A medium-deep geothermal heat exchange system based on 300-meter underground SMA temperature control check valve

Abstract

The application discloses a kind of based on 300 meters underground SMA temperature control check valve middle-deep geothermal well winter and summer layered heat exchange system, belong to middle-deep geothermal energy development and utilization technical field.The system includes coaxial casing heat exchange wellbore, SMA temperature control check valve;Coaxial casing heat exchange wellbore is divided into 0-300m shallow heat exchange section and 300m below middle-deep heat exchange section with 300m depth as boundary;SMA temperature control check valve is fixedly installed in the 300m depth position of coaxial casing heat exchange wellbore outer pipe ring cavity, uses Ti-Ni base shape memory alloy temperature control spring as drive core, sets 30℃~40℃ phase transition critical temperature, and is independently triggered phase transition opening and closing according to downhole fluid temperature.The application realizes single well winter and summer adaptive heat exchange, solves geothermal well utilization rate, double well cost, electric control valve reliability is poor and other pain points, without downhole power supply and signal line, passive maintenance-free, structure is reliable, operation and maintenance cost is low, promote middle-deep geothermal energy large-scale efficient low-cost promotion.

Description

Technical Field

[0001] This invention relates to the field of medium-deep geothermal energy development and utilization technology, specifically to a medium-deep geothermal co-well stratified heat exchange system that uses a shape memory alloy (SMA) passive temperature control valve to achieve physical stratification of shallow and deep strata in a single well and adaptive heat exchange in winter and summer. Background Technology

[0002] Medium-deep geothermal energy, as a clean and renewable energy source, is widely used in building district heating, industrial heating, and other fields. Currently, in existing medium-deep geothermal development projects, geothermal wells are mostly used only for heating in winter and left idle for extended periods in summer. This results in short annual utilization time and extremely low utilization rates for individual wells, directly leading to a longer investment payback period and limited economic benefits. To meet summer cooling demands, the industry conventionally adopts shallow soil heat exchange cooling solutions. However, shallow cooling pipelines and medium-deep heating pipelines cannot be reused in the same well, necessitating an independent dual-well layout. The dual-well solution not only requires a large land area and high construction investment but also suffers from inherent drawbacks such as severe inter-well thermal interference, easy imbalance of the underground thermal field, and rapid decline in heat exchange efficiency over long-term operation. Furthermore, existing geothermal well stratified heat exchange control devices largely rely on surface electrical control systems in conjunction with downhole motors to drive valves for operating condition switching, requiring the installation of power cables and signal transmission lines underground. Geothermal wells operate in harsh environments characterized by high temperatures, high pressures, and high corrosion. Electrical and electromechanical components are prone to aging and damage, resulting in poor overall system reliability, difficult downhole maintenance, high operating costs, and short service life. Currently, the industry lacks an integrated heat exchange system capable of single-well stratification at varying depths, adaptive switching between winter and summer seasons, passive maintenance-free operation, and no electrical control or cables. This hinders the large-scale, efficient, and low-cost promotion and application of medium-deep geothermal energy. Summary of the Invention

[0003] To address the aforementioned problems, this invention employs the following technical solution: a mid-deep geothermal co-well stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve, comprising a coaxial casing heat exchange wellbore and an SMA temperature-controlled check valve; the coaxial casing heat exchange wellbore is divided into a shallow heat exchange section of 0-300m and a mid-deep heat exchange section below 300m, with a depth of 300m as the boundary; the SMA temperature-controlled check valve is fixedly installed at a depth of 300m in the outer tube annulus of the coaxial casing heat exchange wellbore, using a Ti-Ni-based shape memory alloy temperature-controlled spring as the driving core; the SMA temperature-controlled check valve autonomously triggers phase change opening and closing based on the downhole fluid temperature; when the medium temperature is below the critical range of 35℃, the valve opens, and the fluid circulates in the 0-300m shallow heat exchange section to achieve summer cooling; when the medium temperature is above the critical range of 40℃, the valve closes, blocking the shallow flow channel, and the fluid flows into the mid-deep heat exchange section below 300m to achieve winter heating.

[0004] Furthermore, the coaxial casing heat exchange wellbore includes a coaxial outer tube and a coaxial inner tube.

[0005] Furthermore, the SMA temperature-controlled check valve includes an SMA temperature-controlled spring, a fixing component, a hinged fastener, a sealing bevel, and a temperature-sensitive valve disc.

