Device for solidifying and sealing carbon dioxide in seabed artificial hydrate reservoir and using method

Abstract

The invention relates to the field of carbon dioxide seabed sealing, in particular to equipment for solidifying and sealing carbon dioxide in a seabed artificial hydrate reservoir and a using method. According to the technical scheme, a transport ship is connected to a hydrate seabed slurry mixing integrated core system through a carbon dioxide injection marine riser and a surfactant injection marine riser, a slurry seabed collection system is arranged on one side of the transport ship, and a mixed slurry output system is arranged on the other side of the transport ship; sediment slurry is formed through a slurry seabed collection system, a surfactant, the sediment slurry and sea water are pumped into a carbon dioxide hydrate generation seabed slurry mixer and continuously stirred, carbon dioxide hydrate-sediment mixed slurry is prepared, and the carbon dioxide hydrate-sediment mixed slurry is conveyed to a seabed sunken area through a mixed slurry output system; and an artificial carbon dioxide reservoir is formed by covering a sediment layer, so that seabed safe sealing of carbon dioxide is realized. The problems that a traditional carbon dioxide seabed sealing method depends on stratigraphic entrapment and structure, the sealing scale is limited, and leakage is prone to occurring after long-time sealing are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of subsea carbon dioxide storage, and particularly to an apparatus and a method for solidifying and storing carbon dioxide in an artificial hydrate reservoir on the seabed. Background Art

[0002] Currently, in the process of carbon dioxide storage, the following are common carbon dioxide storage technologies: 1. Geological storage: Imitating the mechanism of the natural storage of fossil fuels, carbon dioxide is injected into deep geological strata. Its basic principle is to utilize the physical sealing and chemical stability of geological structures to store carbon dioxide. After carbon dioxide is injected underground, it interacts with the surrounding rocks and fluids, and achieves long-term stable storage through various mechanisms; 2. Mineralization storage: Utilizing the chemical reaction of carbon dioxide with specific minerals (such as basalt, olivine, etc.) to form stable carbonate minerals, thereby achieving the permanent fixation of carbon dioxide. The principle of this storage method is based on the natural weathering process. By artificially accelerating the carbonation reaction of minerals, carbon dioxide is converted into solid minerals, eliminating the risk of carbon dioxide leakage. However, the reaction rate of mineralization storage is relatively slow, and a large amount of mineral resources are required. Currently, it is still in the research and demonstration stage; 3. Ocean storage: Utilizing the huge volume of the ocean water body and the relatively high solubility of carbon dioxide in the water body, the ocean becomes a container for storing carbon dioxide. The total amount of carbon contained in seawater is about 50 times that of the atmosphere, and the ocean has huge carbon storage potential. After carbon dioxide is injected into the deep sea, it dissolves in the seawater and is gradually stored in the deep sea water body with the circulation movement of the seawater. However, there are some potential environmental risks in ocean storage technology, such as increasing the acidity of seawater and having an adverse impact on marine organisms. Currently, ocean storage technology is still in the research and experimental stage and has not been widely applied; 4. Biological storage: Fixing carbon dioxide through the photosynthesis or biochemical reaction of organisms. Organisms (such as plants, algae, etc.) utilize carbon dioxide for growth and metabolism, converting carbon dioxide into organic matter, thereby achieving the fixation of carbon dioxide. However, biological storage completely depends on the quantity and scale of plants and algae, with low efficiency and small potential, and it is difficult to be the main means of carbon dioxide storage.

[0003] According to current research and practical experience, among the above technical means, geological sequestration technology is recognized as one of the most promising ways to sequester carbon dioxide. Geological structures suitable for carbon dioxide sequestration exist both on land and on the seabed. Submarine geological sequestration of carbon dioxide combines the advantages of geological sequestration and ocean sequestration. The submarine geological structure is far from the land aquifer and has the pressure and barrier of the rock cap layer and surface seawater. Compared with land sequestration, submarine geological sequestration of carbon dioxide has the advantages of large sequestration potential, no occupation of land resources, and less impact on human health and safety.

[0004] Common submarine geological sequestration technologies include sequestration in submarine saline aquifers, sequestration in submarine oil and gas reservoirs, sequestration in submarine basalts, sequestration in submarine hydrates, and sequestration of supercritical carbon dioxide in the seabed. These technologies each have their own advantages, but generally have the same disadvantages and limitations: the geological conditions such as porosity, permeability, and integrity of the cap layer in submarine saline aquifers are complex, making it difficult to ensure the long-term stable sequestration of carbon dioxide; the geological conditions of submarine oil and gas reservoirs are also very complex, and there may be fractures and faults, increasing the risk of carbon dioxide leakage. The sequestration capacity of oil and gas reservoirs is relatively limited and the sequestration potential is small; the porosity of submarine basalt layers is relatively low, the injection resistance of carbon dioxide is large, and the reaction process of sequestering carbon dioxide in basalt is relatively complex, with low sequestration efficiency and poor stability; the method of sequestration in submarine hydrates has a certain potential, but it is difficult to monitor and control the formation and decomposition of carbon dioxide hydrates during the implementation process in the deep-sea environment of the seabed, and it will also be affected by the complex geological structure of the seabed, and there is a risk of decomposition or leakage during long-term sequestration; the compression and transportation of supercritical carbon dioxide require high technical and equipment requirements and high costs. At the same time, the long-term stability of supercritical carbon dioxide in geological structures is unknown.

[0005] In summary, under the existing technical path of submarine carbon dioxide sequestration, the sequestration mode of carbon dioxide extremely depends on stratigraphic traps and structures, resulting in limited sequestration scale. At the same time, carbon dioxide exists in the form of a fluid, either gas or liquid, during sequestration, and it is prone to leakage during long-term sequestration. Summary of the Invention

[0006] The purpose of the present invention is to address the above-mentioned defects existing in the prior art, and provide a device and method for solidifying and sequestering carbon dioxide in a submarine artificial hydrate reservoir, which solves the problems that the traditional method of submarine carbon dioxide sequestration needs to rely on stratigraphic traps and structures, has limited sequestration scale, and is prone to leakage during long-term sequestration.

[0007] The equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir mentioned in the present invention has the following technical solution: It includes a transport ship and a liquid carbon dioxide storage tank, and also includes a surfactant storage tank, a carbon dioxide injection pump, a carbon dioxide injection riser pipe, a surfactant injection pump, a surfactant injection riser pipe, a hydrate-seabed slurry integration core system, a seabed mud collection system, and a mixed slurry output system. The lower part of the transport ship is connected to the hydrate-seabed slurry integration core system on the seabed formation through the carbon dioxide injection riser pipe and the surfactant injection riser pipe. A seabed mud collection system is arranged on one side of the hydrate-seabed slurry integration core system, and a mixed slurry output system is arranged on the other side. The carbon dioxide and surfactant on the transport ship are injected into the hydrate-seabed slurry integration core system through the carbon dioxide injection riser pipe and the surfactant injection riser pipe. A sediment slurry is formed through the seabed mud collection system, and the surfactant, sediment slurry, and seawater are pumped into a carbon dioxide hydrate generating seabed slurry mixer and continuously stirred. A carbon dioxide hydrate-sediment mixed slurry is made by using the seabed high pressure and seawater low temperature driving force, and the carbon dioxide hydrate-sediment mixed slurry is transported to a submarine depression area through the mixed slurry output system. Then, an artificial carbon dioxide reservoir is formed by covering a sediment layer to achieve the safe storage of carbon dioxide under the sea.

