Gravity heat pipe heat extraction testing device and method based on heat exchange between wellbore and heat reservoir

Abstract

The invention provides a gravity assisted heat pipe heat extraction testing device and method based on shaft and heat reservoir heat exchange, the gravity assisted heat pipe heat extraction testing device based on shaft and heat reservoir heat exchange comprises a geothermal reservoir simulation chamber and a gravity assisted heat pipe, the geothermal reservoir simulation chamber is filled with geothermal reservoir filling sand to simulate a geothermal reservoir, and the gravity assisted heat pipe is arranged in the geothermal reservoir simulation chamber. The gravity heat pipe comprises a heat removal section, a heat preservation section and a condensation section, the heat removal section extends into the geothermal reservoir simulation chamber, the heat preservation section is connected to the heat removal section and is composed of a metal frame and a high-temperature-resistant quartz glass tube, and the condensation section is connected to the heat preservation section and is composed of a condensation section metal tube, a condensation section cooling pipeline and a condensation section sealing cover. According to the gravity assisted heat pipe heat extraction testing device and method based on heat exchange of the shaft and the heat reservoir, the temperature change rule in the shaft and the reservoir in the starting-running process of the gravity assisted heat pipe is analyzed, and optimal reservoir selection and development scheme design under the open type circulation and closed type circulation conditions of the gravity assisted heat pipe are given.

Description

Technical Field

[0001] The present invention relates to the technical field of gravity heat pipe heat extraction testing, and in particular to a gravity heat pipe heat extraction testing device and method based on heat exchange between a wellbore and a heat storage. Background Art

[0002] In view of the high difficulty of reinjection, fluid leakage, pipeline corrosion and other problems in open-cycle geothermal systems, closed-cycle geothermal systems are increasingly valued by oil and gas development companies. Using existing abandoned or low-yield wells and high-temperature abandoned oil and gas reservoirs to extract geothermal energy and provide heating for surrounding mining areas or residential areas can effectively realize the effective utilization of abandoned well resources in oil fields. Common closed-cycle geothermal systems include: single-well coaxial heat extraction, U-shaped well heat extraction and gravity heat pipe heat extraction. Compared with other closed-cycle heat extraction methods, the gravity heat pipe geothermal system can achieve heat transfer from the bottom of the well to the wellhead without the need for pump work. It can be seen that this heat extraction scheme is of great significance for low-carbon energy supply in mining areas.

[0003] However, in the existing closed-cycle heat extraction field experiments (including), there is a problem of rapid temperature decay of the produced fluid. For gravity heat pipe heat extraction, due to its higher heat extraction efficiency, the temperature decay will be more serious. At the same time, for common closed-cycle heat extraction methods, including single-well coaxial heat exchange, U-shaped butt-joint well heat extraction, and gravity heat pipe heat extraction, the reservoir temperature reduction rate corresponding to different heat extraction methods is still unclear. Analysis of the reasons shows that after a period of development, the reservoir temperature field is difficult to recover after the heat around the wellbore is extracted. Therefore, it is necessary to explore the change law of reservoir temperature during closed-cycle heat extraction and the heat transfer law between reservoir-wellbore-wellbore fluid for gravity heat pipe geothermal systems with high heat extraction efficiency. On this basis, the optimal development plan for gravity heat pipe geothermal systems is further given, including: heat pipe diameter, heat pipe evaporation section length, heat pipe condensation section length, heat exchange medium, start-stop system, etc. At present, there is still no report on the coordinated analysis of closed heat extraction wellbore and formation temperature changes. In addition, there are currently no indoor experiments to compare and analyze the heat extraction performance and influencing factors of the closed heat extraction (heat-carrying fluid circulates in the wellbore and does not flow out of the heat pipe) and open heat extraction (heat-carrying fluid flows out of the heat pipe in gaseous form) methods that exist when using gravity heat pipes to extract geothermal energy.

[0004] In the Chinese patent application with application number: CN201310213879.3, a controllable gravity heat pipe heat transfer efficiency test device is involved, and its structural features are that the upper and lower temperature control barrels are respectively connected to the cold bath, and the condensation section and evaporation section of the gravity heat pipe are independently controlled; the inclination angle of the gravity heat pipe is accurately controlled by the support, brake hand winch, lifting frame, steel strand and inclinometer of the device; temperature sensors are set on the surface of the gravity heat pipe in the upper and lower temperature control barrels and in the cold bath liquid, and heat flow sensors are arranged on the surface of the gravity heat pipe; the test data of the temperature sensor and the heat flow sensor are automatically collected by the data acquisition device and the computer. The invention can freely adjust the inclination angle of the gravity heat pipe within the range of 0° to 90°, thereby realizing the accurate test of the heat transfer efficiency of the gravity heat pipe at different inclination angles, and providing the experimental basis and technical parameters for giving full play to the engineering efficiency of the gravity heat pipe.

[0005] In the Chinese patent application with application number: CN201410539836.9, a test device for an all-glass gravity heat pipe is involved, which belongs to the field of mechanical technology. It solves the technical problems that the test device in the prior art needs to place the heating rod inside the heat collecting tube, and cannot be used for heat pipes with both ends closed, and has a small application range. The test device for the all-glass gravity heat pipe includes a main body, a cover, a heating element and a support. The main body has a recessed heating chamber, the support is fixedly connected to the bottom of the heating chamber and has a positioning notch on the support for positioning the heat pipe, the side of the main body has a through hole communicating with the heating chamber, the heating element is located at the bottom of the heating chamber, the cover is hinged on the main body and can open or close the heating chamber when the cover plate swings around its hinge. The invention has the advantages of intuitive observation and uniform heating.

[0006] In the Chinese patent application with application number: CN202010877586.5, an "endoscopic" heat pipe visualization device and a test method are involved. The "endoscopic" heat pipe visualization device includes an "endoscopic" heat pipe (A1 or A2), a cooling system (B), a shooting system (C) and a heating system (D). The "endoscopic" heat pipe (A1 or A2) is composed of a heat pipe main body (3A1 or 3A2), a transparent glass tube (4) and a working fluid (11), and is sealed by a first Kovar alloy ring (2) and a second Kovar alloy ring (5), an expansion joint (6), a first end cap (1) and a second end cap (7); the transparent glass tube (4) is placed inside the heat pipe main body (3A1 or 3A2), and an endoscope (22) is connected to a high-speed camera (20) and extends into the transparent glass tube (4) to photograph the phase change and two-phase flow pattern of the working fluid (11) inside the heat pipe main body (3A1 or 3A2); the device and method constructed by the invention are suitable for revealing the phase change heat and mass transfer mechanism of the working fluid inside the heat pipe under the metal wall surface, and the test process is closer to the actual working conditions, thereby improving the reliability of the test results.

