Device and method for simulating mud volcano / mud bottom activity in submarine natural gas hydrate system

Abstract

The invention provides a device and method for simulating mud volcano / mud bottom activity in a submarine natural gas hydrate system, and the device comprises an integrated fluid preparation and supply module, a mud volcano / mud bottom activity reaction kettle module, a temperature control module, a hydraulic drive module, a gas supply module, a liquid supply module and a numerical control center module. The complex phenomena such as fluid leakage, stratum fracture and tension, gas invasion and natural gas hydrate generation or decomposition in the activity process of mud volcanic or mud bottom in the seabed stratum are comprehensively simulated; the device has a high-precision temperature and pressure environment control function, and temperature, pressure, pore fluid pressure and sediment internal resistivity tomography data in the experiment process are recorded in real time; the stratigraphic tension rate and displacement are accurately controlled, and the dynamic response in the geological structure is reproduced; particle displacement and sediment redistribution caused by fluid invasion are researched; and a reliable experimental platform is provided for systematically researching the influence of mud volcanic activities on reservoir forming and decomposition of natural gas hydrates.

Description

Technical Field

[0001] The invention belongs to the field of indoor experimental simulation research on natural gas hydrate geological processes, and in particular relates to a device and method for simulating mud volcano / mud diapir activities in a seabed natural gas hydrate system. Background Art

[0002] Natural gas hydrates are solid crystals formed by methane and water molecules under low temperature and high pressure. They have the advantages of pollution-free combustion, high energy density and large reserves, and are therefore regarded as a clean energy with great potential in the future. Mud volcanoes / mud diapir are mound-like geological structures formed by the eruption of water-containing muddy materials deep in the basin strata along high permeability channels such as faults to the surface or seabed. The interpretation results of a large number of field measured data show that the interaction between local active structures such as mud volcanoes and the synthesis and decomposition of natural gas hydrates is mainly manifested in the following three aspects: ① Mud volcano activity (or diapirism) carries a large amount of methane gas, and some gas gathers in local strata, which easily forms a high-pressure environment and promotes the formation of natural gas hydrates; ② Deep water-containing muddy materials will transfer heat to the surrounding sediments during the ascent, affecting the distribution and stability of natural gas hydrates; ③ The methane gas released by the decomposition of natural gas hydrates also provides an additional overpressure driving force for mud volcano activity.

[0003] Traditional methods for studying mud volcanoes include geological surveys, geophysical exploration, and laboratory simulations. Geological surveys and geophysical exploration methods can provide the macroscopic characteristics and distribution of mud volcanoes, but it is difficult to reveal the microscopic mechanisms of their formation and development. Although laboratory simulation methods can control experimental conditions, existing simulation devices often cannot fully simulate the complex process of mud volcano formation, including sediment accumulation, compaction, eruption dynamics, and simulated deep fluid composition changes. In addition, there is an intricate interaction between the activity of mud volcanoes and the synthesis or decomposition process of natural gas hydrates, which spans the boundaries of multiple disciplines such as geology, geochemistry, and fluid mechanics, and constitutes a multi-dimensional and multi-scale scientific problem. Existing research methods mostly rely on single-disciplinary means, making it difficult to fully reproduce the temperature and pressure conditions and fluid dynamics in a real seafloor environment. The experimental data lack authenticity and comprehensiveness, and it is impossible to obtain research results that are closer to the real environment. There is a lack of a comprehensive experimental platform that can capture the key dynamic data of the interaction between mud volcanoes and hydrates by precisely controlling temperature and pressure conditions and reproducing fluid movement and sedimentation processes, achieving higher authenticity. Summary of the invention

[0004] In order to solve the above-mentioned defects of the prior art, the present invention proposes a device and method for simulating mud volcano / mud diapir activities in a submarine natural gas hydrate system. By precisely controlling the temperature and pressure conditions and reproducing the fluid movement and sedimentation process, the key dynamic data of the interaction between mud volcanoes and hydrates can be captured to achieve higher authenticity.

[0005] On the one hand, the present invention proposes a device for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, comprising a fluid preparation and supply module, a mud volcano / mud diapir activity reactor, a temperature control module, a hydraulic drive module, a gas supply module, a liquid supply module and a numerical control center module; the fluid preparation and supply module is located at the bottom of the experimental device, and is used to prepare deep fluid for intrusion, and is connected to the mud volcano / mud diapir activity reactor through a transmission pipeline; the mud volcano / mud diapir activity reactor is located at the upper part of the fluid preparation and supply module, and is used to simulate the temperature and pressure conditions of the overlying submarine strata, simulate the mud volcano / mud diapir activity and prepare natural gas hydrate reservoir samples, and a simulated stratum is arranged inside; the temperature control module is wrapped around the outer periphery of the mud volcano / mud diapir activity reactor, and is used to simulate the temperature and pressure conditions of the overlying submarine strata, simulate the mud volcano / mud diapir activity and prepare natural gas hydrate reservoir samples. The temperature and pressure conditions of the submarine strata provide temperature control to keep the temperature of the mud volcano / mud diapir active reactor constant; the hydraulic drive module controls the lateral and longitudinal movement of the simulated strata in the mud volcano / mud diapir active reactor by driving the hydraulic cylinder provided in the reactor to simulate the tension and strike-slip movement of the strata; the gas supply module is connected to the top and bottom air chambers of the mud volcano / mud diapir active reactor to provide high-pressure methane gas for the experimental device; the liquid supply module supplies liquid to the fluid preparation and supply module and the mud volcano / mud diapir active reactor through a pipeline; the CNC center module is respectively connected to the fluid preparation and supply module, the mud volcano / mud diapir active reactor, the temperature control module, the hydraulic drive module, the gas supply module, and the liquid supply module to realize experimental parameter control and data recording.

