A method for simulating formation landslides caused by the decomposition of natural gas hydrates

Abstract

The present invention discloses a method for simulating the formation collapse caused by the decomposition of natural gas hydrates, comprising: laying a porous medium to form a formation body; pre-burying acceleration sensors, stress sensors and displacement sensors, connecting a gas cylinder and a vacuum interface, and connecting the gas release and pressure regulation port to a solenoid valve; placing the kettle body in a test chamber with adjustable temperature; a camera facing the window on the kettle body so as to be able to photograph the inner cavity of the kettle body; after the air is pumped out to form a vacuum, injecting a mixed gas, standing for a period of time, waiting for the formation of hydrates, measuring the temperature and gas pressure in the inner cavity in real time, and taking videos for recording. After the gas pressure in the inner cavity remains stable for a certain period of time, it is determined that the synthesis of natural gas hydrates is completed; adjusting the kettle body to a certain inclination angle; adjusting the gas pressure to simulate the process of depressurization exploitation; and analyzing the measured data to generate the critical exploitation conditions for the formation collapse.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrate experimental simulation devices, and specifically to a method for simulating formation collapse caused by the decomposition of natural gas hydrates. Background Art

[0002] Natural gas hydrate (referred to simply as hydrate) is a natural resource distributed in deep-sea sediments or permafrost on land. It is an ice-like crystalline substance formed by natural gas (mainly methane, ethane, propane, carbon dioxide, etc.) and water under low-temperature and high-pressure conditions. Natural gas hydrate is a huge reserve and clean unconventional energy resource, and it is also one of China's strategic resources. Extracting natural gas hydrate to obtain its resources has a huge promoting effect on social development. However, during the extraction of hydrates, it is inevitable that the decomposition of hydrates will change the current situation of the formation. Serious consequences include formation collapse and submarine landslides, and even more seriously, natural disasters such as earthquakes and tsunamis may be caused. Therefore, how to find the critical conditions for formation collapse caused by the decomposition of hydrates has important guiding significance for the safe extraction of hydrates.

[0003] At present, there is a serious lack of basic data on the changes in formation characteristics caused by the occurrence of hydrates in sediments, decomposition seepage characteristics, and mechanical properties. The research on the mutual influence between hydrate properties and sediment formation environment is still not deep enough, which greatly restricts the research progress of hydrate exploration and extraction. For example, the Chinese invention application with the publication number CN105840161A discloses an experimental device and working method for electrically heated assisted pressure reduction extraction of natural gas hydrates, which mainly includes a natural gas hydrate generation system, an electric heating system, a gas-liquid separation system, and a control and metering system. Using the device and method of this invention, the process of electrically heated assisted pressure reduction extraction of natural gas hydrates can be simulated, and the extraction effect can be evaluated. The main contents of the evaluation are the evolution of parameters such as extraction rate, extraction efficiency, and gas mass flow rate under different extraction parameters. For the pressure reduction extraction and heating extraction of natural gas hydrates, which are publicly recognized extraction methods, this invention is only an experimental device for carrying out the decomposition experiment of hydrates, and it cannot well simulate the change of formation stability caused by the decomposition of hydrates. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for simulating formation collapse caused by the decomposition of natural gas hydrates, which can solve the problems of formation collapse and submarine landslides during the simulation of hydrate extraction process.

[0005] The technical solution for achieving the purpose of the present invention is: A method for simulating formation collapse caused by the decomposition of natural gas hydrates, comprising the following steps:

[0006] Step 1: laying porous media into the inner cavity of the kettle body to form a stratum body with a certain thickness, adding a certain amount of water between the laid porous media, and setting the same parameters of porosity, permeability and particle adhesion as those in the real environment;

[0007] Step 2: pre-embed the acceleration sensor, stress sensor and displacement sensor in the porous medium, then close the kettle cover of the kettle body, connect the gas cylinder to the air inlet pipe fixed on the kettle body, connect the vacuum interface to the vacuum pump, connect the deflation pressure regulating port to the solenoid valve, and the solenoid valve is used to adjust the opening and closing size of the deflation pressure regulating port to adjust the pressure in the inner cavity by adjusting the deflation volume and deflation speed;

[0008] Step 3: Place the kettle in a temperature-adjustable test chamber so that the air bath can control the temperature of the entire experimental device as a whole, and the ambient temperature in the test chamber is adapted to the temperature required for hydrate formation;

[0009] Step 4: Align the camera with the window on the kettle body so that the camera can capture the inner cavity of the kettle body;

[0010] Step 5: The air in the inner cavity of the kettle is extracted by a vacuum pump to form a vacuum. After the gas cylinder is connected to the air inlet pipe, the gas used to form hydrates is input into the inner cavity.

