Device and method for continuously monitoring isotopes in hydrate formation-decomposition process

Abstract

The invention provides a hydrate formation-decomposition process isotope continuous monitoring device and method, and is applied to the field of natural gas hydrate development, the device comprises: a high pressure reaction system comprising a rubber cylinder, a stainless steel shell, a liquid inlet valve and a hand pump; the fluid control and automatic sampling system comprises a vacuum pump, an electric back pressure valve, a gas sampling line, a one-way valve, a gas inlet valve, a ventilation pipeline and a high-pressure gas cylinder; the continuous analysis and monitoring system comprises a first temperature sensor, a second temperature sensor, a first pressure sensor, a second pressure sensor, a third pressure sensor and an isotope mass spectrometer; the temperature control circulating system comprises a water bath circulating pump and a water bath tank; and the data acquisition and control system comprises an online computer, a programmable logic controller (PLC) unit and a flow meter. According to the device, online continuous monitoring of isotope composition in the natural gas hydrate phase change process is achieved, dynamic collection of parameters such as temperature and pressure is combined, and the precision and continuity of experimental monitoring are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of natural gas hydrate development, and particularly to an isotope continuous monitoring device and method for the hydrate formation - decomposition process. Background Art

[0002] Natural gas hydrate is a cage - like crystal structure compound formed by the hydrogen - bond interaction between water molecules and gas molecules (such as methane) under low - temperature and high - pressure conditions, and is widely distributed in deep - sea sediments and terrestrial permafrost areas. It has an extremely high energy density and has great potential as a clean energy source.

[0003] However, the stability of natural gas hydrate is extremely sensitive to temperature and pressure changes, and it is easy to decompose and release a large amount of methane under disturbed conditions. Methane, as a potent greenhouse gas, has a much higher greenhouse effect than carbon dioxide. Therefore, the large - scale decomposition of natural gas hydrate may become a potential climate risk source, further exacerbating global warming. Therefore, in - depth study of the hydrate formation and decomposition processes is of great significance for both energy development and environmental protection.

[0004] Stable isotope technology has become an important means for studying the hydrate formation and decomposition mechanisms due to its high sensitivity in identifying the source of substances and tracing the transformation path. Especially the fractionation behaviors of carbon isotope (δ 13 C), hydrogen isotope (δD), and oxygen isotope (δ 18 O) can reflect the mass transfer mechanism during the gas - water phase change process, which helps to evaluate the hydrate reserves and formation environment.

[0005] Currently, most laboratory studies adopt static simulation methods, that is, under set temperature and pressure conditions, water and excessive methane are injected into a reaction kettle to generate hydrates, and then intermittent sampling and off - line isotope analysis are carried out on the free gas after generation or the gas released by the decomposition of hydrates. Although such methods are easy to operate, they have the following deficiencies: (1) The sampling method is mainly intermittent and off - line, unable to achieve real - time monitoring of the whole process, and it is difficult to capture the rapid isotope evolution behavior during the hydrate phase change process; (2) Most experimental systems are single - pressure simulations, making it difficult to truly reproduce the multiple - pressure coupling conditions such as water pressure, gas pressure, and confining pressure in real hydrate reservoirs, and the simulation accuracy is limited; (3) Most experiments focus on the initial or final stage of hydrate formation, lacking a systematic study on the continuous isotope changes during the whole formation - decomposition process. Summary of the Invention

[0006] The present disclosure provides an isotope continuous monitoring device and method for the hydrate formation - decomposition process to at least solve the above - mentioned technical problems existing in the prior art.

[0007] According to a first aspect of the present disclosure, there is provided an apparatus for continuously monitoring isotopes during the hydrate formation - decomposition process, the apparatus comprising: The high - pressure reaction system includes a rubber cylinder 1, a stainless - steel outer shell 2, a liquid inlet valve 3, and a hand pump 4, and is used to provide a pressure environment for the formation and decomposition of natural gas hydrates; The fluid control and automatic sampling system includes a vacuum pump 9, an electric back - pressure valve 14, a gas sampling line 15, a one - way valve 16, an air inlet valve 20, a ventilation pipeline 21, and a high - pressure gas cylinder 22, and is used to inject reaction gases into the rubber cylinder 1 and control the automatic sampling of gases; The continuous analysis and monitoring system includes a first temperature sensor 5, a second temperature sensor 11, a first pressure sensor 6, a second pressure sensor 12, a third pressure sensor 13, and an isotope mass spectrometer 17, and is used to monitor the temperature value, pressure value, and gas isotope composition in real time; The temperature - controlled circulation system includes a water - bath circulation pump 7 and a water - bath tank 18, and is used to provide a temperature environment for the formation and decomposition of natural gas hydrates; The data acquisition and control system includes an on - line computer 8, a programmable logic controller PLC unit 10, and a flowmeter 19, and is used for real - time acquisition of experimental data, intelligent control of environmental parameters, and result analysis.

[0008] In an implementable embodiment, in the high - pressure reaction system: The rubber cylinder 1 contains water samples or cores to form a reaction cavity; The stainless - steel outer shell 2 covers the rubber cylinder 1 to form an confining pressure cavity; The hand pump 4 is connected to the confining pressure cavity through the liquid inlet valve 3 and is used to inject water and pressurize the confining pressure cavity.

[0009] In an implementable embodiment, in the fluid control and automatic sampling system: The high - pressure gas cylinder 22 is connected to the inlet end of the rubber cylinder 1 through the ventilation pipeline 21 and the air inlet valve 20, and is used to inject reaction gases into the rubber cylinder 1; The inlet end of the gas sampling line 15 is connected to the outlet end of the rubber cylinder 1, and the outlet end of the gas sampling line is sequentially connected to the isotope mass spectrometer 17 through the electric back - pressure valve 14 and the one - way valve 16, and is used for automatic sampling and supplying to the isotope mass spectrometer 17; The vacuum pump 9 is connected to the rubber cylinder 1 through the gas sampling line 15 and the electric back - pressure valve 14, and is used to evacuate the reaction cavity.

[0010] In an implementable embodiment, in the continuous analysis and monitoring system: The first temperature sensor 5 and the first pressure sensor 6 are connected inside the rubber cylinder 1 for detecting the first temperature value and the first pressure value of the reaction cavity; The second temperature sensor 11 and the second pressure sensor 12 are connected to the confining pressure cavity for detecting the second temperature value and the second pressure value of the confining pressure cavity; The third pressure sensor 13 is disposed in the vent pipeline 21 for detecting the third pressure value in the vent pipeline 21.