[0007] The above existing technologies are significantly different from the present invention and fail to solve the technical problem we want to solve. For this reason, we have invented a new gravity heat pipe heat extraction test device and method based on heat exchange between a wellbore and a heat storage. Summary of the invention

[0008] The purpose of the present invention is to provide a gravity heat pipe heat extraction test device and method which can observe the phase change of the working fluid in the wellbore and take into account the heat exchange between the wellbore and the reservoir.

[0009] The purpose of the present invention can be achieved through the following technical measures: a gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage, the gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage comprises a geothermal reservoir simulation chamber and a gravity heat pipe, the geothermal reservoir simulation chamber is filled with a geothermal reservoir filling sand body to simulate a geothermal reservoir, the gravity heat pipe comprises a heat extraction section, a heat preservation section and a condensation section, the heat extraction section extends into the geothermal reservoir simulation chamber, the heat preservation section is connected to the heat extraction section, and is composed of a metal frame and a high-temperature resistant quartz glass tube, the condensation section is connected to the heat preservation section, and is composed of a condensation section metal tube, a condensation section cooling pipeline and a condensation section sealing cover.

[0010] The purpose of the present invention can also be achieved by the following technical measures:

[0011] The geothermal reservoir simulation chamber also includes a geothermal reservoir simulation chamber sand adding port sealing cover. After the geothermal reservoir filling sand body is added into the geothermal reservoir simulation chamber through the sand adding hole reserved on the top cover plate of the geothermal reservoir simulation chamber, the geothermal reservoir simulation chamber sand adding port sealing cover is installed to close the sand adding hole.

[0012] The geothermal reservoir is filled with 60-80 mesh quartz sand, and a high-frequency vibration table is used to compact the sand body through vibration during the filling process.

[0013] The geothermal reservoir simulation chamber also includes a distributed heating plate and a heating plate temperature measuring point. The distributed heating plate and the heating plate temperature measuring point are installed on the inner wall of the geothermal reservoir simulation chamber to control the temperature inside the geothermal reservoir simulation chamber.

[0014] The geothermal reservoir simulation chamber also includes a first sand body temperature sensor and a second sand body temperature sensor, which are located in the geothermal reservoir filling sand body, respectively located at a distance of 1 / 2R and 3 / 4R from the distributed heating plate, where R is the radius of the cylindrical geothermal reservoir simulation chamber.

[0015] The geothermal reservoir simulation chamber is provided with a device side wall insulation layer outside for heat preservation.

[0016] The heat extraction section is installed at the center of the sand-filling port sealing cover of the geothermal reservoir simulation chamber, is mechanically sealed with the sand-filling port sealing cover of the geothermal reservoir simulation chamber through threads, and is inserted into the geothermal reservoir simulation chamber. The length of the heat extraction section is replaceable, and an injection fluid interface is reserved at the top.

[0017] The high temperature resistant quartz glass tube is fixed by the metal frame, and the metal frames including the high temperature resistant quartz glass tube and the metal frame and the heat extraction section are connected by bolts, and the connection joints are sealed by sealing rings tightened by bolts.

[0018] The heat preservation section also includes a temperature sensor at the inner wall of the wellbore and a temperature sensor at the center of the wellbore. The temperature sensor at the inner wall of the wellbore and the temperature sensor at the center of the wellbore penetrate into the wellbore through the reserved holes in the metal frame and are sealed by threads.

[0019] The condensation section metal tube is connected and sealed to the metal frame by bolts, the condensation section cooling pipeline is wound around the outside of the condensation section metal tube, and the condensation section sealing cover seals the condensation section metal tube and can be disassembled by bolts.

[0020] The purpose of the present invention can also be achieved by the following technical measures: a gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage, which adopts a gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage to test the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the closed cycle heat extraction of the gravity heat pipe, including:

[0021] Step 1: Close the sealing cover of the condensing section, and introduce coolant into the cooling pipeline of the condensing section. The coolant injection flow rate is U c-inj , the temperature of the inlet and outlet of the cooling pipe of the condensation section is measured by temperature sensors;

[0022] Step 2: Inject water into the geothermal reservoir simulation chamber to test the permeability k of the geothermal reservoir sand body according to Darcy's law m ;

[0023] Step 3: Turn on the distributed heating plate and set the heating power Q of the heating plate h , test reservoir thermal conductivity λ m ;

[0024] Step 4: Connect the injection fluid interface of the heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate, set the reservoir temperature, monitor the reservoir temperature changes at different positions through multiple temperature sensors in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature;

[0025] Step 5: Turn on the constant speed and pressure pump and set the injection flow rate U inj , set the injection time to tinj , use a thermostatic bath to set the injection temperature T inj ;

[0026] Step 6, monitoring the temperature evolution law inside the wellbore through the wellbore wall temperature sensor and the wellbore center temperature sensor;

[0027] Step 7: Monitor the temperature evolution law inside the reservoir by using the first sand body temperature sensor and the second sand body temperature sensor;

[0028] Step 8: The temperature increase of the coolant in the condensing section is monitored by the temperature sensors at the inlet and outlet of the coolant pipeline of the condensing section. At this time, the heat-carrying working fluid condenses and releases heat in the condensing section, and the released heat is extracted by the coolant in the coolant pipeline of the condensing section. After the coolant is heated up, the heat energy in it can be utilized;

[0029] Step 9: Change the physical simulation experiment parameters of the gravity heat pipe and analyze the influence of each parameter on the closed-cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature.

[0030] The purpose of the present invention can also be achieved by the following technical measures:

[0031] In step 3, the temperature of the heating plate, the first sand body temperature sensor and the second sand body temperature sensor are used to record D 0 , D 1 / 2 , D 3 / 4 The position corresponds to the radial distance R, 1 / 2R, and 3 / 4R of the wellbore, and the temperature T 0 , T 1 / 2 , T 3 / 4 Change rules, for T 0 , T 1 / 2 , T 3 / 4 The temperature at the simulated formation is set at n temperature measurement points in the direction of height H to test the reservoir thermal conductivity λ m :

[0032]

[0033] or

[0034] In step 6, after the heat-carrying medium is injected into the gravity heat pipe through step 5, the heat-carrying medium is heated and heated. When the phase change temperature is reached, it boils, and the gaseous medium moves rapidly from the heat extraction section to the upper part of the wellbore. The flow of the heat-carrying medium in the insulation section is observed through the high-temperature resistant quartz glass. In the closed cycle of the gravity heat pipe, the gaseous heat-carrying medium is condensed when it reaches the condensation section, and the process of the liquid medium flowing back to the heat extraction section along the pipe wall can also be observed through the high-temperature resistant quartz glass.