[0006] Furthermore, the Ti-Ni-based shape memory alloy temperature control spring is set to a phase transformation critical temperature of 30℃~40℃.

[0007] Furthermore, the SMA temperature-controlled check valve adopts a cable-free, motor-free, and external electrical control design, relying entirely on the temperature of the downhole fluid to autonomously drive its opening and closing, eliminating the need for signal transmission and power supply lines to be laid downhole.

[0008] Furthermore, the system also includes a temperature and pressure monitoring unit and a safety bypass. The temperature and pressure monitoring unit collects temperature and pressure parameters inside the wellbore in real time and links with the safety bypass to build a safety mechanism. When the system experiences over-temperature, over-pressure, or valve failure, the safety bypass automatically activates and switches to the whole-well heat exchange mode to ensure continuous and stable operation of the system.

[0009] Compared with existing technologies, the beneficial effects of this invention are as follows: First, it significantly improves the utilization rate of single-well geothermal energy, solves the problem of traditional geothermal wells being idle in summer, extends the effective utilization time of single wells, and shortens the investment return cycle; Second, it reduces engineering and operation and maintenance costs, eliminates the need for dual-well deployment, reduces land occupation and construction investment, and the SMA temperature control check valve is passive and maintenance-free, avoiding the aging defects of downhole electrical control components and extending the system life; Third, it improves system reliability, relying on Ti-Ni-based shape memory alloys to achieve autonomous valve opening and closing, and is equipped with temperature and pressure monitoring and safety bypass to ensure continuous and stable system operation; Fourth, it promotes the large-scale promotion of medium-deep geothermal energy, with a reasonable structure and strong adaptability, breaking through industry technical bottlenecks and providing a reliable technical solution for its efficient and low-cost promotion. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the planar structure of the downhole SMA temperature control check valve of the present invention.

[0012] Figure 2 This is a schematic diagram of the cross-sectional structure of the downhole SMA temperature control check valve of the present invention under winter operation conditions.

[0013] Figure 3 This is a schematic diagram of the cross-sectional structure of the downhole SMA temperature control check valve under summer operating conditions according to the present invention.

[0014] Figure 4 This is an overall elevation view of the winter operation of the deep geothermal co-well stratified heat exchange system in this invention.

[0015] Figure 5 This is an overall elevation view of the summer operation of the deep geothermal co-well stratified heat exchange system in this invention.

[0016] In the diagram: 1. Coaxial outer tube; 2. Coaxial inner tube; 3. Shallow heat exchange section (0-300m); 4. Medium-deep heat exchange section (below 300m); 5. SMA temperature-controlled check valve; 6. SMA temperature-controlled spring; 7. Fixing component; 8. Hinged fastener; 9. Sealing bevel; 10. Temperature-sensitive valve disc; 11. Coaxial sleeve-type heat exchange wellbore. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1-5 As shown, this embodiment provides a mid-deep geothermal system with winter and summer stratified heat exchange based on a 300-meter downhole SMA temperature-controlled check valve. It includes a coaxial casing heat exchange wellbore 11, an SMA temperature-controlled check valve 5, a temperature and pressure monitoring unit, and a safety bypass. All components work together to achieve winter and summer stratified adaptive heat exchange in a single well, meeting the dual needs of heating and cooling.

[0019] The coaxial casing heat exchange wellbore 11 is made of conventional geothermal well casing material, possessing characteristics of high temperature resistance, high pressure resistance, and corrosion resistance. It includes a coaxial outer tube 1 and a coaxial inner tube 2, forming an outer tube annular cavity for the circulation of heat exchange fluid. A 300-meter depth serves as a clear dividing line: the upper 0-300m section is the shallow heat exchange section 3, and the lower 300-1200m section is the medium-deep heat exchange section 4. The shallow heat exchange section 3 is used to absorb ground heat for cooling in summer, while the medium-deep heat exchange section 4 is used to absorb ground heat for heating in winter.

[0020] The SMA temperature-controlled check valve 5 is fixedly installed at a depth of 300 meters in the outer tube annulus of the coaxial sleeve heat exchange wellbore 11. It is firmly fixed by the fixing component 7 and the hinged fastener 8 to ensure that it is suitable for the harsh environment of high temperature, high pressure and high corrosion downhole, and is not easy to loosen or be damaged. The SMA temperature-controlled check valve 5 is the core component of the system operating condition switching, including the SMA temperature control spring 6, the fixing component 7, the hinged fastener 8, the sealing bevel 9 and the temperature-sensitive valve disc 10. The core driving component is the Ti-Ni based shape memory alloy temperature control spring 6, which is set with a phase change critical temperature of 30℃~40℃. It can accurately trigger the shape phase change according to the change of downhole fluid temperature, thereby driving the temperature-sensitive valve disc 10 to open and close.