[0011] In an implementable embodiment, in the temperature control circulation system: The water bath 18 wraps the stainless steel housing 2; the water bath circulation pump 7 and the water bath 18 form a closed loop for controlling the temperature of the confining pressure cavity.

[0012] In an implementable embodiment, in the data acquisition and control system: The flowmeter 19 is connected in series in the vent pipeline 21 for measuring the gas flow rate in the vent pipeline 21 and transmitting the gas flow rate data to the on-line computer 8; and is further used for controlling the gas flow rate according to the first pressure value of the first pressure sensor 6; The on-line computer 8 is communicatively connected to the output ends of the first temperature sensor 5, the second temperature sensor 11, the first pressure sensor 6, the second pressure sensor 12, the third pressure sensor 13 and the isotope mass spectrometer 17 for obtaining the first temperature value, the second temperature value, the first pressure value, the second pressure value, the third pressure value, the flow rate value and the isotope detection result; The PLC unit 10 is electrically connected to and controls the electric back pressure valve 14 and the vacuum pump 9; The PLC unit 10 performs data interaction with the on-line computer 8.

[0013] According to a second aspect of the present disclosure, there is provided a method for continuous isotope monitoring of the hydrate formation-decomposition process, characterized in that the method is applied to the above-mentioned device for continuous isotope monitoring of the hydrate formation-decomposition process, and the method includes: Performing the following monitoring steps in the target mode: Injecting a sample into the rubber cylinder and sealing the rubber cylinder and the stainless steel housing; the sample is a core sample or a water sample with a set volume; Closing the electric back pressure valve and starting the vacuum pump to perform vacuum pumping on the gas extraction line; Starting the water bath circulation pump to set the water bath temperature to the target temperature; Using a hand pump to pass water into the confining pressure cavity between the rubber cylinder and the stainless steel housing through the liquid inlet valve to establish the target confining pressure condition; Opening the gas inlet valve and injecting a reaction gas into the rubber cylinder through the vent pipeline connecting to a high-pressure gas cylinder; After the gas pressure in the reaction chamber meets the formation conditions of natural gas hydrate, close the intake valve to allow the natural gas hydrate to form spontaneously; Control the electric backpressure valve to release gas through the PLC unit, and enter the isotope mass spectrometer through the one-way valve for real-time isotope monitoring and analysis; After each round of sampling, the PLC unit controls the closing of the electric backpressure valve, and starts the vacuum pump again to evacuate the sampling pipeline to remove the residual gas; Induce the decomposition of natural gas hydrate, and allow the gas released during the decomposition process to enter the isotope mass spectrometer for real-time isotope monitoring and analysis.

[0014] In one implementable mode, the target mode is a single-variable control mode, including: Fix all parameters except the target variable, and the target variable is one of temperature, pressure, salinity, gas composition or sediment medium; Repeat the experiment and conduct hydrate formation and decomposition experiments by changing the value of the target variable.

[0015] In one implementable mode, the target mode is a periodic perturbation mode, including: Control the electric backpressure valve through the PLC unit to automatically cycle and adjust the pressure in the reaction chamber to decrease step by step according to a preset perturbation period; or, control the temperature of the reaction chamber to automatically cycle and adjust through the water bath circulation pump according to a preset perturbation period; And after each preset perturbation period is completed, control the vacuum pump to evacuate the sampling pipeline.

[0016] In one implementable mode, the target mode is a multi-variable coupling mode, including: Synchronously regulate at least two associated variables, and the associated variables include but are not limited to temperature, pressure, gas component type, salinity, and sediment medium type; Repeat the experiment and conduct hydrate formation and decomposition experiments by adjusting the combination of the associated variables.

[0017] The isotope continuous monitoring device and method for the hydrate formation - decomposition process of the present disclosure. The device includes a nested confining pressure structure constructed by a rubber cylinder and a stainless - steel outer shell in the high - pressure reaction system. The liquid inlet valve and the hand pump are only used to inject water into the confining pressure chamber to apply pressure, simulating the formation confining pressure conditions. The fluid control system, through the collaborative design of a vacuum pump, an electric back - pressure valve, and a one - way valve, establishes independent gas injection and sampling channels, completely avoiding the risk of cross - contamination. The monitoring system deploys a multi - sensor network (including temperature and pressure sensors) linked with an isotope mass spectrometer, which can synchronously track the temperature and pressure changes and the gas isotope composition during the phase change process. The temperature control system uses a wrapped heat - conduction structure of a water bath and coordinates with real - time temperature feedback to achieve uniform control of the temperature field, meeting the requirements of the temperature sensitivity of the hydrate phase change. The data system, based on the intelligent architecture of a PLC unit and an on - line computer, realizes the collaborative control of experimental equipment and the fusion analysis of multi - source data, supporting the operation of an automated experimental mode.

[0018] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it used to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the following detailed description with reference to the accompanying drawings, the above - mentioned and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become easily understood. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, where: In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0020] Figure 1 Shows a schematic structural diagram of the isotope continuous monitoring device for the hydrate formation - decomposition process of the embodiments of the present disclosure; Figure 2 Shows a schematic implementation flow diagram of the isotope continuous monitoring method for the hydrate formation - decomposition process of the embodiments of the present disclosure; Figure 3 Shows a schematic diagram of the flow rate change during the gas injection process of the embodiments of the present disclosure; Figure 4 Shows a schematic diagram of the pressure change during the gas injection process of the embodiments of the present disclosure; Figure 5 Shows a schematic diagram of the temperature change during the spontaneous hydrate formation process of the embodiments of the present disclosure; Figure 6 Shows a schematic diagram of the pressure change during the spontaneous hydrate formation process of the embodiments of the present disclosure; Figure 7 Shows a schematic diagram of the temperature change during the hydrate decomposition process of the embodiments of the present disclosure; Figure 8Shows a schematic diagram of the pressure change during the hydrate decomposition process according to an embodiment of the present disclosure; Figure 9 Shows a schematic diagram of the carbon isotope change according to an embodiment of the present disclosure; Figure 10 Shows a schematic diagram of the temperature change of periodic perturbation according to an embodiment of the present disclosure; Figure 11 Shows a schematic diagram of the pressure change of periodic perturbation according to an embodiment of the present disclosure.