[0008] Preferably, the above hydrate-seabed slurry integration core system is composed of a carbon dioxide hydrate generating seabed slurry mixer, a surfactant injection sub-module, a sediment slurry injection sub-module, a seawater injection sub-module, and a mixed slurry output sub-module, which are assembled and installed on the upper side of a core bearing and moving sub-module. The position is moved through the core bearing and moving sub-module. One side of the carbon dioxide hydrate generating seabed slurry mixer is connected to the sediment slurry injection sub-module through a mud injection port, connected to the surfactant injection sub-module through a surfactant injection port. On the other side of the carbon dioxide hydrate generating seabed slurry mixer, it is connected to the seawater injection sub-module through a seawater injection port, and the bottom of the carbon dioxide hydrate generating seabed slurry mixer is connected to the mixed slurry output sub-module.

[0009] Preferably, the above-mentioned carbon dioxide hydrate generating subsea slurry mixer is divided into a slurry mixing function area, a slurry separation function area and a slurry output function area; a carbon dioxide injection port is provided at the top of the slurry mixing function area, a slurry injection port and a surfactant injection port are embedded in the outer wall of the lower half of the left end, and a seawater injection port is embedded in the outer wall of the lower half of the right end; a slurry mixing device is provided on the inner wall of the slurry mixing function area, and the slurry mixing device is composed of a stirring rotation motor, a vertical rotation rod and a horizontal rotation rod, and a plurality of trapezoidal stirring blades are installed on each horizontal rotation rod; a plurality of slurry mixer temperature and pressure sensors are distributed on the inner wall of the carbon dioxide hydrate generating subsea slurry mixer, and a slurry mixer support is provided at the lower part of the outer side to leave enough space at the bottom to realize the connection between the horizontal straight pipe for mixing slurry output and the bottom of the inner wall on the right side of the slurry output function area; the core bearing and moving sub-module includes a core system crawler wheel, a core system bearing base and a towing hook, a plurality of core system crawler wheels are provided at the bottom of the core system bearing base, and towing hooks are respectively provided at both ends of the core system bearing base.

[0010] Preferably, the above-mentioned surfactant injection sub-module is composed of a surfactant stirring storage tank, a surfactant delivery straight pipe and a surfactant delivery pump. A surfactant riser injection port is provided at the top of the surfactant stirring storage tank and is connected to the surfactant injection riser; a surfactant stirring device is installed on the inner wall of the surfactant stirring storage tank, a storage tank temperature and pressure sensor is installed on the inner wall of the surfactant stirring storage tank, and the bottom is connected to the carbon dioxide hydrate generating subsea slurry mixer through the surfactant delivery straight pipe and the surfactant delivery pump.

[0011] Preferably, the above-mentioned sediment slurry injection sub-module is composed of a slurry delivery telescopic hose, a slurry delivery hose expander, a slurry delivery vertical straight pipe, a secondary slurry delivery pump support, a secondary slurry delivery pump and a slurry delivery horizontal straight pipe. The output end of the secondary slurry delivery pump is connected to the carbon dioxide hydrate generating subsea slurry mixer through the slurry delivery horizontal straight pipe; the secondary slurry delivery pump support, the slurry delivery vertical straight pipe and the slurry delivery hose expander are installed on the lower side of the secondary slurry delivery pump, and the distance and relative position between the slurry subsea collection system and the hydrate subsea slurry integration core system are controlled through the slurry delivery telescopic hose and the slurry delivery hose expander.

[0012] Preferably, the above-mentioned seawater injection sub-module is composed of a seawater suction port, a solid filter device, a filter device support, a seawater suction horizontal straight pipe, a seawater suction pump and a seawater suction pump support. The output end of the seawater suction pump is connected to the carbon dioxide hydrate generating subsea slurry mixer, the input end of the seawater suction pump is connected to the seawater suction port through the seawater suction horizontal straight pipe and the solid filter device, the filter device support is installed on the lower side of the solid filter device, and the seawater suction pump support is installed on the lower side of the seawater suction pump.

[0013] Preferably, the above-mentioned mixed slurry output sub-module consists of a horizontal straight pipe for mixed slurry output, a first-stage mixed slurry output pump, a telescopic device for the mixed slurry output hose, and a telescopic hose for the mixed slurry output. The input end of the first-stage mixed slurry output pump is connected to the subsea slurry mixer for carbon dioxide hydrate formation through the horizontal straight pipe for mixed slurry output, and the output end of the first-stage mixed slurry output pump is connected to the mixed slurry output system through the telescopic device for the mixed slurry output hose and the telescopic hose for the mixed slurry output.

[0014] Preferably, the above-mentioned subsea mud collection system consists of a sediment impactor, a mud collector, a mud suction pipe, a mud suction pump and a solid filtration device, a mud suction port, a mud stirring storage tank, a mud stirring device, a temperature and pressure sensor for the mud storage tank, a small seawater suction pump and a solid filtration device, a straight mud conveying pipe, a first-stage mud conveying pump, a telescopic hose for mud conveying, a crawler wheel for the collection system, a bearing base for the collection system, a mobile controller for the collection system, and a small seawater suction inlet. The bottom of the bearing base for the collection system is provided with a crawler wheel for the collection system, and the mud stirring storage tank is installed on the upper side of the bearing base for the collection system. The top of the mud stirring storage tank is connected to the small seawater suction inlet through the small seawater suction pump and the solid filtration device. On the left side of the mud stirring storage tank, there are a mud suction pump and a solid filtration device and a mobile controller for the collection system. The outside of the mud suction pump and the solid filtration device is connected to the mud collector through the mud suction pipe, and the sediment impactor is installed on the lower side of the mud collector; on the right side of the mud stirring storage tank, it is connected to the first-stage mud conveying pump through the straight mud conveying pipe, and the outer end of the first-stage mud conveying pump is connected to the sediment slurry injection sub-module through the telescopic hose for mud conveying; a mud stirring device is installed in the inner cavity of the mud stirring storage tank.

[0015] Preferably, the above-mentioned mixed slurry output system includes a telescopic hose for mixed slurry output, a second-stage mixed slurry output pump, an extendable hose in front of the mixed slurry discharge pipe, a hoist for the mixed slurry discharge pipe, a mixed slurry discharge pipe, a deflector for the mixed slurry discharge, crawler wheels for the output system, a bearing base for the output system, and a mobile controller for the output system. The lower side of the bearing base for the output system is provided with crawler wheels for the output system, and the second-stage mixed slurry output pump and the mobile controller for the output system are installed on the upper side. The left end of the second-stage mixed slurry output pump is connected to the telescopic hose for mixed slurry output, and the right end is connected to the mixed slurry discharge pipe through the extendable hose in front of the mixed slurry discharge pipe. A deflector for the mixed slurry discharge is provided on the lower side of the mixed slurry discharge pipe, and the carbon dioxide hydrate-sediment mixed slurry is transported to the subsea depression area through the mixed slurry discharge pipe and the deflector for the mixed slurry discharge.