[0035] In step 9, the physical simulation experiment parameters of the gravity heat pipe include: reservoir physical properties, reservoir water content characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, gravity heat pipe heat carrying medium type, gravity heat pipe condensation section length, gravity heat pipe condensation section condensation pipeline characteristics, and gravity heat pipe condensation section condensate type.

[0036] The purpose of the present invention can also be achieved by the following technical measures: a gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage, characterized in that the gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage adopts a gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage to test the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the open cycle heat extraction of the gravity heat pipe, including:

[0037] Step 1: Open the sealing cover of the condensing section and connect the temperature sensor and the gas flow meter; during the open cycle heat extraction process of the gravity heat pipe, the top of the condensing section is opened, and the heat-carrying medium is injected into the heat extraction section through the fluid injection port reserved at the top of the heat extraction section. The heat-carrying medium changes into gas after the phase change in the heat extraction section, and flows out from the wellhead under the action of the expansion driving force generated by the phase change. The output gaseous medium is recorded by the temperature sensor and the gas flow meter to record its output temperature and flow rate;

[0038] Step 2: Inject water into the geothermal reservoir simulation chamber to test the permeability k of the geothermal reservoir sand body according to Darcy's law m ;

[0039] Step 3: Turn on the distributed heating plate and set the heating power Q of the heating plate h , test reservoir thermal conductivity λ m ;

[0040] Step 4: Connect the injection fluid interface of the heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate, set the reservoir temperature, monitor the reservoir temperature changes at different positions through multiple temperature sensors in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature;

[0041] Step 5: Turn on the constant speed and pressure pump and set the injection flow rate U inj , set the injection time to t inj , use a thermostatic bath to set the injection temperature T inj ;

[0042] Step 6, monitoring the temperature evolution law inside the wellbore through the wellbore wall temperature sensor and the wellbore center temperature sensor;

[0043] Step 7: Monitor the temperature evolution law inside the reservoir by using the first sand body temperature sensor and the second sand body temperature sensor;

[0044] Step 8: For the gravity heat pipe open cycle heat extraction process, the output gaseous working fluid is recorded through a temperature sensor and a gas flow meter to record its output temperature and flow rate;

[0045] Step 9: Change the physical simulation experiment parameters of the gravity heat pipe and analyze the influence of each parameter on the open cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature.

[0046] The purpose of the present invention can also be achieved by the following technical measures:

[0047] In step 3, the temperature of the heating plate, the first sand body temperature sensor and the second sand body temperature sensor are used to record D 0 , D 1 / 2 , D 3 / 4 The position corresponds to the radial distance R, 1 / 2R, and 3 / 4R of the wellbore, and the temperature T 0 , T 1 / 2 , T 3 / 4 Change rules, for T 0 , T 1 / 2 , T 3 / 4 The temperature at the simulated formation is set at n temperature measurement points in the direction of height H to test the reservoir thermal conductivity λ m :

[0048]

[0049] or

[0050] In step 6, after the heat-carrying medium is injected into the gravity heat pipe through step 5, the heat-carrying medium is heated and rises in temperature. When the phase change temperature is reached, boiling occurs, and the gaseous medium moves rapidly from the heat extraction section to the upper part of the wellbore. The flow of the heat-carrying medium in the insulation section is observed through the high-temperature resistant quartz glass.

[0051] In step 6, the physical simulation experiment parameters of the gravity heat pipe include: reservoir physical parameters, reservoir water characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, and gravity heat pipe heat carrying medium type.

[0052] The gravity heat pipe heat extraction test device and method based on heat exchange between the wellbore and the heat storage in the present invention, through experimental testing, clarify the temperature change law of the reservoir under different production parameters of the gravity heat pipe geothermal system and the heat transfer law between the fluid in the reservoir-wellbore-wellbore, thereby providing theoretical and technical support for the development of the gravity heat pipe geothermal system. The present invention grasps the heat transfer law between the fluid in the reservoir-wellbore-wellbore during the gravity heat pipe heat extraction process and the disturbance of the reservoir temperature field and the temperature field recovery law caused by the gravity heat pipe geothermal system heat extraction, thereby providing the optimal development plan in the gravity heat pipe geothermal system heat extraction process. Compared with the prior art, the present invention can bring the following beneficial effects:

[0053] 1. The present invention can test the heat transfer law between the reservoir-wellbore-wellbore fluid. The use of high-temperature resistant quartz glass to simulate the heat pipe insulation section can realize the observation of the gas-liquid two-phase flow characteristics inside the heat pipe. The temperature sensor at the inner wall of the wellbore and the temperature sensor at the center of the wellbore are inserted into the wellbore through the reserved holes in the metal frame (including the high-temperature resistant quartz glass tube) and can realize the evolution law of the radial temperature in the gravity heat pipe wellbore, thereby realizing the determination of the heat transfer law of the start-up-stabilization-attenuation-heat supplement process of the gravity heat pipe geothermal system;

[0054] 2. The present invention can realize closed-cycle heat extraction and open-cycle heat extraction of the gravity heat pipe by disassembling the sealing port at the top of the gravity heat pipe condensation section. During the open-cycle heat extraction of the gravity heat pipe, the heat-carrying medium is injected into the heat extraction section through the fluid injection port reserved at the top of the heat extraction section of the gravity heat pipe. At the same time, during the open-cycle heat extraction of the gravity heat pipe, no coolant is introduced into the condensation heat exchange pipeline wrapped outside the condensation section. In addition, during the open-cycle heat extraction, a temperature sensor and a gas flow meter are externally connected to the wellhead. During the closed-cycle heat extraction of the gravity heat pipe, the top of the condensation section is sealed, and the gaseous medium therein is cooled by the condensation heat exchange pipeline wrapped outside the condensation section, so that it becomes liquid and flows back to the heat extraction section. The inlet and outlet ends of the condensation heat exchange pipeline are measured by temperature sensors;

