Equipment and method suitable for macroscopic and microscopic research of residual cage structures of hydrates

Abstract

The present invention relates to the technical field of natural gas hydrate mining and submarine carbon dioxide storage, and in particular to a device and method suitable for macroscopic and microscopic research on residual cage structures of hydrates. Its technical solution is: including a gas-liquid injection system, a fluid separation-blocking-unblocking core system, a fluid additional injection core system, a horizontal supercooling flow module, a vertical supercooling flow module and a cage structure microscopic research module. The present invention can efficiently manufacture residual cage structures of hydrates in hydrate decomposition water under high-pressure flow conditions, and then study the mechanism of the effect of residual cage structures on the secondary generation and rapid blockage of hydrates and the effective elimination method of residual cage structures; at the same time, it provides key experimental conditions for molecular-scale microscopic optical research on residual cage structures under high-pressure and low-temperature conditions; in addition, the present invention can also effectively simulate and systematically study hydrate-based submarine carbon dioxide storage technology, providing theoretical support for its engineering application.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas hydrate exploitation and seabed carbon dioxide storage, and in particular to a device and method suitable for macroscopic and microscopic research on residual cage structures of hydrates. Background Art

[0002] Natural gas hydrates are characterized by high energy density, low carbon emissions, clean operation, and wide distribution, making them a reliable alternative to traditional fossil fuels. The internationally mainstream depressurization method is typically used in offshore natural gas hydrate extraction. Solid hydrates in the seabed reservoir decompose into liquid water and natural gas gas under the action of a pressure differential. These hydrates then enter the gas-liquid separator in the extraction system through the extraction mixed pipeline. Subsequently, under the action of gravity separation, the liquid phase forms a bubbling flow with a small amount of gas in the drainage pipeline and is discharged. The gas forms an annular mist flow with a small amount of liquid in the gas production pipeline and is extracted to the offshore platform. However, because portions of the drainage and gas production pipelines are still within the low-temperature, high-pressure hydrate formation zone on the seabed, the residual hydrate cage structures in the produced water pose a significant risk of secondary hydrate formation and blockage in the drainage and gas production pipelines.

[0003] Natural gas hydrates are envelope-like crystals whose molecular structure is a cage-like structure formed by hydrogen-bonded water molecules, with gas guest molecules encapsulated within the water cage structure. During the decomposition process of hydrate extraction using the pressure reduction method, the intact water cage structure is destroyed, and the gas guest molecules escape from the cage structure. However, because the extraction system remains under high pressure, the decomposed hydrate water produced by hydrate extraction still contains a large number of gas molecules dissolved in the liquid phase. As a result, some of the water cage structures are not completely disassembled after hydrate decomposition, forming residual hydrate cage structures. These residual hydrate cage structures, as they flow with the decomposed hydrate water and high-pressure gas in the drainage and gas production pipelines, easily recombine with gas molecules dissolved in the liquid phase to form complete hydrate cage structures. This can lead to secondary hydrate formation and rapid pipeline blockage, threatening the flow and production safety of the entire extraction system.

[0004] On the other hand, CO2 submarine storage is a key global technology. Using produced water from hydrate mining to store CO2 is currently a cutting-edge international carbon storage technology. Its core concept is to rapidly generate CO2 hydrates from produced water containing residual hydrate cage structures and CO2 in a low-temperature, high-pressure environment on the seabed. This hydrates are then transported to the target seabed formation for efficient CO2 submarine storage. However, current research and equipment have struggled to simulate the use of hydrate produced water for hydrate-based submarine CO2 storage. Several key technical issues in this carbon storage technology, such as the rapid generation and flow characteristics of CO2 hydrates, require further investigation.

[0005] In summary, the residual cage structures of hydrates are key factors affecting the flow safety and engineering efficiency of the system during marine hydrate mining and hydrate-based seabed carbon dioxide storage. However, most of the existing experimental equipment in the field of hydrates is only suitable for research under conditions where there are no residual hydrate cage structures. It is difficult to achieve quantitative control of the formation and elimination of hydrate cage structures in high-pressure flow systems and microscopic optical experiments. As a result, the mechanism of the effect of residual hydrate cage structures on the secondary generation and rapid blockage of hydrates and the rapid formation of carbon dioxide hydrates is currently unclear, and there is a lack of effective methods to eliminate the residual cage structures.

[0006] Therefore, there is an urgent need for an apparatus and method suitable for macroscopic and microscopic research on the residual cage structure of hydrates. Summary of the Invention

[0007] The purpose of the present invention is to address the above-mentioned defects in the prior art and provide a device and method suitable for macroscopic and microscopic research on residual hydrate cage structures, so as to meet the needs of in-depth research on the impact of residual hydrate cage structures on the flow safety of marine hydrate mining systems, and to effectively simulate the efficient hydrate method of submarine carbon dioxide storage using residual hydrate cage structures.

[0008] The present invention relates to a device suitable for macroscopic and microscopic research on residual cage structures of hydrates. The technical solution is as follows: it includes a gas-liquid injection system, a fluid separation-blocking-unblocking core system, an additional fluid injection core system, a horizontal subcooling flow module, a vertical subcooling flow module, and a cage structure microscopic research module. The fluid separation-blocking-unblocking core system consists of a primary fluid separation-blocking-unblocking tank, a secondary fluid separation-blocking-unblocking tank, a gas separation tank, and a gas-liquid-solid three-phase input pipeline.

[0009] The top of the first-level fluid separation-blocking-unblocking tank is respectively connected to the vacuum pump, the gas flow control module of the gas-liquid injection system and the gas separation tank, and the left side of the middle is connected to the liquid reflux pipe at the lower end of the gas separation tank and the gas-liquid-solid three-phase output pipeline; the bottom is a ladder-type reduction structure at the bottom of the first-level tank, and two first-level tank reduction structure heating belts connected to the first-level tank bottom heating controller are installed on the outer wall of the ladder-type reduction structure at the bottom of the first-level tank; the lower end of the ladder-type reduction structure at the bottom of the first-level tank is connected to the top of the second-level fluid separation-blocking-unblocking tank through a vertical pipe at the bottom of the first-level tank;

[0010] The middle right side of the secondary fluid separation-blocking-unblocking tank is connected to the fluid additional injection core system and the liquid injection pump; the secondary tank bottom fluid three-way structure is connected just below the bottom, and the outer walls of both are equipped with a secondary tank reduction structure heating belt and a secondary tank bottom three-way heating belt connected to the secondary tank bottom heating controller; one end of the liquid-solid two-phase flow pipeline is connected to the secondary tank bottom fluid three-way structure, and the other end is connected in sequence to a large liquid-solid two-phase flow electromagnetic pump, a liquid-solid two-phase flow flow meter, a micro-module inflow port, a multiphase flow pipeline ball valve at the end, and a gas-liquid-solid flow mixer; the upper end of the gas-liquid-solid flow mixer is connected to a gas-liquid-solid three-phase input pipeline, and the side wall of the gas-liquid-solid flow mixer is connected to a gas cooling pipeline;

[0011] The fluid additional injection core system consists of a fluid additional injection core stirring tank, a small separation tank at the rear end of the stirring tank, a gas recovery tank, and a liquid-solid two-phase flow electromagnetic pump.

[0012] The fluid is additionally injected into the bottom right end of the core stirring tank, which is connected to a liquid injection pipeline. The center position of the bottom is connected to a small separation tank at the rear end of the stirring tank through a liquid phase flow pipeline at the lower end of the stirring tank. The top center position of the small separation tank at the rear end of the stirring tank is connected to a gas recovery tank through a vent line, and the center position of the bottom is connected to a secondary fluid separation-blocking-unblocking tank through a liquid phase flow pipeline at the lower end of the small separation tank.

[0013] The ends of the gas-liquid-solid three-phase input pipeline are connected to the inlet ends of the horizontal subcooling flow module and the vertical subcooling flow module respectively through the small tee of the input pipeline, and the ends of the gas-liquid-solid three-phase output pipeline are connected to the outlet ends of the horizontal subcooling flow module and the vertical subcooling flow module respectively through the small tee of the output pipeline;

[0014] The side wall of the liquid-solid two-phase flow pipeline is connected to the cage structure microscopic research module through the microscopic module inflow port;

[0015] The cage-type structure microscopic research module includes a pressure-resistant upper cover, a circular window on the upper cover, a pressure-resistant base, a temperature-controlled base and a lifting base. The upper part of the pressure-resistant base is provided with a pressure-resistant upper cover, and the pressure-resistant upper cover is provided with multiple circular windows on the upper cover. The lower part of the pressure-resistant base is provided with a temperature-controlled base, and the lower part of the temperature-controlled base is provided with a lifting base.

[0016] Preferably, the gas-liquid injection system includes a stainless steel bucket, a liquid phase inhibitor container, a liquid injection pump, a liquid injection pipeline, a carbon dioxide high-pressure gas cylinder, a methane high-pressure gas cylinder, a gas booster pump and a gas flow control module. The pure water in the stainless steel bucket is injected into the secondary fluid separation-blocking-unblocking tank by the liquid injection pump through the liquid injection pipeline and the liquid phase capillary ball valve; the inhibitor solution in the liquid phase inhibitor container is injected into the fluid additional injection core stirring tank by the liquid injection pump through the liquid injection pipeline and the liquid phase capillary ball valve, and the electronic scale is used to calculate the injection amount of the liquid phase; the gas in the carbon dioxide high-pressure gas cylinder and the methane high-pressure gas cylinder is injected into the primary fluid separation-blocking-unblocking tank and the fluid additional injection core stirring tank in sequence through the gas cylinder pressure relief valve, the ventilation pipeline, the gas booster pump, the gas flow control module and multiple ventilation pipeline valves.

[0017] Preferably, the horizontal subcooling flow module includes a horizontal input pipeline, a horizontal subcooling flow straight pipe, a subcooling pipe insulation layer, a subcooling pipe coolant annulus, a subcooling pipe stainless steel inner pipe, a subcooling pipe flange, a coolant continuous pipe, a polyvinyl chloride horizontal visual tube, a horizontal visual tube support frame, a horizontal subcooling flow U-shaped tube, a high-speed camera, a particle monitoring optical probe insertion port, a data acquisition computer, a subcooling pipe temperature and pressure sensor, a subcooling pipe pressure differential sensor, a sensor data cable, a macro flow system console, and a horizontal output pipeline.

[0018] The right ends of the two horizontal subcooling flow straight pipes are connected to the horizontal subcooling flow U-shaped pipe, and the two horizontal subcooling flow straight pipes are respectively connected to the polyvinyl chloride horizontal sight tube through the subcooling pipe flanges. The left end of the upper horizontal subcooling flow straight pipe is connected to the horizontal input pipeline, and the left end of the lower horizontal subcooling flow straight pipe is connected to the horizontal output pipeline.

[0019] The horizontal subcooling flow straight tube and the horizontal subcooling flow U-shaped tube are both double-layer structures, the interior of which is a subcooling tube stainless steel inner tube for circulating multiphase flow, and the interlayer space is a subcooling tube coolant annulus for circulating the coolant output from the refrigeration circulating water bath in the module. The outermost layer is wrapped with a subcooling tube insulation layer, and coolant continuous pipes are connected on both sides of the polyvinyl chloride horizontal visual tube to achieve communication between the two subcooling tube coolant annuli;

[0020] A plurality of subcooling pipe temperature and pressure sensors and subcooling pipe differential pressure sensors are installed at intervals on the horizontal subcooling flow straight pipe, and are connected to the macro flow system control console through sensor data lines;

[0021] A high-speed camera is installed on the side of the lower polyvinyl chloride horizontal visual tube to capture the multiphase flow morphology during the secondary generation and rapid blockage of hydrates under the influence of the residual cage structure of hydrates; a plurality of obliquely installed particle monitoring optical probe insertion ports are embedded on the horizontal supercooled flow straight tube at the rear end of the high-speed camera, and the high-speed camera and the particle monitoring optical probe insertion ports are connected to the data acquisition computer.

[0022] Preferably, the lower end inlet of the above-mentioned vertical supercooling flow module is connected to the vertical input pipeline, and the outlet is connected to the vertical output pipeline. The vertical supercooling flow module is mounted on a vertical supercooling pipe bracket to keep it vertical to the horizontal ground, and a vertical supercooling pipe bracket base is installed at the bottom of the vertical supercooling pipe bracket.

[0023] Preferably, the top of the pressure-resistant upper cover of the cage-type structure microscopic research module is equipped with an embedded camera and an upper cover pressure probe, and the center positions of the left and right walls are both embedded with upper cover circular windows, and the center of the upper cover circular window is made of sapphire pressure-resistant and light-transmitting glass; the bottom end of the inner wall of the upper cover circular window is equipped with multiple internal liquid level limiters for indicating the injection amount of hydrate decomposition water and limiting the liquid level height of the decomposition water;

[0024] An inflow tube is installed at the center of the right inner wall of the pressure-resistant base. The right end of the inflow tube is connected to the inflow port of the micromodule in the fluid separation-blocking-unblocking core system through the inflow reducer flange, the inflow reducer, the inflow pipeline ball valve, the inflow pipeline tee and the inflow pipeline in sequence, forming a channel for hydrate decomposition water to flow into the high-pressure cavity in the micromodule; the bottom of the inflow pipeline tee is equipped with a pressure relief pipeline, an inflow pipeline ball valve and a small fluid vessel.