[0016] In addition, the usage method of the equipment for solidifying and storing carbon dioxide in the artificial hydrate reservoir on the seabed mentioned in the present invention has the following technical solution: It is mainly divided into four stages: continuous injection stage, hydrate formation and slurry mixing stage, mixed slurry discharge stage, and sediment layer covering stage; First, in the continuous injection stage, the liquid carbon dioxide on the transport ship, the sediment slurry formed by the surfactant and the seabed formation, and the low-temperature seawater near the seabed need to be successively injected into the carbon dioxide hydrate formation seabed slurry mixer, which mainly includes the following steps: a1. Preparation before system layout: Before arranging all equipment on the seabed formation, make the pressure in the carbon dioxide hydrate formation seabed slurry mixer, the mud stirring storage tank, and the surfactant stirring storage tank be 0 MPa and keep it in a completely sealed state; a2. System layout on the seabed: Lower the hydrate seabed slurry integration core system, the mud seabed collection system, and the mixed slurry output system to the seabed formation at a water depth of 800 to 2000 meters according to the positions of different seabed depression areas; Insert the seabed anchoring device installed on the crawler wheels of the core system into the seabed formation, connect the carbon dioxide injection pump and the surfactant injection pump on the transport ship to the carbon dioxide injection port and the surfactant riser injection port respectively through the carbon dioxide injection riser and the surfactant injection riser; Move the mud seabed collection system to a position near the hydrate seabed slurry integration core system through the collection system mobile controller, and insert the seabed anchoring device installed on the crawler wheels of the collection system into the seabed formation; Move the mixed slurry output system to a position near the seabed depression area through the output system mobile controller, and insert the seabed anchoring device installed on the crawler wheels of the output system into the seabed formation; a3. Injection and cooling of the surfactant: Open the ball valve in the surfactant riser injection port, inject the surfactant into the surfactant stirring storage tank, and at the same time turn on the surfactant stirring device. When the pressure in the surfactant stirring storage tank is close to the pressure at the seabed position, stop injecting and close the ball valve in the surfactant riser injection port, and continue stirring to accelerate the heat exchange process of the surfactant through the outer wall of the surfactant stirring storage tank and the low-temperature seawater; a4. Collection and dilution of the seabed sediment slurry: While the injection and cooling of the surfactant are in progress, use the sediment impactor in the mud seabed collection system to disperse and lift the sediment in the seabed formation to initially form a slurry with seawater. At the same time, open the ball valve, the mud suction pump and the solid filtration device, the small seawater suction pump and the solid filtration device, and the mud stirring device in the mud suction port, pump the initially formed slurry and seawater on the seabed into the mud stirring storage tank and continue stirring. Monitor the pressure through the pressure and temperature sensor of the mud storage tank. When the pressure in the mud stirring storage tank reaches the pressure value at the seabed position, close all the pumps and ball valves in the mud seabed collection system; a5. Inject carbon dioxide: When the temperature of the surfactant in the surfactant stirring storage tank drops below the carbon dioxide hydrate phase equilibrium temperature corresponding to the seabed pressure, open the ball valve in the carbon dioxide injection port and inject liquid carbon dioxide into the subsea mixer for carbon dioxide hydrate formation. At the same time, turn on the mixing and stirring device. When the internal pressure reaches 0.8 times the seabed pressure value, stop the injection and close the ball valve in the carbon dioxide injection port; a6. Inject low-temperature surfactant: Start the surfactant delivery pump, open the ball valve in the surfactant injection port, and inject surfactant into the subsea mixer for carbon dioxide hydrate formation. At the same time, keep the surfactant stirring device and the mixing and stirring device on. When the injection volume reaches the design standard, stop the injection and close the ball valve in the surfactant injection port and the surfactant delivery pump; a7. Inject sediment slurry: Start the primary slurry delivery pump and the secondary slurry delivery pump, open the ball valve in the slurry injection port, and deliver the sediment slurry with a reduced sediment concentration after being diluted by seawater into the subsea mixer for carbon dioxide hydrate formation. At the same time, keep the slurry stirring device and the mixing and stirring device on to avoid sediment deposition. When the injection volume reaches the design standard, stop the injection and close the ball valve in the slurry injection port, the primary slurry delivery pump, and the secondary slurry delivery pump; a8. Inject low-temperature seawater: Confirm that the ball valve at the end of the liquid recovery retractable hose is closed, open the ball valve of the seawater suction vertical pipe, start the seawater suction pump, open the ball valve in the seawater injection port, and inject low-temperature seawater filtered by solids near the seabed into the subsea mixer for carbon dioxide hydrate formation. At the same time, keep the mixing and stirring device on. When the injection volume reaches the design standard, stop the injection and close the ball valve in the seawater injection port, the seawater suction pump, and the ball valve of the seawater suction vertical pipe; Second, in the hydrate formation and mixing stage, the main steps are as follows: b1. Hydrate formation: Increase the rotation speed of the mixing and stirring device in the subsea mixer for carbon dioxide hydrate formation, so that carbon dioxide in the sediment slurry stirring system with a high seawater content rapidly forms carbon dioxide hydrate with seawater under the action of seabed high pressure, seawater low temperature driving force, and surfactant. Monitor the temperature and pressure in different areas of the subsea mixer for carbon dioxide hydrate formation through multiple mixer temperature and pressure sensors, and assist the observation with the pressure-resistant high-definition camera lens installed inside. When a significant sudden increase in temperature occurs, it indicates the start of carbon dioxide hydrate formation, and calculate the hydrate formation amount through the real-time changes in temperature and pressure; b2. Formation of carbon dioxide hydrate - sediment mixed slurry: When the temperature and pressure in each area of the subsea slurry mixer where carbon dioxide hydrate is generated no longer change significantly, reduce the rotation speed of the slurry mixing device. Under the influence of the surfactant, gradually form a carbon dioxide hydrate - sediment mixed slurry with good fluidity among hydrate particles, small hydrate aggregates, sediment, and seawater during the agitation process. By monitoring the feedback torque power of the slurry mixing device, when the torque power no longer fluctuates significantly, it indicates that the properties and agitation state of the carbon dioxide hydrate - sediment mixed slurry formed by carbon dioxide hydrate and sediment have tended to be stable; Third, in the stage of discharging the mixed slurry, the main steps are as follows: c1. Discharging the mixed slurry: Keep the slurry mixing device rotating at a constant speed to avoid the deposition of the carbon dioxide hydrate - sediment mixed slurry; Adjust the lifting device of the mixed slurry discharge pipe to the lowest position, open the ball valve of the mixed slurry output pipe, turn on the first - stage mixed slurry output pump and the second - stage mixed slurry output pump, and discharge the carbon dioxide hydrate - sediment mixed slurry to the lowest water level of the subsea depression area. While discharging, adjust the guiding plate of the mixed slurry discharge to ensure the uniform deposition of solid aggregates in the carbon dioxide hydrate - sediment mixed slurry on the lowest water level of the subsea depression area; When the sediment is close to evenly filling the lowest water level of the subsea depression area, raise the lifting device of the mixed slurry discharge pipe, and start discharging to a higher water level section of the subsea depression area, and cycle in turn until the subsea depression area is close to being filled; Fourth, in the stage of covering with sediment layer, the main steps are as follows: d1. Injection of sediment slurry: Repeat the steps of collecting and diluting the subsea sediment slurry, injecting low - temperature surfactant, injecting sediment slurry, and injecting seawater in the continuous injection stage, so that the pressure in the subsea slurry mixer where carbon dioxide hydrate is generated is close to the pressure before discharging the mixed slurry, and at the same time keep the slurry mixing device rotating at a constant speed; d2. Discharging the sediment slurry: Pull out the subsea anchoring device on the crawler wheel of the output system, and discharge the sediment slurry by repeating the steps of discharging the mixed slurry, but do not perform the liquid recovery step. While discharging the sediment slurry, adjust the position of the mixed slurry output system, the lifting device of the mixed slurry discharge pipe, and the state of the guiding plate of the mixed slurry discharge in real time, so that the sediment is evenly deposited on all the carbon dioxide hydrate - sediment mixed solid sediments in the subsea depression area. When the thickness of the overlying sediment layer formed reaches the coverage requirement of the hydrate - sediment mixed solid sediments in the depression area, stop all operations, close all pumps and ball valves in the system, and move the entire system to the vicinity of the next subsea depression area.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention mainly realizes the continuous injection of carbon dioxide, surfactant, subsea sediment slurry, and subsea low-temperature seawater into the carbon dioxide hydrate-forming subsea slurry mixer by adopting a hydrate subsea slurry integration core system, a slurry subsea collection system, and a mixed slurry output system. Utilizing the in-situ environmental conditions of high subsea pressure and low seawater temperature, a carbon dioxide hydrate-sediment mixed slurry with good fluidity is rapidly produced under the promotion of the surfactant and the prevention of deposition. The mixed slurry is then transported to the subsea depression area by the mixed slurry transportation system. Finally, a certain thickness of sediment layer is formed by outputting the sediment slurry to the target area to form an artificial carbon dioxide reservoir, thereby realizing the safe subsea storage of carbon dioxide. The present invention solves the problems that the traditional subsea carbon dioxide storage method extremely relies on formation traps and structures, the storage scale is limited, and leakage is likely to occur during long-term storage, and has important theoretical and practical significance for optimizing the high-efficiency subsea carbon dioxide storage method and controlling the long-term stability of the storage reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the overall system of the present invention; Figure 2 is a schematic diagram of the structure of the hydrate subsea slurry integration core system; Figure 3 is a disassembled view of the hydrate subsea slurry integration core system; Figure 4 is a schematic diagram of the structure of the slurry subsea collection system; Figure 5 is a schematic diagram of the structure of the mixed slurry output system; Figure 6 is a comparison chart of the hydrate concentration and flow time in the seawater-sediment slurry system in the experimental loop before and after adding the surfactant CP; In the figure: 1 - transport ship, 2 - liquid carbon dioxide storage tank, 3 - surfactant storage tank, 4 - carbon dioxide injection pump, 5 - carbon dioxide injection riser, 6 - surfactant injection pump, 7 - surfactant injection riser, 8 - hydrate subsea slurry integration core system, 9 - slurry subsea collection system, 10 - mixed slurry output system, 11 - carbon dioxide hydrate - sediment mixed solid aggregate, 12 - liquid not participating in hydrate formation, 13 - subsea depression area, 14 - subsea formation, 15 - sea level, 16 - carbon dioxide hydrate formation subsea slurry mixer, 17 - surfactant injection sub-module, 18 - sediment slurry injection sub-module, 19 - seawater injection sub-module, 20 - mixed slurry output sub-module, 21 - core bearing and moving sub-module, 22 - core system crawler wheel, 23 - core system bearing base, 24 - towing hook, 25 - sediment impactor, 26 - slurry collector, 27 - slurry suction pipe, 28 - slurry suction pump and solid filter device, 29 - slurry suction port, 30 - slurry stirring storage tank, 31 - slurry stirring device, 32 - slurry storage tank temperature and pressure sensor, 33 - small seawater suction pump and solid filter device, 34 - slurry delivery straight pipe, 35 - primary slurry delivery pump, 36 - slurry delivery telescopic hose, 37 - collection system crawler wheel, 38 - collection system bearing base, 39 - collection system mobile controller, 40 - small seawater suction port, 41 - seawater suction port of slurry storage tank, 42 - mixed slurry output telescopic hose, 43 - secondary mixed slurry output pump, 44 - extendable hose in front of mixed slurry discharge pipe, 45 - mixed slurry discharge pipe lifter, 46 - mixed slurry discharge pipe, 47 - mixed slurry discharge guide plate, 48 - output system crawler wheel, 49 - output system bearing base, 50 - output system mobile controller, 51 - liquid recovery wide-mouth device, 52 - tail baffle of wide-mouth device, 53 - liquid recovery vertical pipe, 54 - liquid recovery horizontal pipe, 55 - liquid recovery horizontal pipe support, 56 - liquid recovery pump, 57 - liquid recovery pump support, 58 - liquid recovery pump lifter, 59 - liquid recovery telescopic hose, 60 - liquid recovery hose telescopic device, 61 - liquid recovery hose telescopic device support, 62 - slurry mixer stirring function area, 63 - slurry mixer separation function area, 64 - slurry mixer output function area, 65 - carbon dioxide injection port, 66 - slurry injection port, 67 - surfactant injection port, 68 - seawater injection port, 69 - slurry mixer temperature and pressure sensor, 70 - slurry mixing device, 71 - stirring rotation motor, 72 - vertical rotation rod, 73 - horizontal rotation rod, 74 - trapezoidal stirring blade, 75 - pressure-resistant high-definition camera lens, 76 - slurry mixer support, 77 - surfactant stirring storage tank, 78 - surfactant delivery straight pipe, 79 - surfactant delivery pump, 80 - surfactant riser injection port, 81 - surfactant stirring device, 82 - storage tank temperature and pressure sensor83 - Mud conveying hose expander, 84 - Vertical straight pipe for mud conveying, 85 - Support for secondary mud conveying pump, 86 - Secondary mud conveying pump, 87 - Horizontal straight pipe for mud conveying, 88 - Seawater suction inlet, 89 - Ball valve for vertical pipe of seawater suction, 90 - Solid filtration device, 91 - Support for filtration device, 92 - Horizontal straight pipe for seawater suction, 93 - Seawater suction pump, 94 - Support for seawater suction pump, 95 - Ball valve at the end of the retractable hose for liquid recovery, 96 - Horizontal straight pipe for output of mixed slurry, 97 - Ball valve for output pipe of mixed slurry, 98 - Primary pump for output of mixed slurry, 99 - Hose expansion device for output of mixed slurry, 100 - Subsea anchoring device., Detailed implementation mode