[0006] Furthermore, the mud volcano / mud diapir active reactor comprises a reactor body, an upper end cover of the reactor and a lower end cover of the reactor; an insulating plate for resistivity tomography measurement is arranged on the inner wall of the reactor body for collecting resistivity data inside the sediment; a plurality of temperature probe groups are arranged at different heights inside the reactor body for monitoring temperature distribution; a push plate is arranged on the left side of the reactor body, and the push plate is connected to the left side of the simulated formation, and the push plate is driven by the connected hydraulic cylinder II to realize lateral movement of the simulated formation, so as to adjust the local pressure inside the formation; a movable plate is installed on the left bottom of the left side of the reactor body, and the movable plate is driven by the hydraulic cylinder I to realize upward movement to form a dislocation of the simulated formation; a plurality of gas diversion plates are installed inside the reactor body, among which the upper gas diversion plates are connected to the lower end of the reactor body. The body splitter plate and the lower gas splitter plate are located between the upper gas chamber and the lower gas chamber of the reactor, and are used to adjust the uniform distribution of the gas. Two gas splitter plates I and gas splitter plates II are arranged inside the right side of the reactor, which are respectively connected to the gas chamber I and the gas chamber II on the right side of the reactor, and are used to further distribute and adjust the flow path of the gas; the right side of the reactor is also provided with a liquid tank I and a liquid tank II, which are connected to the liquid supply module to provide the required liquid for the experiment; the upper end cover of the reactor is provided with a high-pressure gas inlet I, which is connected to the upper gas chamber; the lower end cover is provided with a high-pressure gas inlet II, which is connected to the lower gas chamber; the bottom of the reactor body is designed with a deep fluid injection hole, which is connected to the fluid preparation and supply module through a through hole penetrating the lower end cover of the reactor and the lower gas splitter plate, and the high-pressure stability of the experimental device is ensured by a sealing structure.

[0007] Furthermore, the fluid preparation and supply module is used to prepare deep fluid and transport it to the reactor, including a plunger-type high-pressure cylinder; the periphery of the plunger-type high-pressure cylinder is equipped with a boltier for temperature control; the interior of the plunger-type high-pressure cylinder is provided with a deep fluid transport coil, a stirring paddle, a high-pressure cylinder inner core and a gas transport coil; wherein the deep fluid transport coil extends from the top of the plunger-type high-pressure cylinder to the upper part of the high-pressure cylinder inner core, and is connected to the deep fluid injection hole at the bottom of the reactor; the gas transport coil extends from the lower part of the high-pressure cylinder inner core to the bottom of the plunger-type high-pressure cylinder for gas transport; the stirring paddle is installed at the top of the high-pressure cylinder inner core for mixing fluid;

[0008] The top of the plunger-type high-pressure cylinder is provided with a simulated deep fluid preparation liquid inlet, a venting port and a simulated fluid outlet; the simulated deep fluid preparation liquid inlet is used to be connected to the liquid supply module; the venting port is used to discharge excess gas; the simulated fluid outlet is connected to the reactor through a deep fluid delivery coil;

[0009] A high-pressure cylinder base is installed at the bottom of the plunger-type high-pressure cylinder, and a stirring paddle driver, a simulated deep fluid preparation gas inlet, and a plunger-driven liquid inlet are integrated on the high-pressure cylinder base; the stirring paddle driver is used to drive the stirring paddle; the simulated deep fluid preparation gas inlet is connected to the high-pressure gas tank through a gas delivery pipeline; the plunger-driven liquid inlet is used to be connected to a liquid storage tank to provide prepared liquid;

[0010] The entire module supplies liquid to the simulated deep fluid preparation liquid inlet through the liquid supply module. The pressure and temperature sensors are installed in the plunger-type high-pressure cylinder and communicate with the CNC center module through the data acquisition device to record and monitor parameter changes in the fluid preparation process in real time.

[0011] Furthermore, the temperature control module includes a water bath system and a water bath chamber, wherein the water bath system is connected to the water bath chamber through a pipeline to form a closed water circulation system for maintaining a constant temperature in the water bath chamber; a circulating water pump and a multi-point temperature probe are arranged in the water bath chamber to improve the uniformity of temperature distribution; the water bath chamber is wrapped around the periphery of the reactor body to provide a uniform temperature control environment for it, and limit the temperature change within the range required by the experiment through heat transfer; the periphery of the water bath chamber is covered with an insulation layer to reduce heat loss;

[0012] The entire system realizes real-time monitoring and adjustment of temperature through connection with the CNC center module.

[0013] Furthermore, the hydraulic drive module includes a hydraulic tank and a hydraulic pump connected to hydraulic cylinder I and hydraulic cylinder II. A proportional control valve is installed between the hydraulic pump and hydraulic cylinder I and hydraulic cylinder II to accurately control the flow of hydraulic oil through electrical signals to achieve precise adjustment of the formation movement rate; a layer of elastic plate is also fixed to the end face of the push plate that abuts against the simulated formation.

[0014] Furthermore, the methane gas cylinder I, methane gas cylinder II and gas flow controller I, gas flow controller II of the gas supply module are connected with gas inlet II, gas inlet I, simulated deep fluid injection hole, gas chamber I, and gas chamber II;

[0015] The liquid storage tank and liquid flow controllers I, II and III of the liquid supply module are connected with liquid tanks I and II;

[0016] The numerical control center module includes a computer, a data controller and a data collector; the data controller is mainly used to control the injection velocity and flow rate of the gas, the flow rate of the hydraulic pump, the injection velocity and flow rate of the liquid, and the tracking of the effective stress of the overlying formation; the data collector is mainly used to collect resistivity tomography data, temperature data, and pressure data; the data of the data collector and the data controller are finally summarized in the computer.

[0017] On the other hand, the present invention provides a method for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, which is applicable to the above-mentioned device and comprises the following steps:

[0018] S1: Initial simulation of overlying seafloor formation preparation, including:

[0019] Install the experimental device, compact the sediments in layers and fill them into the reactor body, and inject salt water into the reactor through liquid tank I and liquid tank II by the liquid supply module to simulate the mineral dehydration reaction and fluid circulation in the system;

[0020] The temperature control module uses a water bath system to cool the reactor and injects high-pressure methane gas into the reactor to synthesize natural gas hydrates in the sediments. It tests the temperature changes inside the sediments during the hydrate synthesis process and obtains the hydrate distribution pattern inside the sediments in real time to complete the initial simulation of the overlying seabed formation preparation.