[0021] Description of reference numerals: 1. Rubber cylinder; 2. Stainless steel outer shell; 3. Liquid inlet valve; 4. Hand pump; 5. First temperature sensor; 6. First pressure sensor; 7. Water bath circulation pump; 8. On-line computer; 9. Vacuum pump; 10. PLC unit; 11. Second temperature sensor; 12. Second pressure sensor; 13. Third pressure sensor; 14. Electric back pressure valve; 15. Gas sampling line; 16. Check valve; 17. Isotope mass spectrometer; 18. Water bath; 19. Flowmeter; 20. Gas inlet valve; 21. Vent pipe; 22. High-pressure gas cylinder. Detailed implementation manners

[0022] To make the objectives, features, and advantages of the present disclosure more obvious and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present disclosure.

[0023] The present disclosure provides an isotope continuous monitoring device for the hydrate formation - decomposition process, as Figure 1 shown, the device includes: The high-pressure reaction system includes a rubber cylinder 1, a stainless steel outer shell 2, a liquid inlet valve 3, and a hand pump 4, and is used to provide a pressure environment for the formation and decomposition of natural gas hydrates.

[0024] In this example, the rubber cylinder 1 serves as the reaction core cavity to accommodate the sample; the stainless steel outer shell 2 covers the rubber cylinder 1 to form a sealed confining pressure cavity; the hand pump 4 injects water into the confining pressure cavity to pressurize and simulate the formation pressure; the liquid inlet valve 3 is located at the top of the rubber cylinder 1 to achieve manual liquid injection. This design reproduces the multi-pressure coupling environment of the reservoir through the physical confining pressure cavity structure, ensuring the safety of high-pressure experiments.

[0025] The fluid control and automatic sampling system includes a vacuum pump 9, an electric back pressure valve 14, a gas sampling line 15, a check valve 16, a gas inlet valve 20, a vent pipe 21, and a high-pressure gas cylinder 22, and is used to inject reaction gas into the rubber cylinder 1 and control the automatic sampling of the gas.

[0026] In this example, the gas injection path is: high-pressure gas cylinder 22 → ventilation pipeline 21 → intake valve 20 → inlet of rubber cylinder 1; the sampling path is: outlet of rubber cylinder 1 → gas sampling line 15 → electric back pressure valve 14 → one-way valve 16 → isotope mass spectrometer 17; the vacuum pump 9 is connected to the gas sampling line 15 to perform the vacuum pumping operation. Physical isolation of gas injection and sampling is achieved through the split-path design to avoid cross-contamination of gas components.

[0027] The continuous analysis and monitoring system includes a first temperature sensor 5, a second temperature sensor 11, a first pressure sensor 6, a second pressure sensor 12, a third pressure sensor 13, and an isotope mass spectrometer 17, which are used to monitor the temperature value, pressure value, and gas isotope composition in real time.

[0028] In this example, the first temperature sensor 5 and the first pressure sensor 6 are directly connected to the inside of the rubber cylinder 1 to monitor the temperature value and pressure value in the reaction environment; the second temperature sensor 11 and the second pressure sensor 12 are located in the confining pressure chamber to monitor pressure transmission; the third pressure sensor 13 is arranged on the ventilation pipeline 21 to monitor the intake pressure; the isotope mass spectrometer 17 receives the gas through the one-way valve 16 for real-time analysis. Through the multi-position sensor network setting and combined with real-time online isotope mass spectrometry detection, synchronous tracking of all parameters in the phase change process is achieved.

[0029] The temperature control and circulation system includes a water bath circulation pump 7 and a water bath tank 18, which are used to provide the temperature environment for the formation and decomposition of natural gas hydrate.

[0030] In this example, the water bath tank 18 is coated with a stainless steel shell 2 to form a direct heat exchange interface; the water bath circulation pump 7 drives the closed-loop flow of the fluid, and cooperates with the feedback of the second temperature sensor 11 to achieve precise temperature control. Through the coated heat conduction structure, a uniform temperature field distribution is ensured, meeting the stringent requirements of the temperature sensitivity of the phase change of natural gas hydrate.

[0031] The data acquisition and control system includes an on-line computer 8, a programmable logic controller PLC unit 10, and a flow meter 19, which are used for real-time acquisition of experimental data, intelligent control of environmental parameters, and result analysis.

[0032] In this example, the on-line computer 8 receives the signals of all sensors and the isotope mass spectrometer 17, the PLC unit 10 controls the opening and closing cycle of the electric back pressure valve 14 and the timed start and stop of the vacuum pump 9, the flow meter 19 adjusts the gas velocity according to the air pressure in the reaction chamber; the on-line computer 8 integrates the data flow and executes the programs of three experimental modes. This architecture realizes the closed-loop control of multi-source data fusion and ensures the timing accuracy of continuous sampling.

[0033] The present disclosure provides a continuous isotope monitoring device for the hydrate formation-decomposition process, including a high-pressure reaction system comprising a nested confining pressure structure constructed of a rubber tube and a stainless steel shell, a hand-cranked pump for simulating formation pressure, and a liquid inlet valve for forming a safe and stable reaction environment. A fluid control system establishes independent gas injection and sampling channels through the coordinated design of a vacuum pump, an electric back-pressure valve, and a one-way valve, thereby completely avoiding the risk of cross-contamination. A multi-sensor network (including temperature and pressure sensors) deployed in the monitoring system is linked to an isotope mass spectrometer to synchronously track temperature and pressure changes and gas isotope composition during phase change. A temperature control system utilizes the encapsulated heat conduction structure of a water bath in conjunction with real-time temperature feedback to achieve uniform control of the temperature field, thereby meeting the temperature sensitivity requirements of hydrate phase change. A data system, based on the intelligent architecture of a PLC unit and an online computer, enables coordinated control of experimental equipment and multi-source data fusion analysis, supporting automated experimental mode operation.

[0034] In one example, in the high-pressure reaction system: the rubber tube 1 is filled with a water sample or a rock core to form a reaction chamber; the stainless steel shell 2 covers the rubber tube 1 to form a confined pressure chamber; the hand pump 4 is connected to the confined pressure chamber through the liquid inlet valve 3, and is used to inject water into the confined pressure chamber to increase pressure.

[0035] In this example, the rubber cylinder 1 serves as the core reaction container, directly accommodating water samples or core samples, such as 10 mL of deionized water or saturated water cores, to form a closed reaction chamber; the stainless steel shell 2 tightly wraps the rubber cylinder 1, and the cavity formed between the two is the confining pressure chamber, which is simulated by injecting water into the cavity and pressurizing it to simulate the formation confining pressure environment; the hand pump 4 is connected to the water injection port of the confining pressure chamber through a pipeline, and the liquid inlet valve 3 is actually located at the top of the rubber cylinder and is independently used to inject liquid samples.