[0025] Preferably, the above-mentioned temperature-controlled base has an appearance of a rectangular structure, and its outer wall is an integrated structure with the outer wall of the pressure-resistant base. A temperature-conducting metal cylinder is installed at the center of its internal cavity, and the metal cylinder temperature control and monitor are connected through the metal cylinder control interface. The front of the temperature-controlled base is connected to the micro-module temperature-controlled water bath through the coolant input / output port and the coolant input / output pipe; a lifting control lever is installed on one side of the lifting base, and a micro-module placement platform is provided on the lower side of the lifting base.

[0026] The present invention describes a method for macroscopic and microscopic studies of residual hydrate cage structures. The technical solution is as follows: Experimental methods for macroscopic flow studies of residual hydrate cage structures include the following three types: a. an experimental method to investigate the impact of residual cage structures on secondary hydrate formation and rapid blockage; b. an experimental method to investigate effective methods for eliminating residual cage structures; and c. an experimental method to simulate the use of produced water from hydrate extraction for subsea carbon dioxide solidification and storage.

[0027] The experimental method for investigating the effect of residual cage structures on the secondary formation and rapid blockage of hydrates includes three stages: the formation of complete hydrate cage structures, the formation of residual hydrate cage structures, and the secondary formation and rapid blockage of hydrates. The specific steps are as follows:

[0028] S1, the stage of formation of complete hydrate cage structure:

[0029] First, check the air tightness of the entire system. Close the ball valves at the bottom of the small separation tank at the rear end of the stirred tank and the multiphase flow pipeline at the rear end of the inlet port of the micromodule. Reduce the pressure in the entire system to -0.1 MPa using a vacuum pump. Then, inject a certain amount of pure water and methane into the entire system through the gas-liquid injection system from the lower right end of the secondary fluid separation-blocking-unblocking tank and the top of the primary fluid separation-blocking-unblocking tank, respectively. Stop when the preset experimental pressure is reached.

[0030] Then, the refrigeration circulating water bath corresponding to the gas cooling pipeline, the refrigeration circulating water bath corresponding to the horizontal subcooling flow module and the vertical subcooling flow module, the high-pressure air pump, and the large liquid-solid two-phase flow electromagnetic pump were turned on in sequence to form a gas-liquid two-phase stratified flow with a porosity of less than 30% in the stainless steel inner tube of the subcooling tube. The target temperature of the multiple refrigeration circulating water baths was set to -3 degrees to continuously cool the flow system.

[0031] Subsequently, when the temperature in the flow system drops below the hydrate phase equilibrium temperature, the macroscopic induction period of hydrate formation begins, and water molecule cage structures gradually begin to form at the gas-liquid interface. When the macroscopic induction period of hydrate formation ends, hydrates begin to form, and the number of complete hydrate cage structures gradually increases. The aggregation, adhesion, accumulation, and sedimentation of hydrates during the flow process lead to the rapid formation and gradual increase of hydrate aggregates. The ladder-type reduction structure at the bottom of the primary fluid separation-blocking-unblocking tank and the ladder-type reduction structure at the bottom of the secondary fluid separation-blocking-unblocking tank, as well as the change-of-direction pipe structure within the fluid tee structure at the bottom of the secondary tank, induce and accelerate the blockage of hydrate aggregates.

[0032] Finally, when the flow rate displayed on the liquid-solid two-phase flow meter reaches 0, indicating the formation of complete blockage and the end of the formation of a complete hydrate cage structure, the refrigeration circulating water bath and high-pressure air pump are turned off; the power of the large liquid-solid two-phase flow electromagnetic pump is increased and the small liquid-solid two-phase flow electromagnetic pump is turned on. If the displayed flow rate is 0, it indicates that hydrate blockage has formed at the bottom of both the primary fluid separation-blocking-unblocking tank and the secondary fluid separation-blocking-unblocking tank. If the displayed flow rate is not 0 but drops to 0 quickly, it indicates that hydrate blockage exists at the bottom of the secondary fluid separation-blocking-unblocking tank.

[0033] S2, the formation stage of residual hydrate cage structure:

[0034] First, the large liquid-solid two-phase flow electromagnetic pump and the small liquid-solid two-phase flow electromagnetic pump are turned off. The heating controller at the bottom of the first tank, the heating controller at the bottom of the second tank, and the heating controller at the starting end of the liquid-solid flow pipeline are used to maintain the temperature of the first tank diameter reduction structure heating zone, the second tank diameter reduction structure heating zone, the second tank bottom three-way heating zone, and the liquid-solid flow pipeline starting end heating zone in the range of 35 to 38 degrees Celsius. This heats the hydrates blocked in the stepped diameter reduction structure at the bottom of the first tank, the stepped diameter reduction structure at the bottom of the second tank, and the inner direction-changing pipe structure of the fluid three-way structure at the bottom of the second tank at the bottom of the first fluid separation-blocking-unblocking tank and the second fluid separation-blocking-unblocking tank. During the gradual decomposition of the hydrates, the gas molecules gradually detach from the complete hydrate cage structure, and the residual hydrate cage structure begins to form and gradually increases with the decomposition of the hydrates.

[0035] Subsequently, the large liquid-solid two-phase flow electromagnetic pump and the small liquid-solid two-phase flow electromagnetic pump are turned on once every heating period. If the liquid-solid two-phase flow meter shows a flow rate of 0, indicating that the system has not recovered its fluidity, the two electromagnetic pumps are turned off and heating is continued; if the liquid-solid two-phase flow meter shows a flow rate not of 0, the two electromagnetic pumps are kept on and heating is continued;

[0036] Finally, when the flow rate indicated by the liquid-solid two-phase flow meter returns to the level before hydrate formation under the same electromagnetic pump power conditions, it indicates that the hydrate blockage in the system has been completely eliminated; at this time, all heating controllers are turned off and the high-pressure air pump is turned on to form a stratified flow containing residual hydrate cage structures in the liquid phase in the horizontal subcooling flow module and the vertical subcooling flow module; the refrigeration circulating water bath corresponding to the subcooling flow module is turned on and the target temperature is adjusted to the laboratory room temperature before the start of step S1, so that the temperature and pressure in the flow system are increased to avoid other effects of undecomposed hydrates on the residual cage structures. When the pressure of the flow system returns to the level before the cooling in step S1 begins, the target temperature of the refrigeration circulating water bath is adjusted to 0 degrees;

[0037] S3, Hydrate secondary formation-rapid plugging stage:

[0038] First, the refrigeration circulating water bath corresponding to the gas cooling pipeline was turned on and the target temperature of the refrigeration circulating water bath was set to -3 degrees Celsius to continuously cool the stratified flow system containing residual hydrate cage structures in the liquid phase.

[0039] Subsequently, during the hydrate secondary formation induction period, secondary hydrate formation, and rapid clogging after formation, the subcooling tube temperature and pressure sensors, subcooling tube differential pressure sensors, high-speed cameras mounted on the sides of the polyvinyl chloride horizontal visual tubes, and optical devices embedded in the insertion port of the particle monitoring optical probe in the horizontal and vertical subcooling flow modules were used to monitor, calculate, and record data on the hydrate secondary formation induction time, secondary formation rate, evolution of secondary formation flow barriers, hydrate aggregate morphology, and changes in hydrate aggregate particle size. These data were then compared and analyzed with the data from step S1 to explore the influence and mechanism of residual cage structures on hydrate secondary formation and rapid clogging.

[0040] Finally, when the secondary hydrate blockage is completely formed, the entire system is heated. When the system fluidity is restored, all the methane gas in the system is displaced by injecting carbon dioxide gas into the gas recovery tank, and the entire system is emptied through the fluid discharge pipeline at the bottom of the secondary tank to start the next set of experiments.

[0041] Preferably, the above experimental method for exploring the effective elimination method of the residual cage structure further includes a chemical inhibitor injection stage and a hydrate secondary generation-mobilization stage, and the specific steps are as follows:

[0042] A1. Chemical inhibitor injection stage:

[0043] First, start the liquid injection pump and inject the hydrate kinetic inhibitor or the combined inhibitor of kinetic inhibitor and polymerization inhibitor from the liquid-phase inhibitor container into the fluid additional injection core stirring tank, and record the injection amount of the inhibitor using an electronic scale. Turn on the core stirring tank rotation motor and the core stirring tank temperature-controlled water bath to ensure that the inhibitor is evenly distributed under stirring and gradually reaches its optimal working temperature. Inject methane into the fluid additional injection core stirring tank through the gas-liquid injection system, and stop the injection when the pressure in the tank is 1 MPa higher than the pressure in the secondary fluid separation-blocking-unblocking tank.

[0044] Subsequently, the core agitator's rotating motor is kept turned on, and the multiphase flow pipeline ball valve on the liquid phase flow pipeline at the lower end of the agitator is opened, allowing the inhibitor to flow into the small separation tank at the rear end of the agitator under the action of the pressure difference; then, the large liquid-solid two-phase flow electromagnetic pump and the high-pressure air pump are turned off, and the liquid-solid two-phase flow electromagnetic pumps on the liquid phase flow pipeline at the lower end of the agitator and the liquid phase flow pipeline at the lower end of the small separation tank are turned on in sequence, allowing all the inhibitor to flow into the secondary fluid separation-blocking-unblocking tank;

[0045] Finally, the liquid phase flow pipeline at the lower end of the small separation tank is closed, and the small air pump is turned on to pump the methane gas in the core system of the entire fluid into the gas recovery tank. At the same time, carbon dioxide gas is injected into the core stirring tank and the small separation tank at the rear end of the stirring tank through the gas-liquid injection system to ensure that all methane gas is displaced into the gas recovery tank.

[0046] A2. Hydrate secondary formation-mobilization stage:

[0047] The high-pressure gas pump and the large liquid-solid two-phase flow electromagnetic pump were turned on in sequence to form a stratified flow in the system containing residual hydrate cage structures and chemical inhibitors in the liquid phase. At the same time, a refrigeration circulating water bath was turned on to continuously cool the flow system. Through the subcooling tube temperature and pressure sensors, subcooling tube pressure difference sensors, high-speed cameras installed on the side of the visual tube, and optical equipment embedded in the insertion port of the particle monitoring optical probe in the horizontal and vertical subcooling flow modules, key data such as the induction time, generation rate, flow morphology, and changes in aggregate particle size during the secondary formation and flow barrier evolution of hydrates in the presence of different types of inhibitors were monitored, calculated, and recorded. The data were compared and analyzed with those from experiments without inhibitors to explore effective methods and mechanisms for eliminating residual hydrate cage structures.

[0048] After the experiment, the entire fluid needs to be injected into the core system through the pressure relief port of a small separation tank equipped with a built-in valve to displace the carbon dioxide gas injected into the methane gas. The fluid is also injected into the core system through the gas-liquid injection system. Pure water is injected multiple times into the fluid and then emptied to clean the residual inhibitors in the system so that subsequent experiments containing different types of inhibitors can be carried out.

[0049] Preferably, the above-mentioned experimental method for simulating the use of hydrate production water for seabed carbon dioxide solidification and storage includes four stages: the formation stage of the complete cage structure of methane hydrate in the kettle, the formation stage of the residual cage structure of hydrate in the kettle, the injection stage of decomposition of water and carbon dioxide into the separation tank, and the carbon dioxide hydrate generation and flow stage. The specific steps are as follows:

[0050] B1, the stage of formation of complete cage structure of methane hydrate in the kettle:

[0051] First, after checking the air tightness of the entire system, use a vacuum pump to reduce the pressure in the entire system to -0.1MPa. Close the liquid flow pipeline at the lower end of the stirring kettle and the liquid flow pipeline at the lower end of the small separation tank. Use the gas-liquid injection system to inject additional fluid into the core stirring kettle and then inject pure water and methane gas. Stop the injection when the experimental set pressure is reached.

[0052] Subsequently, the core stirring kettle's rotating motor and temperature-controlled water bath were turned on, and the target temperature of the temperature-controlled water bath was set to -3 degrees Celsius. This allowed the high-pressure methane gas and pure water in the kettle to continue to cool while stirring. When the system temperature fell below the hydrate phase equilibrium temperature, a hydrate cage structure began to form at the gas-liquid interface. When additional fluid was injected into the core stirring kettle, the temperature suddenly rose, and the feedback torque of the core stirring kettle's rotating motor increased, indicating the formation of methane hydrate and the formation of a complete hydrate cage structure.