[0021] S2: Preparation of simulated deep fluid, the steps include:

[0022] S21: The deep fluid mixture formed by the muddy sediment used for simulation has a lower density than the sediment of the simulated formation in step S1. The density difference between the deep fluid mixture with lower density and the simulated formation can help the deep fluid break through to the surface; the deep fluid mixture is loaded into a plunger-type high-pressure cylinder, and salt water is injected into the plunger-type high-pressure cylinder, and a stirring paddle is started to stir, so that the salt water and the muddy sediment are fully mixed;

[0023] S22: injecting high-pressure but low-density methane gas into the plunger-type high-pressure cylinder, stirring it at the same time, and heating the mixture inside the plunger-type high-pressure cylinder. By continuous stirring, the methane gas is ensured to be fully dissolved and evenly distributed in the mixture. The heating process raises the temperature of the mixture to a preset value to simulate the high-temperature environment deep in the formation. After the internal fluid is saturated with methane and the fluid temperature reaches the preset temperature value, the obtained mixture is pushed into the reactor body;

[0024] S3: Mud volcano / mud diapir activity simulation, steps include:

[0025] S31: adjusting the fluid outlet pressure to be equal to the simulated overlying seafloor pore pressure, and then connecting the fluid preparation and supply module and the mud volcano / mud diapir activity reactor module;

[0026] S32: distilled water is injected into the lower part of the plunger-type high-pressure cylinder at a constant rate to drive the inner core of the high-pressure cylinder to move upward, simulating that the deep fluid is pressed into the reactor at a constant rate;

[0027] S33: Synchronously record the temperature data, displacement sensor data, resistivity tomography data and pore pressure data of the sediment internal space during the invasion simulation process; collect sediment samples after fluid invasion, study the changes in sediment particle distribution through particle size analysis technology, and evaluate the displacement and re-deposition of particles during fluid invasion;

[0028] S34: When the deep simulated fluid injection volume reaches a preset value, the invasion simulation is stopped.

[0029] Furthermore, step S1 further includes:

[0030] The sediments were compacted and filled into the reactor body in layers, and the specific stratigraphic arrangement was as follows: at the beginning of the experiment, loose sand or soft sediment was first laid on the bottom of the reactor as the bottom layer; then, a composite sand layer was constructed, and mineral particles of different densities were added to reflect the density distribution gradient of the sediments, and particle tracking markers were added to the sediments; then, a low-permeability clay isolation layer was designed between the composite sand layer and the hydrate layer, forcing the fluid to accumulate pressure during the ascent, thereby intensifying the effects of buoyancy and density differences and enhancing the driving force for eruption; finally, a sand layer was laid on the topmost layer.

[0031] Furthermore, step S1 further includes:

[0032] The reactor was cooled down using the water bath system of the temperature control module. High-pressure methane gas was then injected into the upper gas chamber, the lower gas chamber, the gas chamber I, and the gas chamber II. The methane gas evenly penetrated the upper gas diverter plate, the lower gas diverter plate, the gas diverter plate I, and the gas diverter plate II to synthesize natural gas hydrates in the sediments. During the experiment, the temperature changes inside the sediments during the hydrate synthesis process were tested in real time, and the hydrate distribution pattern inside the sediments was obtained in real time to complete the initial simulation of the overlying seabed strata preparation.

[0033] Furthermore, step S1 further includes:

[0034] Before the experiment officially begins, all components of the hydraulic system should be thoroughly checked to ensure their normal operation and no leakage; then, a trial run is performed through hydraulic cylinders I and II of the hydraulic drive module to simulate the movement of the strata, and relevant parameters are calibrated according to the feedback data. By calibrating the parameters, the possible initial deviation of the hydraulic system is eliminated to improve the consistency and reliability of the experimental results; then, the movement of the left strata is controlled by hydraulic cylinders I and II, and reasonable initial displacement parameters are set to simulate the tensile tectonic movement of the strata; the hydraulic system will gradually apply horizontal stress to promote the slow displacement of the strata, thereby simulating the extension effect in the geological structure and ensuring that the stratum structure and experimental conditions during the movement meet the expected requirements.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] 1. The embodiment of the present invention integrates a fluid preparation and supply module, a mud volcano / mud diapir activity reactor module, a temperature control module, a hydraulic drive module, a gas supply module, a liquid supply module and a numerical control center module to comprehensively simulate complex phenomena such as fluid leakage, formation rupture and tension, gas intrusion and natural gas hydrate formation or decomposition during mud volcano or mud diapir activity in the submarine strata. The device has a high-precision temperature and pressure environment control function, and can record the temperature, pressure, pore fluid pressure and internal resistivity tomography data of the sediment in real time during the experiment; the hydraulic drive module is used to accurately control the formation tension rate and displacement to reproduce the dynamic response in the geological structure; and the particle displacement and sediment redistribution caused by fluid intrusion are studied through particle size analysis and particle tracking technology. The device provides a reliable experimental platform for systematically studying the impact of mud volcano activity on the accumulation and decomposition of natural gas hydrates, and can be widely used in geology, fluid mechanics, energy resource development and other fields.

[0037] 2. The device and method of the present invention can achieve:

[0038] (1) Simulation of the entire process from deep fluid intrusion to surface mud volcano eruption;

[0039] (2) The two-way interaction mechanism between deep fluid and hydrate formation and decomposition. The experimental device can capture the following interaction phenomena: hydrate formation and decomposition - deep methane fluid forms hydrate in a low-temperature environment, and hydrate decomposes to release methane, forming a feedback driving mechanism; the role of mud volcano driving force - overpressure fluid breaks through the clay isolation layer under the action of density difference, natural compaction and tectonic movement, driving the mud volcano eruption, and the decomposition of hydrate also provides part of the power for the eruption of mud volcanoes. Particle movement and redistribution of sediments - through particle size analysis and particle tracking technology, study how the interaction between fluid and sediment changes the sedimentary environment, how mud volcanoes affect the distribution of hydrate deposits, and the material source of the fluid that breaks into the surface of the mud volcano. Pore pressure changes - monitor the pore pressure of different layers and analyze the material exchange and fluid migration between the hydrate layer and the composite sand layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of a fluid preparation and supply module according to an embodiment of the present invention.

[0041] Figure 2 It is a schematic diagram of the structure of an experimental device for mud volcano / mud diapir activities in a submarine natural gas hydrate system according to an embodiment of the present invention.

[0042] Figure 3 It is a partial enlarged view of the push plate of an embodiment of the present invention.

[0043] Figure 4 It is a partial enlarged view of the movable plate of the embodiment of the present invention.