[0055] 3. The present invention can utilize the thermal reservoir simulation chamber in the physical simulation test system of the gravity heat pipe geothermal system to measure the reservoir permeability and thermal conductivity after the thermal reservoir is filled with sand, providing a basis for the analysis of the reservoir temperature decay rate during the development of the geothermal system and the analysis of the reservoir temperature recovery rate during the suspension of the geothermal system;

[0056] 4. Based on the multi-point temperature sensors arranged inside the reservoir, inside the wellbore and in the coolant pipeline, the testing method provided by the present invention can realize the integrated simulation of geothermal reservoir-heat pipe heat extraction (evaporation) section-heat pipe insulation section-heat pipe condensation section-condensate utilization, providing a basis for the optimization of heat extraction reservoir and development plan design of gravity heat pipe geothermal system. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a structural schematic diagram of a gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage in a specific embodiment of the present invention;

[0058] Figure 2 It is a schematic diagram of a temperature measurement module of a wellbore inner wall surface and a center position in a specific embodiment of the present invention;

[0059] Figure 3 is a schematic diagram of a gravity heat pipe condensation section module in a specific embodiment of the present invention;

[0060] Figure 4It is a schematic diagram of the temperature evolution law inside the wellbore obtained by monitoring the temperature sensor arranged in the gravity heat pipe wellbore in a specific embodiment of the present invention;

[0061] Figure 5 It is a schematic diagram of the temperature evolution law in the reservoir obtained by monitoring by multiple temperature sensors arranged in the reservoir in a specific embodiment of the present invention;

[0062] In the figure: 1-geothermal reservoir filling sand body; 2-distributed heating plate; 3-insulation layer of device side wall; 4-sealing cover of sand filling port of geothermal reservoir simulation chamber; 5-gravity heat pipe heat extraction section (evaporation section); 6-visible wellbore of gravity heat pipe insulation section; 7-metal frame of gravity heat pipe insulation section; 8-wellbore inner wall temperature measuring device; 9-wellbore center position temperature measuring device; 10-condensation section coolant pipeline; 11-condensation section sealing cover; 12-D3 / 4 temperature measuring point; 13-D1 / 2 temperature measuring point; 14-heating plate temperature measuring point; 15-geothermal reservoir injection port; 16-gravity heat pipe condensation section. DETAILED DESCRIPTION

[0063] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0064] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0065] The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage comprises two parts: a heat pipe and a reservoir; the gravity heat pipe comprises a heat extraction (evaporation) section, a heat preservation section, and a condensation section; the heat extraction section extends into the geothermal reservoir, the top of the heat extraction section is connected to the geothermal reservoir simulation chamber by a threaded connection, and the heat extraction section and the heat preservation section of the heat pipe are connected by bolts and a sealing ring; the heat preservation section is composed of a metal frame and a high-temperature resistant quartz glass tube, and the quartz glass tube is fixed by a metal frame in this part to improve the strength and sealing performance; the heat pipe condensation section is composed of a condensation section metal tube, a condensation section cooling pipeline and a condensation section sealing cover, the condensation section metal tube is connected and sealed to the insulation section metal frame by bolts, the condensation section cooling pipeline is wound around the outside of the condensation section metal tube, and the condensation section sealing cover can be disassembled by bolts; the heat reservoir is realized by filling a geothermal reservoir simulation chamber with sand, and two sand adding ports are provided at the top of the chamber.

[0066] The present invention provides a gravity heat pipe heat extraction test method that takes into account the heat exchange between the wellbore and the heat storage, which belongs to the field of renewable utilization of geothermal energy and involves the open and closed cycle heat extraction process when using gravity heat pipes to extract geothermal energy. The technical solution is to use a gravity heat pipe heat extraction performance test device with a visualized wellbore, combined with multi-point temperature measurement in the wellbore and the reservoir, to observe the phase change of the fluid in the wellbore, measure the radial temperature distribution inside the wellbore and the temperature distribution in the reservoir, monitor the temperature increase in the condensation pipeline during the closed heat extraction process of the gravity heat pipe, and monitor the temperature and flow rate of the gaseous working fluid produced at the wellhead during the open heat extraction process of the gravity heat pipe. Analyze the temperature change law in the wellbore and the reservoir during the startup and operation of the gravity heat pipe, and provide the optimal reservoir selection and development plan design under the conditions of open and closed cycles of the gravity heat pipe.

[0067] The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage of the present invention comprises:

[0068] S1: A gravity heat pipe heat extraction (evaporation) section wellbore is installed at the center of the top cover plate of the geothermal reservoir simulation chamber of the physical simulation experiment device. The length of the gravity heat pipe heat extraction (evaporation) section is replaceable. An injection fluid interface is reserved at the top of the gravity heat pipe heat extraction section. The gravity heat pipe heat extraction (evaporation) section is mechanically sealed with the top cover plate of the geothermal reservoir simulation chamber through threads. The temperature in the geothermal reservoir simulation chamber is controlled by a distributed heating plate and a temperature sensor;

[0069] S2: Add quartz sand through the sand adding hole reserved on the top cover of the geothermal reservoir simulation chamber to fill the simulated geothermal reservoir. During the filling process, the high-frequency vibration table provided by the device is used to fill the sand body by vibration. During the sand filling process, the temperature sensor in the sand body is adjusted to a preset position. After the sand filling is completed, the sand adding hole is closed;

[0070] S3: A high temperature resistant quartz glass tube is used to simulate the heat preservation section of the gravity heat pipe. The high temperature resistant quartz glass tube is fixed by a metal frame. The metal frames containing the high temperature resistant quartz glass tube and the metal frame are connected to the heat extraction section of the gravity heat pipe by bolts. The connection joints are sealed by sealing rings tightened by bolts;

[0071] S4: The temperature sensor at the inner wall of the wellbore and the temperature sensor at the center of the wellbore penetrate into the wellbore through the reserved holes in the metal frame (including the high temperature resistant quartz glass tube) and are sealed by threads;

