Gas migration path monitoring system and method during hydrate extraction

Abstract

This invention discloses a gas migration path monitoring system and method during hydrate extraction. A marine radiometric detector is installed inside a high-pressure vessel; radioactive carbon isotopes are used. 14 C-labeled methane gas was used to prepare natural gas hydrates with radioactive tracer properties; methane with tracer properties was obtained through depressurization extraction. 14 CH4, using marine radiometric detectors to detect methane generated during depressurization mining. 14 This invention analyzes the content and distribution of CH4 to reveal the gas migration pathways during natural gas hydrate extraction. It is simple and quick to operate, provides reliable and accurate experimental results, and enables remote real-time monitoring of gas migration pathways during hydrate extraction, solving the current problem of difficulty in obtaining gas migration pathways during natural gas hydrate extraction.

Description

Technical Field

[0001] This invention belongs to the fields of geotechnical engineering, energy engineering, and marine science and relates to a dynamic monitoring system and method for gas production and migration characteristics during the extraction of natural gas hydrates. In particular, it relates to a monitoring system and method for gas migration paths during the extraction of natural gas hydrates based on marine radiometric detection technology, which is applicable to the problem of gas migration monitoring in the simulation of deep-sea natural gas hydrate extraction. Background Technology

[0002] Natural gas hydrates are characterized by their cleanliness, efficiency, wide distribution, and large reserves, making them an important alternative energy source for addressing the global energy gap. Many countries are conducting exploratory trials of natural gas hydrate production. In the competition among nations, mastering large-scale commercial extraction technology for hydrates can allow countries to take the lead in energy strategic transformation and gain a competitive advantage. However, current in-situ natural gas hydrate trials are difficult to conduct for extended periods. The main reason is that during extraction, the decomposition of natural gas hydrates near the wellhead leads to a reduction in the solid phase, weakens the cementation between soil skeletons, reduces reservoir strength, and causes significant changes in pore pressure due to the generated water and gas. Under the influence of reservoir and seabed stress, this can lead to reservoir deformation, well instability, or gas migration inducing sand production, resulting in production shutdowns or even well closures.

[0003] During hydrate extraction, the large amounts of gas and water produced by decomposition create a significant gas-liquid two-phase flow field within the reservoir. The migration of decomposition-generated gas becomes the driving force for reservoir material migration. Strong gas-liquid flow forces can induce soil particle migration and even lead to severe sand production problems. Developing a device or technology to monitor gas migration paths during hydrate extraction and exploring the migration trajectory of gas produced at different reservoir locations from the extraction point to the wellhead could potentially reveal the mechanisms of sand production and gradual reservoir deformation during hydrate extraction, and elucidate the intrinsic causes of reservoir disasters induced by hydrate extraction. However, current technologies for preparing natural gas hydrates often lack the ability to track gas diffusion paths, leaving the monitoring and research of gas migration paths during hydrate extraction largely unexplored. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of this application is to provide a gas migration path monitoring system and method for indoor simulated natural gas hydrate extraction, so as to accurately and conveniently monitor the gas migration path during the natural gas hydrate extraction process.

[0005] The technical solution adopted in this invention is as follows:

[0006] I. A gas migration path monitoring system during hydrate extraction:

[0007] This invention includes a high-pressure vessel, a high-pressure vessel cover, a extraction well, a gas injection interface, a circulating water bath jacket, a marine radioactivity detector, a signal processor, and a data analysis terminal. The high-pressure vessel contains an overlying soil layer, a hydrate simulated reservoir, and an underlying soil layer, with a confined aquifer above the overlying soil layer. The high-pressure vessel cover is mounted on the high-pressure vessel, and includes temperature and pressure sensor interfaces for mounting corresponding sensors. An extraction well interface is located at the center of the high-pressure vessel cover, extending the extraction well into the high-pressure vessel to a certain depth. A gas injection interface is located at the center of the bottom of the high-pressure vessel. The circulating water bath jacket is located around the outer perimeter of the high-pressure vessel, with several pre-reserved channels penetrating both the jacket and the outer perimeter (allowing for the installation of a marine radioactivity detector interface on the outer perimeter of the high-pressure vessel; corresponding marine radioactivity detector interfaces are also installed at corresponding positions on the circulating water bath jacket and the outer perimeter of the high-pressure vessel). The high-pressure vessel is equipped with marine radioactivity detectors arranged in layers along the height, with several detectors installed in each layer. Each detector is connected to a signal processor and a data analysis terminal via a signal connector. The connections between the detectors and the high-pressure vessel and the circulating water bath jacket are all waterproof and sealed.