[0019] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0020] Example 1, referring to Figures 1-5 , the equipment for solidifying and storing carbon dioxide in a subsea artificial hydrate reservoir mentioned in the present invention includes a transport ship 1 and a liquid carbon dioxide storage tank 2, and also includes a surfactant storage tank 3, a carbon dioxide injection pump 4, a carbon dioxide injection riser 5, a surfactant injection pump 6, a surfactant injection riser 7, a hydrate subsea slurry integration core system 8, a subsea mud collection system 9 and a mixed slurry output system 10. The liquid carbon dioxide storage tank 2 and the surfactant storage tank 3 are provided on the transport ship 1. The lower part of the transport ship 1 is connected to the hydrate subsea slurry integration core system 8 on the subsea formation 14 through the carbon dioxide injection riser 5 and the surfactant injection riser 7. A subsea mud collection system 9 is provided on one side of the hydrate subsea slurry integration core system 8, and a mixed slurry output system 10 is provided on the other side. Carbon dioxide and surfactant on the transport ship 1 are injected into the hydrate subsea slurry integration core system 8 through the carbon dioxide injection riser 5 and the surfactant injection riser 7. A sediment slurry is formed through the subsea mud collection system 9. The surfactant, the sediment slurry and seawater are pumped into the carbon dioxide hydrate formation subsea slurry mixer 16 and continuously stirred. Using the subsea high pressure and the driving force of low-temperature seawater, a carbon dioxide hydrate-sediment mixed slurry is made. The carbon dioxide hydrate-sediment mixed slurry is transported to the subsea depression area 13 through the mixed slurry output system 10. Then, an artificial carbon dioxide reservoir is formed by covering the sediment layer to achieve the safe subsea storage of carbon dioxide.

[0021] Referring to Figure 2 - and Figure 3, the integrated hydrate-seabed slurry core system 8 mentioned in the present invention is composed of a carbon dioxide hydrate generating seabed slurry mixer 16, a surfactant injection sub-module 17, a sediment slurry injection sub-module 18, a seawater injection sub-module 19, and a mixed slurry output sub-module 20, which are assembled and installed on the upper side of the core bearing and moving sub-module 21. The position is moved through the core bearing and moving sub-module 21. One side of the carbon dioxide hydrate generating seabed slurry mixer 16 is connected to the sediment slurry injection sub-module 18 through a slurry injection port 66, and is connected to the surfactant injection sub-module 17 through a surfactant injection port 67. On the other side of the carbon dioxide hydrate generating seabed slurry mixer 16, it is connected to the seawater injection sub-module 19 through a seawater injection port 68, and the bottom of the carbon dioxide hydrate generating seabed slurry mixer 16 is connected to the mixed slurry output sub-module 20.