[0011] The reactor is left to stand for a period of time to wait for the formation of hydrates. During the hydrate formation process, the temperature and gas pressure of the inner cavity are measured in real time by the temperature sensor and pressure sensor pre-installed in the inner cavity of the reactor body, and the camera shoots the hydrate formation process and forms a video record.

[0012] After the gas pressure in the inner cavity remains stable for a certain period of time (generally no more than 24 hours), it is determined that the natural gas hydrate synthesis is completed;

[0013] Step 6: Adjust the kettle body, which is currently placed flat, to a certain tilt angle;

[0014] Step 7: By presetting the pressure reduction amplitude, pressure reduction rate and single-stage or multi-stage pressure reduction, the gas pressure in the inner cavity is controlled by regulating the solenoid valve to complete the simulation of the pressure reduction and extraction process of natural gas hydrate;

[0015] Step 8: Use a camera to record the movement trajectory of the formation body in the inner cavity, and use the acceleration sensor, stress sensor and unique sensor to record the acceleration, stress and displacement data when the formation body slides. Analyze the mechanism of formation collapse during hydrate decomposition, and analyze the critical mining conditions that cause formation collapse by combining the pressure correlation of depressurization mining.

[0016] Further, in step 7, it also includes heating by an electric heating rod, and simulating the depressurization production of hydrates at different temperatures and / or different pressures through a segmented or continuous heating mode, so as to simulate the experimental conditions of different natural gas hydrate thermal injection production.

[0017] Further, the porous medium used is quartz sand particles or marine soil samples.

[0018] Further, the porous medium is laid flat on the inner wall surface of the inner cavity, and the surface of the formation body formed by the porous medium is not flat or uneven.

[0019] Further, based on the on-site sampling of marine natural gas hydrate marine mud samples, indoor geotechnical experiments, and three-dimensional scanning analysis method, the composition of the original structural plane and the surface topography of the structural plane are analyzed. After measuring the physical property parameters such as the porosity, permeability, and particle bonding force of the real hydrate, according to the physical property parameters, a certain amount of water is added between the laid porous media, as well as parameters of porosity, permeability, and particle bonding force that are roughly the same as the real environment.

[0020] Further, the camera is installed on the bracket, and the height and shooting angle of the camera are adjusted so that the camera is directly facing the window on the kettle body.

[0021] Further, the gas components are one or more combinations of methane, ethane, propane, and carbon dioxide.

[0022] Further, in step 6, a certain inclination angle is adjusted through the stepless rotating shaft. The kettle body is installed on the base bracket through the stepless rotating shaft, and the base bracket is installed in the test chamber, so as to place the kettle body in the test chamber for air bath.

[0023] Wherein, after the kettle body is adjusted to a certain inclination angle, it is fixed at the current inclination angle through the tightening member on the stepless rotating shaft.

[0024] The beneficial effects of the present invention are as follows: The present invention creates an experimental space that is convenient for observation and simulation experiments, can simulate the production process of natural gas hydrates under different formation dip angles, production conditions, and reservoir conditions, and finally uses sensors to specifically study the mechanism of formation collapse during the decomposition of natural gas hydrates from aspects such as stress, acceleration, displacement, and pressure. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of an experimental device for simulating the formation collapse caused by the decomposition of natural gas hydrates;

[0026] Figure 2 It is a schematic structural diagram of an experimental device for simulating the formation collapse caused by the decomposition of natural gas hydrates under another visual angle;

[0027] Figure 3 Schematic diagram of the process of the present invention;

[0028] In the figure, 1 - kettle body, 2 - viewing window, 3 - camera, 4 - control terminal, 5 - signal transmission line, 6 - temperature acquisition module, 7 - pressure acquisition module, 8 - gas cylinder, 9 - vacuum pump, 10 - base bracket, 11 - infinitely variable rotating shaft, 12 - bracket, 13 - intake pipe, 14 - vacuum interface, 15 - inclination sensor, 16 - temperature sensor, 17 - pressure sensor, 18 - gas release and pressure regulation port, 19 - acceleration sensor, 20 - stress sensor, 21 - displacement sensor, 22 - electric heating rod, 23 - porous medium. Specific embodiments