[0008] The circulating water bath jacket is used to circulate refrigerant at a certain temperature to maintain temperature stability within the required temperature range of the high-pressure vessel. The model temperature is fed back through a temperature probe. In addition, a temperature parameter measurement and control module can be used to control the temperature inside the high-pressure vessel.

[0009] The marine radioactivity detector includes a radioactive crystal detector, a high-pressure waterproof cap, and a signal connector. The radioactive crystal detector is installed into the high-pressure vessel through a pre-drilled hole. The front end of the radioactive crystal detector, extending into the vessel, is encapsulated by the high-pressure waterproof cap. The rear end of the radioactive crystal detector is connected to a signal processor and a data analysis terminal via the signal connector. The connection between the radioactive crystal detector and the pressure vessel and water bath jacket can be double-sealed using a pressure ring and pressure cap.

[0010] The high-pressure waterproof end cap material can be made of polyoxymethylene, which has the functions of pressure bearing and waterproofing, and can allow radioactive rays to pass through, so as to achieve effective sealing of marine radioactive detectors in low temperature and high pressure environments.

[0011] Thus, this invention utilizes a marine radioactivity detector to detect radioactivity in real time under low temperature and high pressure conditions. 14 C-labeled natural gas hydrates produced by decomposition after extraction 14 The location of CH4 gas can be used to infer the gas migration path during hydrate extraction.

[0012] II. A method for monitoring gas migration paths during hydrate extraction based on isotope tracing, specifically including the following steps:

[0013] Step 1: Install the detector

[0014] Temperature and pressure sensors are installed at pre-drilled holes on the top of the high-pressure vessel. The connections between the temperature and pressure sensors and the high-pressure vessel are sealed with pressure rings and caps for a double-layer waterproof seal. A marine radioactivity detector is installed at a pre-drilled hole on the periphery of the high-pressure vessel. The radioactive crystal detector is encapsulated with a high-pressure waterproof cap. The connections between the radioactive crystal detector and the high-pressure vessel and water bath jacket are sealed with pressure rings and caps for a double-layer waterproof seal. The radioactive crystal detector is connected to a signal processor and a data analysis terminal via a signal connector.

[0015] Step 2: Preparation of reservoir model framework

[0016] First, a layer of low-permeability soil of a certain thickness is laid in a high-pressure container as the underlying soil layer, and compacted to achieve the specified density. Then, standard sand with a particle size distribution simulating the original soil is thoroughly mixed with a measured amount of deionized water to prepare unsaturated soil with a specific moisture content. This unsaturated soil is then laid on top of the underlying soil layer and compacted in layers to form a hydrate reservoir soil skeleton with a specific porosity. Finally, an overburden layer of a certain thickness is laid on top of the hydrate reservoir soil skeleton. This completes the preparation of the hydrate reservoir model soil skeleton.

[0017] Step 3: 14 Preparation of CH4-labeled hydrates

[0018] Close all channels of the high-pressure vessel, evacuate the gas inside the high-pressure vessel to a vacuum state from the production well, and check the airtightness of the device; open the bottom gas injection channel, and inject the radiocarbon-labeled gas through the gas injection device. 14 CH4 gas is injected to the predetermined pressure. The water bath circulation system is activated to lower the internal temperature of the high-pressure vessel to the predetermined temperature, generating... 14 C-labeled radioactive tracer properties of natural gas hydrates. Multiple injections using a constant-volume method are performed to determine the required hydrate content. 14 CH4 gas is used until the pressure inside the high-pressure container remains stable, at which point the hydrate formation is considered complete.