[0044] In the above figures: 1-1, plunger type high pressure cylinder; 1-2, simulated deep fluid preparation liquid inlet; 1-3, simulated deep fluid outlet; 1-4, vent; 1-5, deep fluid delivery coil; 1-6, stirring paddle; 1-7, high pressure cylinder core; 1-8, gas delivery coil; 1-9, high pressure cylinder base; 1-10, stirring paddle driver; 1-11, bottom simulated deep fluid preparation gas inlet; 1-12, liquid storage tank; 1-13, plunger push liquid inlet; 1-14, Boertier; 2, reactor body; 3, reactor upper end cover; 4, reactor lower end cover; 5, resistivity tomography measurement insulation plate; 6, temperature probe group; 7-1, upper gas diverter plate; 7-2, lower gas diverter plate; 7-3, gas diverter plate I; 7-4, gas diverter plate II; 8-1, upper gas chamber; 8- 2. Lower air chamber; 8-3. Air chamber Ⅰ; 8-4. Air chamber Ⅱ; 9-1. High-pressure gas inlet Ⅰ; 9-2. High-pressure gas inlet Ⅱ; 10. Simulated deep fluid injection hole; 11. Movable plate; 12-1. Hydraulic cylinder Ⅰ; 12-2. Hydraulic cylinder Ⅱ; 13. Push plate; 14-1. Liquid tank Ⅰ; 14-2. Liquid tank Ⅱ; 15. Water bath system; 16. Water bath cavity; 17. Insulation layer; 19. Hydraulic tank; 20. Hydraulic pump; 21-1. Methane gas cylinder Ⅰ; 21-2. Methane gas cylinder Ⅱ; 22-1. Gas flow controller Ⅰ; 22-2. Gas flow controller Ⅱ; 22-3 Proportional control valve; 23. Liquid storage tank; 24-1. Liquid flow controller Ⅰ; 24-2 Liquid flow controller Ⅱ; 24-3. Liquid flow controller Ⅲ; 25. Computer; 26. Data controller. DETAILED DESCRIPTION

[0045] To facilitate those skilled in the art to understand the present invention, specific implementations of the present invention are described below with reference to the accompanying drawings.

[0046] Embodiment 1

[0047] like Figures 1 to 4 As shown, the present invention discloses a device for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, including a fluid preparation and supply module, a mud volcano / mud diapir activity reactor module, a temperature control module, a hydraulic drive module, a gas supply module, a liquid supply module and a numerical control center module.

[0048] The fluid preparation and supply module is located at the bottom of the device, prepares the invading deep fluid, and is connected to the bottom injection hole of the mud volcano / mud diapir active reactor module through a transmission pipeline; the mud volcano / mud diapir active reactor module is located at the core of the device, simulates the temperature and pressure conditions of the overlying seabed strata and prepares natural gas hydrate reservoir samples; the temperature control module is wrapped around the reactor and maintains a constant temperature through a water bath system; the hydraulic drive module controls the lateral and longitudinal movement of the simulated strata in the reactor through hydraulic cylinders to simulate the tension and strike-slip movement of the strata; the gas supply module is connected to the top and bottom air chambers of the reactor to provide high-pressure methane gas to the system; the liquid supply module supplies liquid to the fluid preparation module and the reactor through a pipeline; the CNC center module is connected to each module to achieve precise control of experimental parameters and data recording.

[0049] The specific modules are introduced as follows:

[0050] 1. Fluid preparation and supply module

[0051] The fluid preparation and supply module is used to prepare deep fluid and transport it to the reactor, including a plunger-type high-pressure cylinder 1-1. The periphery of the plunger-type high-pressure cylinder 1-1 is equipped with a Poltier 1-14 for temperature control; the interior is provided with a deep fluid transport coil 1-5, a stirring paddle 1-6, a high-pressure cylinder inner core 1-7 and a gas transport coil 1-8. Among them, the deep fluid transport coil 1-5 extends from the top of the plunger-type high-pressure cylinder 1-1 to the upper part of the high-pressure cylinder inner core 1-7, and is connected to the deep fluid injection hole 10 at the bottom of the reactor; the gas transport coil 1-8 extends from the lower part of the high-pressure cylinder inner core 1-7 to the bottom of the plunger-type high-pressure cylinder 1-1 for gas transport; the stirring paddle 1-6 is installed at the top of the high-pressure cylinder inner core 1-7 for mixing fluids.

[0052] The top of the plunger-type high-pressure cylinder 1-1 is provided with three interfaces: a simulated deep fluid preparation liquid inlet 1-2, which is used to connect to the liquid supply module; a vent 1-4, which is used to discharge excess gas; and a simulated fluid outlet 1-3, which is connected to the reactor through a deep fluid delivery coil 1-5. A high-pressure cylinder base 1-9 is installed at the bottom of the plunger-type high-pressure cylinder 1-1, and a stirring paddle driver 1-10 is integrated on the base to drive the stirring paddle; a simulated deep fluid preparation gas inlet 1-11, which is connected to the high-pressure gas tank 20 through a gas delivery pipeline; and a plunger-driven liquid inlet 1-13, which is used to connect to a liquid storage tank 1-12 to provide prepared liquid.

[0053] The entire module supplies liquid to the simulated deep fluid preparation liquid inlet 1-2 through the liquid supply module. The pressure and temperature sensors are installed in the plunger high-pressure cylinder and communicate with the CNC center module through the data acquisition device 27 to record and monitor parameter changes in the fluid preparation process in real time.

[0054] 2. Mud volcano / mud diapir activity reactor module

[0055] The mud volcano / mud diapir activity reactor module is the core device for simulating mud volcano or mud diapir activity, and mainly includes a reactor body 2, a reactor upper end cover 3 and a reactor lower end cover 4. A simulated stratum is set inside the reactor body 2, and an insulating plate 5 for resistivity tomography measurement is installed on the inner wall to collect resistivity data inside the sediment; a group of temperature probes 6 are arranged at different heights inside the reactor body to monitor the temperature distribution. A push plate 13 is set on the left side of the reactor body 2, which is connected to the left side of the simulated stratum. The push plate is driven by a hydraulic cylinder II 12-2 to adjust the local pressure inside the stratum. Specifically, the initial position of the hydraulic cylinder 12-2 is an extended state. During the experiment, the hydraulic cylinder II 12-2 retracts and synchronously drives the push plate 13 to move to the left. A movable plate 11 is installed at the bottom of the left side of the reactor. The movable plate 11 is driven by the connected hydraulic cylinder I 12-1 to achieve longitudinal movement to form a dislocation of the simulated stratum. Specifically, the initial position of the hydraulic cylinder 12-2 is the retracted state. During the experiment, the hydraulic cylinder I12-1 is extended, and the movable plate 11 is synchronously driven to move upward. A plurality of gas diverter plates are installed inside the reactor body 2, wherein the gas diverter plates 7-1 and 7-2 are located between the upper and lower air chambers 8-1 and 8-2 of the reactor, and are used to adjust the uniform distribution of gas. Two gas diverter plates I7-3 and II7-4 are arranged inside the right side of the reactor, which are respectively connected to the air chamber I8-3 and the air chamber II8-4 on the right side, and are used to further distribute and adjust the flow path of the gas. Two liquid tanks I14-1 and II14-2 are also arranged on the right side, which are connected to the liquid supply module to provide the required liquid for the experiment. The upper end cover 3 of the reactor is provided with a high-pressure gas inlet I9-1, which is connected to the upper air chamber 8-1; the lower end cover 4 is provided with a high-pressure gas inlet II9-2, which is connected to the lower air chamber 8-2. The bottom of the reactor body 2 is designed with a deep fluid injection hole 10, which is connected to the fluid preparation and supply module through a through hole that penetrates the lower end cover of the reactor and the lower gas diverter plate 7-2, and the high pressure stability of the system is ensured by a sealing structure. The entire reactor module is directly connected to the gas supply module, the fluid preparation and supply module, and the liquid supply module, and the temperature, pressure, and resistivity data are monitored and recorded in real time during the experiment through the CNC center module.