[0029] The following further describes the present invention in conjunction with the accompanying drawings and specific implementation schemes:

[0030] As Figures 1-3 shown, a method for simulating the formation collapse caused by the decomposition of natural gas hydrates is applied to an experimental device for simulating the formation collapse caused by the decomposition of natural gas hydrates. The device includes a kettle body 1, a camera 3, a control terminal 4, a temperature acquisition module 6, a pressure acquisition module 7, a gas cylinder 8, a vacuum pump 9, a base bracket 10, an infinitely variable rotating shaft 11, a bracket 12, an intake pipe 13, a vacuum interface 14, an inclination sensor 15, a temperature sensor 16, a pressure sensor 17, a gas release and pressure regulation port 18, an acceleration sensor 19, a stress sensor 20, a displacement sensor 21, an electric heating rod 22, and a porous medium 23. The gas cylinder 8 is located outside the kettle body 1. The gas cylinder 8 is connected to the intake pipe 13 fixed on the kettle body 1 through a connecting pipe (such as a plastic pipe), and the intake pipe 13 is communicated with the inner cavity of the kettle body 1. The gas cylinder 8 is used to store gases such as methane, ethane, propane, carbon dioxide, or a mixed gas prepared in a certain proportion, and this gas is the gas source required for forming hydrates. That is, the components of the gas can be one or a combination of methane, ethane, propane, and carbon dioxide. The vacuum pump 9 is connected to the vacuum interface 14 fixed on the kettle body 1 through another connecting pipe, and the vacuum interface 14 is communicated with the inner cavity of the kettle body 1. The vacuum pump 9 is used to pump out the gas in the inner cavity of the kettle body 1 to form a vacuum environment (close to or completely vacuum), and also enables the residual gas to be discharged after the experiment.

[0031] The control terminal 4 is connected to the temperature acquisition module 6 and the pressure acquisition module 7 respectively through two signal transmission lines 5 to upload the temperature data collected by the temperature acquisition module 6 and the pressure data collected by the pressure acquisition module 7 to the control terminal 4. The control terminal 4, the temperature acquisition module 6, and the pressure acquisition module 7 are all located outside the kettle body 1 to avoid affecting the decomposition of hydrates in the kettle body 1.

[0032] The temperature acquisition module 6 is electrically connected to the temperature sensor 16 located in the inner cavity of the kettle body 1, and the pressure acquisition module 7 is electrically connected to the pressure sensor 17 located in the inner cavity of the kettle body 1. The temperature sensor 16 and the pressure sensor 17 are both fixed on the upper inner wall of the kettle body 1 so as to be spaced from the formation body located on the bottom wall of the inner cavity to avoid affecting the sliding of the simulated formation body.

[0033] The kettle body 1 is movably mounted on the base bracket 10 through the stepless rotating shaft 11, and the stepless rotating shaft 11 is located in the middle of the lower end of the kettle body 1. The kettle body 1 can rotate on the base bracket 10 through the stepless rotating shaft 11, so as to adjust the inclination angle between the kettle body 1 and the horizontal plane (i.e., the ground where the base bracket 10 is located). In addition, a locking piece is installed on the stepless rotating shaft 11, so that after the kettle body 1 is rotated to the current inclination angle, the kettle body 1 can be locked at the current inclination angle through the locking piece; when the inclination angle needs to be changed, it is only necessary to apply external force to the kettle body 1 again and then lock it again through the locking piece, so that the kettle body 1 can stay at any inclination angle. Among them, the kettle body 1 is made of 304 or 316 stainless steel, so as to be able to provide a maximum pressure bearing capacity of not less than 20MPa, so as to meet the pressure conditions of hydrate synthesis.

[0034] A window 2 is provided on one side of the kettle body 1. The window 2 is embedded in the kettle body 1. The window 2 can be formed by embedding glass or other transparent materials in the through hole of the kettle body 1. A camera 3 is provided on the outside of the kettle body 1 where the window 2 is located. The camera 3 is installed on a bracket 12 and faces the window 2. The bracket 12 is located on the outside of the kettle body 1. The camera 3 can shoot the inner cavity of the kettle body 1 through the window 2. In actual use, by adjusting the height of the bracket 12 and the shooting angle of the camera 3 on the bracket 12, the camera 3 can be made to face the window 2, so that the environment in the inner cavity can be well photographed, that is, the changes in the stratum body in the inner cavity can be photographed.