[0022] Among them, the above-mentioned carbon dioxide hydrate generating seabed slurry mixer 16 is divided into a slurry mixer stirring function area 62, a slurry mixer separation function area 63, and a slurry mixer output function area 64; a carbon dioxide injection port 65 is provided at the top of the slurry mixer stirring function area 62, and a slurry injection port 66 and a surfactant injection port 67 are embedded in the outer wall of the lower half of the left end, and a seawater injection port 68 is embedded in the outer wall of the lower half of the right end; a slurry mixing and stirring device 70 is provided on the inner wall of the slurry mixer stirring function area 62, and the slurry mixing and stirring device 70 is composed of a stirring rotation motor 71, a vertical rotating rod 72, and a horizontal rotating rod 73. A plurality of trapezoidal stirring blades 74 are installed on each horizontal rotating rod 73; a plurality of slurry mixer temperature and pressure sensors 69 are distributed on the inner wall of the carbon dioxide hydrate generating seabed slurry mixer 16, and a slurry mixer support 76 is provided at the lower part of the outside, so as to leave enough space at the bottom to realize the connection between the horizontal straight pipe 96 of the mixed slurry output and the bottom of the inner wall on the right side of the slurry mixer output function area 64; the above-mentioned core bearing and moving sub-module 21 includes a core system crawler wheel 22, a core system bearing base 23, and a towing hook 24. A plurality of core system crawler wheels 22 are provided at the bottom of the core system bearing base 23, and towing hooks 24 are provided at both ends of the core system bearing base 23 respectively.

[0023] The above-mentioned surfactant injection sub-module 17 is composed of a surfactant stirring storage tank 77, a surfactant conveying straight pipe 78, and a surfactant conveying pump 79. A surfactant riser injection port 80 is provided at the top of the surfactant stirring storage tank 77, which is connected to the surfactant injection riser 7; a surfactant stirring device 81 is installed on the inner wall of the surfactant stirring storage tank 77, a storage tank temperature and pressure sensor 82 is installed on the inner wall of the surfactant stirring storage tank 77, and the bottom is connected to the carbon dioxide hydrate generating seabed slurry mixer 16 through the surfactant conveying straight pipe 78 and the surfactant conveying pump 79.

[0024] Among them, it should be noted that: the compounding method of the surfactant is: it is compounded by soy lecithin and coconut oil diethanolamide in a ratio of 2:1, and the standard concentration is 300ppm. Soy lecithin and coconut oil diethanolamide both have the properties of foaming, reducing gas-liquid interfacial tension, and forming steric hindrance on the surface of hydrate particles. The latter can also reduce the critical micelle concentration of the former, so that more soybean lecithin molecules act on the gas-liquid interface. After the two are compounded, they can effectively promote the formation of carbon dioxide hydrates, and at the same time, they can effectively prevent the aggregation formed by carbon dioxide hydrates and sediment from depositing and clogging in the carbon dioxide hydrate generation seabed mixer 16 and the mixed slurry output system 10, which provides conditions for the rapid generation of carbon dioxide hydrates and the stable and continuous discharge of mixed slurry. On the other hand, the two substances in the surfactant are natural active substances, which can be naturally decomposed after being discharged to the seabed with the mixed slurry, and are friendly to the marine environment. For specific reference Figure 6 It can be seen that: after the addition of surfactant, the concentration of carbon dioxide hydrate increased significantly, indicating that the surfactant promoted the formation of carbon dioxide hydrate; in addition, the loop flow experiment time was significantly prolonged, so it can be explained that the surfactant prevented the deposition of carbon dioxide hydrate-sediment mixed solid aggregates 11.

[0025] The above-mentioned mud slurry injection submodule 18 is composed of a mud conveying telescopic hose 36, a mud conveying hose telescope 83, a mud conveying vertical straight pipe 84, a secondary mud conveying pump bracket 85, a secondary mud conveying pump 86, and a mud conveying horizontal straight pipe 87. The output end of the secondary mud conveying pump 86 is connected to the carbon dioxide hydrate generating seabed mixer 16 through the mud conveying horizontal straight pipe 87; the secondary mud conveying pump bracket 85, the mud conveying vertical straight pipe 84 and the mud conveying hose telescope 83 are installed on the lower side of the secondary mud conveying pump 86, and the distance and relative position between the mud seabed collection system 9 and the hydrate seabed mixing integrated core system 8 are controlled by the mud conveying telescopic hose 36 and the mud conveying hose telescope 83.

[0026] The above-mentioned seawater injection submodule 19 consists of a seawater suction port 88, a seawater suction vertical pipe ball valve 89, a solid filtering device 90, a filtering device bracket 91, a seawater suction horizontal straight pipe 92, a seawater suction pump 93, a seawater suction pump bracket 94, a liquid recovery telescopic hose 59, and a liquid recovery telescopic hose tail end ball valve 95. The output end of the seawater suction pump 93 is connected to the carbon dioxide hydrate generating seabed mixer 16, and the input end of the seawater suction pump 93 is connected to the seawater suction port 88 through the seawater suction horizontal straight pipe 92 and the solid filtering device 90. The filtering device bracket 91 is installed on the lower side of the solid filtering device 90, and the seawater suction pump bracket 94 is installed on the lower side of the seawater suction pump 93.

[0027] The solid filtration device 90 is mainly used to filter solids and fish drawn in with seawater. The left end of the seawater pumping pump 93 is connected through a horizontal seawater pumping straight pipe 92 to the seawater injection port 68 on the subsea slurry mixer 16 for carbon dioxide hydrate formation. When the seawater injection step is carried out separately, the spherical valve 95 at the end of the liquid recovery telescopic hose is closed, and the spherical valve 89 of the vertical seawater pumping pipe is opened to prevent seawater from directly flowing into the mixed slurry output system 10. When the liquid recovery step in the mixed slurry output system 10 is carried out separately, the spherical valve 89 of the vertical seawater pumping pipe is closed, and the spherical valve 95 at the end of the liquid recovery telescopic hose is opened to prevent the recovered liquid from flowing out from the seawater pumping inlet 88. The liquid 12 that has not participated in hydrate formation is recovered from the mixed slurry output system 10 and pumped into the subsea slurry mixer 16 for carbon dioxide hydrate formation through the seawater injection sub-module 19.

[0028] The above-mentioned mixed slurry output sub-module 20 is composed of a horizontal mixed slurry output straight pipe 96, a spherical valve 97 of the mixed slurry output pipe, a primary mixed slurry output pump 98, a telescopic device 99 for the mixed slurry output hose, and a telescopic mixed slurry output hose 42. The input end of the primary mixed slurry output pump 98 is connected through the horizontal mixed slurry output straight pipe 96 to the subsea slurry mixer 16 for carbon dioxide hydrate formation. The output end of the primary mixed slurry output pump 98 is connected through the telescopic device 99 for the mixed slurry output hose and the telescopic mixed slurry output hose 42 to the mixed slurry output system 10.

[0029] When the processes of injecting carbon dioxide, surfactant, mud, and seawater, as well as hydrate formation and mixing slurry stirring, are carried out in the subsea slurry mixer 16 for carbon dioxide hydrate formation, the spherical valve 97 of the mixed slurry output pipe is closed and opened when the mixed slurry is output. The mixed slurry in the subsea slurry mixer 16 for carbon dioxide hydrate formation is discharged to the subsea depression area 13 successively through the mixed slurry output sub-module 20 and the mixed slurry output system 10. The telescopic device 99 for the mixed slurry output hose and the telescopic mixed slurry output hose 42 can freely control the distance and relative position between the mixed slurry output system 10 and the core system 8 of the subsea slurry mixing for hydrate, so as to facilitate the movement of the equipment after the replacement of the subsea depression area 13, and to control the deposition position and accumulation form of the solid such as the carbon dioxide hydrate-sediment mixed solid aggregate 11 and sediment during the formation process of the artificial carbon dioxide hydrate reservoir.