[0053] Finally, a high-pressure camera with additional fluid injected into the core agitator was used to assist in determining the hydrate formation and agitation within the agitator. When the rotational speed of the core agitator's rotary motor dropped to 0, indicating complete hydrate blockage and the formation of a complete hydrate cage structure, the core agitator's rotary motor was shut down.

[0054] B2, the formation stage of the residual cage structure of hydrate in the kettle:

[0055] First, the target temperature of the core stirred tank temperature-controlled water bath was set to 25 degrees Celsius. The hydrates blocked in the tank were heated for a period of time and then closed to simulate the process of self-heating materials promoting hydrate decomposition during marine hydrate mining.

[0056] Subsequently, the liquid phase flow pipeline at the lower end of the stirred tank was slowly opened, allowing the additional fluid to be injected into the core stirred tank, causing the hydrate to gradually decompose during the decompression process, simulating the process of decompression recovery of hydrates in the sea. At the same time, the hydrate decomposition water and the gas produced by the decomposition flowed into the small separation tank at the rear end of the stirred tank. As the gas molecules gradually separated from the intact hydrate cage structure, the hydrate cage structure remaining in the hydrate decomposition water gradually increased.

[0057] Finally, when the pressure in the small separation tank at the rear end of the stirred tank no longer increases, the liquid phase flow pipeline at the lower end of the stirred tank is fully opened;

[0058] B3, decomposition of water and injection of carbon dioxide into the separation tank stage:

[0059] First, the liquid flow pipeline at the lower end of the small separation tank is kept closed, and carbon dioxide gas is injected into the fluid separation-blocking-unblocking core system, as well as the horizontal subcooling flow module and the vertical subcooling flow module through the gas-liquid injection system. The injection is stopped when the pressure in the system reaches 2 MPa.

[0060] Subsequently, the methane gas in the core system needs to be additionally injected with fluid to displace it with carbon dioxide, and the vent line valve between the small separation tank at the rear end of the stirred tank and the methane gas pumped into the gas recovery tank is opened, so that the methane gas in the core system additionally injected with fluid flows into the gas recovery tank driven by the pressure difference. When the pressure in the system no longer changes significantly, a new gas recovery tank is replaced to continue collecting methane gas; when the pressure in the system drops to 2MPa, a new gas recovery tank is replaced and carbon dioxide gas is continuously injected into the core system additionally injected with fluid through the gas-liquid injection system, and the small air pump is turned on to allow the carbon dioxide gas to displace all the remaining methane gas in the core system additionally injected with fluid into the gas recovery tank; when the gas drying and methane concentration monitoring device shows that the methane concentration is 0, the small air pump is turned off and the injection of carbon dioxide is stopped;

[0061] Finally, the liquid flow pipeline at the lower end of the small separation tank was opened, and all the hydrate decomposition water containing the residual hydrate cage structure in the small separation tank at the rear end of the stirred tank was injected into the secondary fluid separation-plugging-unplugging tank to simulate the process of injecting produced water from marine hydrate mining into the submarine carbon dioxide hydrate generation system. When the pressure in the secondary fluid separation-plugging-unplugging tank no longer changed, the liquid flow pipeline at the lower end of the small separation tank was closed.

[0062] B4. Carbon dioxide hydrate formation-mobilization stage:

[0063] First, carbon dioxide gas is continuously injected into the fluid separation-blocking-unblocking core system, the horizontal subcooling flow module, and the vertical subcooling flow module through the gas-liquid injection system. The injection is stopped when the pressure in the system reaches 5 MPa.

[0064] Subsequently, the primary fluid separation-blocking-unblocking tank, the secondary fluid separation-blocking-unblocking tank, and the gas separation tank were closed, the gas cooling pipeline was closed, and the refrigeration circulating water baths corresponding to the horizontal subcooling flow module and the vertical subcooling flow module, as well as the large liquid-solid two-phase flow electromagnetic pumps, were turned on to form a gas-liquid two-phase bubbly flow with a porosity of less than 10% and containing residual hydrate cage structures in the stainless steel inner tubes of the subcooling tubes in the horizontal and vertical subcooling flow modules. The target temperature of the refrigeration circulating water bath was set to -3 degrees Celsius to continuously cool the flow system.

[0065] Then, during the continuous cooling process of the flow system, the carbon dioxide gas gradually dissolves in the methane hydrate decomposition water. Along with the induction and rapid formation of carbon dioxide hydrate, the carbon dioxide gas molecules and the residual hydrate cage structure in the methane hydrate decomposition water reform into a complete carbon dioxide hydrate cage structure.

[0066] Finally, through the horizontal supercooled flow module and the vertical supercooled flow module, the key data of the induction time, generation rate, flow morphology, and flow pressure difference changes during the formation and flow of carbon dioxide hydrates are monitored, calculated, and recorded, thereby studying multiple key scientific issues in the process of using hydrate mining produced water for submarine carbon dioxide solidification and storage.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] (1) The present invention innovatively sets up a fluid separation-blocking-unblocking core system, which is mainly composed of a first-level fluid separation-blocking-unblocking tank, a second-level fluid separation-blocking-unblocking tank, a gas separation tank, a gas-liquid-solid three-phase input pipeline and other equipment; the ladder-type reduction structure at the bottom of the tank, the change-direction pipe structure in the tee and the heating belt equipment in the system provide conditions for inducing hydrate blockage at a specific position under flow conditions and controlling the hydrate decomposition process, and can efficiently and quantitatively form hydrate residual cage structures in the flow system, and can carry out flow loop experimental research on the mechanism of the effect of hydrate residual cage structures on hydrate secondary generation-rapid blockage, solving the problem that traditional devices cannot quantitatively control the formation and elimination of hydrate residual cage structures under macroscopic flow conditions, and has important theoretical and practical significance for the effective prevention and control of hydrate secondary generation-rapid blockage in the process of marine hydrate mining, as well as the optimization of multiphase flow safety control strategy;

[0069] (2) The present invention sets up a fluid additional injection core system, which provides conditions for the in-situ injection of residual cage structure inhibitors and different types of hydrate decomposition water into the high-pressure flow system. When combined with the fluid separation-blocking-unblocking core system, on the one hand, it can carry out experimental research on the effective elimination method of residual hydrate cage structure under macroscopic flow conditions; on the other hand, it can effectively simulate and systematically study the hydrate method for submarine carbon dioxide storage technology, providing reliable theoretical support and decision-making basis for its engineering application;

[0070] (3) The present invention innovatively sets up a cage structure microscopic research module, which can collect hydrate decomposition water containing residual hydrate cage structures in situ under the same high pressure as the macro flow loop experimental system; it can be separated and moved from the macro flow loop experimental system while keeping the high-pressure inner cavity sealed; at the same time, the design of two sets of upper cover circular windows and sapphire pressure-resistant transparent glass provides key experimental conditions for the molecular-scale microscopic optical characterization of residual hydrate cage structures under high pressure and variable temperature conditions. When used in combination with existing technologies and frequency resonance spectrometers, it can realize in situ, molecular-level visualization research on the evolution process of residual hydrate cage structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1It is a schematic diagram of the overall system of the present invention;

[0072] Figure 2 It is a structural diagram of the fluid separation-blocking-unblocking core system and the cage structure microscopic research module;

[0073] Figure 3 It is a schematic diagram of the structure of the additional fluid injection core system and the gas-liquid injection system;

[0074] Figure 4 It is a structural diagram of the horizontal subcooling flow module;

[0075] Figure 5 It is a structural diagram of the vertical subcooling flow module;

[0076] Figure 6 This is a schematic diagram and side view of the structure of the cage-type structure microscopic research module when it is separated and used;

[0077] Figure 7 This is a schematic diagram of the internal structure of the cage-type microscopic research module when it is separated and used in combination with optical equipment;

[0078] Figure 8 This is a schematic diagram of the temperature and flow rate variation curves in the fluid separation-blocking-unblocking core system and the horizontal supercooling flow module during the experimental process of creating hydrate residual cage structures;

[0079] In the figure: 1-fluid separation-blocking-unblocking core system, 2-fluid additional injection core system, 3-gas-liquid injection system, 4-horizontal supercooling flow module, 5-vertical supercooling flow module, 6-cage structure microscopic research module, 7-first-level fluid separation-blocking-unblocking tank, 8-high-pressure camera, 9-first-level tank bottom ladder-type reduction structure, 10-first-level tank reduction structure heating belt, 11-first-level tank bottom vertical pipe, 12-first-level tank bottom vertical pipe heating belt, 13-first-level tank bottom heating controller, 14-small liquid-solid two-phase flow electromagnetic pump, 15-secondary fluid separation-blocking-unblocking tank, 16-secondary tank internal high-pressure camera, 17-secondary tank bottom ladder-type reduction structure, 18-secondary tank reduction structure heating belt, 19- Secondary tank bottom heating controller, 20-secondary tank bottom fluid three-way structure, 21-secondary tank bottom three-way heating belt, 22-secondary tank bottom fluid discharge pipeline, 23-liquid-solid flow pipeline starting end heating belt, 24-liquid-solid flow pipeline starting end heating controller, 25-liquid-solid two-phase flow pipeline, 26-multiphase flow pipeline ball valve, 27-large liquid-solid two-phase flow electromagnetic pump, 28-liquid-solid two-phase flow flow meter, 29-micro module inflow port, 30-gas-liquid-solid flow mixer, 31-vacuum pump, 32-venting pipeline valve, 33-venting pipeline, 34-gas separation tank, 35-gas separation tank lower end liquid reflux pipe, 36-high-pressure gas pump, 37-gas flow meter, 38-gas cooling pipeline, 39-refrigeration cycle Circular water bath, 40-gas-liquid-solid three-phase input pipeline, 41-small tee for input pipeline, 42-small tee for output pipeline, 43-gas-liquid-solid three-phase output pipeline, 44-inflow pipeline ball valve, 45-inflow pipeline, 46-inflow pipeline tee, 47-pressure relief pipeline, 48-small fluid container, 49-inflow reducer, 50-inflow reducer flange, 51-inflow capillary, 52-liquid phase capillary ball valve, 53-pressure-resistant upper cover, 54-circular window on the upper cover, 55-pressure-resistant base, 56-temperature control base, 57-lifting base, 58-lifting joystick, 59-micro module placement table, 60-sapphire pressure-resistant transparent glass, 61-embedded camera, 62-upper cover pressure probe, 63-temperature conductive metal cylinder Body, 64-Metal Cylinder Control Interface, 65-Metal Cylinder Temperature Control and Monitoring, 66-Coolant Input / Output Port, 67-Coolant Input / Output Pipe, 68-Micro Module Temperature Control Water Bath, 69-Micro Module Pressure Recorder, 70-Micro Module Supporting Computer, 71-Internal Liquid Level Limiter, 72-Upper Cover-Base Sealing Bolt, 73-Liquid Containing Residual Hydrate Cage Structure, 74-Gas-Liquid Interface of Liquid Containing Residual Cage Structure, 75-Visible Light, 76-Infrared Light, 77-Light Overlap Point, 78-Sum Frequency Resonance Signal Light, 79-Micro Module Coolant, 80-Sum Frequency Resonance Spectrometer Signal Synthesis Box, 81-Additional Fluid Injection into the Core Agitator, 82-Outer Annulus of the Core Agitator,83-core stirring kettle rotating motor, 84-core stirring kettle rotating rod, 85-core stirring kettle rotating blade, 86-internal temperature and pressure sensor, 87-core stirring kettle temperature control water bath, 88-cooling liquid input / output pipe, 89-liquid phase flow pipeline at the lower end of stirring kettle, 90-small separation tank at the rear end of stirring kettle, 91-gas drying and methane concentration monitoring device, 92-small air pump, 93-gas recovery tank, 94-small separation tank pressure relief port, 95-liquid phase at the lower end of small separation tank Flow pipeline, 96-liquid-solid two-phase flow electromagnetic pump, 97-stainless steel bucket, 98-liquid phase inhibitor container, 99-electronic scale, 100-liquid injection pump, 101-liquid injection pipeline, 102-carbon dioxide high-pressure gas cylinder, 103-methane high-pressure gas cylinder, 104-gas cylinder pressure relief valve, 105-gas booster pump, 106-gas flow control module, 107-horizontal input pipeline, 108-horizontal subcooling flow straight pipe, 109-subcooling pipe insulation layer, 110- Coolant annulus of cooling pipe, 111-stainless steel inner tube of subcooling pipe, 112-subcooling pipe flange, 113-cooling liquid continuous pipe, 114-polyvinyl chloride horizontal visual tube, 115-horizontal visual tube support frame, 116-horizontal subcooling flow U-tube, 117-high-speed camera, 118-particle monitoring optical probe insertion port, 119-data acquisition computer, 120-subcooling pipe temperature and pressure sensor, 121-subcooling pipe differential pressure sensor, 122-sensor data cable, 123-macro Flow observation system console, 124-horizontal output pipeline, 125-vertical subcooling tube bracket base, 126-vertical subcooling tube bracket, 127-vertical input pipeline, 132-vertical output pipeline, 133-visible light transmitter, 134-visible light transmission aperture, 135-infrared light transmitter, 136-infrared light transmission aperture, 137-SFG signal light transmission aperture, 138-SFG signal light receiver, 139-inner baffle of signal synthesis box. DETAILED DESCRIPTION

[0080] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0081] Example 1, reference Figures 1-8 The present invention relates to a device suitable for macroscopic and microscopic research on residual cage structures of hydrates, comprising a fluid separation-blocking-unblocking core system 1, a fluid additional injection core system 2, a gas-liquid injection system 3, a horizontal subcooling flow module 4, a vertical subcooling flow module 5, and a cage structure microscopic research module 6. The fluid separation-blocking-unblocking core system 1 comprises a primary fluid separation-blocking-unblocking tank 7, a secondary fluid separation-blocking-unblocking tank 15, a gas separation tank 34, and a gas-liquid-solid three-phase input pipeline 40.