[0036] In one example, in the fluid control and automatic sampling system: the high-pressure gas cylinder 22 is connected to the inlet end of the rubber cylinder 1 through the ventilation pipe 21 and the air inlet valve 20, for injecting reaction gas into the rubber cylinder 1; the inlet end of the gas extraction line 15 is connected to the outlet end of the rubber cylinder 1, and the outlet end of the gas extraction line is connected to the isotope mass spectrometer 17 through the electric back pressure valve 14 and the one-way valve 16 in sequence, for automatic sampling and providing to the isotope mass spectrometer 17; the vacuum pump 9 is connected to the rubber cylinder 1 through the gas extraction line 15 and the electric back pressure valve 14, for evacuating the reaction chamber.

[0037] In this example, a high-pressure gas cylinder 22 is connected to an air inlet valve 20 via a vent line 21 and ultimately to the top inlet of the rubber tube 1. This path is used to inject gas, such as methane, into the reaction chamber, and the air inlet rate is controlled by a flow meter 19.

[0038] The inlet end of the gas extraction line 15 is connected to the top outlet end of the rubber cylinder 1 and is physically isolated from the air inlet. The gas flow sequentially passes through the electric backpressure valve 14 and the one-way valve 16 for controlling the release rate to prevent backflow, and finally enters the isotope mass spectrometer 17 for real-time analysis.

[0039] The vacuum pump 9 is directly connected to the gas extraction line 15, and the reaction cavity in the rubber cylinder 1 is evacuated by sucking this pipeline.

[0040] In one example, in the continuous analysis and monitoring system: the first temperature sensor 5 and the first pressure sensor 6 are connected to the inside of the rubber cylinder 1 for detecting the first temperature value and the first pressure value of the reaction cavity; the second temperature sensor 11 and the second pressure sensor 12 are connected to the confining pressure cavity for detecting the second temperature value and the second pressure value of the confining pressure cavity; the third pressure sensor 13 is arranged in the ventilation pipeline 21 for detecting the third pressure value in the ventilation pipeline 21.

[0041] In this example, the first temperature sensor 5 and the first pressure sensor 6 are connected to the reaction cavity inside the rubber cylinder 1 to capture the temperature and pressure data during the reaction process in real time, that is, the first temperature value and the first pressure value; the second temperature sensor 11 and the second pressure sensor 12 are arranged in the confining pressure cavity space between the stainless steel shell 2 and the rubber cylinder 1 to continuously monitor the state of the confining pressure environment simulating the formation stress, that is, to detect and obtain the second temperature value and the second pressure value of the confining pressure cavity; the third pressure sensor 13 is embedded inside the ventilation pipeline 21 to dynamically feedback the gas injection pressure fluctuation. Through the multi-level sensing architecture, the reaction core area, the pressure transmission interface and the gas source input channel are synchronously covered, and a multi-dimensional parameter monitoring network for the hydrate formation-decomposition process is completely constructed, providing a basis for the whole-domain environment perception for closed-loop control.

[0042] In one example, in the temperature control circulation system: the water bath 18 covers the stainless steel shell 2; the water bath circulation pump 7 and the water bath 18 form a closed-loop circuit for controlling the temperature of the confining pressure cavity.

[0043] In this example, the water bath 18 completely covers the outer surface of the stainless steel shell 2 through physical covering to form a direct heat conduction interface; the water bath circulation pump 7 drives the constant-temperature fluid to form a closed-loop flow between the water bath 18 and the external circulation equipment, and precisely regulates the temperature environment of the confining pressure cavity by continuously exchanging heat. By immersing the whole reaction system in a uniform temperature field and cooperating with the real-time feedback of the second temperature sensor 11, the influence of the local temperature gradient on the hydrate phase change process is eliminated, and the stability of the low-temperature and high-pressure experimental conditions is ensured.

[0044] In one example, in the data acquisition and control system: the flowmeter 19 is connected in series in the ventilation pipeline 21, and is used to measure the gas flow rate in the ventilation pipeline 21 and transmit the gas flow rate data to the on-line computer 8; it is also used to control the gas flow rate according to the first pressure value of the first pressure sensor 6; the on-line computer 8 is communicatively connected to the output ends of the first temperature sensor 5, the second temperature sensor 11, the first pressure sensor 6, the second pressure sensor 12, the third pressure sensor 13 and the isotope mass spectrometer 17, and is used to obtain the first temperature value, the second temperature value, the first pressure value, the second pressure value, the third pressure value, the flow rate value and the isotope detection result; the PLC unit 10 is electrically connected to and controls the electric back pressure valve 14 and the vacuum pump 9; the PLC unit 10 performs data interaction with the on-line computer 8.

[0045] In this example, the flowmeter 19 is connected in series and integrated in the ventilation pipeline 21, and the gas injection rate is monitored in real time, and the gas flow rate data is transmitted into the on-line computer 8, and the gas flow rate injected into the reaction cavity is also controlled according to the first pressure value of the first pressure sensor 6.

[0046] The on-line computer 8 receives the first temperature value and the first pressure value from the reaction chamber, the second temperature value and the second pressure value from the confining pressure chamber, the third pressure value of the ventilation pipeline 21 and the isotope result output by the isotope mass spectrometer 17, and forms a global parameter synchronous acquisition network.

[0047] The PLC unit 10 directly controls the opening and closing timing of the electric back pressure valve 14 and the working cycle of the vacuum pump 9.

[0048] In addition, the on-line computer 8 and the PLC unit 10 communicate bidirectionally, integrate and analyze the data stream and issue three experimental mode control strategies. Through multi-source data fusion to drive the dynamic closed-loop regulation of the actuator, the precise control of the environmental parameters in the hydrate phase change process and the coordination of the continuous sampling timing are realized, and the stability and reliability of the on-line isotope monitoring are ensured.

[0049] The present disclosure also provides a method for continuous isotope monitoring during the hydrate formation-decomposition process, and the method is applied to the above-mentioned device for continuous isotope monitoring during the hydrate formation-decomposition process, as Figure 2 shown, the method includes: Execute the following monitoring steps in the target mode: Step 201: Inject a sample into the rubber cylinder and seal the rubber cylinder and the stainless steel shell; the sample is a core sample or a set volume of water sample.

[0050] In this example, a core sample or a set volume of water sample (such as deionized water or saline-simulated pore water) is injected into the rubber cylinder, and then the cavity formed by sealing the rubber cylinder and the stainless steel shell is ensured to be safely isolated from the high-pressure environment to avoid experimental leakage.