[0030] Refer to Figure 4, the mud seabed collection system 9 mentioned in the present invention is composed of a sediment impactor 25, a mud collector 26, a mud suction pipeline 27, a mud suction pump and a solid filtration device 28, a mud suction port 29, a mud stirring storage tank 30, a mud stirring device 31, a mud storage tank temperature and pressure sensor 32, a small seawater suction pump and a solid filtration device 33, a mud conveying straight pipe 34, a primary mud conveying pump 35, a mud conveying telescopic hose 36, a collection system crawler wheel 37, a collection system bearing base 38, a collection system mobile controller 39, and a small seawater suction port 40. The bottom of the collection system bearing base 38 is provided with the collection system crawler wheel 37, and the mud stirring storage tank 30 is installed on the upper side of the collection system bearing base 38. The top of the mud stirring storage tank 30 is connected to the small seawater suction port 40 through the small seawater suction pump and the solid filtration device 33. On the left side of the mud stirring storage tank 30, there are the mud suction pump and the solid filtration device 28 and the collection system mobile controller 39. The outside of the mud suction pump and the solid filtration device 28 is connected to the mud collector 26 through the mud suction pipeline 27, and the sediment impactor 25 is installed on the lower side of the mud collector 26; on the right side of the mud stirring storage tank 30, it is connected to the primary mud conveying pump 35 through the mud conveying straight pipe 34, and the outer end of the primary mud conveying pump 35 is connected to the sediment slurry injection sub-module 18 through the mud conveying telescopic hose 36; the mud stirring device 31 is installed in the inner cavity of the mud stirring storage tank 30.

[0031] The sediment impactor 25 scatters and raises the sediment on the surface of the seabed formation, initially forming mud with seawater. The mud is successively pumped into the mud stirring storage tank 30 through the mud collector 26, the mud suction pipeline 27, the mud suction pump and the solid filtration device 28, and the mud suction port 29, and is continuously stirred under the rotation of the mud stirring device 31 to prevent the sediment from depositing in the static state. At the same time, the seawater at the top of the mud stirring storage tank 30 is successively pumped into the mud stirring storage tank 30 through the small seawater suction port 40, the small seawater suction pump and the solid filtration device 33, and the mud storage tank seawater suction port 41 and is stirred and mixed with the original mud to reduce the concentration of sediment in the tank, thereby avoiding the negative impact of too high a concentration of sediment on the conveying device and the formation of carbon dioxide hydrate. The outer shape of the mud stirring storage tank 30 is a cylinder, and two mud storage tank temperature and pressure sensors 32 are provided at the symmetric side walls at the middle position of the axial direction. When the temperature and pressure in the tank reach the set standard, the sediment slurry that has been in a stirring state in the tank is successively conveyed to the hydrate seabed mud mixing integrated core system 8 through the mud conveying straight pipe 34, the primary mud conveying pump 35, and the mud conveying telescopic hose 36.

[0032] Refer to Figure 5, the hybrid slurry output system 10 mentioned in the present invention includes a hybrid slurry output telescopic hose 42, a secondary hybrid slurry output pump 43, an extensible hose 44 in front of the hybrid slurry discharge pipe, a hybrid slurry discharge pipe lifter 45, a hybrid slurry discharge pipe 46, a hybrid slurry discharge guide plate 47, an output system crawler wheel 48, an output system bearing base 49 and an output system movement controller 50. The output system crawler wheel 48 is installed on the lower side of the output system bearing base 49, and the secondary hybrid slurry output pump 43 and the output system movement controller 50 are installed on the upper side. The left end of the secondary hybrid slurry output pump 43 is connected to the hybrid slurry output telescopic hose 42, and the right end is connected to the hybrid slurry discharge pipe 46 through the extensible hose 44 in front of the hybrid slurry discharge pipe. A hybrid slurry discharge guide plate 47 is provided on the lower side of the hybrid slurry discharge pipe 46. The carbon dioxide hydrate-sediment hybrid slurry is transported to the submarine depression area 13 through the hybrid slurry discharge pipe 46 and the hybrid slurry discharge guide plate 47.

[0033] The extensible hose 44 in front of the hybrid slurry discharge pipe and the hybrid slurry discharge pipe lifter 45 can adjust the vertical height of the hybrid slurry discharge point; the hybrid slurry discharge guide plate 47 has a telescopic function and can arbitrarily adjust the opening and closing angle with the tail end outlet of the hybrid slurry discharge pipe 46, and can adjust the horizontal lateral position of the hybrid slurry discharge point. The combination of the above three can control the deposition position and accumulation form of the solid aggregates of carbon dioxide hydrate, sediment, and carbon dioxide hydrate-sediment hybrid solid aggregates 11 in the hybrid slurry.