[0082] The top of the primary fluid separation-blocking-unblocking tank 7 is respectively connected to the vacuum pump 31, the gas flow control module 106 of the gas-liquid injection system 3 and the gas separation tank 34, and the left side of the middle is connected to the liquid reflux pipe 35 at the lower end of the gas separation tank and the gas-liquid-solid three-phase output pipeline 43; the bottom is a ladder-type reducing structure 9 at the bottom of the primary tank, and two primary tank reducing structure heating belts 10 connected to the primary tank bottom heating controller 13 are installed on the outer wall of the ladder-type reducing structure 9 at the bottom of the primary tank; the lower end of the ladder-type reducing structure 9 at the bottom of the primary tank is connected to the top of the secondary fluid separation-blocking-unblocking tank 15 through the vertical pipe 11 at the bottom of the primary tank; the outer wall of the vertical pipe 11 at the bottom of the primary tank is wrapped with the vertical pipe heating belt 12 at the bottom of the primary tank;

[0083] The middle right side of the secondary fluid separation-blocking-unblocking tank 15 is connected to the fluid additional injection core system 2 and the liquid injection pump 100; the bottom is connected to the secondary tank bottom fluid three-way structure 20, and the outer walls of both are equipped with a secondary tank reduction structure heating belt 18 and a secondary tank bottom three-way heating belt 21 connected to the secondary tank bottom heating controller 19. A secondary tank internal high-pressure camera 16 is installed in the secondary fluid separation-blocking-unblocking tank 15; one end of the liquid-solid two-phase flow pipeline 25 It is connected to the fluid tee structure 20 at the bottom of the secondary tank, and the other end is connected in sequence to a large liquid-solid two-phase flow electromagnetic pump 27, a liquid-solid two-phase flow flow meter 28, a micro-module inlet port 29, a multiphase flow pipeline ball valve 26 at the end, and a gas-liquid-solid flow mixer 30; the upper end of the gas-liquid-solid flow mixer 30 is connected to a gas-liquid-solid three-phase input pipeline 40, and the side wall of the gas-liquid-solid flow mixer 30 is connected to a gas cooling pipeline 38, on which a gas flow meter 37 is provided;

[0084] Reference Figure 3 The fluid additional injection core system 2 mentioned in the present invention is composed of a fluid additional injection core stirring tank 81, a small separation tank 90 at the rear end of the stirring tank, a gas recovery tank 93, and a liquid-solid two-phase flow electromagnetic pump 96.

[0085] The fluid is additionally injected into the bottom right end of the core stirring tank 81, which is connected to a liquid injection pump 100 via a liquid injection pipeline 101. The center position of the bottom is connected to a small separation tank 90 at the rear end of the stirring tank via a liquid phase flow pipeline 89 at the lower end of the stirring tank. The outer wall is provided with an outer annulus 82 of the core stirring tank, and the inner cavity is provided with a core stirring tank rotating rod 84, a core stirring tank rotating blade 85 and an internal temperature and pressure sensor 86. The outer annulus 82 of the core stirring tank is connected to a core stirring tank temperature-controlled water bath 87 via a coolant input / output pipe 88.

[0086] The top center of the small separation tank 90 at the rear end of the stirring tank is connected to the gas recovery tank 93 through the ventilation pipeline 33, and the bottom center is connected to the secondary fluid separation-blocking-unblocking tank 15 through the liquid phase flow pipeline 95 at the lower end of the small separation tank;

[0087] The ends of the gas-liquid-solid three-phase input pipeline 40 are connected to the inlet ends of the horizontal subcooling flow module 4 and the vertical subcooling flow module 5 respectively through the small input pipeline tee 41, and the ends of the gas-liquid-solid three-phase output pipeline 43 are connected to the outlet ends of the horizontal subcooling flow module 4 and the vertical subcooling flow module 5 respectively through the small output pipeline tee 42;

[0088] The side wall of the liquid-solid two-phase flow pipeline 25 is connected to the cage-type structure microscopic research module 6 through the microscopic module inflow port 29;

[0089] Reference Figure 2 The cage-type structure microscopic research module 6 mentioned in the present invention includes a pressure-resistant upper cover 53, a circular window 54 on the upper cover, a pressure-resistant base 55, a temperature-controlled base 56 and a lifting base 57. The upper part of the pressure-resistant base 55 is provided with a pressure-resistant upper cover 53, and the pressure-resistant upper cover 53 is provided with multiple circular windows 54 on the upper cover. The lower part of the pressure-resistant base 55 is provided with a temperature-controlled base 56, and the lower part of the temperature-controlled base 56 is provided with a lifting base 57.

[0090] Reference Figure 3 The gas-liquid injection system 3 mentioned in the present invention includes a stainless steel water bucket 97, a liquid phase inhibitor container 98, a liquid injection pump 100, a liquid injection pipeline 101, a carbon dioxide high-pressure gas cylinder 102, a methane high-pressure gas cylinder 103, a gas booster pump 105 and a gas flow control module 106. The pure water in the stainless steel water bucket 97 is injected into the secondary fluid separation-blocking-unblocking tank 15 by the liquid injection pump 100 through the liquid injection pipeline 101 and the liquid phase capillary ball valve 52; the inhibitor solution in the liquid phase inhibitor container 98 is injected into the secondary fluid separation-blocking-unblocking tank 15 through the liquid injection pipeline 101 and the liquid phase capillary ball valve 52; The liquid is injected into the additional fluid injection core stirring tank 81 by the liquid injection pump 100 through the liquid injection pipeline 101 and the liquid phase capillary ball valve 52, and the electronic scale 99 is used to calculate the injection amount of the liquid phase; the gas in the carbon dioxide high-pressure gas cylinder 102 and the methane high-pressure gas cylinder 103 is injected into the primary fluid separation-blocking-deblocking tank 7 and the additional fluid injection core stirring tank 81 in turn through the gas cylinder pressure relief valve 104, the ventilation pipeline 33, the gas booster pump 105, the gas flow control module 106 and multiple ventilation pipeline valves 32.

[0091] Reference Figure 4The horizontal subcooling flow module 4 mentioned in the present invention includes a horizontal input pipeline 107, a horizontal subcooling flow straight pipe 108, a subcooling pipe insulation layer 109, a subcooling pipe coolant annulus 110, a subcooling pipe stainless steel inner pipe 111, a subcooling pipe flange 112, a coolant continuous pipe 113, a polyvinyl chloride horizontal visual tube 114, a horizontal visual tube support frame 115, a horizontal subcooling flow U-shaped tube 116, a high-speed camera 117, a particle monitoring optical probe insertion port 118, a data acquisition computer 119, a subcooling pipe temperature and pressure sensor 120, a subcooling pipe pressure difference sensor 121, a sensor data line 122, a macro flow system console 123, and a horizontal output pipeline 124.

[0092] The right ends of the two horizontal subcooling flow straight pipes 108 are connected to the horizontal subcooling flow U-shaped pipe 116, and the two horizontal subcooling flow straight pipes 108 are respectively connected to the polyvinyl chloride horizontal sight tube 114 through the subcooling pipe flange 112. The left end of the upper horizontal subcooling flow straight pipe 108 is connected to the horizontal input pipeline 107, and the left end of the lower horizontal subcooling flow straight pipe 108 is connected to the horizontal output pipeline 124.

[0093] The horizontal subcooling flow straight pipe 108 and the horizontal subcooling flow U-shaped pipe 116 are both double-layer structures, with a subcooling pipe stainless steel inner pipe 111 inside for circulating multiphase flow, and an interlayer space for the subcooling pipe coolant annulus 110 for circulating the coolant output from the refrigeration circulating water bath 39 in the module. The outermost layer is wrapped with a subcooling pipe insulation layer 109, and a coolant continuous pipe 113 is connected to both sides of a polyvinyl chloride horizontal visual tube 114 to achieve communication between the two subcooling pipe coolant annuli 110;

[0094] Multiple subcooling pipe temperature and pressure sensors 120 and subcooling pipe differential pressure sensors 121 are installed at intervals on the horizontal subcooling flow straight pipe 108, and are connected to the macro flow system control console 123 through sensor data lines 122;

[0095] A high-speed camera 117 is installed on the side of the lower polyvinyl chloride horizontal visual tube 114, which is used to capture the multiphase flow morphology during the secondary generation and rapid blockage of hydrates under the influence of the residual cage structure of hydrates; the horizontal supercooled flow straight pipe 108 at the rear end of the high-speed camera 117 is embedded with multiple obliquely installed particle monitoring optical probe insertion ports 118, and the high-speed camera 117 and the particle monitoring optical probe insertion port 118 are connected to the data acquisition computer 119.

[0096] Reference Figure 5 The lower inlet of the vertical subcooling flow module 5 mentioned in the present invention is connected to the vertical input pipeline 127, and the outlet is connected to the vertical output pipeline 132. The vertical subcooling flow module 5 is mounted on the vertical subcooling pipe bracket 126 to keep it vertical to the horizontal ground, and the vertical subcooling pipe bracket base 125 is installed at the bottom of the vertical subcooling pipe bracket 126.

[0097] Reference Figure 2 The top of the pressure-resistant cover 53 of the cage-type structure microscopic research module 6 of the present invention is equipped with an embedded camera 61 and a cover pressure probe 62. A circular cover window 54 is embedded in the center of the left and right walls. The center of the circular cover window 54 is made of sapphire pressure-resistant and transparent glass 60. The bottom end of the inner wall of the circular cover window 54 is equipped with multiple internal liquid level limiters 71 for indicating the injection amount of hydrate decomposition water and limiting the liquid level of the decomposition water.

[0098] The top of the pressure-resistant base 55 is connected to the pressure-resistant upper cover 53 through the upper cover-base sealing bolts 72. The inner cavity contains liquid 73 containing residual hydrate cage structure. The center position of the right inner wall of the pressure-resistant base 55 is equipped with an inflow tube 51. The right end of the inflow tube 51 is connected to the micro-module inflow port 29 in the fluid separation-blocking-unblocking core system 1 through the inflow reducer flange 50, the inflow reducer 49, the inflow pipeline ball valve 44, the inflow pipeline tee 46 and the inflow pipeline 45 in sequence, forming a channel for the hydrate decomposition water to flow into the high-pressure cavity in the micro-module; the bottom of the inflow pipeline tee 46 is equipped with a pressure relief pipeline 47, an inflow pipeline ball valve 44 and a small fluid container 48.

[0099] Preferably, the temperature-controlled base 56 has a rectangular structure, and its outer wall is an integrated structure with the outer wall of the pressure-resistant base 55. A temperature-conducting metal cylinder 63 is installed at the center of its internal cavity, and the metal cylinder temperature control and monitor 65 is connected through the metal cylinder control interface 64. The front of the temperature-controlled base 56 is connected to the micro-module temperature-controlled water bath 68 through the coolant input / output port 66 and the coolant input / output pipe 67; a lifting control lever 58 is installed on one side of the lifting base 57, and a micro-module placement platform 59 is provided on the lower side of the lifting base 57.

[0100] The present invention describes a method for macroscopic and microscopic studies of residual hydrate cage structures. The technical solution is as follows: Experimental methods for macroscopic flow studies of residual hydrate cage structures include the following three types: a. an experimental method to investigate the impact of residual cage structures on secondary hydrate formation and rapid blockage; b. an experimental method to investigate effective methods for eliminating residual cage structures; and c. an experimental method to simulate the use of produced water from hydrate extraction for subsea carbon dioxide solidification and storage.

[0101] The experimental method for investigating the effect of residual cage structures on the secondary formation and rapid blockage of hydrates includes three stages: the formation of complete hydrate cage structures, the formation of residual hydrate cage structures, and the secondary formation and rapid blockage of hydrates. The specific steps are as follows:

[0102] S1, the stage of formation of complete hydrate cage structure:

[0103] First, check the air tightness of the entire system. Close the multiphase flow pipeline ball valve 26 at the lower end of the small separation tank 90 at the rear end of the stirred tank and the rear end of the micromodule inlet port 29. Reduce the pressure in the entire system to -0.1 MPa via the vacuum pump 31. Then, inject a certain amount of pure water and methane into the entire system through the gas-liquid injection system 3 from the lower right end of the secondary fluid separation-blocking-unblocking tank 15 and the top of the primary fluid separation-blocking-unblocking tank 7, respectively. Stop when the preset experimental pressure is reached.