[0019] Step 4: Initial State Calibration

[0020] Connect the nitrogen cylinder to the bottom inlet of the high-pressure container to displace excess nitrogen gas in the container using a gas-driven method. 14CH4 gas (excess methane gas in the container is replaced by nitrogen gas via a booster pump through the bottom gas injection port, and the displaced gas is discharged through the production well); subsequently, the hydrate reservoir model is saturated with water through the bottom gas injection port. After water injection is complete, the bottom gas injection port is closed, and a confined aquifer with a certain pressure is formed on top of the overlying soil layer. The marine radiometric detector is activated to initialize the data. The detected data shows... 14 C-labeled natural gas hydrates 14 The initial position and distribution of CH4·H2O.

[0021] Step 5: Gas migration path monitoring

[0022] Reduce the pressure inside the production well to the target production pressure to allow the marked natural gas hydrates to decompose and release. 14 CH4 gas reacts with water in the hydrate reservoir as follows:

[0023]

[0024] Capturing methane gas using marine radiometric detectors 14 The radioactive rays emitted by CH4 are monitored in real time. 14 Radioactive nuclides in CH4 14 The transport distribution and content of C are determined, and real-time voltage pulse signals are generated as signal data.

[0025] Step Six: Signal Processing

[0026] The signal data is transmitted to the signal processor, which then transmits the radioactive nuclide. 14 The distribution and content data of C are processed, for example, by step-by-step amplification and pulse amplitude analysis, to obtain radionuclides. 14 C-spectral data were collected and energy spectrum curves were generated.

[0027] Step Seven: Data Analysis and Presentation

[0028] Radioactive nuclides can 14 C-ray spectral data is transmitted to a data analysis terminal for spectral data processing to form radionuclides. 14 Distribution and content data of C are plotted in cloud shape; multiple sets of data are reconstructed in three dimensions to generate radionuclides. 14 A three-dimensional cloud map of C distribution and content data is used to visualize the gas migration path during hydrate extraction.

[0029] In step five, radioactive rays irradiate the crystal detector inside the marine radioactivity detector, emitting fluorescence. These fluorescences then irradiate the photocathode of the photomultiplier tube inside the detector, generating photoelectrons. After being multiplied stepwise, these photoelectrons form a real-time voltage pulse signal on the output load of the photomultiplier tube. This allows for the detection of radionuclides at different locations within the hydrate reservoir at different times. 14 Detection of the dynamic distribution and content of C.

[0030] Compared with existing technologies, the technical solution provided in this application, as an example and not a limitation, has the following beneficial effects: This application is applicable to the field of deep-sea energy extraction technology, and can reliably and accurately obtain the gas migration path in the natural gas hydrate extraction process, and can detect it at the atomic level. 14 The migration pathway of CH4 is crucial for investigating the process of hydrate extraction. 14 This method provides experimental evidence to determine whether CH4 participates in the cage structure reorganization, solving the problem of difficulty in obtaining gas migration paths during natural gas hydrate extraction. Compared with other methods, this method eliminates the need for sampling and enables remote real-time monitoring of gas migration paths during hydrate extraction without disturbing the experimental model, demonstrating significant technical advantages. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of an example of the device of the present invention;

[0032] Figure 2 This is a top view of the structure of the device of the present invention;

[0033] Figure 3 This is a flowchart illustrating one aspect of the technical principle implementation of the device of the present invention.