[0051] Step 202: Close the electric back pressure valve and start the vacuum pump to evacuate the gas extraction line.

[0052] In this example, after closing the electric back pressure valve, start the vacuum pump to evacuate the gas extraction pipeline (for example, continuously for ≥5 minutes) to completely remove the residual gas and eliminate its interference with the isotope detection results.

[0053] Step 203: Start the water bath circulation pump and set the water bath temperature to the target temperature.

[0054] In this example, start the water bath circulation pump and precisely set the temperature to the target value (such as 2°C ± 0.1°C). Through real-time feedback control by the temperature sensor, maintain the stable temperature range for hydrate formation / decomposition.

[0055] Step 204: Use a hand pump to pass water through the inlet valve into the confining pressure chamber between the rubber cylinder and the stainless-steel shell to establish the target confining pressure condition.

[0056] In this example, use a hand pump to inject water into the confining pressure chamber to pressurize it to the target confining pressure (such as 8–12 MPa) to simulate the real reservoir pressure. The second pressure sensor monitors in real time and ensures that the pressure is constant.

[0057] Step 205: Open the intake valve and connect a high-pressure gas cylinder through the gas pipeline to inject the reaction gas into the rubber cylinder.

[0058] In this example, open the intake valve, and the reaction gas (such as methane) in the high-pressure gas cylinder is injected into the rubber cylinder through the gas pipeline. The flowmeter is linked with the third pressure sensor to dynamically adjust the intake rate (20 - 80 mL / min).

[0059] Step 206: When the gas pressure in the reaction chamber meets the conditions for natural gas hydrate formation, close the intake valve to allow the natural gas hydrate to form spontaneously.

[0060] In this example, when the pressure in the reaction chamber reaches the hydrate stable zone (such as 6 MPa), close the intake valve, and the reaction system forms hydrates spontaneously under constant temperature conditions. The corresponding pressure sensor continuously records the pressure change.

[0061] Step 207: Control the electric back pressure valve to release gas through the PLC unit, and enter the isotope mass spectrometer through the one-way valve for real-time isotope monitoring and analysis.

[0062] In this example, the PLC unit controls the electric back pressure valve to open periodically (5 - 10 seconds / round) according to the preset program. The released gas enters the isotope mass spectrometer through the one-way valve for real-time analysis of the isotope compositions such as δ 13 C, δD.

[0063] Step 208: After each round of sampling, the PLC unit controls to close the electric backpressure valve and starts the vacuum pump again to evacuate the gas sampling pipeline to remove residual gas.

[0064] In this example, after each round of sampling, the PLC automatically closes the backpressure valve and starts the vacuum pump to evacuate the gas sampling pipeline, removing the residual gas to ensure the purity of subsequent sampling.

[0065] Step 209: Induce the decomposition of natural gas hydrate and allow the gas released during the decomposition process to enter the isotope mass spectrometer for real-time isotope monitoring and analysis.

[0066] In this example, by inducing the decomposition of hydrate, the decomposed gas is continuously monitored for isotope evolution through the mass spectrometer.

[0067] The above-described isotope continuous monitoring method for the hydrate formation-decomposition process of the present disclosure covers the following three usage modes: univariate control mode, periodic perturbation mode, and multivariable coupling mode. Specifically as follows: In one example, the target mode is the univariate control mode, including: fixing all parameters except the target variable, where the target variable is one of temperature, pressure, salinity, gas composition, or deposition medium; repeating the experiment and conducting hydrate formation and decomposition experiments by changing the value of the target variable.

[0068] In this example, the univariate control mode is to regulate only one key variable (such as temperature, pressure, salinity, gas composition, or deposition medium) in a constant experimental environment to systematically study its influence on the isotope fractionation effect during the hydrate formation and decomposition process. This mode obtains isotope evolution data under different control conditions by keeping other parameters constant, thereby realizing the analysis of the quantitative relationship between variables and fractionation effects. This method is applicable to the exploration of basic mechanisms and is an important way to construct an isotope fractionation model for the hydrate system.

[0069] In one example, the target mode is the periodic perturbation mode, including: controlling the electric backpressure valve by the PLC unit to automatically cycle and adjust the pressure in the reaction chamber in a stepped manner according to a preset perturbation period; or, controlling the temperature of the reaction chamber to automatically cycle and adjust by the water bath circulation pump according to a preset perturbation period; and after each preset perturbation period is completed, controlling the vacuum pump to evacuate the gas sampling pipeline.

[0070] In this example, the periodic perturbation mode simulates the unsteady process in the natural environment by setting experimentally controlled parameters that vary periodically (such as temperature cycling or pressure perturbation). During the experiment, a PLC unit or a water bath circulation pump is used to control the cyclic variation of pressure or temperature over multiple perturbation cycles, and gas isotope data is continuously collected to capture the transient variation patterns during the perturbation response process. This mode can be used to study the dynamic response characteristics of gas hydrates in scenarios such as submarine geological disasters, geothermal activities, and artificial exploitation of natural gas hydrates, and to reveal the evolution mechanism of isotopes under non-equilibrium conditions.

[0071] In one example, the target mode is a multivariable coupling mode, including: synchronously regulating at least two associated variables, where the associated variables include but are not limited to temperature, pressure, gas component type, salinity, and sediment medium type; repeating the experiment and conducting gas hydrate formation and decomposition experiments by adjusting the combination of associated variables.

[0072] In this example, the multivariable coupling mode introduces two or more variables in the experiment (such as the coordinated variation of temperature and pressure, the combined regulation of gas components and salinity, etc.), and simulates the evolution process of natural gas hydrates under the synergistic influence of multiple factors in the actual sedimentary environment by constructing complex experimental conditions. This mode focuses on the study of the interaction between variables, helps to restore the fractionation scenario of the natural system, optimize numerical simulation parameters, and provides support for resource evaluation and research on geological environment response.

[0073] The present disclosure details the above experimental procedures through the following examples: The test conditions and setting ranges are described as follows: To ensure the scientificity and reproducibility of the natural gas hydrate formation - decomposition experiment, each experimental step needs to comply with the following key parameters: Vacuum pumping condition: For the vacuum pumping operation, a vacuum pump is used to pre-pump the gas sampling pipeline, aiming to remove the residual air and reduce the interference of the initial mixed gas on the isotope results.

[0074] Vacuum pumping duration: not less than 5 minutes, and it can be set to automatically re-pump at regular intervals (such as every 2 hours) to maintain a stable low-pressure environment.