[0104] Then, the refrigeration circulating water bath 39 corresponding to the gas cooling pipeline 38, the refrigeration circulating water bath 39 corresponding to the horizontal subcooling flow module 4 and the vertical subcooling flow module 5, the high-pressure air pump 36, and the large liquid-solid two-phase flow electromagnetic pump 27 are sequentially turned on to form a gas-liquid two-phase stratified flow with a porosity of less than 30% in the stainless steel inner tube 111 of the subcooling tube. The target temperature of the multiple refrigeration circulating water baths 39 is set to -3 degrees to continuously cool the flow system.

[0105] Subsequently, when the temperature in the flow system drops below the hydrate phase equilibrium temperature, the macroscopic induction period of hydrate formation begins, and the cage structure of water molecules gradually begins to form at the gas-liquid interface. When the macroscopic induction period of hydrate formation ends, hydrates begin to form, and the number of complete hydrate cage structures gradually increases. The aggregation, adhesion, accumulation, and deposition of hydrates during the flow process cause the rapid formation and gradual increase of hydrate aggregates. The ladder-type reducing structure 9 at the bottom of the primary fluid separation-blocking-unblocking tank 7 and the ladder-type reducing structure 17 at the bottom of the secondary tank at the bottom of the secondary fluid separation-blocking-unblocking tank 15, as well as the change-direction pipe structure within the fluid three-way structure 20 at the bottom of the secondary tank, induce and accelerate the blockage of hydrate aggregates.

[0106] Finally, when the flow rate displayed by the liquid-solid two-phase flow meter 28 reaches 0, indicating the formation of complete blockage and the end of the formation of a complete hydrate cage structure, the refrigeration circulating water bath 39 and the high-pressure air pump 36 are turned off; the power of the large liquid-solid two-phase flow electromagnetic pump 27 is increased and the small liquid-solid two-phase flow electromagnetic pump 14 is turned on. If the displayed flow rate is 0, it indicates that hydrate blockage has formed at the bottom of both the primary fluid separation-blocking-unblocking tank 7 and the secondary fluid separation-blocking-unblocking tank 15; if the displayed flow rate is not 0 but drops to 0 quickly, it indicates that hydrate blockage exists at the bottom of the secondary fluid separation-blocking-unblocking tank 15.

[0107] S2, the formation stage of residual hydrate cage structure:

[0108] First, the large liquid-solid two-phase flow electromagnetic pump 27 and the small liquid-solid two-phase flow electromagnetic pump 14 are turned off, and the first tank bottom heating controller 13, the second tank bottom heating controller 19, and the liquid-solid flow pipeline starting end heating controller 24 are used to keep the first tank diameter reduction structure heating zone 10, the second tank diameter reduction structure heating zone 18, the second tank bottom three-way heating zone 21, and the liquid-solid flow pipeline starting end heating zone 23 in the temperature range of 35 to 38 degrees Celsius, thereby heating the hydrates blocked in the first tank bottom ladder-type diameter reduction structure 9, the second tank bottom ladder-type diameter reduction structure 17, and the second tank bottom three-way fluid structure 20 at the bottom of the first fluid separation-blocking-unblocking tank 7 and the second fluid separation-blocking-unblocking tank 15. During the gradual decomposition of the hydrates, the gas molecules gradually detach from the complete hydrate cage structure, and the residual hydrate cage structure begins to form and gradually increases with the decomposition of the hydrates.

[0109] Subsequently, the large liquid-solid two-phase flow electromagnetic pump 27 and the small liquid-solid two-phase flow electromagnetic pump 14 are turned on once every heating period. If the liquid-solid two-phase flow meter 28 shows a flow rate of 0, indicating that the system has not recovered its fluidity, the two electromagnetic pumps are turned off and heating is continued; if the liquid-solid two-phase flow meter 28 shows a flow rate not of 0, the two electromagnetic pumps are kept on while heating is continued;

[0110] Finally, when the flow rate indicated by the liquid-solid two-phase flow meter 28 returns to the level before hydrate formation under the same electromagnetic pump power conditions, it indicates that the hydrate blockage in the system has been completely eliminated; at this time, all heating controllers are turned off and the high-pressure air pump 36 is turned on to form a stratified flow containing residual hydrate cage structures in the liquid phase in the horizontal subcooling flow module 4 and the vertical subcooling flow module 5; the refrigeration circulating water bath 39 corresponding to the subcooling flow module is turned on and the target temperature is adjusted to the laboratory room temperature before the start of step S1, so that the temperature and pressure in the flow system are increased to prevent the undecomposed hydrates from having other effects on the residual cage structures. When the pressure of the flow system returns to the level before the cooling in step S1 is started, the target temperature of the refrigeration circulating water bath 39 is adjusted to 0 degrees;

[0111] S3, Hydrate secondary formation-rapid plugging stage:

[0112] First, the refrigeration circulating water bath 39 corresponding to the gas cooling pipeline 38 is turned on and the target temperature of the refrigeration circulating water bath 39 is set to -3 degrees Celsius to continuously cool the stratified flow system containing residual hydrate cage structures in the liquid phase;

[0113] Subsequently, during the hydrate secondary formation induction period, secondary hydrate formation, and rapid blockage after formation, the subcooling pipe temperature and pressure sensor 120, subcooling pipe differential pressure sensor 121, high-speed camera 117 mounted on the side of the polyvinyl chloride horizontal visual tube 114, and optical equipment embedded in the particle monitoring optical probe insertion port 118 in the horizontal subcooling flow module 4 and the vertical subcooling flow module 5 are used to monitor, calculate, and record data on the hydrate secondary formation induction time, secondary formation rate, secondary formation flow barrier evolution morphology, hydrate aggregate morphology, and hydrate aggregate particle size change. These data are then compared and analyzed with the data in step S1 to explore the influence of the residual cage structure on the hydrate secondary formation and rapid blockage and its mechanism of action.

[0114] Finally, when the secondary hydrate blockage is completely formed, the entire system is heated. When the system fluidity is restored, all the methane gas in the system is displaced by injecting carbon dioxide gas into the gas recovery tank 93, and the entire system is emptied through the fluid discharge pipeline 22 at the bottom of the secondary tank to start the next set of experiments.

[0115] Preferably, the above experimental method for exploring the effective elimination method of the residual cage structure further includes a chemical inhibitor injection stage and a hydrate secondary generation-mobilization stage, and the specific steps are as follows:

[0116] A1. Chemical inhibitor injection stage:

[0117] First, the liquid injection pump 100 is turned on to inject the hydrate kinetic inhibitor or the combined kinetic inhibitor and polymerization inhibitor from the liquid-phase inhibitor container 98 into the fluid additional injection core stirring tank 81. The injection amount of the inhibitor is recorded using the electronic scale 99. The core stirring tank rotation motor 83 and the core stirring tank temperature-controlled water bath 87 are turned on to ensure that the inhibitor is evenly distributed under stirring and gradually reaches its optimal working temperature. Methane is injected into the fluid additional injection core stirring tank 81 via the gas-liquid injection system 3. Injection is stopped when the pressure in the tank is 1 MPa higher than the pressure in the secondary fluid separation-blocking-unblocking tank 15.

[0118] Subsequently, the core stirring tank rotation motor 83 is kept turned on, and the multiphase flow pipeline ball valve 26 on the liquid phase flow pipeline 89 at the lower end of the stirring tank is opened, allowing the inhibitor to flow into the small separation tank 90 at the rear end of the stirring tank under the action of the pressure difference; then, the large liquid-solid two-phase flow electromagnetic pump 27 and the high-pressure air pump 36 are turned off, and the liquid-solid two-phase flow electromagnetic pump 96 on the liquid phase flow pipeline 89 at the lower end of the stirring tank and the liquid phase flow pipeline 95 at the lower end of the small separation tank are turned on in sequence, allowing all the inhibitor to flow into the secondary fluid separation-blocking-unblocking tank 15;

[0119] Finally, the liquid phase flow pipeline 95 at the lower end of the small separation tank is closed, and the small air pump 92 is turned on to pump the methane gas in the entire fluid additional injection core system 2 into the gas recovery tank 93. At the same time, carbon dioxide gas is injected into the fluid additional injection core stirring tank 81 and the small separation tank 90 at the rear end of the stirring tank through the gas-liquid injection system 3 to ensure that all methane gas is displaced and enters the gas recovery tank 93.

[0120] A2. Hydrate secondary formation-mobilization stage:

[0121] The high-pressure air pump 36 and the large liquid-solid two-phase flow electromagnetic pump 27 are sequentially turned on to form a stratified flow in the system containing residual hydrate cage structures and chemical inhibitors in the liquid phase. Simultaneously, the refrigeration circulating water bath 39 is turned on to continuously cool the flow system. Using the subcooling tube temperature and pressure sensors 120, subcooling tube pressure differential sensors 121, high-speed cameras 117 mounted on the side of the visual tube, and optical equipment embedded in the particle monitoring optical probe insertion port 118 within the horizontal subcooling flow module 4 and the vertical subcooling flow module 5, key data on the induction time, generation rate, flow morphology, and aggregate size changes during the secondary hydrate generation and flow barrier evolution process under the presence of different types of inhibitors are monitored, calculated, and recorded. The data is then compared and analyzed with data from experiments without inhibitors to explore effective methods and mechanisms for eliminating residual hydrate cage structures.

[0122] After the experiment, the entire fluid needs to be additionally injected into the core system 2 through the pressure relief port 94 of the small separation tank equipped with a built-in valve to displace the carbon dioxide gas injected into the methane gas and emptied. The fluid is additionally injected into the core system 2 through the gas-liquid injection system 3 and pure water is injected multiple times and then emptied to clean the residual inhibitors in the system so that subsequent experiments containing different types of inhibitors can be carried out.

[0123] Preferably, the above-mentioned experimental method for simulating the use of hydrate production water for seabed carbon dioxide solidification and storage includes four stages: the formation stage of the complete cage structure of methane hydrate in the kettle, the formation stage of the residual cage structure of hydrate in the kettle, the injection stage of decomposition of water and carbon dioxide into the separation tank, and the carbon dioxide hydrate generation and flow stage. The specific steps are as follows:

[0124] B1, the stage of formation of complete cage structure of methane hydrate in the kettle:

[0125] First, after checking the air tightness of the entire system, the pressure in the entire system was reduced to -0.1 MPa using the vacuum pump 31. The liquid phase flow line 89 at the lower end of the stirring tank and the liquid phase flow line 95 at the lower end of the small separation tank were closed. Pure water and methane gas were injected into the core stirring tank 81 through the gas-liquid injection system 3. The injection was stopped after the experimental set pressure was reached.

[0126] Subsequently, the core stirring kettle rotation motor 83 and the core stirring kettle temperature-controlled water bath 87 were turned on, and the target temperature of the temperature-controlled water bath was set to -3 degrees Celsius, allowing the high-pressure methane gas and pure water in the kettle to continue to cool down while stirring. When the system temperature fell below the hydrate phase equilibrium temperature, the hydrate cage structure began to initially form at the gas-liquid interface. When additional fluid was injected into the core stirring kettle 81, the temperature suddenly rose, and the feedback torque of the core stirring kettle rotation motor 83 increased, indicating the formation of methane hydrate and the formation of a complete hydrate cage structure.

[0127] Finally, the high-pressure camera 8 injected with additional fluid into the core stirring tank 81 assists in determining the formation and agitation of the hydrate in the tank. When the speed of the core stirring tank rotating motor 83 drops to 0, indicating that the hydrate in the tank is completely blocked and the formation of a complete hydrate cage structure is complete, the core stirring tank rotating motor 83 is turned off.

[0128] B2, the formation stage of the residual cage structure of hydrate in the kettle:

[0129] First, the target temperature of the core stirred tank temperature-controlled water bath 87 was set to 25 degrees Celsius. The hydrates blocked in the tank were heated for a period of time and then closed to simulate the process of self-heating materials promoting hydrate decomposition during marine hydrate mining.

[0130] Subsequently, the liquid phase flow line 89 at the lower end of the stirred tank is slowly opened, allowing the fluid to be additionally injected into the core stirred tank 81, causing the hydrate to gradually decompose during the decompression process, simulating the process of decompression recovery of hydrates in the sea. At the same time, the hydrate decomposition water and the gas produced by the decomposition flow into the small separation tank 90 at the rear end of the stirred tank. As the gas molecules gradually detach from the complete hydrate cage structure, the hydrate cage structure remaining in the hydrate decomposition water gradually increases.