[0034] Explanation of reference numerals in the attached diagram: 1. Production well; 2. High-pressure vessel cover; 3. Temperature sensor; 4. Pressure sensor; 5. High-pressure vessel; 6. Confined aquifer; 7. Overlying soil layer; 8. Hydrate simulated reservoir; 9. Underlying soil layer; 10. Inner wall of high-pressure vessel; 11. Refrigerant; 12. Bolt; 13. Circulating water bath jacket; 14. High-pressure waterproof end cap; 15. Radioactive crystal detector; 16. Signal connector; 17. Signal processor; 18. Data analysis terminal; 19. Gas injection interface. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0036] like Figure 1 and Figure 2As shown, this device includes a high-pressure vessel 5, a high-pressure vessel cover 2, a production well 1, a gas injection interface 19, a circulating water bath jacket 13, a marine radioactivity detector, a signal processor 17, and a data analysis terminal 18. The high-pressure vessel 5 contains an overlying soil layer 7, a hydrate simulated reservoir 8, and an underlying soil layer 9. A confined water layer 6 is arranged above the overlying soil layer 7. The high-pressure vessel cover 2 is installed on the high-pressure vessel 5, and a temperature sensor interface 3 and a pressure sensor interface 3 are provided on the cover 2. A production well interface is located at the center of the high-pressure vessel cover 2, and the production well 1 extends into the high-pressure vessel 5 to a certain depth through the production well interface. A gas injection interface 19 is located at the center of the bottom of the high-pressure vessel 5. A marine radioactivity detector signal interface 16 is located on the periphery of the high-pressure vessel 5. Corresponding marine radioactivity detector signal interfaces 16 are located at positions corresponding to the circulating water bath jacket 13 and the inner wall 10 of the high-pressure vessel. The high-pressure container 5 is equipped with marine radioactivity detectors arranged in layers along the height direction, with several marine radioactivity detectors installed in each layer; the marine radioactivity detector signal connector 16 is connected to the signal processor 17 and the data analysis terminal 18.

[0037] The high-pressure vessel 5 is a cylindrical titanium alloy container with an internal volume of 200L. It can operate under a maximum centrifugal acceleration of 300g, with a pressure range of 0-35MPa and an operating temperature of 0-90℃. The pressure vessel lid 2 is sealed with O-rings. The high-pressure vessel 5 contains, from top to bottom, a pressurized water layer 6, an overlying soil layer 7, a hydrate simulated reservoir 8, and an underlying soil layer 9. The inner wall of the high-pressure vessel 5 is provided with reserved holes for installing a marine radioactive detector.

[0038] In practice, the circulating water bath jacket 13 is used to circulate refrigerant 11 at a certain temperature to maintain the temperature stability of the high-pressure vessel 5 within a certain temperature range. The model temperature is fed back through a temperature probe, and the temperature is controlled by a temperature parameter measurement and control module.

[0039] In practice, the marine radioactivity detector consists of a radioactive crystal detector 15, a high-pressure waterproof cap 14, and a signal connector 16. The radioactive crystal detector 15 is installed into the high-pressure container 5 through a pre-drilled hole. The front end of the radioactive crystal detector 15 extending into the container is encapsulated by the high-pressure waterproof cap 14. The tail end of the radioactive crystal detector 15 is equipped with a signal connector 16, which connects to the signal processor 17 and the data analysis terminal 18. The connection between the radioactive crystal detector 15 and the high-pressure container 5 and the circulating water bath jacket 13 is sealed with a pressure ring and pressure cap for double-layer waterproof sealing.

[0040] In practice, the high-pressure waterproof end cap 14 is made of 20mm polyoxymethylene, which has the functions of pressure bearing and waterproofing, and can allow radioactive rays to pass through, so as to achieve effective sealing of marine radioactive detectors in low temperature and high pressure environments.

[0041] The specific experimental process and details of this invention are as follows:

[0042] Step 1: Install the detector

[0043] Temperature sensor 3 and pressure sensor 4 are installed at the pre-drilled hole on the top of high-pressure vessel 5. The connection between temperature sensor 3 and pressure sensor 4 and high-pressure vessel 5 is sealed with a pressure ring and pressure cap for double-layer waterproof treatment. Marine radioactive crystal detector 15 is installed at the pre-drilled hole on the inner wall 10 of high-pressure vessel. Radioactive crystal detector 15 is encapsulated with a high-pressure waterproof cap 14. The connection between radioactive crystal detector 15 and high-pressure vessel 5 and circulating water bath jacket 13 is sealed with a pressure ring and pressure cap for double-layer waterproof treatment. Signal connector 16 connects signal processor 17 and data analysis terminal 18.