[0072] S5: The condensing section of the gravity heat pipe is connected to the metal frame containing the high temperature resistant quartz glass tube by bolts, and the connection joint is sealed by a sealing ring tightened by bolts. The condensing section of the gravity heat pipe can realize closed cycle heat extraction and open cycle heat extraction by disassembling the sealing port at the top of the condensing section. When the gravity heat pipe is closed cycle heat extraction, the top of the condensing section is sealed, and the gaseous working medium therein is cooled by the condensation heat exchange pipeline wrapped outside the condensing section, so that it becomes liquid and flows back to the heat extraction section. The inlet and outlet ends of the cooling pipeline of the condensing section are measured by temperature sensors. During the open cycle heat extraction process of the gravity heat pipe, the top of the condensation section is open, and a heat-carrying medium is injected into the heat extraction section through a fluid injection port reserved at the top of the gravity heat pipe heat extraction section. The heat-carrying medium changes into a gas state after a phase change in the heat extraction section, and flows out from the wellhead under the action of the expansion driving force generated by the phase change. The output gaseous medium is recorded by a temperature sensor and a gas flow meter to record its output temperature and flow rate. During the open cycle heat extraction process of the gravity heat pipe, no coolant is introduced into the condensation heat exchange pipeline wound outside the condensation section;

[0073] S6: inject water into the reservoir to test the permeability km of the filled sand body thermal reservoir;

[0074] S7: using a distributed heating sheet combined with a multi-point temperature sensor arranged in the reservoir to test the reservoir thermal conductivity λm;

[0075] S8: Connect the injection fluid interface of the gravity heat pipe heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate, set the reservoir temperature through the device control program, monitor the reservoir temperature changes at different positions through the temperature sensor in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature;

[0076] S9: Steps S1-S8 are the preparation stage of the experiment. Turn on the constant speed and constant pressure pump and set the injection flow rate U inj , set the injection time to t inj , use a thermostatic bath to set the injection temperature T inj ;

[0077] S10. Monitor the temperature evolution law inside the wellbore through the temperature sensors arranged in the wellbore of the gravity heat pipe. The temperature sensors arranged in the wellbore include the wellbore wall temperature sensor and the wellbore center temperature sensor. After the heat-carrying medium is injected into the gravity heat pipe through step S9, the heat-carrying medium is heated and heated. When the phase change temperature is reached, it boils. The gaseous medium moves rapidly from the evaporation section to the upper part of the wellbore. The flow of the heat-carrying medium in the heat-insulating section of the heat pipe is observed through high-temperature resistant quartz glass. For closed-loop heat extraction of gravity heat pipes, the process of the gaseous medium refluxing along the wall to the evaporation section after condensation in the condensation section can also be observed through high-temperature resistant quartz glass;

[0078] S11: monitoring the temperature evolution law inside the reservoir through multiple temperature sensors arranged in the reservoir;

[0079] S12: For the closed-cycle heat extraction process of the gravity heat pipe, the temperature increase of the coolant in the gravity heat pipe is monitored by the temperature sensors at the inlet and outlet of the condensation heat exchange pipeline. At this time, the heat-carrying working fluid condenses and releases heat in the condensation section of the gravity heat pipe, and the released heat is extracted by the coolant in the condensation heat exchange pipeline. After the coolant temperature is increased, it can be used for heating. For the open-cycle heat extraction process of the gravity heat pipe, the output gaseous working fluid is recorded by the temperature sensor and the gas flow meter to record its output temperature and flow rate. After the gaseous working fluid flows out of the open gravity heat pipe wellhead, it can be used for direct heating, power generation, etc.;

[0080] S13: Change the physical simulation experiment parameters of the gravity heat pipe, including: reservoir physical properties (bedrock permeability, bedrock porosity, bedrock thermal conductivity), reservoir water content characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, gravity heat pipe heat carrying medium type, gravity heat pipe condensation section length, gravity heat pipe condensation section condensation pipeline characteristics, gravity heat pipe condensation section condensate type, etc., analyze the influence of various parameters on the heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature. The research results will provide a basis for reservoir optimization and development plan design of gravity heat pipe geothermal system.

[0081] The following are several specific embodiments of the present invention.

[0082] Example 1

[0083] In a specific embodiment 1 of the present invention, Figure 1 As shown, Figure 1 It is a structural schematic diagram of a gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage; the gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage of the present invention is used to test the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the closed cycle heat extraction of the gravity heat pipe, and includes a geothermal reservoir simulation chamber and a gravity heat pipe. The geothermal reservoir simulation chamber is filled with a geothermal reservoir filling sand body 1 to simulate the geothermal reservoir. The geothermal reservoir simulation chamber sand adding port sealing cover 4 is located at the top of the heat reservoir simulation chamber. The geothermal reservoir filling sand body is added with 60-80 mesh quartz sand through the sand adding hole reserved on the top cover plate of the geothermal reservoir simulation chamber to fill the simulated geothermal reservoir as the geothermal reservoir filling sand body 1. During the filling process, the high-frequency vibration table provided by the device is used to fill the sand body by shaking. After the sand filling is completed, the sand adding hole is closed by installing the geothermal reservoir simulation chamber sand adding port sealing cover 4.

[0084] A distributed heating plate 2 and a heating plate temperature measuring point 14 are installed on the inner wall of the geothermal reservoir simulation chamber to control the temperature in the geothermal reservoir simulation chamber. The geothermal reservoir filling sand body 1 has sand body temperature sensors 13 and 12, which are located at 1 / 2R and 3 / 4R positions from the distributed heating plate 2 (R is the radius of the cylindrical geothermal reservoir simulation). The outside of the geothermal reservoir simulation chamber is installed with a device side wall insulation layer 3 for heat preservation.

[0085] The heat extraction section 5 of the gravity heat pipe is installed at the center of the sealing cover 4 of the sand port of the geothermal reservoir simulation chamber and inserted into the geothermal reservoir simulation chamber. The length of the heat extraction section 5 of the gravity heat pipe is replaceable, and a fluid injection interface 15 is reserved at the top of the heat extraction section 5 of the gravity heat pipe. The heat extraction section 5 of the gravity heat pipe is mechanically sealed with the sealing cover 4 of the sand port of the geothermal reservoir simulation chamber through threads.

[0086] The high temperature resistant quartz glass tube 6 simulates the heat preservation section of the gravity heat pipe. The high temperature resistant quartz glass tube 6 is fixed by a metal frame 7. The metal frames 7 containing the high temperature resistant quartz glass tube and the metal frame 7 and the heat extraction section 5 of the gravity heat pipe are connected by bolts. The connection joints are sealed by sealing rings tightened by bolts.