[0056] Furthermore, a layer of elastic plate is fixed to the end surface of the push plate 13 that abuts against the simulated stratum. The push plate 13 equipped with the elastic plate can ensure that the horizontal displacement of the stratum, that is, the lateral displacement, will not be too large, making the simulation closer to reality.

[0057] 3. Temperature control module

[0058] The temperature control module includes a water bath system 15 connected to a water bath chamber 16 through a pipe to form a closed water circulation system for maintaining a constant temperature in the water bath chamber. An efficient circulating water pump and a multi-point temperature probe are added to the water bath chamber 16 to improve the uniformity of temperature distribution. The water bath chamber 16 is wrapped around the periphery of the reactor body 2 to provide it with a uniform temperature control environment and limit the temperature change to the range required by the experiment through heat transfer. The periphery of the water bath chamber 16 is covered with an insulation layer 17 to reduce heat loss. The insulation layer material uses a composite material with a lower thermal conductivity to reduce heat loss and ensure the efficiency and stability of temperature control. The entire system realizes real-time monitoring and adjustment of temperature through connection with the CNC center module.

[0059] 4. Hydraulic drive module

[0060] The hydraulic drive module includes a hydraulic tank 19 and a hydraulic pump 20 connected to the hydraulic cylinder Ⅰ12-1 and the hydraulic cylinder Ⅱ12-2. A proportional control valve 22-3 is installed between the hydraulic pump 20 and the hydraulic cylinder Ⅰ12-1 and the hydraulic cylinder Ⅱ12-2. The hydraulic oil flow is accurately controlled by an electrical signal to achieve precise adjustment of the formation movement rate. In addition, the hydraulic system's ability to accurately control the formation movement rate can be further improved by optimizing the response speed and control algorithm of the proportional control valve, so that the hydraulic drive module can simulate the geological structure movement process more realistically, providing reliable guarantee for studying the influence of the diapir fluid on the formation mechanics. The initial state of the hydraulic cylinder Ⅰ12-1 is set to the retracted state, that is, the piston rod is located in the cylinder body, and the initial state of the hydraulic cylinder Ⅱ12-2 is set to the extended state, that is, the piston rod is extended out of the cylinder body.

[0061] The device of the present invention can realize controllable stratum movement simulation. Through the cooperation of the hydraulic drive module and the reactor module, it can fully simulate tectonic movements such as tension and strike-slip of the stratum. Its controllability and diversity enable the device to truly reproduce the dynamic interaction between mud volcano activity and hydrate system under different tectonic stress environments.

[0062] The tensioning movement can be achieved in the following way: the hydraulic cylinder II 12-2 retracts and pushes the push plate 13 to move leftward, so that the simulated stratum stretches.

[0063] The strike-slip movement can be achieved in the following ways: adjust the movement direction and speed of the hydraulic cylinder Ⅰ12-1 to make the movable plate move longitudinally so that the simulated stratum located above the movable plate is displaced with other simulated strata, simulating the sliding of the strike-slip fault.

[0064] In order to simulate more complex tectonic movements in actual strata, such as the combined effects of tension and strike-slip, the device can: set up multiple stages of movement in the same experiment, such as horizontal tension first, then switch to strike-slip movement. Combined with deep fluid injection, observe the triggering effect of different tectonic movements on the mud volcano eruption mechanism.

[0065] 5. Gas supply module

[0066] The high-pressure methane gas cylinder Ⅰ21-1, high-pressure methane gas cylinder Ⅱ21-2 and gas flow controller Ⅰ22-1, gas flow controller Ⅱ22-2 of the gas supply module are connected to the high-pressure gas inlet Ⅱ9-2, high-pressure gas inlet 9-1, simulated deep fluid injection hole 10, gas chamber Ⅰ8-3, gas chamber Ⅱ8-4.

[0067] 6. Liquid supply module

[0068] The liquid supply module includes a liquid storage tank 23 and liquid flow controllers Ⅰ24-1, Ⅱ24-2 and Ⅲ24-3 which are connected to liquid tanks Ⅰ14-1 and Ⅱ14-2.

[0069] 7. CNC center module

[0070] The CNC center module includes a computer 25, a data controller 26, and a data collector 27. The data controller 26 is mainly used to control the injection velocity and flow rate of the gas, the flow rate of the hydraulic pump, the injection velocity and flow rate of the liquid, and the tracking of the effective stress of the overlying formation; the data collector 27 is mainly used to collect resistivity tomography data, temperature data, and pressure data; the data of the data collector 27 and the data controller 26 are finally summarized in the computer 26.

[0071] Embodiment 2

[0072] The present invention discloses a method for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, comprising the following steps:

[0073] Step 1: Initial simulation of the overlying seafloor strata preparation, including:

[0074] Step 11, install the device, compact the sediments in layers and fill them into the reactor body to form a simulated stratum. The specific stratum layout is as follows: At the beginning of the experiment, first lay loose sand or soft sediment as the bottom layer at the bottom of the reactor. This layer has high porosity and permeability, which is convenient for simulating the breakthrough of deep fluids. Next, construct a composite sand layer, add mineral particles of different densities such as quartz, heavy minerals and clay particles to reflect the density distribution gradient of the sediments, and add particle tracking markers such as fluorescent marker particles or magnetic particles to the sediments. Then, design a low-permeability clay isolation layer between the composite sand layer and the hydrate layer, forcing the fluid to accumulate pressure during the ascent, thereby exacerbating the effects of buoyancy and density differences and enhancing the driving force of the eruption. This can help study the buoyancy effect and material exchange mechanism caused by density differences during the intrusion of mud volcanoes, and at the same time increase the driving force for the upward movement of deep fluids, further helping the fluids to break through to the surface. Finally, a sand layer is laid on the top to simulate the seabed surface sediments. After the formation is set, brine is injected into the reactor through liquid tanks 14-1 and 14-2 to simulate the mineral dehydration reaction and fluid circulation in the system. This arrangement provides a stable environment similar to the actual seabed, which is helpful to study the mechanism of fluid breaking through the overlying sediment layer and the impact on the stability of the surface sediments.