[0075] Vacuum condition: The pressure inside the gas sampling line is less than -0.085 MPa, which is used to ensure the full evacuation of residual gas and improve the sampling accuracy.

[0076] Temperature control range: The temperature control equipment consists of a water bath and a water bath circulation pump, which cooperate with a temperature sensor for real-time feedback control.

[0077] Temperature control accuracy: ±0.1 °C.

[0078] Adjustable temperature range: 0 °C to 30 °C.

[0079] The commonly used temperature setting value for hydrate formation is 2°C ± 0.5°C; the temperature during the decomposition stage is usually set to 8°C to 15°C.

[0080] Confining pressure setting range: Confining pressure establishment method: It is established by injecting water into the cavity between the rubber cylinder and the outer shell through a hand pump.

[0081] Pressure range: 0.5 MPa to 20 MPa.

[0082] The commonly used experimental confining pressure setting value: 8 MPa to 12 MPa, which is determined according to the actual simulated formation pressure.

[0083] Reaction gas injection pressure and flow rate: Reaction gas pressure control range: 2 MPa to 20 MPa.

[0084] The initial gas injection pressure is usually set to 6 MPa to 12 MPa to ensure entering the hydrate stable zone at the set temperature.

[0085] Flow control: It is set through a flowmeter, and the commonly used flow rate range is 20 to 80 mL / min.

[0086] Back pressure valve control setting: Back pressure setting value: 0.1 MPa to 0.5 MPa, which is used to adjust the release rate to ensure that the sample enters the mass spectrometer stably.

[0087] Back pressure valve opening time: 5 to 10 seconds / round.

[0088] Working conditions of the isotope mass spectrometer: Analysis method: Continuous flow - isotope ratio mass spectrometry (CF - IRMS) mode.

[0089] Isotopes to be measured: , etc.

[0090] Analysis frequency: A single sampling can be completed within 1 to 3 minutes, and high - frequency continuous sampling is supported.

[0091] Example 1 (single - variable control mode): An isotope continuous monitoring method for the formation - decomposition process of natural gas hydrate under single - variable (such as temperature) control: (1) Open the stainless - steel outer shell, clean the rubber cylinder with distilled water and dry it thoroughly; add the cored sample soaked in water or a set volume of water sample (such as 10 mL of deionized water) into the cylinder; then, close the stainless - steel outer shell and seal the high - pressure reaction system to complete the initial preparation.

[0092] (2) Close the electric back pressure valve, start the vacuum pump, and evacuate the gas pipeline to remove residual gas in the system to ensure sampling accuracy.

[0093] (3) Start the water bath circulation pump, set the water bath temperature to the target temperature of this round of experiments (such as 2°C), start the online computer, check whether the status of the first temperature sensor and the first pressure sensor are normal, and confirm that the PLC control unit is well connected to each module.

[0094] (4) Use a hand pump to pass water into the cavity between the rubber tube and the stainless steel shell to establish and maintain a consistent confining pressure (e.g., 6 MPa), which is monitored and adjusted in real time by a second pressure sensor.

[0095] (5) Open the air inlet valve and inject the reaction gas into the rubber cylinder through the ventilation pipe to connect the high-pressure gas cylinder to ensure that the composition and flow rate of the injected gas in each experimental group are consistent (such as pure methane). The pressure of the reaction chamber is monitored by the first pressure sensor, and the air inlet rate is adjusted by the third pressure sensor and the flow meter. The system records the injection flow and pressure dynamics in real time ( Figure 3 、 Figure 4 ).

[0096] (6) When the gas pressure in the reaction chamber meets the hydrate formation conditions, the air inlet valve is closed, the system maintains the set temperature, and enters the spontaneous hydrate formation stage; the sensor continuously records the changes in the reaction chamber temperature, pressure and other parameters ( Figure 5 、 Figure 6 ).

[0097] (7) During the hydrate formation stage, the PLC unit opens the electric back pressure valve according to the preset program, so that the free gas in the rubber cylinder is slowly released under the control of the set back pressure; the released gas enters the isotope mass spectrometer through the one-way valve for real-time online isotope analysis; the system automatically records the key parameters such as temperature, pressure, flow rate, etc. corresponding to each round of gas extraction.

[0098] (8) After each round of sampling, the PLC unit controls the closing of the electric back pressure valve and restarts the vacuum pump to evacuate the gas pipeline and remove residual gas.

[0099] (9) When the second pressure sensor shows that the confining pressure is stable and hydrate formation is complete, the confining pressure is kept constant and the water bath temperature is raised to a temperature higher than the stable temperature to induce hydrate decomposition; the system continuously monitors and records changes in temperature, pressure and other parameters ( Figure 7 、 Figure 8 ).

[0100] (10) During the hydrate decomposition process, the PLC unit continuously controls the electric back pressure valve to allow the released gas to stably enter the isotope mass spectrometer, realizing continuous sampling and isotope online analysis throughout the process. Figure 9 ) After sampling is completed, continue to start the vacuum pump to evacuate the gas sampling pipeline to prepare for the next experiment (such as the hydrate formation experiment at 6°C). (12) When the pressure of the first pressure sensor drops close to the atmospheric pressure, it indicates that the hydrate has completely decomposed. Turn off the online computer and save and analyze the obtained data.

[0101] (13) Repeat steps (1)-(12) and run the experimental groups under different control variables (such as 4°C and 6°C) respectively to establish the functional relationship between this variable and the fractionation effect.

[0102] Example 2 (periodic perturbation mode): A method for continuous isotope monitoring of the natural gas hydrate formation-decomposition process in the periodic perturbation mode: (1) Open the stainless steel shell, wash the rubber cylinder with distilled water and dry it thoroughly; add the cored samples soaked in water or a set volume of water sample (such as 10 mL of deionized water) into the cylinder. Then, close the stainless steel shell and seal the high-pressure reaction system to complete the initial preparation.

[0103] (2) Close the electric back pressure valve, start the vacuum pump, and evacuate the gas sampling pipeline to remove the residual gas in the system and ensure the sampling accuracy.

[0104] (3) Start the water bath circulation pump, set the target temperature (such as 2°C), then connect to the computer, and check the status of the first temperature sensor and the first pressure sensor to ensure normal communication between the PLC control unit and each module.

[0105] (4) Use a hand pump to inject water into the cavity between the rubber cylinder and the stainless steel shell to establish and maintain a constant confining pressure (such as 6 MPa), and adjust it in real time through the second pressure sensor. The system automatically records parameters such as temperature and pressure.