[0087] Figure 2 It is a schematic diagram of the temperature measurement module at the inner wall and the center of the wellbore; the temperature sensor 8 at the inner wall of the wellbore and the temperature sensor 9 at the center of the wellbore penetrate into the wellbore through the reserved holes in the metal frame 7 (including the high-temperature resistant quartz glass tube) and are sealed by threads.

[0088] The gravity heat pipe condensation section 16 is connected to the metal frame 7 containing the high temperature resistant quartz glass tube by bolts, and the connection joint is sealed by a sealing ring through bolts. The gravity heat pipe condensation section sealing cover 11 is closed. The condensation heat exchange pipeline 10 is wound around the outside of the gravity heat pipe condensation section, such as Figure 3 As shown, Figure 3 This is a schematic diagram of the gravity heat pipe condensation section module. The coolant is introduced into the condensation heat exchange pipeline, and the coolant injection flow rate is U c-inj The inlet and outlet ends of the condensing heat exchange pipeline are measured by temperature sensors.

[0089] Example 2

[0090] In a specific embodiment 2 of the present invention, the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the closed cycle heat extraction of the gravity heat pipe are tested.

[0091] S1: A gravity heat pipe heat extraction (evaporation) section wellbore is installed at the center of the top cover plate of the geothermal reservoir simulation chamber of the physical simulation experiment device. The length of the gravity heat pipe heat extraction (evaporation) section is replaceable. An injection fluid interface 15 is reserved at the top of the gravity heat pipe heat extraction section. The gravity heat pipe heat extraction (evaporation) section is mechanically sealed with the top cover plate of the geothermal reservoir simulation chamber through threads. The temperature in the geothermal reservoir simulation chamber is controlled by a distributed heating plate 2 and a temperature sensor 14;

[0092] S2: Add 60-80 mesh quartz sand through the sand adding hole reserved in the top cover of the geothermal reservoir simulation chamber to fill the simulated geothermal reservoir. During the filling process, the high-frequency vibration table provided by the device is used to fill the sand body by vibration. During the sand filling process, the temperature sensor in the sand body is adjusted to the position of 1 / 2R and 3 / 4R from the heating plate (R is the radius of the cylindrical simulated geothermal reservoir). After the sand filling is completed, the sand adding hole sealing cover 4 is installed to close the sand adding hole;

[0093] S3: A high temperature resistant quartz glass tube 6 is used to simulate the heat preservation section of the gravity heat pipe. The high temperature resistant quartz glass tube is fixed by a metal frame. The metal frames 7 containing the high temperature resistant quartz glass tube and the metal frame 7 are connected to the heat extraction section shaft 5 of the gravity heat pipe by bolts. The connection joints are sealed by sealing rings tightened by bolts;

[0094] S4: The temperature sensor 8 at the inner wall of the wellbore and the temperature sensor 9 at the center of the wellbore penetrate into the wellbore through the reserved holes in the metal frame (including the high temperature resistant quartz glass tube) and are sealed by threads;

[0095] S5: The gravity heat pipe condensing section 16 is connected to the metal frame 7 containing the high temperature resistant quartz glass tube by bolts, and the connection joint is sealed by a sealing ring through bolts. The gravity heat pipe condensing section sealing cover 11 is closed. The condensing heat exchange pipeline 10 is wound around the condensing section of the gravity heat pipe, and the cooling liquid is passed into the condensing heat exchange pipeline. The cooling liquid injection flow rate is U c-inj The inlet and outlet ends of the condensing heat exchange pipeline are measured by temperature sensors.

[0096] S6: Inject water into the reservoir and test the permeability k of the filled sand thermal reservoir according to Darcy's law m ;

[0097] S7: Turn on the distributed heating plate and set the heating power Q of the heating plate h , D is recorded by multiple temperature sensors arranged in the reservoir 0 , D 1 / 2 , D 3 / 4 Temperature T at position (corresponding to the wellbore radial distance R, 1 / 2R, 3 / 4R) 0 , T 1 / 2 , T 3 / 4 Change rules, for T 0 , T 1 / 2 , T 3 / 4 The temperature at the simulated formation is set at n temperature measurement points in the direction of height H to test the reservoir thermal conductivity λ m ;

[0098]

[0099] or

[0100] S8: Connect the injection fluid interface of the gravity heat pipe heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate 2, set the reservoir temperature through the device control program, monitor the reservoir temperature changes at different positions through the temperature sensor in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature;

[0101] S9: Steps S1-S8 are the preparation stage of the experiment. Turn on the constant speed and constant pressure pump and set the injection flow rate U inj , set the injection time to t inj , use a thermostatic bath to set the injection temperature T inj ;

[0102] S10. Monitor the temperature evolution law inside the wellbore through the temperature sensors arranged in the wellbore of the gravity heat pipe. The temperature sensors arranged in the wellbore include the wellbore wall temperature sensor 8 and the wellbore center temperature sensor 9. After the heat-carrying medium is injected into the gravity heat pipe through step S9, the heat-carrying medium is heated and heated. When the phase change temperature is reached, it boils. The gaseous medium moves rapidly from the evaporation section to the upper part of the wellbore. The flow of the heat-carrying medium in the heat-insulating section of the heat pipe is observed through high-temperature resistant quartz glass. In the closed cycle of the gravity heat pipe, the gaseous heat-carrying medium condenses when it reaches the condensation section and the liquid medium refluxes along the pipe wall to the heat extraction section (evaporation section). This process can also be observed through high-temperature resistant quartz glass; Figure 4 As shown, Figure 4 It is a schematic diagram of the temperature evolution rule inside the wellbore obtained by monitoring the temperature sensor arranged in the gravity heat pipe wellbore in a specific embodiment of the present invention;

[0103] S11: Monitor the temperature evolution law inside the reservoir through the multi-point temperature sensors 12 and 13 arranged in the reservoir; Figure 5 As shown, Figure 5 It is a schematic diagram of the temperature evolution law in the reservoir obtained by monitoring by multiple temperature sensors arranged in the reservoir in a specific embodiment of the present invention;

[0104] S12: The temperature increase of the coolant in the gravity heat pipe is monitored by the temperature sensors at the inlet and outlet of the condensation heat exchange pipeline 10. At this time, the heat-carrying medium condenses and releases heat in the condensation section of the gravity heat pipe, and the released heat is extracted by the coolant in the condensation heat exchange pipeline. After the coolant is heated up, the heat energy in it can be utilized;

[0105] S13: Change the physical simulation experiment parameters of the gravity heat pipe, including: reservoir physical properties (bedrock permeability, bedrock porosity, bedrock thermal conductivity), reservoir water content characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, gravity heat pipe heat carrying medium type, gravity heat pipe condensation section length, gravity heat pipe condensation section condensation pipeline characteristics, gravity heat pipe condensation section condensate type, etc., and analyze the influence of various parameters on the closed-cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature. The research results will provide a basis for reservoir optimization and development plan design of gravity heat pipe geothermal system.