[0044] Step 2: Preparation of reservoir model framework

[0045] First, a 30cm layer of low-permeability soil is laid in the high-pressure container 5 as the underlying soil layer 9, and compacted to achieve the specified density. Then, standard sand with a simulated undisturbed soil particle size distribution is thoroughly mixed with a measured amount of deionized water to prepare unsaturated soil with a moisture content of 10%. This unsaturated soil is then laid on the underlying soil layer 9 and compacted in layers to form a hydrate reservoir soil skeleton with a porosity of 0.4. Finally, a 30cm overburden soil layer 7 is laid on top of the hydrate reservoir soil skeleton. This completes the preparation of the hydrate reservoir model soil skeleton.

[0046] Step 3: 14 Preparation of CH4-labeled hydrates

[0047] Close all channels of high-pressure vessel 5, evacuate the gas inside high-pressure vessel 5 to a vacuum state and check the airtightness of the device; open the bottom gas injection port 19, and inject the radiocarbon-labeled gas through the gas injection device. 14 CH4 gas is injected to 3.5 MPa. The water bath circulation system is started to lower the internal temperature of high-pressure vessel 5 to 4.0–5.0 °C, generating a gas with… 14 C-labeled radioactive tracer properties of natural gas hydrates. Multiple injections using a constant-volume method are performed to determine the required hydrate content. 14 CH4 gas is applied until the internal pressure of high-pressure container 5 remains stable, at which point the formation of hydrates is considered complete.

[0048] Step 4: Initial State Calibration

[0049] Connect the nitrogen cylinder to the gas injection port 19 at the bottom of the high-pressure container 5 to displace excess gas in the container using a gas-driven method. 14CH4 gas was then injected; subsequently, the hydrate reservoir model was saturated with water. After water injection was completed, the bottom gas injection port 19 was closed, and a confined aquifer 6 with a certain pressure was formed on top of the overlying soil layer 7. The marine radiometric detector was activated to initialize the data. The detected radiometric data... 14 C-labeled natural gas hydrates 14 The initial position and distribution of CH4·H2O.

[0050] Step 5: Gas migration path monitoring

[0051] The pressure inside production well 1 was reduced to 2.2 MPa, causing the marked natural gas hydrates to decompose and be released. 14 CH4 gas reacts with water in the hydrate reservoir as follows:

[0052]

[0053] Capturing methane gas using marine radiometric detectors 14 The radioactive rays emitted by CH4 are monitored in real time. 14 Radioactive nuclides in CH4 14 The transport distribution and content of C are determined, and real-time voltage pulse signals are generated as signal data.

[0054] Step Six: Signal Processing

[0055] The signal data is transmitted to the signal processor 17, which then transmits the radionuclide. 14 The distribution and content data of C were amplified step by step, and pulse amplitude analysis was performed to obtain radionuclides. 14 C-spectral data were collected and energy spectrum curves were generated.

[0056] Step Seven: Data Analysis and Presentation

[0057] radioactive nuclides 14 C-spectral data is transmitted to data analysis terminal 18 for energy spectrum data processing to form radionuclides. 14 Distribution and content data of C are plotted in cloud shape; multiple sets of data are reconstructed in three dimensions to generate radionuclides. 14 A three-dimensional cloud map of C distribution and content data is used to visualize the gas migration path during hydrate extraction.

[0058] In this process, radioactive rays irradiate the crystal detector inside the marine radioactivity detector, emitting fluorescence. These fluorescences then irradiate the photocathode of a photomultiplier tube inside the detector, generating photoelectrons. After being multiplied stage by stage, these photoelectrons form a real-time voltage pulse signal on the output load of the photomultiplier tube, thus detecting the radionuclide. 14 Detection of the dynamic distribution and content of C.

[0059] In practice, the overlying soil layer and the underlying soil layer are low-permeability materials of a certain thickness. When the low-permeability material is clay, it usually refers to a permeability coefficient of 10. -9 The following types of clay are generally considered impermeable.

[0060] In practice, the pressure of the overlying confined aquifer should be controlled to 20 MPa and kept stable through a water pressure control subsystem.

[0061] As can be seen from the present invention, it solves the problem of the difficulty in obtaining gas migration paths during the current natural gas hydrate extraction process, and achieves the goal of accurate, efficient, and real-time remote monitoring of gas migration paths during natural gas hydrate experimental extraction.