[0021] The sealing bevel 9 is made of corrosion-resistant alloy material, forming a good sealing structure with the temperature-sensitive valve disc 10 and valve seat, which can effectively prevent fluid cross-flow between different heat exchange sections and ensure heat exchange efficiency. The temperature-sensitive valve disc 10 is made of high-temperature and corrosion-resistant metal material and is directly driven by the SMA temperature control spring 6, with rapid and reliable action response. At the same time, the SMA temperature control check valve 5 adopts a passive design without cables, motors, or external electrical control. It is autonomously driven to open and close by the downhole fluid temperature throughout the process. There is no need to lay signal transmission and power supply lines downhole, which completely avoids the problem of easy aging and damage of electrical control components in the harsh downhole environment, reduces maintenance difficulty and operation and maintenance costs, and extends the service life of the system.

[0022] The temperature and pressure monitoring unit employs high-temperature, high-pressure, and corrosion-resistant monitoring sensors, installed within the coaxial casing heat exchange wellbore 11. It can collect temperature and pressure parameters at different depths within the wellbore in real time and transmit the monitoring data to the ground control terminal, allowing staff to monitor the system's operational status in real time. The temperature and pressure monitoring unit is linked to a safety bypass, establishing a comprehensive safety mechanism. When abnormal conditions such as over-temperature, over-pressure, or a malfunction of the SMA temperature control check valve 5 occur, the safety bypass automatically activates, switching to the whole-well overall heat exchange mode to prevent system shutdown and ensure continuous satisfaction of heat exchange requirements. After the fault is cleared, the system automatically returns to the normal stratified heat exchange mode.

[0023] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A mid-deep geothermal stratified heat exchange system for winter and summer in a single well based on a 300-meter downhole SMA temperature-controlled check valve, characterized in that, The system includes a coaxial casing heat exchange wellbore and an SMA temperature-controlled check valve. The coaxial casing heat exchange wellbore is divided into a shallow heat exchange section (0-300m) and a medium-deep heat exchange section (below 300m) at a depth of 300m. The SMA temperature-controlled check valve is fixedly installed at a depth of 300m in the outer tube annulus of the coaxial casing heat exchange wellbore and uses a Ti-Ni-based shape memory alloy temperature-controlled spring as the driving core. The SMA temperature-controlled check valve automatically triggers phase change opening and closing based on the downhole fluid temperature. When the medium temperature is below the critical range of 35℃, the valve opens, and the fluid circulates in the shallow heat exchange section (0-300m) to provide cooling in summer. When the medium temperature is above the critical range of 40℃, the valve closes, blocking the shallow flow channel, and the fluid flows into the medium-deep heat exchange section (below 300m) to provide heating in winter.

2. The mid-deep geothermal co-well winter-summer stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve according to claim 1, characterized in that, The coaxial casing heat exchange wellbore includes a coaxial outer tube and a coaxial inner tube.

3. The mid-deep geothermal stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve, as described in claim 1, is characterized in that... The SMA temperature-controlled check valve includes an SMA temperature-controlled spring, a fixing component, a hinged fastener, a sealing bevel, and a temperature-sensitive valve disc.

4. The mid-deep geothermal co-well winter-summer stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve according to claim 3, characterized in that, The Ti-Ni based shape memory alloy SMA temperature control spring is set to a phase transformation critical temperature of 30℃~40℃.

5. The mid-deep geothermal stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve, as described in claim 1, is characterized in that... The SMA temperature-controlled check valve adopts a cable-free, motor-free, and external electrical control design. It is driven to open and close autonomously by the temperature of the downhole fluid throughout the process, and there is no need to lay signal transmission and power supply lines downhole.

6. The mid-deep geothermal stratified heat exchange system based on a 300-meter downhole SMA temperature-controlled check valve, as described in claim 1, is characterized in that... The temperature and pressure monitoring unit collects temperature and pressure parameters inside the wellbore in real time and links with the safety bypass to build a safety mechanism. When the system experiences over-temperature, over-pressure, or valve failure, the safety bypass is automatically activated, switching to the whole-well heat exchange mode to ensure continuous and stable operation of the system.

Images