[0131] Finally, when the pressure in the small separation tank 90 at the rear end of the stirring kettle no longer increases, the liquid phase flow pipeline 89 at the lower end of the stirring kettle is fully opened;

[0132] B3, decomposition of water and injection of carbon dioxide into the separation tank stage:

[0133] First, keep the liquid phase flow pipeline 95 at the lower end of the small separation tank closed, and inject carbon dioxide gas into the fluid separation-blocking-unblocking core system 1, the horizontal subcooling flow module 4, and the vertical subcooling flow module 5 through the gas-liquid injection system 3. Stop the injection when the pressure in the system reaches 2 MPa.

[0134] Subsequently, the methane gas in the core system 2 that is additionally injected with the fluid needs to be displaced with carbon dioxide, and the vent line valve 32 between the small separation tank 90 at the rear end of the stirred tank and the methane gas pumped into the gas recovery tank 93 is opened, so that the methane gas in the core system 2 that is additionally injected with the fluid flows into the gas recovery tank 93 driven by the pressure difference. When the pressure in the system no longer changes significantly, a new gas recovery tank 93 is replaced to continue collecting methane gas; when the pressure in the system drops to 2 MPa, a new gas recovery tank 93 is replaced and carbon dioxide gas is continuously injected into the core system 2 that is additionally injected with the fluid through the gas-liquid injection system 3, and the small air pump 92 is turned on to allow the carbon dioxide gas to displace all the remaining methane gas in the core system 2 that is additionally injected with the fluid and enter the gas recovery tank 93; when the gas drying and methane concentration monitoring device 91 shows that the methane concentration is 0, the small air pump 92 is turned off and the injection of carbon dioxide is stopped;

[0135] Finally, the liquid phase flow line 95 at the lower end of the small separation tank was opened, and all the hydrate decomposition water containing the residual hydrate cage structure in the small separation tank 90 at the rear end of the stirred tank was injected into the secondary fluid separation-blocking-unblocking tank 15, simulating the process of injecting produced water from marine hydrate production into the submarine carbon dioxide hydrate generation system. When the pressure in the secondary fluid separation-blocking-unblocking tank 15 no longer changed, the liquid phase flow line 95 at the lower end of the small separation tank was closed.

[0136] B4. Carbon dioxide hydrate formation-mobilization stage:

[0137] First, carbon dioxide gas is continuously injected into the fluid separation-blocking-unblocking core system 1, the horizontal subcooling flow module 4, and the vertical subcooling flow module 5 through the gas-liquid injection system 3. The injection is stopped when the pressure in the system reaches 5 MPa.

[0138] Subsequently, the primary fluid separation-blocking-unblocking tank 7 and the secondary fluid separation-blocking-unblocking tank 15 and the gas separation tank 34 are closed, the gas cooling pipeline 38 is closed, and the refrigeration circulating water bath 39 corresponding to the horizontal subcooling flow module 4 and the vertical subcooling flow module 5 and the large liquid-solid two-phase flow electromagnetic pump 27 are turned on to form a gas-liquid two-phase bubbly flow with a porosity of less than 10% and containing residual hydrate cage structures in the stainless steel inner tubes 111 of the subcooling tubes in the horizontal subcooling flow module 4 and the vertical subcooling flow module 5. The target temperature of the refrigeration circulating water bath 39 is set to -3 degrees to continuously cool the flow system.

[0139] Then, during the continuous cooling process of the flow system, the carbon dioxide gas gradually dissolves in the methane hydrate decomposition water. Along with the induction and rapid formation of carbon dioxide hydrate, the carbon dioxide gas molecules and the residual hydrate cage structure in the methane hydrate decomposition water reform into a complete carbon dioxide hydrate cage structure.

[0140] Finally, through the horizontal supercooled flow module 4 and the vertical supercooled flow module 5, key data such as the induction time, generation rate, flow morphology, and flow pressure difference changes during the formation and flow of carbon dioxide hydrates are monitored, calculated, and recorded, thereby studying multiple key scientific issues in the process of using hydrate mining produced water for submarine carbon dioxide solidification and storage.

[0141] Example 2, the method for using the device for macroscopic and microscopic research of residual hydrate cage structures mentioned in the present invention, differs from Example 1 in that:

[0142] The present invention's microscopic optical research experimental method for residual hydrate cage structures includes five stages: micromodule injection, micromodule separation, micromodule and optical device assembly, micromodule temperature and height adjustment, and micromolecular structure change analysis. The specific steps are as follows:

[0143] C1. Micro-module injection phase:

[0144] First, methane hydrate decomposition water containing residual hydrate cage structures is generated under high pressure in the fluid separation-blocking-unblocking core system 1 and the horizontal supercooling flow module 4;

[0145] Subsequently, the high-pressure air pump 36 is turned off, and the power of the large liquid-solid two-phase flow electromagnetic pump 27 is adjusted to the minimum value that can maintain the circulation of the liquid phase in the system. The inflow pipeline ball valve 44 on the pressure relief pipeline 47 is ensured to be closed, and the two inflow pipeline ball valves 44 on the inflow pipeline 45 are opened to a quarter of the opening. Then, the liquid phase capillary ball valve 52 is fully opened, so that the methane hydrate decomposition water containing the residual cage-type structure of the hydrate in the liquid-solid two-phase flow pipeline 25 passes through the micro-module inflow port 29, the inflow pipeline 45, the inflow reducer 49, and the inflow capillary 51, and flows into the inner cavity of the cage-type structure microscopic research module 6 at a relatively slow flow rate;

[0146] Finally, the liquid level in the micromodule cavity is observed through the embedded camera 61 and the circular window 54 on the upper cover. When the liquid level is about to reach the height of the internal liquid level limiter 71, the liquid phase capillary ball valve 52 is quickly closed. Then, the inflow pipe ball valve 44 on the right side of the inflow pipe tee 46 and the large liquid-solid two-phase flow electromagnetic pump 27 are closed.

[0147] C2, Micro-module separation stage:

[0148] Keep the inflow pipe ball valve 44 on the left side of the inflow pipe tee 46 open, and open the inflow pipe ball valve 44 on the pressure relief pipe 47 to one-quarter of its opening. This allows the high-pressure gas and liquid in the pipe between the inflow pipe ball valve 44 on the right side of the inflow pipe tee 46 and the liquid phase capillary ball valve 52 to be discharged into the small fluid container 48 through the pressure relief pipe 47 due to the pressure difference. Then, remove the inflow reducer flange 50, completing the separation of the inflow capillary 51 on the right end of the cage-type structure microscopic research module 6 from the inflow reducer 49.

[0149] C3, Micro-module and optical equipment combination stage:

[0150] Keep the liquid phase capillary ball valve 52 closed, and place the cage-type structure microscopic research module 6 between the two internal baffles 139 of the signal synthesis box 80 of the sum frequency resonance spectrometer; connect the embedded camera 61 and the upper cover pressure probe 62 to the microscopic module pressure recorder 69 and the microscopic module supporting computer 70 through the sensor data line 122; connect the coolant input / output port 66 on the temperature control base 56 of the microscopic module to the microscopic module temperature control water bath 68 through the coolant input / output pipe 67; and connect the metal cylinder control interface 64 in the temperature control base 56 to the metal cylinder temperature control and monitoring device 65 through the sensor data line 122;

[0151] C4, Micro module temperature and height adjustment stage:

[0152] First, the temperature of the temperature-conducting metal cylinder 63 is maintained at a level 0.5 degrees higher than the hydrate phase equilibrium temperature corresponding to the pressure in the inner cavity of the cage-type structure microscopic research module 6 at that time through the metal cylinder temperature control and monitoring device 65, so as to prevent the formation of complete hydrate cage structures when the temperature in the microscopic module inner cavity is too low and the decomposition of residual hydrate cage structures when the temperature is too high. The set temperature of the microscopic module temperature-controlled water bath 68 is adjusted so that the temperature of the microscopic module coolant 79 is consistent with the temperature of the temperature-conducting metal cylinder 63, thereby achieving the purpose of heat dissipation for the metal cylinder.

[0153] Subsequently, the visible light emitter 133, infrared light emitter 135, and SFG signal light receiver 138 on one side of the internal baffle 139 of the signal synthesizer box 80 of the sum frequency resonance spectrometer are turned on, and the height of the lifting base 57 is slowly adjusted by the lifting control lever 58 to achieve the purpose of controlling the horizontal height of the gas-liquid interface 74 containing the residual cage structure liquid in the inner cavity of the microscopic module; wherein, the visible light emitter 133 is along the visible light transmission aperture 134; the infrared light emitter 135 is along the infrared light transmission aperture 136; and the SFG signal light receiver 138 is along the SFG signal light transmission aperture 137;

[0154] Finally, when the level of the gas-liquid interface 74 containing the residual cage-type structure liquid in the microscopic module cavity reaches a specific position with the following requirements, the height adjustment of the lifting base 57 is stopped. The specific position must meet the following requirements: a. The visible light 75 and infrared light 76 emitted by the sum frequency resonance spectrometer can simultaneously enter the high-pressure cavity of the microscopic module through the sapphire pressure-resistant transparent glass 60 on the left side of the pressure-resistant upper cover 53 of the microscopic module, and can overlap at the same point on the gas-liquid interface 74 containing the residual cage-type structure to form a sum frequency resonance signal light 78; b. The sum frequency resonance signal light 78 reflected from the gas-liquid interface 74 containing the residual cage-type structure liquid in the high-pressure cavity of the microscopic module can successively pass through the sapphire pressure-resistant transparent glass 60 on the right side of the pressure-resistant upper cover 53 and the SFG signal light transmission aperture 137 to enter the SFG signal light receiver 138;

[0155] C5. Microscopic molecular structure change analysis stage:

[0156] First, continue adjusting the height of the lifting base 57. When the intensity of the SFG signal light reaches its maximum, stop adjusting. Then, use the sum frequency resonance spectrometer signal synthesis box 80 to scan the spectrum of the molecular structure in the liquid phase at the point 77 where the visible light 75 and the infrared light 76 overlap at the gas-liquid interface.

[0157] Subsequently, the temperature of the liquid containing the residual hydrate cage structure in the micromodule cavity is changed according to the experimentally set metal cylinder temperature control and monitoring device 65 and the micromodule temperature-controlled water bath 68. Then, the module height adjustment step in step C4 is repeated and the spectrum of the molecular structure in the liquid phase at the overlapping point 77 of the incident light is scanned again.

[0158] Finally, by analyzing the spectral characteristics of the residual cage structure of hydrate in the liquid phase at 77 overlapping points of the incident light under different temperature conditions, we explored the influence of the temperature / pressure changes of the system at the microscopic molecular scale and the amount of gas dissolved in the liquid phase on the residual cage structure of hydrate and its mechanism of action.

[0159] The above descriptions are merely some preferred embodiments of the present invention. Anyone skilled in the art may be able to modify the above-described technical solutions or convert them into equivalent technical solutions. Therefore, any corresponding simple modifications or equivalent transformations based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An apparatus suitable for macroscopic and microscopic studies of residual cage structures of hydrates, comprising a gas-liquid injection system (3), characterized in that: It also includes a fluid separation-blocking-unblocking core system (1), a fluid additional injection core system (2), a horizontal subcooling flow module (4), a vertical subcooling flow module (5) and a cage structure microscopic research module (6). The fluid separation-blocking-unblocking core system (1) is composed of a primary fluid separation-blocking-unblocking tank (7), a secondary fluid separation-blocking-unblocking tank (15), a gas separation tank (34), and a gas-liquid-solid three-phase input pipeline (40). The top of the first-stage fluid separation-blocking-unblocking tank (7) is respectively connected to the vacuum pump (31), the gas flow control module (106) of the gas-liquid injection system (3) and the gas separation tank (34), and the left side of the middle part is connected to the liquid reflux pipe (35) at the lower end of the gas separation tank and the gas-liquid-solid three-phase output pipeline (43); the bottom is a first-stage tank bottom ladder-type reduction structure (9), and two first-stage tank bottom-type reduction structure heating belts (10) connected to the first-stage tank bottom heating controller (13) are installed on the outer wall of the first-stage tank bottom ladder-type reduction structure (9); the lower end of the first-stage tank bottom ladder-type reduction structure (9) is connected to the top of the second-stage fluid separation-blocking-unblocking tank (15) through the first-stage tank bottom vertical pipe (11); The middle right side of the secondary fluid separation-blocking-unblocking tank (15) is connected to the fluid additional injection core system (2) and the liquid injection pump (100); the bottom is connected to the secondary tank bottom fluid three-way structure (20), and the outer walls of both are equipped with a secondary tank reduction structure heating belt (18) and a secondary tank bottom three-way heating belt (21) connected to the secondary tank bottom heating controller (19); one end of the liquid-solid two-phase flow pipeline (25) is connected to the secondary tank bottom fluid three-way structure (20), and the other end is connected in sequence to a large liquid-solid two-phase flow electromagnetic pump (27), a liquid-solid two-phase flow flow meter (28), a micro module inflow port (29), a terminal multiphase flow pipeline ball valve (26) and a gas-liquid-solid flow mixer (30); the upper end of the gas-liquid-solid flow mixer (30) is connected to the gas-liquid-solid three-phase input pipeline (40), and the side wall of the gas-liquid-solid flow mixer (30) is connected to the gas cooling pipeline (38); The fluid additional injection core system (2) is composed of a fluid additional injection core stirring tank (81), a small separation tank (90) at the rear end of the stirring tank, a gas recovery tank (93), and a liquid-solid two-phase flow electromagnetic pump (96). The fluid is additionally injected into the core stirred tank (81), the right end of which is connected to the liquid injection pipeline (101), and the center position of the bottom is connected to the small separation tank (90) at the rear end of the stirred tank through the liquid phase flow pipeline (89) at the lower end of the stirred tank; the top center position of the small separation tank (90) at the rear end of the stirred tank is connected to the gas recovery tank (93) through the ventilation pipeline (33), and the center position of the bottom is connected to the secondary fluid separation-blocking-unblocking tank (15) through the liquid phase flow pipeline (95) at the lower end of the small separation tank; The ends of the gas-liquid-solid three-phase input pipeline (40) are respectively connected to the inlet ends of the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) through the small input pipeline tee (41), and the ends of the gas-liquid-solid three-phase output pipeline (43) are respectively connected to the outlet ends of the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) through the small output pipeline tee (42); The side wall of the liquid-solid two-phase flow pipeline (25) is connected to the cage structure microscopic research module (6) through the microscopic module inflow port (29); The cage-type structure microscopic research module (6) comprises a pressure-resistant upper cover (53), an upper cover circular window (54), a pressure-resistant base (55), a temperature-controlled base (56) and a lifting base (57), wherein the upper portion of the pressure-resistant base (55) is provided with a pressure-resistant upper cover (53), a plurality of upper cover circular windows (54) are provided on the pressure-resistant upper cover (53), the lower portion of the pressure-resistant base (55) is provided with a temperature-controlled base (56), and the lower portion of the temperature-controlled base (56) is provided with a lifting base (57).

