to its decreased density, rapidly rises to the surface along the interior of the stainless steel central tube, completing the heat extraction process. This cycle repeats continuously, achieving efficient development and utilization of deep geothermal resources while maintaining the stability and sustainability of the underground environment.

Claims

1. A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure, comprising a vertically downward-opened exploration and production well, characterized in that: The upper part of the exploration well is equipped with a casing for reinforcement. The casing depth is 70-90% of the exploration well depth. A central tube is set in the center of the casing. The wall of the central tube is equipped with a heat insulation layer. A cold water injection channel is formed between the inner wall of the casing and the outer wall of the central tube. A hot water rising channel is formed inside the central tube. The bottom of the exploration well is drilled to a dry hot rock layer. The exploration well has cracks in a section of the dry hot rock layer below the casing.

2. The single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: Both the sleeve and the central tube are made of stainless steel.

3. The single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The insulation layer is an aerogel insulation layer.

4. The single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The bottom of the central pipe is 0.5-2 meters higher than the bottom of the exploration and production well.

5. A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The inner diameter of the sleeve is 0.8-1.5 meters, and the outer diameter of the central tube does not exceed 60% of the inner diameter of the sleeve.

6. A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The depth of the exploration well is 3,000-10,000 meters.

7. A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The cracks in the dry, hot rock layer were artificially created using a splitting method.

8. A single-well structure for deep geothermal energy exploration and production using a pipe-in-pipe structure as described in claim 1, characterized in that: The cracks in the dry, hot rock layer were formed using controlled blasting or hydraulic fracturing techniques.

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