[0035] A porous medium 23 is laid on the bottom wall of the inner cavity to form a stratum body with a certain thickness, that is, the porous medium 23 to be laid is used to simulate the stratum body. An acceleration sensor 19, a stress sensor 20 and a displacement sensor 21 are pre-buried in the porous medium 23. The acceleration sensor 19, the stress sensor 20 and the displacement sensor 21 can be installed at the same height or at different heights, and the acceleration sensor 19, the stress sensor 20 and the displacement sensor 21 are distributed and installed at different positions in the porous medium 23 (i.e., different positions on the same horizontal plane).

[0036] The porous medium 23 can be selected as quartz sand particles or marine soil samples to replace the sea mud sediment, so as to simulate the formation body of the hydrate location, and then the porosity, permeability and particle cohesion of the hydrate can be simulated based on this formation body, so as to better carry out the mechanism of formation landslide, the judgment of the instability critical point, and the experimental simulation of landslide occurrence during the hydrate production process.

[0037] A number of electric heating rods 22 are fixedly installed on the bottom wall of the kettle body 1. The electric heating rods are laid along the length and width directions of the bottom wall of the kettle body 1, so that each position of the bottom wall of the kettle body 1 can be heated and the heating is uniform. The electric heating rods 22 are located below the porous medium 23 and are arranged at intervals through the inner wall of the kettle body 1 to avoid affecting the movement of the porous medium 23 and directly heating the porous medium 23, which may cause damage to the porous medium 23 due to excessive heating temperature. Each of the electric heating rods 22 is arranged at intervals.

[0038] Among them, the camera 3 is a high-speed camera 3, so as to better capture the change of the reaction state in the kettle body 1.

[0039] One end of the kettle body 1 opposite to the intake pipe 13 and the vacuum interface 14 is also fixedly provided with a gas release and pressure regulating port 18. The gas release and pressure regulating port 18 is communicated with the inner cavity. The gas release and pressure regulating port 18 is used to discharge the gas in the kettle body 1 to adjust the pressure in the inner cavity of the kettle body 1. The connection joints of the gas release and pressure regulating port 18, the intake pipe 13 and the vacuum interface 14 with the inner cavity are all located directly above the formation body, so as to avoid interfering with the formation body during the processes of gas filling, exhaust, vacuum formation, etc., and thus avoid affecting the formation landslide of the simulated formation body.

[0040] Among them, the gas release and pressure regulating port 18 is connected with an electromagnetic valve. The electromagnetic valve is installed on the kettle body 1. The electromagnetic valve is used to adjust the opening size of the gas release and pressure regulating port 18, so as to be able to adjust the gas outlet volume and outlet speed, and thus be able to adjust the gas pressure in the inner cavity of the kettle body 1 to simulate the natural gas pressure reduction production condition. And the key parameters such as the pressure reduction amplitude, pressure reduction rate and single / multistage pressure reduction mode can be controlled.

[0041] The method includes the following steps:

[0042] Step 1: Lay the porous medium 23 in the inner cavity of the kettle body 1 to form a formation body with a certain thickness.

[0043] The porous medium 23 is made of quartz sand particles or marine soil samples, etc., which are laid flat on the inner wall surface of the inner cavity. Among them, the upper surface of the stratum body can be flat or uneven to simulate the sediment stratum where the hydrate is located in the real environment. And according to the on-site sampling of marine natural gas hydrate sea mud samples, indoor geotechnical experiments and three-dimensional scanning analysis methods, the original structural surface composition and the surface morphology of the structural surface are analyzed, and the key physical parameters such as porosity, permeability and particle adhesion of the real hydrate are measured. Then, a certain amount of water is added between the laid porous media 23, as well as the parameters of porosity, permeability and particle adhesion that are roughly the same as those in the real environment.

[0044] Step 2: Pre-embed the acceleration sensor 19, the stress sensor 20 and the displacement sensor 21 in the porous medium 23, and then close the kettle cover (not shown in the figure) of the kettle body 1. Connect the gas cylinder 8 to the air inlet pipe 13 fixed on the kettle body 1, connect the vacuum interface 14 to the vacuum pump 9, and connect the deflation pressure regulating port 18 to the solenoid valve, which is used to adjust the opening and closing size of the deflation pressure regulating port 18 (i.e., adjust the opening size) to adjust the deflation volume and deflation speed, thereby adjusting the pressure in the inner cavity.