2. The device for macroscopic and microscopic research of residual hydrate cage structures according to claim 1, characterized in that: The gas-liquid injection system (3) comprises a stainless steel water bucket (97), a liquid phase inhibitor container (98), a liquid injection pump (100), a liquid injection pipeline (101), a carbon dioxide high-pressure gas cylinder (102), a methane high-pressure gas cylinder (103), a gas booster pump (105) and a gas flow control module (106). The pure water in the stainless steel water bucket (97) is injected into the secondary fluid separation-blocking-unblocking tank (15) by the liquid injection pump (100) through the liquid injection pipeline (101) and the liquid phase capillary ball valve (52); the inhibitor solution in the liquid phase inhibitor container (98) is injected into the secondary fluid separation-blocking-unblocking tank (15) through the liquid phase capillary ball valve (52). The liquid injection pipeline (101) and the liquid phase capillary ball valve (52) are injected into the fluid additional injection core stirring kettle (81) by the liquid injection pump (100), and the electronic scale (99) is used to calculate the injection amount of the liquid phase; the gas in the carbon dioxide high-pressure gas cylinder (102) and the methane high-pressure gas cylinder (103) is injected into the primary fluid separation-blocking-unblocking tank (7) and the fluid additional injection core stirring kettle (81) in sequence through the gas cylinder pressure relief valve (104), the ventilation pipeline (33), the gas booster pump (105), the gas flow control module (106) and the multiple ventilation pipeline valves (32).

3. The device for macroscopic and microscopic research of residual hydrate cage structures according to claim 2, characterized in that: The horizontal subcooling flow module (4) includes a horizontal input pipeline (107), a horizontal subcooling flow straight pipe (108), a subcooling pipe insulation layer (109), a subcooling pipe coolant annulus (110), a subcooling pipe stainless steel inner pipe (111), a subcooling pipe flange (112), a coolant continuous pipe (113), a polyvinyl chloride horizontal visual tube (114), a horizontal visual tube support frame (115), a horizontal subcooling flow U-shaped tube (116), a high-speed camera (117), a particle monitoring optical probe insertion port (118), a data acquisition computer (119), a subcooling pipe temperature and pressure sensor (120), a subcooling pipe pressure difference sensor (121), a sensor data line (122), a macro flow system console (123), and a horizontal output pipeline (124). The right ends of the two horizontal subcooling flow straight pipes (108) are connected to the horizontal subcooling flow U-shaped pipe (116), and the two horizontal subcooling flow straight pipes (108) are respectively connected to the polyvinyl chloride horizontal visual tube (114) through the subcooling pipe flange (112), the left end of the upper horizontal subcooling flow straight pipe (108) is connected to the horizontal input pipeline (107), and the left end of the lower horizontal subcooling flow straight pipe (108) is connected to the horizontal output pipeline (124); The horizontal subcooling flow straight pipe (108) and the horizontal subcooling flow U-shaped pipe (116) are both double-layer structures, the interior of which is a subcooling pipe stainless steel inner pipe (111) for circulating multiphase flow, and the interlayer space thereof is a subcooling pipe coolant annulus (110) for circulating the coolant output from the refrigeration circulating water bath (39) in the module, the outermost layer is wrapped with a subcooling pipe insulation layer (109), and a coolant continuous pipe (113) is connected to both sides of the polyvinyl chloride horizontal visual tube (114) to achieve communication between the two subcooling pipe coolant annuli (110); A plurality of subcooling pipe temperature and pressure sensors (120) and subcooling pipe differential pressure sensors (121) are installed at intervals on the horizontal subcooling flow straight pipe (108), and are connected to the macro flow system control console (123) via sensor data lines (122); A high-speed camera (117) is installed on the side of the polyvinyl chloride horizontal visual tube (114) on the lower side, which is used to shoot the multiphase flow morphology during the secondary generation and rapid blockage of hydrates under the influence of the residual cage structure of hydrates; a plurality of obliquely installed particle monitoring optical probe insertion ports (118) are embedded on the horizontal supercooled flow straight pipe (108) at the rear end of the high-speed camera (117), and the high-speed camera (117) and the particle monitoring optical probe insertion port (118) are connected to a data acquisition computer (119).

4. The device for macroscopic and microscopic research of residual hydrate cage structures according to claim 3, characterized in that: The lower inlet of the vertical subcooling flow module (5) is connected to the vertical input pipeline (127), and the outlet is connected to the vertical output pipeline (132). The vertical subcooling flow module (5) is mounted on the vertical subcooling pipe bracket (126) to maintain verticality with the horizontal ground. The bottom of the vertical subcooling pipe bracket (126) is installed with a vertical subcooling pipe bracket base (125).

5. The device for macroscopic and microscopic research of residual hydrate cage structures according to claim 4, characterized in that: The top of the pressure-resistant upper cover (53) of the cage-type structure microscopic research module (6) is equipped with an embedded camera (61) and an upper cover pressure probe (62), and the center positions of the left and right walls are both embedded with upper cover circular windows (54), and the center of the upper cover circular window (54) is made of sapphire pressure-resistant and light-transmitting glass (60); the bottom end of the inner wall of the upper cover circular window (54) is equipped with a plurality of internal liquid level limiters (71) for indicating the injection amount of hydrate decomposition water and limiting the liquid level of the decomposition water; An inflow tube (51) is installed at the center of the right inner wall of the pressure-resistant base (55). The right end of the inflow tube (51) is connected to the micro-module inflow port (29) in the fluid separation-blocking-unblocking core system (1) through the inflow reducer flange (50), the inflow reducer (49), the inflow pipeline ball valve (44), the inflow pipeline tee (46) and the inflow pipeline (45) in sequence, forming a channel for the hydrate decomposition water to flow into the high-pressure cavity in the micro-module; the bottom of the inflow pipeline tee (46) is equipped with a pressure relief pipeline (47), an inflow pipeline ball valve (44) and a small fluid container (48).

6. The device for macroscopic and microscopic research of residual hydrate cage structures according to claim 5, characterized in that: The temperature control base (56) is in the shape of a rectangular parallelepiped structure, and its outer wall is an integrated structure with the outer wall of the pressure-resistant base (55). A temperature-conducting metal cylinder (63) is installed at the center of its internal cavity, and is connected to the metal cylinder temperature control and monitoring device (65) through the metal cylinder control interface (64). The front of the temperature control base (56) is connected to the micro-module temperature-controlled water bath (68) through the coolant input / output port (66) and the coolant input / output pipe (67); a lifting control lever (58) is installed on one side of the lifting base (57), and a micro-module placement platform (59) is provided on the lower side of the lifting base (57).

7. The method for macroscopic and microscopic research of residual hydrate cage structures according to claim 6, characterized in that: The experimental methods for studying the macroscopic flow of residual hydrate cage structures include the following three types: a. Experimental methods to investigate the impact of residual cage structures on the secondary formation and rapid blockage of hydrates; b. Experimental methods to investigate the effective elimination of residual cage structures; c. Experimental methods to simulate the use of hydrate production water for subsea CO2 solidification and storage; The experimental method for investigating the effect of residual cage structures on the secondary formation and rapid blockage of hydrates includes three stages: the formation of complete hydrate cage structures, the formation of residual hydrate cage structures, and the secondary formation and rapid blockage of hydrates. The specific steps are as follows: S1, the stage of formation of complete hydrate cage structure: First, check the air tightness of the entire system, close the multiphase flow pipeline ball valve (26) at the lower end of the small separation tank (90) at the rear end of the stirring kettle and the rear end of the micro module inlet port (29), and reduce the pressure in the entire system to -0.1 MPa through the vacuum pump (31); inject a certain amount of pure water and methane into the entire system from the lower end of the right side of the secondary fluid separation-blocking-unblocking tank (15) and the top of the primary fluid separation-blocking-unblocking tank (7) through the gas-liquid injection system (3), and stop after reaching the preset experimental pressure; Then, the refrigeration circulating water bath (39) corresponding to the gas cooling pipeline (38), the refrigeration circulating water bath (39) corresponding to the horizontal subcooling flow module (4) and the vertical subcooling flow module (5), the high-pressure gas pump (36) and the large liquid-solid two-phase flow electromagnetic pump (27) are turned on in sequence, so that a gas-liquid two-phase stratified flow with a porosity of less than 30% is formed in the stainless steel inner tube (111) of the subcooling tube, and the target temperature of the multiple refrigeration circulating water baths (39) is set to -3 degrees, so that the flow system is continuously cooled; Subsequently, when the temperature in the flow system drops below the hydrate phase equilibrium temperature, the macroscopic induction period of hydrate formation begins, and the cage structure of water molecules gradually begins to form preliminarily at the gas-liquid interface. When the macroscopic induction period of hydrate formation ends, hydrates begin to form, and the number of complete hydrate cage structures gradually increases. The aggregation, adhesion, accumulation, and deposition of hydrates during the flow process lead to the rapid formation and gradual increase of hydrate aggregates. The ladder-type reduction structure (9) at the bottom of the first-stage fluid separation-blocking-unblocking tank (7) and the ladder-type reduction structure (17) at the bottom of the second-stage tank, as well as the change-direction pipe structure in the fluid three-way structure (20) at the bottom of the second-stage tank, induce and accelerate the blockage of hydrate aggregates. Finally, when the flow rate displayed by the liquid-solid two-phase flow meter (28) is 0, indicating the formation of complete blockage and the end of the formation of the complete hydrate cage structure, the refrigeration circulating water bath (39) and the high-pressure air pump (36) are turned off; the power of the large liquid-solid two-phase flow electromagnetic pump (27) is increased and the small liquid-solid two-phase flow electromagnetic pump (14) is turned on. If the displayed flow rate is 0, it indicates that hydrate blockage has formed at the bottom of both the primary fluid separation-blocking-unblocking tank (7) and the secondary fluid separation-blocking-unblocking tank (15); if the displayed flow rate is not 0 but drops to 0 quickly, it indicates that hydrate blockage exists at the bottom of the secondary fluid separation-blocking-unblocking tank (15); S2, the formation stage of residual hydrate cage structure: First, the large liquid-solid two-phase flow electromagnetic pump (27) and the small liquid-solid two-phase flow electromagnetic pump (14) are turned off, and the first tank bottom heating controller (13), the second tank bottom heating controller (19), and the liquid-solid flow pipeline starting end heating controller (24) are used to keep the first tank diameter reduction structure heating zone (10), the second tank diameter reduction structure heating zone (18), the second tank bottom three-way heating zone (21), and the liquid-solid flow pipeline starting end heating zone (23) in the temperature range of 35 to 38 degrees, thereby heating the hydrates blocked in the first tank bottom ladder diameter reduction structure (9), the second tank bottom ladder diameter reduction structure (17), and the second tank bottom fluid three-way structure (20) at the bottom of the first fluid separation-blocking-unblocking tank (7) and the second fluid separation-blocking-unblocking tank (15); in the process of gradual decomposition of the hydrates, the gas molecules gradually detach from the complete hydrate cage structure, and the residual hydrate cage structure begins to form and gradually increases with the decomposition of the hydrates; Subsequently, the large liquid-solid two-phase flow electromagnetic pump (27) and the small liquid-solid two-phase flow electromagnetic pump (14) are turned on once every heating period. If the liquid-solid two-phase flow meter (28) shows a flow rate of 0, indicating that the system has not recovered its fluidity, the two electromagnetic pumps are turned off and heating is continued; If the liquid-solid two-phase flow meter (28) shows that the flow rate is not 0, keep the two electromagnetic pumps turned on and continue heating; Finally, when the flow rate indicated by the liquid-solid two-phase flow meter (28) returns to the level before hydrate formation under the same electromagnetic pump power conditions, it indicates that the hydrate blockage in the system has been completely eliminated; at this time, all heating controllers are turned off and the high-pressure air pump (36) is turned on to form a stratified flow containing residual hydrate cage structures in the liquid phase in the horizontal subcooling flow module (4) and the vertical subcooling flow module (5); the refrigeration circulating water bath (39) corresponding to the subcooling flow module is turned on and the target temperature is adjusted to the laboratory room temperature before the start of step S1, so that the temperature and pressure in the flow system are increased to avoid other effects of hydrates that have not been completely decomposed on the residual cage structures. When the pressure of the flow system returns to the level before the start of cooling in step S1, the target temperature of the refrigeration circulating water bath (39) is adjusted to 0 degrees; S3, Hydrate secondary formation-rapid plugging stage: First, the refrigeration circulating water bath (39) corresponding to the gas cooling pipeline (38) is turned on, and the target temperature of the refrigeration circulating water bath (39) is set to -3 degrees, so that the stratified flow system containing the residual cage structure of the hydrate in the liquid phase is continuously cooled; Subsequently, during the hydrate secondary generation induction period, hydrate secondary generation, and rapid blockage after generation, the subcooling pipe temperature and pressure sensor (120), subcooling pipe pressure difference sensor (121), high-speed camera (117) mounted on the side of the polyvinyl chloride horizontal visual tube (114), and optical equipment embedded in the particle monitoring optical probe insertion port (118) in the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) are used to monitor, calculate, and record the data of hydrate secondary generation induction time, secondary generation rate, secondary generation flow barrier evolution morphology, hydrate aggregate morphology, and hydrate aggregate particle size change, and compare and analyze the data in step S1, so as to explore the influence of the residual cage structure on hydrate secondary generation-rapid blockage and its mechanism of action; Finally, when the secondary hydrate blockage is completely formed, the entire system is heated. When the system fluidity is restored, all the methane gas in the system is displaced by injecting carbon dioxide gas into the gas recovery tank (93), and the entire system is emptied through the fluid discharge pipeline (22) at the bottom of the secondary tank to start the next set of experiments.