[0075] Step 12, using a water bath system to cool down the reactor. This precise temperature control method can effectively simulate the low temperature conditions on the seabed, while reducing the interference of external heat on the experimental results, creating an ideal environment for the synthesis of natural gas hydrates. Then, high-pressure methane gas is injected into the upper gas chamber 8-1, the lower gas chamber 8-2, the gas chamber I 8-3, and the gas chamber II 8-4. The methane gas evenly penetrates the upper gas diverter plate 7-1, the lower gas diverter plate 7-2, the gas diverter plate I 7-3, and the gas diverter plate II 7-4 to synthesize natural gas hydrates in the sediments. This design can ensure that the distribution of methane gas in the sediments is more uniform, thereby avoiding non-uniform reactions caused by local pressure or excessive concentration, and ensuring the stability of the natural gas hydrate synthesis process and the repeatability of the experimental results. During the experiment, the temperature changes inside the sediments during the hydrate synthesis process are tested in real time, and the hydrate distribution law inside the sediments is obtained in real time to complete the initial simulation of the preparation of the overlying seabed strata.

[0076] Step 13. Before the experiment officially begins, a comprehensive inspection should be carried out on all components of the hydraulic system, such as hydraulic cylinders, hydraulic tanks, hydraulic pumps and proportional control valves, to ensure that they operate normally and without leakage. Subsequently, the hydraulic cylinders Ⅰ12-1 and Ⅱ12-2 in the hydraulic drive module are used to perform a trial run to simulate the movement of the strata, and the relevant parameters, such as displacement and speed, are calibrated according to the feedback data. By calibrating the parameters, the initial deviation that may exist in the hydraulic system is eliminated to improve the consistency and reliability of the experimental results. Then, the movement of the left strata is controlled by the hydraulic device hydraulic cylinders Ⅰ12-1 and Ⅱ12-2, and reasonable initial displacement parameters are set. According to the experimental requirements, the rate curve of the strata movement can be set before the experiment, including the initial acceleration, constant speed movement and deceleration stages, to ensure the continuity and stability of the strata movement, so as to simulate the tensile structural movement of the strata. The hydraulic system will gradually apply horizontal stress to push the slow displacement of the strata, thereby simulating the extension effect in the geological structure, and ensuring that the strata structure and experimental conditions during the movement meet the expected requirements.

[0077] Step 2: Preparation of simulated deep fluid, including:

[0078] Step 21, the density difference between the simulated muddy sediment and the low-density deep fluid mixture and the simulated formation can help the deep fluid break through to the surface; then load it into the plunger-type high-pressure cylinder 1-1, inject brine into the plunger-type high-pressure cylinder 1-1, start the stirring paddle 1-6 to stir, and fully mix the brine and muddy sediment.

[0079] Step 22, high-pressure but low-density methane gas is then injected into the plunger-type high-pressure cylinder 1-1, and stirred at the same time, and the mixture inside the plunger-type high-pressure cylinder 1-1 is heated. By continuous stirring, the methane gas is ensured to be fully dissolved and evenly distributed in the mixture. The heating process raises the temperature of the mixture to a preset value to simulate the high-temperature environment deep in the formation. After the internal fluid is saturated with methane and the fluid temperature reaches a preset temperature value, the obtained mixture is pushed into the reactor 2.

[0080] Step 3: Mud volcano / mud diapir activity simulation, including:

[0081] Step 31, adjust the fluid outlet pressure to be equal to the simulated overlying seafloor pore pressure, and then connect the fluid preparation and supply module and the mud volcano / mud diapir activity reactor module.

[0082] Step 32, inject distilled water into the lower part of the plunger-type high-pressure cylinder 1-1 at a constant rate to drive the inner core of the high-pressure cylinder to move upward, simulating the deep fluid being pressed into the reactor at a constant rate. This operation method can ensure the stability of the deep fluid injection rate and reproduce the dynamic process of real formation fluid migration.

[0083] Step 33, synchronously record the temperature data, displacement sensor data, resistivity tomography data and pore pressure data of the internal space of the sediment during the invasion simulation process; collect sediment samples after fluid invasion, study the changes in the particle distribution of the sediment through particle size analysis technology, and evaluate the displacement and re-deposition of particles during the fluid invasion process.

[0084] Step 34: When the deep simulated fluid injection volume reaches a preset value, the invasion simulation is stopped.

[0085] In order to make the experimental device and method of the present invention closer to the real mud volcano eruption conditions, different from the prior art, the present invention takes into account the driving factors of mud volcano eruption and reveals the driving factors of mud volcano eruption, which specifically include three major driving mechanisms:

[0086] First, material exchange caused by density difference: By optimizing the density gradient arrangement of the composite sand layer and the hydrate layer, the buoyancy effect and material exchange mechanism caused by density difference during the intrusion of deep fluid are simulated. The device uses a high-pressure fluid preparation module to inject a low-density methane gas and deep fluid mixture into the bottom of the reactor, and combines the distribution of mineral particles of different densities in the composite sand layer to study the particle movement, redistribution and material exchange laws of the sedimentary environment. Through real-time resistivity tomography and particle tracking technology, the influence of density difference on the driving force of mud volcano eruption and sediment stability is quantitatively analyzed, providing an experimental basis for the buoyancy driving mechanism of mud volcano activity.

[0087] Second, deep overpressure drive: using the high-pressure gas supply module to reproduce the overpressure caused by methane accumulation in deep formations.

[0088] Third, mineral dehydration reaction caused by natural compaction: a clay isolation layer needs to be embedded between the two layers to reduce the permeability between the layers, thereby simulating the natural compaction effect of the overlying strata on the lower strata. Furthermore, a high-pressure methane gas tank is connected to the bottom of the lower strata to simulate the overpressure phenomenon caused by geological compaction.