[0106] Example 3

[0107] In a specific embodiment 3 of the present invention, the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the open cycle heat extraction of the gravity heat pipe are tested.

[0108] Compared with Example 2, Example 3 adopts an open cycle heat extraction method, so there are differences from Example 1 in steps S5, S10, S12, and S13, which are described in detail here.

[0109] S5: The condensing section 16 of the gravity heat pipe is connected to the metal frame 7 containing the high-temperature resistant quartz glass tube by bolts, and the connection joint is sealed by a sealing ring tightened by bolts. The sealing cover 11 of the condensing section of the gravity heat pipe is opened, and the temperature sensor and the gas flow meter are connected. During the open cycle heat extraction process of the gravity heat pipe, the top of the condensing section is opened, and the heat-carrying medium is injected into the heat extraction section through the fluid injection port reserved at the top of the heat extraction section of the gravity heat pipe. The heat-carrying medium changes into a gaseous state after the phase change in the heat extraction section, and flows out from the wellhead under the action of the expansion driving force generated by the phase change. The output gaseous medium is recorded by the temperature sensor and the gas flow meter to record its output temperature and flow rate;

[0110] S10: The temperature evolution law inside the wellbore is monitored by the temperature sensor arranged in the wellbore of the gravity heat pipe. The temperature sensor arranged in the wellbore includes a wellbore wall temperature sensor 8 and a wellbore center temperature sensor 9. After the heat-carrying medium is injected into the gravity heat pipe through step S9, the heat-carrying medium is heated and heated. When the phase change temperature is reached, boiling occurs, and the gaseous medium moves rapidly from the evaporation section to the upper part of the wellbore. The flow of the heat-carrying medium in the heat insulation section of the heat pipe is observed through the high-temperature resistant quartz glass.

[0111] S12: For the gravity heat pipe open cycle heat extraction process, the output gaseous working fluid is recorded by the temperature sensor and the gas flow meter to record its output temperature and flow rate

[0112] S13: Change the physical simulation experiment parameters of the gravity heat pipe, including reservoir physical properties (bedrock permeability, bedrock porosity, bedrock thermal conductivity), reservoir water content characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, gravity heat pipe heat carrying medium type, etc., and analyze the influence of various parameters on the open cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature. The research results will provide a basis for reservoir optimization and development plan design of gravity heat pipe geothermal system.

[0113] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0114] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. Gravity heat pipe heat extraction test device based on heat exchange between wellbore and heat storage, It is characterized in that The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage comprises a geothermal reservoir simulation chamber and a gravity heat pipe. The geothermal reservoir simulation chamber is filled with a geothermal reservoir filling sand body to simulate a geothermal reservoir. The gravity heat pipe comprises a heat extraction section, a heat preservation section and a condensation section. The heat extraction section extends into the geothermal reservoir simulation chamber. The heat preservation section is connected to the heat extraction section and is composed of a metal frame and a high-temperature resistant quartz glass tube. The condensation section is connected to the heat preservation section and is composed of a condensation section metal tube, a condensation section cooling pipeline and a condensation section sealing cover.

2. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The geothermal reservoir simulation chamber also includes a geothermal reservoir simulation chamber sand adding port sealing cover. After the geothermal reservoir filling sand body is added into the geothermal reservoir simulation chamber through the sand adding hole reserved on the top cover plate of the geothermal reservoir simulation chamber, the geothermal reservoir simulation chamber sand adding port sealing cover is installed to close the sand adding hole.

3. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 2, It is characterized in that The geothermal reservoir is filled with 60-80 mesh quartz sand, and a high-frequency vibration table is used to compact the sand body through vibration during the filling process.

4. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The geothermal reservoir simulation chamber also includes a distributed heating plate and a heating plate temperature measuring point. The distributed heating plate and the heating plate temperature measuring point are installed on the inner wall of the geothermal reservoir simulation chamber to control the temperature inside the geothermal reservoir simulation chamber.

5. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 4, It is characterized in that The geothermal reservoir simulation chamber also includes a first sand body temperature sensor and a second sand body temperature sensor, which are located in the geothermal reservoir filling sand body, respectively located at a distance of 1 / 2R and 3 / 4R from the distributed heating plate, where R is the radius of the cylindrical geothermal reservoir simulation chamber.

6. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The geothermal reservoir simulation chamber is provided with a device side wall insulation layer outside for heat preservation.

7. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 2, It is characterized in that The heat extraction section is installed at the center of the sand-filling port sealing cover of the geothermal reservoir simulation chamber, is mechanically sealed with the sand-filling port sealing cover of the geothermal reservoir simulation chamber through threads, and is inserted into the geothermal reservoir simulation chamber. The length of the heat extraction section is replaceable, and an injection fluid interface is reserved at the top.

8. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The high temperature resistant quartz glass tube is fixed by the metal frame, and the metal frames including the high temperature resistant quartz glass tube and the metal frame and the heat extraction section are connected by bolts, and the connection joints are sealed by sealing rings tightened by bolts.

9. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The heat preservation section also includes a temperature sensor at the inner wall of the wellbore and a temperature sensor at the center of the wellbore. The temperature sensor at the inner wall of the wellbore and the temperature sensor at the center of the wellbore penetrate into the wellbore through the reserved holes in the metal frame and are sealed by threads.

10. The gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage according to claim 1, It is characterized in that The condensation section metal tube is connected and sealed to the metal frame by bolts, the condensation section cooling pipeline is wound around the outside of the condensation section metal tube, and the condensation section sealing cover seals the condensation section metal tube and can be disassembled by bolts.