[0045] Step 3: Place the kettle 1 in a temperature-adjustable test chamber so that the air bath can control the temperature of the entire experimental device. The ambient temperature in the test chamber is adapted to the temperature required for hydrate formation, and the specific temperature value can be set by the experimenter based on experience or relevant data.

[0046] Step 4: Install the camera 3 on the bracket 12 and adjust the height and shooting angle of the camera 3 so that the camera 3 is facing the window 2 on the kettle body 1 so that the camera 3 can capture the inner cavity of the kettle body 1 .

[0047] Step 5: The air in the inner cavity of the kettle body 1 is extracted by the vacuum pump 9. After forming a vacuum, and after the gas cylinder 8 is connected to the air inlet pipe 13, the operator opens the gas cylinder 8 and inputs the gas used to form hydrates into the inner cavity. The gas components include but are not limited to methane, ethane, propane, carbon dioxide and other substances. Let it stand for a period of time to wait for the formation of hydrates. During the hydrate formation process, the temperature and gas pressure of the inner cavity are measured in real time by the temperature sensor 16 and the pressure sensor 17 pre-set in the inner cavity of the kettle body 1, and the camera 3 takes a video record of the hydrate formation process. During the hydrate synthesis process, the gas pressure in the inner cavity will continue to decrease due to the continuous consumption of gas to form hydrates. After the gas pressure in the inner cavity remains stable for a certain period of time (generally not more than 24 hours), it is determined that the natural gas hydrate synthesis is completed.

[0048] Step 6: Adjust the kettle body 1, which is currently placed flat, to a certain inclination angle through the stepless rotating shaft 11. The kettle body 1 is installed on the base bracket 10 through the stepless rotating shaft 11, and the base bracket 10 is installed in the test chamber, so as to place the kettle body 1 in the test chamber for air bath.

[0049] Wherein, after the kettle body 1 is adjusted to a certain inclination angle, it is fixed at the current inclination angle through the tightening member on the stepless rotating shaft 11.

[0050] Step 7: Through the preset pressure reduction amplitude, pressure reduction rate and single-stage or multi-stage pressure reduction, control the solenoid valve through the control terminal 4, so as to control the gas pressure in the inner cavity and complete the mining process of simulating the pressure reduction for mining natural gas hydrate.

[0051] Step 8: Use the camera 3 to record the movement trajectory of the formation body in the inner cavity, and combine the acceleration sensor 19, stress sensor 20 and displacement sensor to record the acceleration, stress and displacement data when the formation landslide occurs, analyze the mechanism of formation landslide during the decomposition process of hydrate, and combine the pressure correlation of pressure reduction mining to analyze the critical mining conditions for generating formation landslide, so as to guide the actual hydrate mining according to the critical mining conditions and avoid safety accidents during the actual hydrate mining process.

[0052] Wherein, the critical mining conditions refer to the parameters such as pressure, temperature and stress corresponding to the moment when the formation body just starts to slide.

[0053] In an alternative embodiment, in step 7, it further includes heating through the electric heating rod 22, and simulating the pressure reduction mining of hydrate at different temperatures and / or different pressures through segmented or continuous heating modes, so as to simulate different experimental conditions of heat injection mining of natural gas hydrates.

[0054] Wherein, the electric heating rod 22 is fixed in the inner cavity of the kettle body 1. The electric heating rod 22 can be embedded and installed on the bottom wall of the inner cavity and is located below the formation body. The electric heating rod 22 is spaced from the formation body through the inner wall of the kettle body 1 to avoid directly heating the formation body and prevent damage to the formation body due to excessive heating temperature.

[0055] In the present invention, through the stepless rotating shaft 11 and multiple sensors, the simulation of formation landslide during the decomposition process of natural gas hydrate under various formation dip conditions can be realized, and the parameter correlation between the formation dip and the formation landslide can be analyzed; it can also realize the simulation of various mining conditions such as pressure reduction mining, heat injection mining and combined mining of both of natural gas hydrates, analyze the critical mining conditions for generating formation landslide accordingly, and propose preventive measures for submarine landslide in the natural gas hydrate mining plan.