[0062] It should be noted that the embodiments of this application are preferred for implementation and are not intended to limit the application in any way. The technical features or combinations of technical features described in the embodiments of this application should not be considered isolated; they can be combined with each other to achieve better technical effects. The scope of the preferred embodiments of this application may also include other implementations, and this should be understood by those skilled in the art to which the embodiments of this application pertain.

[0063] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of exemplary embodiments may have different values.

[0064] The accompanying drawings in this application are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this application, and are not intended to limit the implementation of this application. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that this application can produce, should fall within the scope of the technical content disclosed in this application.

[0065] The above description is merely a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above-disclosed technical content should be considered as equivalent and valid embodiments and fall within the scope of protection of the technical solution of this application.

Claims

1. A gas migration path monitoring system during hydrate extraction, characterized in that: The system includes a high-pressure vessel (5), a high-pressure vessel cover (2), a production well (1), a gas injection interface (19), a circulating water bath jacket (13), a marine radioactivity detector, a signal processor (17), and a data analysis terminal (18). The high-pressure vessel (5) contains an overlying soil layer (7), a hydrate simulated reservoir (8), and an underlying soil layer (9). A confined aquifer (6) is arranged above the overlying soil layer (7). The high-pressure vessel cover (2) is installed on the high-pressure vessel (5). A temperature sensor (3) interface and a pressure sensor (4) interface are provided on the high-pressure vessel cover (2) for installing corresponding sensors. A production well interface is provided at the center of the high-pressure vessel cover (2). The production well (1) extends into the high-pressure vessel (5) through the production well interface. Inside, a gas injection port (19) is provided at the center of the bottom of the high-pressure container (5); a circulating water bath jacket (13) is provided on the outer periphery of the high-pressure container (5), and several reserved channels are provided through the circulating water bath jacket (13) and the periphery of the high-pressure container (5). A signal connector (16) is provided on the outer wall of the circulating water bath jacket (13) corresponding to each reserved channel; marine radioactivity detectors are arranged in layers inside the high-pressure container (5), with several layers in the height direction, and several marine radioactivity detectors installed in a single layer; each marine radioactivity detector is connected to a signal processor (17) and a data analysis terminal (18) through a reserved channel and a signal connector (16), and the marine radioactivity detector and the reserved channel are waterproof and sealed.

2. The gas migration path monitoring system during hydrate extraction according to claim 1, characterized in that: The circulating water bath jacket (13) is used to circulate the refrigerant (11) to maintain the temperature stability of the high-pressure vessel (5) within the required temperature range, and the model temperature is fed back by the temperature sensor.

3. The gas migration path monitoring system during hydrate extraction according to claim 1, characterized in that: The marine radioactivity detector includes a radioactive crystal detector (15) and a high-pressure waterproof cap (14). The radioactive crystal detector (15) is installed into the high-pressure container through a reserved channel on the high-pressure container (5). The part of the front end of the radioactive crystal detector (15) that extends into the high-pressure container is sealed with a high-pressure waterproof cap (14). The tail end of the radioactive crystal detector (15) is connected to the signal processor (17) and the data analysis terminal (18) through a signal connector (16).

4. The gas migration path monitoring system during hydrate extraction according to claim 3, characterized in that: The high-pressure waterproof end cap (14) is made of polyoxymethylene and has the functions of pressure bearing and waterproofing. It can allow radioactive rays to pass through, so as to achieve effective sealing of marine radioactive detectors in low temperature and high pressure environments.