[0034] The usage method of the equipment for solidifying and storing carbon dioxide in the submarine artificial hydrate reservoir mentioned in the present invention has the following technical solution: It is mainly divided into four stages: continuous injection stage, hydrate formation and slurry mixing stage, hybrid slurry discharge stage, and sediment layer covering stage; First, in the continuous injection stage, the liquid carbon dioxide on the transport ship 1, the sediment slurry formed by the surfactant and the submarine formation 14, and the low-temperature seawater near the seabed need to be injected into the carbon dioxide hydrate formation submarine slurry mixer 16 in sequence, mainly including the following steps: a1. Preparation before system layout: Before arranging all equipment on the submarine formation 14, make the pressures in the carbon dioxide hydrate formation submarine slurry mixer 16, the mud stirring storage tank 30, and the surfactant stirring storage tank 77 be 0 MPa and keep them in a completely sealed state; a2. Deployment of the system to the seabed: The transport ship 1 floats on the sea level 15. The hydrate subsea slurry integration core system 8, the slurry subsea collection system 9, and the mixed slurry output system 10 are lowered to the seabed formation 14 at a water depth of 800 to 2000 meters according to the positions of different seabed depression areas 13. The subsea anchoring device 100 installed on the core system crawler wheel 22 is inserted into the seabed formation 14. The carbon dioxide injection pump 4 and the surfactant injection pump 6 on the transport ship 1 are respectively connected to the carbon dioxide injection port 65 and the surfactant riser injection port 80 through the carbon dioxide injection riser 5 and the surfactant injection riser 7. The slurry subsea collection system 9 is moved to a position near the hydrate subsea slurry integration core system 8 by the collection system mobile controller 39, and the subsea anchoring device 100 installed on the collection system crawler wheel 37 is inserted into the seabed formation 14. The mixed slurry output system 10 is moved to a position near the seabed depression area 13 by the output system mobile controller 50, and the subsea anchoring device 100 installed on the output system crawler wheel 48 is inserted into the seabed formation 14; a3. Injection and cooling of the surfactant: Open the ball valve in the surfactant riser injection port 80 to inject the surfactant into the surfactant mixing storage tank 77, and at the same time turn on the surfactant mixing device 81. Stop injecting and close the ball valve in the surfactant riser injection port 80 when the pressure in the surfactant mixing storage tank 77 is close to the pressure at the seabed position, and continue stirring to accelerate the heat exchange process between the surfactant and the low-temperature seawater through the outer wall of the surfactant mixing storage tank 77; a4. Collection and dilution of the subsea sediment slurry: While the injection and cooling steps of the surfactant are being carried out, the sediment impactor 25 in the slurry subsea collection system 9 is used to disperse and lift the sediment in the seabed formation 14 to initially form a slurry with seawater. At the same time, open the ball valve in the slurry suction port 29, the slurry suction pump and the solid filtration device 28, the small seawater suction pump and the solid filtration device 33, and the slurry mixing device 31. Pump the initially formed slurry and seawater on the seabed into the slurry mixing storage tank 30 and continue stirring. Monitor the pressure through the slurry storage tank temperature and pressure sensor 32. When the pressure in the slurry mixing storage tank 30 reaches the pressure value at the seabed position, close all the pumps and ball valves in the slurry subsea collection system 9; a5. Injection of carbon dioxide: When the temperature of the surfactant in the surfactant mixing storage tank 77 drops below the carbon dioxide hydrate phase equilibrium temperature corresponding to the seabed pressure, open the ball valve in the carbon dioxide injection port 65 to inject liquid carbon dioxide into the carbon dioxide hydrate formation subsea slurry mixer 16, and at the same time turn on the slurry mixing device 70. Stop injecting and close the ball valve in the carbon dioxide injection port 65 when the internal pressure reaches 0.8 times the pressure at the seabed position; a6. Inject low-temperature surfactant: Start the surfactant delivery pump 79, open the ball valve in the surfactant injection port 67, and inject surfactant into the subsea slurry mixer 16 for carbon dioxide hydrate formation. At the same time, keep the surfactant stirring device 81 and the slurry mixing device 70 running. Stop injecting when the injection volume reaches the design standard, and then close the ball valve in the surfactant injection port 67 and the surfactant delivery pump 79. a7. Inject sediment slurry: Start the primary slurry delivery pump 35 and the secondary slurry delivery pump 86, open the ball valve in the slurry injection port 66, and deliver the sediment slurry with a reduced sediment concentration after dilution by seawater into the subsea slurry mixer 16 for carbon dioxide hydrate formation. At the same time, keep the slurry stirring device 31 and the slurry mixing device 70 running to avoid sediment deposition. Stop injecting when the injection volume reaches the design standard, and then close the ball valve in the slurry injection port 66, the primary slurry delivery pump 35, and the secondary slurry delivery pump 86. a8. Inject low-temperature seawater: Confirm that the ball valve 95 at the end of the liquid recovery retractable hose is closed, open the ball valve 89 of the seawater suction vertical pipe, start the seawater suction pump 93, open the ball valve in the seawater injection port 68, and inject low-temperature seawater filtered by solids near the seabed into the subsea slurry mixer 16 for carbon dioxide hydrate formation. At the same time, keep the slurry mixing device 70 running. Stop injecting when the injection volume reaches the design standard, and then close the ball valve in the seawater injection port 68, the seawater suction pump 93, and the ball valve 89 of the seawater suction vertical pipe. Second, in the hydrate formation and slurry mixing stage, the main steps are as follows: b1. Hydrate formation: Increase the rotation speed of the slurry mixing device 70 in the subsea slurry mixer 16 for carbon dioxide hydrate formation, so that carbon dioxide in the sediment slurry agitation system with high seawater content rapidly forms carbon dioxide hydrate with seawater under the action of high seabed pressure, low seawater temperature driving force, and surfactant. Monitor the temperature and pressure in different areas of the subsea slurry mixer 16 for carbon dioxide hydrate formation through multiple slurry mixer temperature and pressure sensors 69, and assist the observation with the pressure-resistant high-definition camera lens 75 installed inside. When a significant sudden increase in temperature occurs, it indicates the start of carbon dioxide hydrate formation, and calculate the hydrate formation amount based on the real-time changes in temperature and pressure. b2. Formation of carbon dioxide hydrate - sediment mixed slurry: When the temperature and pressure in each area of the subsea mixer 16 for carbon dioxide hydrate formation no longer change significantly, reduce the rotation speed of the mixing and stirring device 70. Under the influence of the surfactant, gradually form a carbon dioxide hydrate - sediment mixed slurry with good fluidity from hydrate particles, small hydrate aggregates, sediment, and seawater during the agitation process. By monitoring the feedback torque power of the mixing and stirring device 70, when the torque power no longer fluctuates significantly, it indicates that the properties and agitation state of the carbon dioxide hydrate - sediment mixed slurry formed by carbon dioxide hydrate and sediment have tended to be stable; Third, in the stage of discharging the mixed slurry, the main steps are as described below: c1. Discharging the mixed slurry: Keep the mixing and stirring device 70 rotating at a constant speed to avoid sedimentation of the carbon dioxide hydrate - sediment mixed slurry; adjust the hoist 45 of the mixed slurry discharge pipe to the lowest position, open the ball valve 97 of the mixed slurry output pipe, turn on the primary mixed slurry output pump 98 and the secondary mixed slurry output pump 43, and discharge the carbon dioxide hydrate - sediment mixed slurry to the lowest water level of the subsea depression area 13. While discharging, adjust the guiding plate 47 for discharging the mixed slurry to ensure the uniform deposition of the solid aggregates in the carbon dioxide hydrate - sediment mixed slurry on the lowest water level of the subsea depression area 13; when the sediment is close to evenly filling the lowest water level of the subsea depression area 13, raise the hoist 45 of the mixed slurry discharge pipe so that it starts to discharge to a higher water level of the subsea depression area 13, and cycle in turn until the subsea depression area 13 is nearly filled; Fourth, in the stage of covering with sediment layer, the main steps are as described below: d1. Injecting sediment slurry: Repeat the steps of collecting and diluting the subsea sediment slurry, injecting low-temperature surfactant, injecting sediment slurry, and injecting seawater in the continuous injection stage, so that the pressure in the subsea mixer 16 for carbon dioxide hydrate formation is close to the pressure before discharging the mixed slurry, and at the same time keep the mixing and stirring device 70 rotating at a constant speed; d2. Discharging the sediment slurry: Pull out the subsea anchoring device 100 on the crawler wheel 48 of the output system, and discharge the sediment slurry by repeating the steps of discharging the mixed slurry, but do not perform the liquid recovery step. While discharging the sediment slurry, adjust the position of the mixed slurry output system 10, the hoist 45 of the mixed slurry discharge pipe, and the state of the guiding plate 47 for discharging the mixed slurry in real time, so that the sediment is evenly deposited on all the carbon dioxide hydrate - sediment mixed solid deposits in the subsea depression area 13. When the thickness of the overlying sediment layer formed reaches the covering requirement of the hydrate - sediment mixed solid deposits in the depression area, stop all operations, close all pumps and ball valves in the system, and move the entire system to the vicinity of the next subsea depression area 13.

[0035] Example 2. The difference between this example and Example 1 is as follows: Referring to Figure 5 , the mixed slurry output system 10 mentioned in this example further includes a liquid recovery wide-mouth device 51, a wide-mouth device end baffle 52, a liquid recovery vertical pipe 53, a liquid recovery horizontal pipe 54, a liquid recovery horizontal pipe support 55, a solid filtration device 90, a liquid recovery pump 56, a liquid recovery pump support 57, a liquid recovery pump lifter 58, a liquid recovery telescopic hose 59, a liquid recovery hose telescopic device 60, and a liquid recovery hose telescopic device support 61. The liquid recovery pump 56 is installed on the upper surface of the output system bearing base 49 through the liquid recovery pump support 57 and the liquid recovery pump lifter 58. The solid filtration device 90 is installed on the top of the output system mobile controller 50 through the liquid recovery horizontal pipe support 55. One end of the liquid recovery pump 56 is connected to the liquid recovery hose telescopic device 60 through the liquid recovery telescopic hose 59, and the other end is connected to the liquid recovery wide-mouth device 51 through the liquid recovery horizontal pipe 54, the solid filtration device 90, and the liquid recovery vertical pipe 53. A wide-mouth device end baffle 52 is provided on the outside of the liquid recovery wide-mouth device 51.

[0036] The liquid recovery wide-mouth device 51 and the wide-mouth device end baffle 52 can reduce the loss of the liquid 12 that did not participate in the hydrate formation after being discharged with the mixed slurry. The liquid recovery horizontal pipe support 55, the liquid recovery pump support 57, and the liquid recovery pump lifter 58 can realize the synchronous lifting and lowering of the liquid recovery wide-mouth device 51, the liquid recovery horizontal pipe 54, and the mixed slurry discharge pipe 46, and the purpose is also to reduce the loss of the liquid 12 that did not participate in the hydrate formation after being discharged. The solid filtration device 90 is used to filter out the solids and fish accidentally drawn in during the liquid recovery process.