[0089] The above-described embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A device for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, characterized in that: It includes a fluid preparation and supply module, a mud volcano / mud diapir activity reactor, a temperature control module, a hydraulic drive module, a gas supply module, a liquid supply module and a CNC center module; the fluid preparation and supply module is located at the bottom of the experimental device, and is used to prepare the deep fluid for intrusion, and is connected to the mud volcano / mud diapir activity reactor through a transmission pipeline; the mud volcano / mud diapir activity reactor is located at the upper part of the fluid preparation and supply module, and is used to simulate the temperature and pressure conditions of the overlying submarine strata, simulate the mud volcano / mud diapir activity and prepare natural gas hydrate reservoir samples, and a simulated stratum is set inside; the temperature control module is wrapped around the outer periphery of the mud volcano / mud diapir activity reactor, and is used to provide temperature control for simulating the temperature and pressure conditions of the submarine strata , keeping the temperature of the mud volcano / mud diapir active reactor constant; the hydraulic drive module controls the lateral and longitudinal movement of the simulated strata in the mud volcano / mud diapir active reactor by driving the hydraulic cylinder set in the reactor to simulate the tension and strike-slip movement of the strata; the gas supply module is connected to the gas chamber of the mud volcano / mud diapir active reactor to provide high-pressure methane gas for the experimental device; the liquid supply module supplies liquid to the fluid preparation and supply module and the mud volcano / mud diapir active reactor through a pipeline; the CNC center module is respectively connected to the fluid preparation and supply module, the mud volcano / mud diapir active reactor, the temperature control module, the hydraulic drive module, the gas supply module, and the liquid supply module to realize experimental parameter control and data recording.

2. The device according to claim 1, characterized in that The mud volcano / mud diapir activity reactor comprises a reactor body (2), an upper end cover (3) and a lower end cover (4); the inner wall of the reactor body (2) is provided with a resistivity tomography measurement insulating plate (5) for collecting resistivity data inside the sediment; a plurality of temperature probe groups (6) are arranged at different heights inside the reactor body (2) for monitoring temperature distribution; a push plate (13) is provided on the left side of the reactor body (2), and the push plate (13) is in contact with the left side of the simulated formation. The push plate (13) is abutted against each other, and is driven by the connected hydraulic cylinder II (12-2) to realize lateral movement of the simulated formation, so as to adjust the local pressure inside the formation; a movable plate (11) is arranged on the left side of the bottom of the reactor body (2), and the movable plate (11) is driven by the connected hydraulic cylinder I (12-1) to realize longitudinal movement, so as to form the displacement of the simulated formation; a plurality of gas diverter plates are installed inside the reactor body (2), wherein the upper gas diverter plate (7-1) and the lower gas diverter plate (7- 2) is located between the upper gas chamber (8-1) and the lower gas chamber (8-2) of the reactor, and is used to adjust the uniform distribution of gas. Two gas distribution plates I (7-3) and gas distribution plates II (7-4) are arranged inside the right side of the reactor, which are respectively connected to the gas chamber I (8-3) and the gas chamber II (8-4) on the right side of the reactor, and are used to further distribute and adjust the flow path of the gas. The right side of the reactor is also provided with a liquid tank I (14-1) and a liquid tank II (14-2), which are connected to the liquid supply module for the experiment. The required liquid is provided; the upper end cover (3) of the reactor is provided with a high-pressure gas inlet I (9-1) connected to the upper gas chamber (8-1); the lower end cover (4) of the reactor is provided with a high-pressure gas inlet II (9-2) connected to the lower gas chamber (8-2); the bottom of the reactor body (2) is designed with a deep fluid injection hole (10), which is connected to the fluid preparation and supply module through a through hole penetrating the lower end cover (4) of the reactor and the lower gas diverter plate (7-2), and the high-pressure stability of the experimental device is ensured by a sealing structure.

3. The device according to claim 1, characterized in that The fluid preparation and supply module is used to prepare deep fluid and transport it to the reactor, and comprises a plunger-type high-pressure cylinder (1-1); the periphery of the plunger-type high-pressure cylinder (1-1) is equipped with a Poltier (1-14) for temperature control; the interior of the plunger-type high-pressure cylinder (1-1) is provided with a deep fluid transport coil (1-5), a stirring paddle (1-6), a high-pressure cylinder inner core (1-7) and a gas transport coil (1-8); wherein the deep fluid transport coil (1-5) extends from the top of the plunger-type high-pressure cylinder (1-1) to the upper part of the high-pressure cylinder inner core (1-7), and is connected to the deep fluid injection hole (10) at the bottom of the reactor; the gas transport coil (1-8) extends from the lower part of the high-pressure cylinder inner core (1-7) to the bottom of the plunger-type high-pressure cylinder (1-1) for transporting gas; the stirring paddle (1-6) is installed at the top of the high-pressure cylinder inner core (1-7) for mixing fluid; The top of the plunger-type high-pressure cylinder (1-1) is provided with a simulated deep fluid preparation liquid inlet (1-2), a venting port (1-4) and a simulated fluid outlet (1-3); the simulated deep fluid preparation liquid inlet (1-2) is used to be connected to a liquid supply module; the venting port (1-4) is used to discharge excess gas; the simulated fluid outlet (1-3) is connected to the reactor via a deep fluid delivery coil (1-5); A high-pressure cylinder base (1-9) is installed at the bottom of the plunger-type high-pressure cylinder (1-1), and a stirring paddle driver (1-10), a simulated deep fluid preparation gas inlet (1-11), and a plunger-driven liquid inlet (1-13) are integrated on the high-pressure cylinder base (1-9); the stirring paddle driver (1-10) is used to drive the stirring paddle (1-6); the simulated deep fluid preparation gas inlet (1-11) is connected to a high-pressure gas tank (20) through a gas delivery pipeline; the plunger-driven liquid inlet (1-13) is used to be connected to a liquid storage tank (1-12) to provide prepared liquid; and a pressure and temperature sensor and a displacement sensor are installed in the plunger-type high-pressure cylinder.

4. The device according to claim 1, characterized in that The temperature control module comprises a water bath system (15) and a water bath chamber (16); the water bath system (15) is connected to the water bath chamber (16) through a pipeline to form a closed water circulation system for maintaining a constant temperature in the water bath chamber; a circulating water pump and a multi-point temperature probe are arranged in the water bath chamber (16) to improve the uniformity of temperature distribution; the water bath chamber (16) is wrapped around the periphery of the reactor body (2) to provide a uniform temperature control environment for it and limit the temperature change within the range required by the experiment through heat transfer; the periphery of the water bath chamber (16) is covered with a thermal insulation layer (17) to reduce heat loss.