8. The method for macroscopic and microscopic research of residual hydrate cage structures according to claim 7, characterized in that: The experimental method for exploring the effective elimination method of the residual cage structure also includes a chemical inhibitor injection stage and a hydrate secondary generation-mobilization stage. The specific steps are as follows: A1. Chemical inhibitor injection stage: First, the liquid injection pump (100) is turned on to inject the hydrate kinetic inhibitor or the kinetic inhibitor and polymerization inhibitor compound inhibitor in the liquid phase inhibitor container (98) into the fluid additional injection core stirring tank (81), and the injection amount of the inhibitor is recorded by the electronic scale (99); the core stirring tank rotation motor (83) and the core stirring tank temperature control water bath (87) are turned on to make the inhibitor evenly distributed under the stirring action and gradually reach its optimal working temperature; methane is injected into the fluid additional injection core stirring tank (81) through the gas-liquid injection system (3), and the injection is stopped when the pressure in the tank is higher than the pressure in the secondary fluid separation-blocking-unblocking tank (15) by 1 MPa; Subsequently, the core stirring tank rotation motor (83) is kept turned on, and the multiphase flow pipeline ball valve (26) on the liquid phase flow pipeline (89) at the lower end of the stirring tank is opened, so that the inhibitor flows into the small separation tank (90) at the rear end of the stirring tank under the action of the pressure difference; then, the large liquid-solid two-phase flow electromagnetic pump (27) and the high-pressure air pump (36) are turned off, and the liquid-solid two-phase flow electromagnetic pump (96) on the liquid phase flow pipeline (89) at the lower end of the stirring tank and the liquid phase flow pipeline (95) at the lower end of the small separation tank are turned on in sequence, so that all the inhibitor flows into the secondary fluid separation-blocking-unblocking tank (15); Finally, the liquid phase flow pipeline (95) at the lower end of the small separation tank is closed, and the small air pump (92) is turned on to pump the methane gas in the entire fluid additional injection core system (2) into the gas recovery tank (93). At the same time, carbon dioxide gas is injected into the fluid additional injection core stirring tank (81) and the small separation tank (90) at the rear end of the stirring tank through the gas-liquid injection system (3) to ensure that all methane gas is displaced and enters the gas recovery tank (93); A2. Hydrate secondary formation-mobilization stage: The high-pressure gas pump (36) and the large liquid-solid two-phase flow electromagnetic pump (27) are sequentially turned on to form a stratified flow containing residual cage structures of hydrates and chemical inhibitors in the liquid phase in the system, and the refrigeration circulating water bath (39) is turned on at the same time to continuously cool the flow system; through the subcooling pipe temperature and pressure sensor (120), the subcooling pipe pressure difference sensor (121), the high-speed camera (117) installed on the side of the visual tube, and the optical device embedded in the particle monitoring optical probe insertion port (118) in the horizontal subcooling flow module (4) and the vertical subcooling flow module (5), the key data of the induction time, generation rate, flow morphology, and aggregate particle size change in the process of hydrate secondary generation-flow barrier evolution under the conditions of different types of inhibitors are monitored, calculated, and recorded, and compared with the data in the experiment without inhibitors, so as to explore the effective elimination method and elimination mechanism of the residual cage structure of hydrates; After the experiment, the entire fluid is injected into the core system (2) through the pressure relief port (94) of the small separation tank equipped with a built-in valve to displace the carbon dioxide gas injected into the methane gas to be emptied, and the fluid is injected into the core system (2) through the gas-liquid injection system (3) multiple times of pure water injection and then emptied to clean the residual inhibitors in the system so that subsequent experiments containing different types of inhibitors can be carried out.

9. The method for macroscopic and microscopic studies of residual hydrate cage structures according to claim 8, characterized in that: The experimental method for simulating the use of hydrate production water for subsea carbon dioxide solidification and storage includes four stages: the formation of a complete methane hydrate cage structure in the kettle, the formation of residual hydrate cage structures in the kettle, the injection of water and carbon dioxide into a separation tank, and the formation and flow of carbon dioxide hydrate. The specific steps are as follows: B1, the stage of formation of complete cage structure of methane hydrate in the kettle: First, after checking the air tightness of the entire system, the pressure in the entire system is reduced to -0.1 MPa using a vacuum pump (31). The liquid phase flow pipeline (89) at the lower end of the stirring tank and the liquid phase flow pipeline (95) at the lower end of the small separation tank are closed. Pure water and methane gas are injected into the core stirring tank (81) through the gas-liquid injection system (3). The injection is stopped after the experimental set pressure is reached. Subsequently, the core stirring kettle rotation motor (83) and the core stirring kettle temperature-controlled water bath (87) are turned on, and the target temperature of the temperature-controlled water bath is set to -3 degrees, so that the high-pressure methane gas and pure water in the kettle are continuously cooled while being stirred. When the system temperature is lower than the hydrate phase equilibrium temperature, the hydrate cage structure begins to form preliminarily at the gas-liquid interface; when the fluid is additionally injected into the core stirring kettle (81), the temperature suddenly rises and the feedback torque of the core stirring kettle rotation motor (83) increases, indicating the formation of methane hydrate and the formation of a complete hydrate cage structure; Finally, the high-pressure camera (8) in the core stirring tank (81) is used to assist in judging the formation and agitation of the hydrate in the tank. When the rotation speed of the core stirring tank rotating motor (83) is reduced to 0, it indicates that the hydrate in the tank is completely blocked and the formation of a complete hydrate cage structure is completed. The core stirring tank rotating motor (83) is turned off. B2, the formation stage of the residual cage structure of hydrate in the kettle: First, the target temperature of the core stirred tank temperature-controlled water bath (87) was set to 25 degrees, and the hydrate blocked in the tank was heated for a period of time before being closed to simulate the process of self-heating materials promoting hydrate decomposition during marine hydrate mining; Subsequently, the liquid phase flow pipeline (89) at the lower end of the stirring tank is slowly opened, so that the fluid is additionally injected into the hydrate in the core stirring tank (81) and gradually decomposes during the pressure relief process, so as to simulate the process of hydrate decompression mining in the sea area. At the same time, the hydrate decomposition water and the gas generated by the decomposition flow into the small separation tank (90) at the rear end of the stirring tank. As the gas molecules gradually separate from the complete hydrate cage structure, the hydrate cage structure remaining in the hydrate decomposition water gradually increases. Finally, when the pressure in the small separation tank (90) at the rear end of the stirring kettle no longer increases, the liquid phase flow pipeline (89) at the lower end of the stirring kettle is fully opened; B3, decomposition of water and injection of carbon dioxide into the separation tank stage: First, the liquid phase flow pipeline (95) at the lower end of the small separation tank is kept closed, and carbon dioxide gas is injected into the fluid separation-blocking-unblocking core system (1) and the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) through the gas-liquid injection system (3). The injection is stopped when the pressure in the system reaches 2 MPa; Subsequently, the methane gas in the fluid additional injection core system (2) needs to be displaced with carbon dioxide, and the vent line valve (32) between the small separation tank (90) at the rear end of the stirred tank and the methane gas pumped into the gas recovery tank (93) is opened, so that the methane gas in the fluid additional injection core system (2) flows into the gas recovery tank (93) driven by the pressure difference. When the pressure in the system no longer changes significantly, a new gas recovery tank (93) is replaced to continue collecting methane gas; when the pressure in the system drops to 2MPa, a new gas recovery tank (93) is replaced and carbon dioxide gas is continuously injected into the fluid additional injection core system (2) through the gas-liquid injection system (3), and the small air pump (92) is opened to allow the carbon dioxide gas to displace all the remaining methane gas in the fluid additional injection core system (2) into the gas recovery tank (93); when the gas drying and methane concentration monitoring device (91) shows that the methane concentration is 0, the small air pump (92) is closed and the injection of carbon dioxide is stopped; Finally, the liquid phase flow pipeline (95) at the lower end of the small separation tank is opened successively, and all the hydrate decomposition water containing the residual hydrate cage structure in the small separation tank (90) at the rear end of the stirred tank is injected into the secondary fluid separation-blocking-unblocking tank (15) to simulate the process of injecting the produced water from the marine hydrate mining into the submarine carbon dioxide hydrate generation system; when the pressure in the secondary fluid separation-blocking-unblocking tank (15) no longer changes, the liquid phase flow pipeline (95) at the lower end of the small separation tank is closed; B4. Carbon dioxide hydrate formation-mobilization stage: First, carbon dioxide gas is continuously injected into the fluid separation-blocking-unblocking core system (1) and the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) through the gas-liquid injection system (3). The injection is stopped when the pressure in the system reaches 5 MPa. Subsequently, the first-stage fluid separation-blocking-unblocking tank (7) and the second-stage fluid separation-blocking-unblocking tank (15) and the gas separation tank (34) are closed, the gas cooling pipeline (38) is closed, and the refrigeration circulating water bath (39) corresponding to the horizontal subcooling flow module (4) and the vertical subcooling flow module (5) and the large liquid-solid two-phase flow electromagnetic pump (27) are turned on, so that a gas-liquid two-phase bubble flow containing a residual hydrate cage structure with a porosity of less than 10% is formed in the stainless steel inner tube (111) of the subcooling tube in the horizontal subcooling flow module (4) and the vertical subcooling flow module (5), and the target temperature of the refrigeration circulating water bath (39) is set to -3 degrees to continuously cool the flow system; Then, during the continuous cooling process of the flow system, the carbon dioxide gas gradually dissolves in the methane hydrate decomposition water. Along with the induction and rapid formation of carbon dioxide hydrate, the carbon dioxide gas molecules and the residual hydrate cage structure in the methane hydrate decomposition water reform into a complete carbon dioxide hydrate cage structure. Finally, through the horizontal supercooled flow module (4) and the vertical supercooled flow module (5), key data such as the induction time, generation rate, flow morphology, and flow pressure difference changes during the formation and flow of carbon dioxide hydrates are monitored, calculated, and recorded, thereby studying multiple key scientific issues in the process of using hydrate mining produced water for submarine carbon dioxide solidification and storage.

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