5. A method for monitoring gas migration paths during hydrate extraction using the system described in any one of claims 1-4, characterized in that: The method specifically includes the following steps: Step 1: Install the detector Temperature sensor (3) and pressure sensor (4) are installed at the top interface hole of the high pressure vessel (5). The connection between temperature sensor (3) and pressure sensor (4) and the high pressure vessel (5) is water-sealed. Radioactive crystal detector (15) is installed at the reserved hole in the inner wall (10) of the high pressure vessel. Its front end is sealed with a high pressure waterproof end cap (14), and its tail end is connected to signal processor (17) and data analysis terminal (18) through signal connector (16). The connection between radioactive crystal detector (15) and high pressure vessel (5) and circulating water bath jacket (13) is waterproof-sealed. Step 2: Preparation of reservoir model framework First, a low-permeability soil body is laid in the high-pressure container (5) as the underlying soil layer (9), and the soil body is compacted to reach the specified density. The standard sand with simulated original soil particle size distribution is thoroughly mixed with deionized water to prepare unsaturated soil. The prepared unsaturated soil is laid on the underlying soil layer (9), and the hydrate reservoir soil skeleton is formed by layer compaction. Finally, the overlying soil layer (7) is laid on the hydrate reservoir soil skeleton to finally prepare the hydrate reservoir model soil skeleton. Step 3: 14 Preparation of CH4-labeled hydrates Close all channels of the high-pressure container (5), evacuate the gas in the high-pressure container (5) from the mining well to a vacuum state and check the airtightness of the device; Open the bottom gas injection port (19), and inject the radiocarbon-labeled gas through the gas injection device. 14 CH4 gas is injected to a predetermined pressure; the water bath circulation system is started to lower the internal temperature of the high-pressure vessel (5) to a predetermined temperature, generating a gas with... 14 C-labeled radioactive tracer natural gas hydrates; multiple injections using a constant volume method, depending on the required hydrate content. 14 CH4 gas is used until the internal pressure of the high-pressure container (5) remains stable, at which point the hydrate is determined to be formed. Step 4: Initial State Calibration Connect the nitrogen cylinder to the gas injection port (19) at the bottom of the high-pressure container (5) to replace excess gas in the container using a gas-driven method. 14 CH4 gas; then, the hydrate reservoir model was saturated with water through the bottom gas injection port (19). After the water injection was completed, the bottom gas injection port (19) was closed, and a confined aquifer (6) was formed on top of the overlying soil layer (7); the marine radiometric detector was started to initialize the data and detect the generated... 14 C-labeled natural gas hydrates 14 The initial position and distribution of CH4·H2O; Step 5: Monitoring Gas Migration Paths The pressure inside the production well (1) is reduced to the target production pressure, causing the marked natural gas hydrates to decompose and be released. 14 CH4 gas and water, Capturing methane gas using marine radiometric detectors 14 The radioactive rays emitted by CH4 are monitored in real time. 14 Radioactive nuclides in CH4 14 The transport distribution and content of C are analyzed, and real-time voltage pulse signals are generated as signal data. Step Six: Signal Processing The signal data is transmitted to the signal processor (17), which transmits the radionuclide. 14 The distribution and content data of C were processed; Step Seven: Data Analysis and Presentation The processed data is transmitted to the data analysis terminal (18) to visualize the gas migration path during hydrate extraction.

6. The method for monitoring gas migration paths during hydrate extraction according to claim 5, characterized in that: In step five, the radioactive rays irradiate the radioactive crystal detector (15) inside the marine radioactivity detector, emitting fluorescence. These fluorescence then irradiate the photocathode of the photomultiplier tube inside the detector, generating photoelectrons. After being multiplied stepwise, these photoelectrons form a real-time voltage pulse signal on the output load of the photomultiplier tube, thereby realizing the emission of radioactive nuclides. 14 Detection of C; through detection at different locations and times within the hydrate reservoir. 14 Changes in C content are used to monitor gas migration pathways.

7. The method for monitoring gas migration paths during hydrate extraction according to claim 5, characterized in that: Steps six and seven may specifically include: Step Six: Signal Processing The signal data is transmitted to the signal processor (17), which transmits the radionuclide. 14 The distribution and content data of C were amplified step by step, and pulse amplitude analysis was performed to obtain radionuclides. 14 C-energy spectral data and generate energy spectral curves; Step Seven: Data Analysis and Presentation radioactive nuclides 14 C-spectral data is transmitted to a data analysis terminal (18) for energy spectrum data processing to form radionuclides. 14 C distribution and content data slice cloud map; three-dimensional reconstruction of multiple sets of data to generate radionuclides. 14 A three-dimensional cloud map of C distribution and content data is used to visualize the gas migration path during hydrate extraction.

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