5. The device according to claim 1, characterized in that The hydraulic drive module comprises a hydraulic tank (19) and a hydraulic pump (20) connected to hydraulic cylinder I (12-1) and hydraulic cylinder II (12-2); a proportional control valve (22-3) is installed between the hydraulic pump (20) and hydraulic cylinder I (12-1) and hydraulic cylinder II (12-2); and an elastic plate is also fixed to the end surface of the push plate (13) that abuts against the simulated formation.

6. The device according to claim 2, characterized in that The methane gas cylinder I (21-1), the methane gas cylinder II (21-2) and the gas flow controller I (22-1), the gas flow controller II (22-2) of the gas supply module are connected to the gas inlet II (9-2), the gas inlet I (9-1), the simulated deep fluid injection hole (10), the gas chamber I (8-3), and the gas chamber II (8-4); The liquid storage tank (23) and the liquid flow controller I (24-1), the liquid flow controller II (24-2), and the liquid flow controller III (24-3) of the liquid supply module are connected to the liquid tank I (14-1) and the liquid tank II (14-2); The numerical control center module comprises a computer (25), a data controller (26) and a data acquisition device (27); the data controller (26) is mainly used to control the injection velocity and flow rate of the gas, the flow rate of the hydraulic pump, the injection velocity and flow rate of the liquid, and the tracking of the effective stress of the overlying stratum; the data acquisition device (27) is mainly used to collect resistivity tomography data, temperature data and pressure data; The data from the data collector (27) and the data controller (26) are finally collected by the computer (25).

7. A method for simulating mud volcano / mud diapir activity in a submarine natural gas hydrate system, applicable to the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Initial simulation of overlying seafloor formation preparation, including: The experimental device is installed, and the sediment is compacted and filled into the reactor body in layers to form a simulated stratum. The liquid supply module injects brine into the reactor through the liquid tank I (14-1) and the liquid tank II (14-2) to simulate the mineral dehydration reaction and the fluid circulation in the system; The temperature control module uses a water bath system to cool the reactor and injects high-pressure methane gas into the reactor to synthesize natural gas hydrates in the sediments. It tests the temperature changes inside the sediments during the hydrate synthesis process and obtains the hydrate distribution pattern inside the sediments in real time to complete the initial simulation of the overlying seabed formation preparation. S2: Preparation of simulated deep fluid, the steps include: S21: The deep fluid mixture formed by the muddy sediment used for simulation has a density lower than that of the sediment of the simulated formation in step S1; the deep fluid mixture is loaded into the plunger type high pressure cylinder (1-1), and salt water is injected into the plunger type high pressure cylinder (1-1), and the stirring paddle (1-6) is started to stir, so that the salt water and the muddy sediment are fully mixed; S22: injecting high-pressure but low-density methane gas into the plunger-type high-pressure cylinder (1-1), stirring it at the same time, and heating the mixture inside the plunger-type high-pressure cylinder (1-1). By continuously stirring, it is ensured that the methane gas is fully dissolved and evenly distributed in the mixture. The heating process raises the temperature of the mixture to a preset value to simulate the high-temperature environment deep in the formation. After the internal fluid is saturated with methane and the fluid temperature reaches a preset temperature value, the obtained mixture is pushed into the reactor body (2); S3: Mud volcano / mud diapir activity simulation, steps include: S31: adjusting the fluid outlet pressure to be equal to the simulated overlying seafloor pore pressure, and then connecting the fluid preparation and supply module and the mud volcano / mud diapir activity reactor module; S32: injecting distilled water into the lower part of the plunger-type high-pressure cylinder (1-1) at a constant rate, driving the inner core of the high-pressure cylinder to move upward, simulating deep fluid to be pressed into the reactor at a constant rate; S33: Synchronously record the temperature data, displacement sensor data, resistivity tomography data and pore pressure data of the sediment internal space during the invasion simulation process; collect sediment samples after fluid invasion, study the changes in sediment particle distribution through particle size analysis technology, and evaluate the displacement and re-deposition of particles during fluid invasion; S34: When the deep simulated fluid injection volume reaches a preset value, the invasion simulation is stopped.

8. The method according to claim 7, characterized in that Step S1 also includes: The sediments were compacted and filled into the reactor body in layers, and the specific stratigraphic arrangement was as follows: at the beginning of the experiment, loose sand or soft sediment was first laid on the bottom of the reactor as the bottom layer; then, a composite sand layer was constructed, and mineral particles of different densities were added to reflect the density distribution gradient of the sediments, and particle tracking markers were added to the sediments; then, a low-permeability clay isolation layer was designed between the composite sand layer and the hydrate layer, forcing the fluid to accumulate pressure during the ascent, thereby intensifying the effects of buoyancy and density differences and enhancing the driving force for eruption; finally, a sand layer was laid on the topmost layer.

9. The method according to claim 7, characterized in that: Step S1 also includes: The temperature in the reactor is lowered using the water bath system of the temperature control module; high-pressure methane gas is then injected into the upper gas chamber (8-1), the lower gas chamber (8-2), the gas chamber I (8-3), and the gas chamber II (8-4), and the methane gas evenly penetrates the upper gas diverter plate (7-1), the lower gas diverter plate (7-2), the gas diverter plate I (7-3), and the gas diverter plate II (7-4) to synthesize natural gas hydrates in the sediments; during the experiment, the temperature changes inside the sediments during the hydrate synthesis process are tested in real time, and the hydrate distribution law inside the sediments is obtained in real time to complete the initial simulation of the overlying seabed strata preparation.

10. The method according to claim 7, characterized in that Step S1 also includes: Before the experiment officially begins, all components of the hydraulic system should be thoroughly checked to ensure their normal operation and no leakage. Subsequently, a trial run is performed through the hydraulic cylinder I (12-1) and hydraulic cylinder II (12-2) of the hydraulic drive module to simulate the movement of the strata, and relevant parameters are calibrated according to the feedback data. By calibrating the parameters, the possible initial deviation of the hydraulic system is eliminated to improve the consistency and reliability of the experimental results. Then, the movement of the left strata is controlled by hydraulic cylinders I (12-1) and hydraulic cylinders II (12-2), and reasonable initial displacement parameters are set to simulate the tensile tectonic movement of the strata. The hydraulic system will gradually apply horizontal stress to promote the slow displacement of the strata, thereby simulating the extension effect in the geological structure and ensuring that the stratum structure and experimental conditions during the movement meet the expected requirements.

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