[0106] (5) Open the intake valve, inject the reaction gas (such as pure methane) into the rubber cylinder through the gas pipeline, and keep the gas composition injected in each experimental cycle unchanged; monitor the pressure in the cavity through the first pressure sensor, and the third pressure sensor and the flow meter are linked to adjust the intake rate. The system records the injection flow rate and the pressure change curve ( Figure 3 、 Figure 4 ).

[0107] (6) When the gas pressure in the reaction chamber meets the hydrate formation conditions, close the intake valve, and the system maintains the set temperature and enters the self-generation stage of hydrate; the sensor continuously records the changes in parameters such as the temperature and pressure in the reaction chamber ( Figure 5 、 Figure 6 ).

[0108] During the hydrate formation stage, the PLC unit periodically opens the electric back-pressure valve according to a preset program, so that the free gas in the rubber cylinder is slowly released under the set back-pressure control; the released gas enters the isotope mass spectrometer through the one-way valve for real-time online isotope analysis; meanwhile, the system automatically records key parameters such as temperature, pressure, and flow rate corresponding to each gas sampling round.

[0109] (8)After each round of sampling, the PLC unit controls to close the electric back-pressure valve and starts the vacuum pump again to evacuate the gas sampling pipeline and remove the residual gas.

[0110] (9)When the pressure of the second pressure sensor is stable, the hydrate formation is completed. Thereafter, according to the experimental design, periodic control is applied to the perturbation variables. For example, the temperature is set to cycle between 2°C, 4°C, and 6°C at a specific period (such as every 2 hours), or the pressure is set to slowly decrease in a stepwise manner to simulate the natural perturbation environment. The PLC system automatically adjusts the target variables according to the set period, and the other variables remain unchanged ( Figure 10 、 Figure 11 )。

[0111] (10)Under the condition of periodic perturbation, the PLC unit continuously controls the electric back-pressure valve to make the gas released during the decomposition process stably enter the isotope mass spectrometer, realizing continuous sampling and online isotope analysis throughout the process ( Figure 9 )。

[0112] (11)After each round of perturbation during the experiment, the gas sampling pipeline is automatically evacuated until the end of the last perturbation cycle.

[0113] (12)When the first pressure sensor drops to the same level as the external atmospheric pressure, it indicates that the hydrate has been completely decomposed. Shut down the connected computer and save and analyze the obtained data.

[0114] Example 3 (multivariable coupling mode): An isotope continuous monitoring method for the formation-decomposition process of natural gas hydrate in the multivariable coupling mode: (1)Open the stainless steel shell, clean the rubber cylinder with distilled water and dry it thoroughly; according to the experimental requirements, add the water-soaked core sample or a set volume of water sample into the cylinder. The water sample can be pure water, deionized water or simulated pore water containing specific salt ions to meet the simulation requirements of different experimental conditions; then, close the stainless steel shell and seal the high-pressure reaction system to complete the preparation of the initial state before the experiment.

[0115] (2)Close the electric back-pressure valve, start the vacuum pump, and evacuate the gas sampling pipeline to remove the residual gas in the system and ensure the sampling accuracy.

[0116] (3) Start the water bath circulation pump, set the target temperature, start the online computer, check whether the status of various sensors (including the first temperature sensor and the first pressure sensor) is normal, and confirm the communication connection between the PLC control unit and each module.

[0117] (4) Use a hand pump to pass water into the cavity between the rubber tube and the stainless steel shell to establish confining pressure; based on the data from the second pressure sensor, determine in real time whether the confining pressure level reaches the experimental set value.

[0118] (5) Open the air inlet valve and inject the reaction gas into the rubber tube through the ventilation pipe connected to the high-pressure gas cylinder. The reaction gas can be methane, ethane or other multi-component mixed gas; monitor the pressure in the cavity through the first pressure sensor, and adjust the air inlet rate through the linkage of the third pressure sensor and the flow meter. The system synchronously records the dynamic curve of the gas injection flow and pressure ( Figure 3 、 Figure 4 ).

[0119] (6) When the gas pressure in the reaction chamber meets the conditions for hydrate formation, the air inlet valve is closed, the system maintains the set temperature, and enters the spontaneous hydrate formation stage; during this stage, each sensor continuously records the changes in parameters such as the temperature and pressure of the reaction chamber.

[0120] (7) During the hydrate formation stage, the PLC unit opens the electric back pressure valve according to the preset program, so that the free gas in the rubber cylinder is slowly released under the control of the set back pressure; the released gas enters the isotope mass spectrometer through the one-way valve for real-time online isotope analysis; at the same time, the system automatically records the key parameters such as temperature, pressure, flow rate, etc. corresponding to each round of gas extraction.

[0121] (8) After each round of sampling, the PLC unit controls the closing of the electric back pressure valve and restarts the vacuum pump to evacuate the gas pipeline and remove residual gas.

[0122] (9) When the pressure of the second pressure sensor is stable, hydrate formation is complete. At this time, according to the experimental design, the water bath temperature can be adjusted or the electric back pressure valve can be opened to release the pressure, so that the system enters the hydrate decomposition stage. The system continuously monitors and records the changes in physical parameters such as temperature and pressure ( Figure 7 、 Figure 8 ).

[0123] (10) During the hydrate decomposition process, the PLC unit continuously controls the electric back pressure valve, so that the gas released during the decomposition process can stably enter the isotope mass spectrometer, realizing continuous sampling and isotope online analysis throughout the process ( Figure 9 ).

[0124] (11) After completing the sampling, continue to start the vacuum pump and evacuate the gas pipeline to prepare for the next experimental cycle.

[0125] When the first pressure sensor drops to the same level as the external atmospheric pressure, it indicates that the hydrate has completely decomposed. Turn off the online computer and save and analyze the obtained data.

[0126] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of this disclosure can be achieved, and no limitations are imposed herein.

[0127] In addition, the terms "first" and "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "a plurality" means two or more, unless otherwise specifically defined.

[0128] As described above, this is only the specific implementation manner of this disclosure, but the protection scope of this disclosure is not limited thereto. Any person skilled in the art within the technical scope disclosed by this disclosure can easily think of changes or substitutions, which should all be covered within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be subject to the protection scope of the claimed rights.