11. Gravity heat pipe heat extraction test method based on heat exchange between wellbore and heat storage, It is characterized in that The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage adopts the gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage as described in claim 1 to test the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the closed cycle heat extraction of the gravity heat pipe, including: Step 1: Close the sealing cover of the condensing section, and introduce coolant into the cooling pipeline of the condensing section. The coolant injection flow rate is U c-inj , the temperature of the inlet and outlet of the cooling pipe of the condensation section is measured by temperature sensors; Step 2: Inject water into the geothermal reservoir simulation chamber to test the permeability k of the geothermal reservoir sand body according to Darcy's law m ; Step 3: Turn on the distributed heating plate and set the heating power Q of the heating plate h , test reservoir thermal conductivity λ m ; Step 4: Connect the injection fluid interface of the heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate, set the reservoir temperature, monitor the reservoir temperature changes at different positions through multiple temperature sensors in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature; Step 5: Turn on the constant speed and pressure pump and set the injection flow rate U inj , set the injection time to t inj , use a thermostatic bath to set the injection temperature T inj ; Step 6, monitoring the temperature evolution law inside the wellbore through the wellbore wall temperature sensor and the wellbore center temperature sensor; Step 7: Monitor the temperature evolution law inside the reservoir by using the first sand body temperature sensor and the second sand body temperature sensor; Step 8: The temperature increase of the coolant in the condensing section is monitored by the temperature sensors at the inlet and outlet of the coolant pipeline of the condensing section. At this time, the heat-carrying working fluid condenses and releases heat in the condensing section, and the released heat is extracted by the coolant in the coolant pipeline of the condensing section. After the coolant is heated up, the heat energy in it can be utilized; Step 9: Change the physical simulation experiment parameters of the gravity heat pipe and analyze the influence of each parameter on the closed-cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature.

12. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 11, It is characterized in that In step 3, the temperature of the heating plate, the first sand body temperature sensor and the second sand body temperature sensor are used to record D 0 , D 1 / 2 , D 3 / 4 The position corresponds to the radial distance R, 1 / 2R, and 3 / 4R of the wellbore, and the temperature T 0 , T 1 / 2 , T 3 / 4 Change rules, for T 0 , T 1 / 2 , T 3 / 4 The temperature at the simulated formation is set at n temperature measurement points in the direction of height H to test the reservoir thermal conductivity λ m : or 13. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 11, It is characterized in that In step 6, after the heat-carrying medium is injected into the gravity heat pipe through step 5, the heat-carrying medium is heated and heated. When the phase change temperature is reached, it boils. The gaseous medium moves rapidly from the heat extraction section to the upper part of the wellbore. The flow of the heat-carrying medium in the insulation section is observed through the high-temperature resistant quartz glass. In the closed cycle of the gravity heat pipe, the gaseous heat-carrying medium is condensed when it reaches the condensation section. The process of the liquid medium flowing back to the heat extraction section along the pipe wall can also be observed through the high-temperature resistant quartz glass.

14. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 11, It is characterized in that In step 9, the physical simulation experiment parameters of the gravity heat pipe include: reservoir physical properties, reservoir water content characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, gravity heat pipe heat carrying medium type, gravity heat pipe condensation section length, gravity heat pipe condensation section condensation pipeline characteristics, and gravity heat pipe condensation section condensate type.

15. Gravity heat pipe heat extraction test method based on heat exchange between wellbore and heat storage, It is characterized in that The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage adopts the gravity heat pipe heat extraction test device based on heat exchange between a wellbore and a heat storage as described in claim 1 to test the heat extraction performance of the gravity heat pipe and the evolution law of the reservoir temperature during the open cycle heat extraction of the gravity heat pipe, including: Step 1: Open the sealing cover of the condensing section and connect the temperature sensor and the gas flow meter; during the open cycle heat extraction process of the gravity heat pipe, the top of the condensing section is opened, and the heat-carrying medium is injected into the heat extraction section through the fluid injection port reserved at the top of the heat extraction section. The heat-carrying medium changes into gas after the phase change in the heat extraction section, and flows out from the wellhead under the action of the expansion driving force generated by the phase change. The output gaseous medium is recorded by the temperature sensor and the gas flow meter to record its output temperature and flow rate; Step 2: Inject water into the geothermal reservoir simulation chamber to test the permeability k of the geothermal reservoir sand body according to Darcy's law m ; Step 3: Turn on the distributed heating plate and set the heating power Q of the heating plate h , test reservoir thermal conductivity λ m ; Step 4: Connect the injection fluid interface of the heat extraction section to the constant speed and constant pressure pump, turn on the distributed heating plate, set the reservoir temperature, monitor the reservoir temperature changes at different positions through multiple temperature sensors in the sand body, and continue to keep warm for 60 minutes after the temperature in the sand body reaches the set temperature; Step 5: Turn on the constant speed and pressure pump and set the injection flow rate U inj , set the injection time to t inj , use a thermostatic bath to set the injection temperature T inj ; Step 6, monitoring the temperature evolution law inside the wellbore through the wellbore wall temperature sensor and the wellbore center temperature sensor; Step 7: Monitor the temperature evolution law inside the reservoir by using the first sand body temperature sensor and the second sand body temperature sensor; Step 8: For the gravity heat pipe open cycle heat extraction process, the output gaseous working fluid is recorded through a temperature sensor and a gas flow meter to record its output temperature and flow rate; Step 9: Change the physical simulation experiment parameters of the gravity heat pipe and analyze the influence of each parameter on the open cycle heat extraction performance of the gravity heat pipe and the evolution of reservoir temperature.

16. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 15, It is characterized in that In step 3, the temperature of the heating plate, the first sand body temperature sensor and the second sand body temperature sensor are used to record D 0 , D 1 / 2 , D 3 / 4 The position corresponds to the radial distance R, 1 / 2R, and 3 / 4R of the wellbore, and the temperature T 0 , T 1 / 2 , T 3 / 4 Change rules, for T 0 , T 1 / 2 , T 3 / 4 The temperature at the simulated formation is set at n temperature measurement points in the direction of height H to test the reservoir thermal conductivity λ m : or 17. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 15, It is characterized in that In step 6, after the heat-carrying medium is injected into the gravity heat pipe through step 5, the heat-carrying medium is heated and rises in temperature. When the phase change temperature is reached, boiling occurs, and the gaseous medium moves rapidly from the heat extraction section to the upper part of the wellbore. The flow of the heat-carrying medium in the insulation section is observed through the high-temperature resistant quartz glass.

18. The gravity heat pipe heat extraction test method based on heat exchange between a wellbore and a heat storage according to claim 15, It is characterized in that In step 6, the physical simulation experiment parameters of the gravity heat pipe include: reservoir physical parameters, reservoir water characteristics, gravity heat pipe well diameter, gravity heat pipe evaporation section length, and gravity heat pipe heat carrying medium type.

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