[0056] The embodiments disclosed in this specification are only an illustration of the unilateral features of the present invention. The protection scope of the present invention is not limited to these embodiments, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for simulating landslide caused by decomposition of natural gas hydrates, It is characterized in that The following steps are involved: Step 1: laying porous media into the inner cavity of the kettle body to form a stratum body with a certain thickness, adding a certain amount of water between the laid porous media, and setting the same parameters of porosity, permeability and particle adhesion as those in the real environment; Step 2: pre-embed the acceleration sensor, stress sensor and displacement sensor in the porous medium, then close the kettle cover of the kettle body, connect the gas cylinder to the air inlet pipe fixed on the kettle body, connect the vacuum interface to the vacuum pump, connect the deflation pressure regulating port to the solenoid valve, and the solenoid valve is used to adjust the opening and closing size of the deflation pressure regulating port to adjust the pressure in the inner cavity by adjusting the deflation volume and deflation speed; Step 3: Place the kettle in a temperature-adjustable test chamber so that the air bath can control the temperature of the entire experimental device as a whole, and the ambient temperature in the test chamber is adapted to the temperature required for hydrate formation; Step 4: Align the camera with the window on the kettle body so that the camera can capture the inner cavity of the kettle body; Step 5: The air in the inner cavity of the kettle is extracted by a vacuum pump to form a vacuum. After the gas cylinder is connected to the air inlet pipe, the gas used to form hydrates is input into the inner cavity. The reactor is left to stand for a period of time to wait for the formation of hydrates. During the hydrate formation process, the temperature and gas pressure of the inner cavity are measured in real time by the temperature sensor and pressure sensor pre-installed in the inner cavity of the reactor body, and the camera shoots the hydrate formation process and forms a video record. After the gas pressure in the inner cavity remains stable for a certain period of time, it is determined that the natural gas hydrate synthesis is completed; Step 6: Adjust the kettle body, which is currently placed flat, to a certain tilt angle; Step 7: By presetting the pressure reduction amplitude, pressure reduction rate and single-stage or multi-stage pressure reduction, the gas pressure in the inner cavity is controlled by regulating the solenoid valve to complete the simulation of the pressure reduction and extraction process of natural gas hydrate; Step 8: Use a camera to record the movement trajectory of the formation body in the inner cavity, and use acceleration sensors, stress sensors and displacement sensors to record the acceleration, stress and displacement data when the formation body slides. Analyze the mechanism of formation collapse during hydrate decomposition, and analyze the critical mining conditions that cause formation collapse by combining the pressure correlation of depressurized mining. In step 7, it also includes heating by an electric heating rod, simulating decompression production of hydrates at different temperatures and / or pressures through segmented or continuous heating modes, thereby simulating different natural gas hydrate heat injection production experimental conditions. In step 6, the kettle is mounted on the base bracket through the stepless rotating shaft to adjust a certain tilt angle, and the base bracket is mounted in the test box, so that the kettle is placed in the test box for air bath. Among them, after the kettle body is adjusted to a certain tilt angle, it is fixed at the current tilt angle through the tightening parts on the stepless rotating shaft.

2. The method for simulating stratum collapse caused by decomposition of natural gas hydrate according to claim 1, It is characterized in that The porous medium is made of quartz sand particles or marine soil samples.

3. The method for simulating formation slumping caused by the decomposition of natural gas hydrates according to claim 1, characterized in that, a porous medium is laid flat on the inner wall surface of the inner cavity, and the surface of the formation body formed by the porous medium is not flat or uneven.

4. The method for simulating formation slumping caused by the decomposition of natural gas hydrates according to claim 1, characterized in that, after analyzing the original structural plane composition and the surface topography of the structural plane of the marine mud sample according to the on-site sampling of the marine mud sample of marine natural gas hydrates, indoor geotechnical experiments and three-dimensional scanning analysis method, and measuring the porosity, permeability and particle bonding force physical property parameters of the real hydrate, according to the physical property parameters, a certain amount of water is added between the laid porous media, and the porous media is selected with parameters of the same porosity, permeability and particle bonding force as the real environment.

5. The method for simulating formation slumping caused by the decomposition of natural gas hydrates according to claim 1, characterized in that, a camera is installed on a bracket, and the height and shooting angle of the camera are adjusted so that the camera is directly facing the window on the kettle body.

6. The method for simulating formation slumping caused by the decomposition of natural gas hydrates according to claim 1, characterized in that, the gas components are one or more combinations of methane, ethane, propane, and carbon dioxide.

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