Claims

1. An isotope continuous monitoring device for the hydrate formation - decomposition process, characterized in that, The device includes: The high-pressure reaction system includes a rubber cylinder (1), a stainless-steel outer shell (2), a liquid inlet valve (3), and a hand pump (4), and is used to provide a pressure environment for the formation and decomposition of natural gas hydrates; The fluid control and automatic sampling system includes a vacuum pump (9), an electric back-pressure valve (14), a gas sampling line (15), a one-way valve (16), an air inlet valve (20), a ventilation pipeline (21), and a high-pressure gas cylinder (22), and is used to inject reaction gases into the rubber cylinder (1) and control the automatic sampling of gases; The continuous analysis and monitoring system includes a first temperature sensor (5), a second temperature sensor (11), a first pressure sensor (6), a second pressure sensor (12), a third pressure sensor (13), and an isotope mass spectrometer (17), and is used to monitor the temperature value, pressure value, and gas isotope composition in real time; The temperature control circulation system includes a water bath circulation pump (7) and a water bath (18), and is used to provide a temperature environment for the formation and decomposition of natural gas hydrates; The data acquisition and control system includes an on-line computer (8), a programmable logic controller PLC unit (10), and a flowmeter (19), and is used for the real-time acquisition of experimental data, the intelligent control of environmental parameters, and the result analysis.

2. The device according to claim 1, characterized in that, In the high-pressure reaction system: The rubber cylinder (1) contains water samples or cores to form a reaction cavity; The stainless-steel outer shell (2) covers the rubber cylinder (1) to form an confining pressure cavity; The hand pump (4) is connected to the confining pressure cavity through the liquid inlet valve (3) and is used to inject water into the confining pressure cavity to apply pressure.

3. The device according to claim 2, characterized in that [[ID=*10]]In the fluid control and automatic sampling system: The high-pressure gas cylinder (22) is connected to the inlet end of the rubber cylinder (1) through the ventilation pipeline (21) and the air inlet valve (20) and is used to inject reaction gases into the rubber cylinder (1); The inlet end of the gas sampling line (15) is connected to the outlet end of the rubber cylinder (1), and the outlet end of the gas sampling line is sequentially connected to the isotope mass spectrometer (17) through the electric back-pressure valve (14) and the one-way valve (16) and is used for automatic sampling and providing samples to the isotope mass spectrometer (17); The vacuum pump (9) is connected to the rubber cylinder (1) through the gas sampling line (15) and the electric back-pressure valve (14) and is used to evacuate the reaction cavity.

4. The device according to claim 2, characterized in that, In the continuous analysis and monitoring system: The first temperature sensor (5) and the first pressure sensor (6) are connected to the inside of the rubber cylinder (1) and are used to detect the first temperature value and the first pressure value of the reaction cavity; The second temperature sensor (11) and the second pressure sensor (12) are connected to the confining pressure cavity and are used to detect the second temperature value and the second pressure value of the confining pressure cavity; The third pressure sensor (13) is arranged in the ventilation pipeline (21) and is used to detect the third pressure value in the ventilation pipeline (21).

5. The device according to claim 2, characterized in that, In the temperature control circulation system: The water bath (18) covers the stainless-steel outer shell (2); the water bath circulation pump (7) and the water bath (18) form a closed-loop circuit and are used to control the temperature of the confining pressure cavity.

6. The device according to claim 1, characterized in that, In the data acquisition and control system: The flowmeter (19) is connected in series in the ventilation pipeline (21) for measuring the gas flow rate in the ventilation pipeline (21) and transmitting the gas flow rate data to the on-line computer (8); it is also used for controlling the gas flow rate according to the first pressure value of the first pressure sensor (6). The on-line computer (8) is communicatively connected to the output ends of the first temperature sensor (5), the second temperature sensor (11), the first pressure sensor (6), the second pressure sensor (12), the third pressure sensor (13) and the isotope mass spectrometer (17) for obtaining the first temperature value, the second temperature value, the first pressure value, the second pressure value, the third pressure value, the flow rate value and the isotope detection result. The PLC unit (10) is electrically connected to and controls the electric back pressure valve (14) and the vacuum pump (9). The PLC unit (10) performs data interaction with the on-line computer (8).

7. An isotope continuous monitoring method for the hydrate formation - decomposition process, characterized in that, The method is applied to the isotope continuous monitoring device for the hydrate formation-decomposition process described in claims 1-6, and the method includes: Performing the following monitoring steps in the target mode: Injecting a sample into the rubber cylinder and sealing the rubber cylinder and the stainless steel housing; the sample is a core sample or a water sample with a set volume. Closing the electric back pressure valve and starting the vacuum pump to evacuate the gas extraction line. Starting the water bath circulation pump to set the water bath temperature to the target temperature. Using a hand pump to pass water through the confining pressure chamber between the rubber cylinder and the stainless steel housing through the liquid inlet valve to establish the target confining pressure condition. Opening the gas inlet valve and injecting a reaction gas into the rubber cylinder through the ventilation pipeline connecting to the high-pressure gas cylinder. When the air pressure in the reaction cavity meets the natural gas hydrate formation condition, closing the gas inlet valve to allow the natural gas hydrate to form spontaneously. Controlling the electric back pressure valve to release gas through the PLC unit and entering the isotope mass spectrometer through the one-way valve for real-time isotope monitoring and analysis. After each round of sampling, the PLC unit controls to close the electric back pressure valve and starts the vacuum pump again to evacuate the gas extraction pipeline to remove the residual gas. Inducing the decomposition of the natural gas hydrate and allowing the gas released during the decomposition process to enter the isotope mass spectrometer for real-time isotope monitoring and analysis.

8. The method according to claim 7, wherein The target mode is a single variable control mode, including: Fixing all parameters except the target variable, and the target variable is one of temperature, pressure, salinity, gas composition or sedimentary medium. Repeating the experiment and performing hydrate formation and decomposition experiments by changing the value of the target variable.

9. The method according to claim 7, wherein The target mode is a periodic perturbation mode, including: Controlling the electric back pressure valve through the PLC unit to automatically cycle and adjust the pressure of the reaction cavity in a stepped manner according to a preset perturbation period; or, controlling the water bath circulation pump to automatically cycle and adjust the temperature of the reaction cavity according to a preset perturbation period. And after each preset perturbation period is completed, controlling the vacuum pump to evacuate the gas extraction pipeline.

10. The method according to claim 7, characterized in that, The target mode is a multi-variable coupling mode, including: Synchronously regulating at least two associated variables, and the associated variables include but are not limited to temperature, pressure, gas component type, salinity and sedimentary medium type. Repeating the experiment and performing hydrate formation and decomposition experiments by adjusting the combination of associated variables.

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