[0037] In addition, in the third stage: the mixed slurry discharge stage, it further includes: the recovery of the liquid that did not participate in the hydrate formation, the discharge of the mixed slurry, and the stop of the liquid recovery and the secondary formation, mixing, and discharge of the hydrate; In the mixed slurry discharge stage, the main steps are as follows: c1. Discharge of the mixed slurry: Keep the mixing slurry stirring device 70 rotating at a constant speed to avoid the deposition of the carbon dioxide hydrate-sediment mixed slurry; synchronously adjust the mixed slurry discharge pipe lifter 45 and the liquid recovery pump lifter 58 to the lowest position, open the ball valve 97 of the mixed slurry output pipe, turn on the primary mixed slurry output pump 98 and the secondary mixed slurry output pump 43, and discharge the carbon dioxide hydrate-sediment mixed slurry to the lowest water level of the submarine depression area 13. While discharging, adjust the mixed slurry discharge guide plate 47 to ensure the uniform deposition of the solid aggregates in the carbon dioxide hydrate-sediment mixed slurry on the lowest water level of the submarine depression area 13; when the sediment is close to evenly filling the lowest water level of the submarine depression area 13, synchronously raise the mixed slurry discharge pipe lifter 45 and the liquid recovery pump lifter 58 so that it starts to discharge to a higher water level of the submarine depression area 13, and cycle in turn until the submarine depression area 13 is close to being filled; c2. Recovery of the liquid not participating in hydrate formation: While the carbon dioxide hydrate-sediment mixed slurry is discharged outward through the mixed slurry discharge pipe 46, ensure that the ball valve 89 of the seawater suction vertical pipe is closed, open the ball valve at the end of the liquid recovery telescopic hose 95 and the ball valve in the seawater injection port 68, and turn on the liquid recovery pump 56 and the seawater suction pump 93 at the power sum standard of 0.5 times the total power of the primary mixed slurry output pump 98 and the secondary mixed slurry output pump 43, so that the liquid carbon dioxide that has been discharged through the mixed slurry discharge pipe 46 and has not participated in hydrate formation and the seawater saturated with carbon dioxide pass through the liquid recovery wide-mouth device 51, the liquid recovery vertical pipe 53, the liquid recovery horizontal pipe 54, the solid filtration device 90, the liquid recovery pump 56, the liquid recovery telescopic hose 59, the solid filtration device 90 in the seawater injection sub-module 19, the seawater suction horizontal straight pipe 92, the seawater suction pump 93, and the seawater injection port 68 in sequence and then are recovered into the carbon dioxide hydrate formation submarine slurry mixer 16; c3. Stopping the discharge of the mixed slurry and the recovery of the liquid: During the cycle of discharging the carbon dioxide hydrate-sediment mixed slurry at 1 times the power and recovering the liquid at 0.5 times the power, the agitation state of the mixed slurry in the subsea mixer 16 for carbon dioxide hydrate formation is monitored in real time through the feedback torque power of the pressure-resistant high-definition camera lens 75, the temperature and pressure sensor 69 of the slurry mixer, and the slurry mixing and stirring device 70; when the light transmittance of the mixed slurry in the pressure-resistant high-definition camera lens 75 is close to that of seawater, it indicates that the content of the hydrate-sediment mixed aggregate in the carbon dioxide hydrate-sediment mixed slurry is close to 0; when the temperature in a certain area inside the subsea mixer 16 for carbon dioxide hydrate formation suddenly rises significantly or the feedback torque power of the slurry mixing and stirring device 70 suddenly increases, it indicates the secondary formation of carbon dioxide hydrate; when any one of the above three situations occurs, stop the discharge of the mixed slurry and the recovery of the liquid 12 that has not participated in hydrate formation, and close all pumps and ball valves in the mixed slurry output sub-module 20, the mixed slurry output system 10, and the seawater injection sub-module 19; c4. Secondary formation, mixing, and discharging of hydrates: Repeat the steps of carbon dioxide injection, surfactant injection, and sediment slurry injection in the continuous injection stage, and stop injecting when the pressure inside the subsea mixer 16 for carbon dioxide hydrate formation is close to the pressure before the discharge of the mixed slurry; repeat all the steps in the hydrate formation and mixing stage. When the secondary formation of hydrates is monitored and the properties and agitation state of the mixed slurry are stable, repeat all the steps in the mixed slurry discharge stage; repeat the cycle in the 4 steps described in the mixed slurry discharge stage until the subsea depression area 13 is close to being completely filled with the carbon dioxide hydrate-sediment mixed solid sediment, and then stop the discharge of the mixed slurry and the recovery of the liquid.

[0038] The above are only some preferred embodiments of the present invention. Any person skilled in the art may modify the technical solutions described above or modify them into equivalent technical solutions. Therefore, the corresponding simple modifications or equivalent transformations made according to the technical solutions of the present invention all fall within the scope of protection required by the present invention.

Claims

1. An equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir, comprising a transport ship (1) and a liquid carbon dioxide storage tank (2), characterized in that: It also includes a surfactant storage tank (3), a carbon dioxide injection pump (4), a carbon dioxide injection riser (5), a surfactant injection pump (6), a surfactant injection riser (7), a hydrate subsea slurry integration core system (8), a slurry subsea collection system (9), and a mixed slurry output system (10). Below the transport ship (1), it is connected to the hydrate subsea slurry integration core system (8) on the subsea formation (14) through the carbon dioxide injection riser (5) and the surfactant injection riser (7). A slurry subsea collection system (9) is provided on one side of the hydrate subsea slurry integration core system (8), and a mixed slurry output system (10) is provided on the other side. Carbon dioxide and surfactant on the transport ship (1) are injected into the hydrate subsea slurry integration core system (8) through the carbon dioxide injection riser (5) and the surfactant injection riser (7). A sediment slurry is formed through the slurry subsea collection system (9). The surfactant, sediment slurry, and seawater are pumped into the carbon dioxide hydrate formation subsea mixer (16) and continuously stirred. Using the subsea high pressure and seawater low temperature driving force, a carbon dioxide hydrate-sediment mixed slurry is made. The carbon dioxide hydrate-sediment mixed slurry is transported to the subsea depression area (13) through the mixed slurry output system (10). Then, an artificial carbon dioxide reservoir is formed by covering with a sediment layer to achieve the subsea safe storage of carbon dioxide.

2. The equipment for solidifying and storing carbon dioxide in the artificial hydrate reservoir on the seabed according to claim 1, characterized in that: The hydrate subsea slurry integration core system (8) is composed of a carbon dioxide hydrate formation subsea mixer (16), a surfactant injection sub-module (17), a sediment slurry injection sub-module (18), a seawater injection sub-module (19), and a mixed slurry output sub-module (20) which are assembled and installed on the upper side of the core bearing and moving sub-module (21). The position is moved through the core bearing and moving sub-module (21). One side of the carbon dioxide hydrate formation subsea mixer (16) is connected to the sediment slurry injection sub-module (18) through a slurry injection port (66), connected to the surfactant injection sub-module (17) through a surfactant injection port (67). On the other side of the carbon dioxide hydrate formation subsea mixer (16), it is connected to the seawater injection sub-module (19) through a seawater injection port (68). At the bottom of the carbon dioxide hydrate formation subsea mixer (16), it is connected to the mixed slurry output sub-module (20).

3. The equipment for solidifying and storing carbon dioxide in the artificial hydrate reservoir on the seabed according to claim 2, characterized in that: The described subsea slurry mixer (16) for carbon dioxide hydrate formation is divided into a slurry mixing function area (62), a slurry separation function area (63), and a slurry output function area (64); at the top of the slurry mixing function area (62), there is a carbon dioxide injection port (65), on the outer wall of the lower half of the left end, there are embedded a slurry injection port (66) and a surfactant injection port (67), and on the outer wall of the lower half of the right end, there is an embedded seawater injection port (68); inside the wall of the slurry mixing function area (62), there is a slurry mixing device (70), and the slurry mixing device (70) consists of a stirring rotation motor (71), a vertical rotating rod (72), and a horizontal rotating rod (73), and multiple trapezoidal stirring blades (74) are installed on each horizontal rotating rod (73); on the inner wall of the described subsea slurry mixer (16) for carbon dioxide hydrate formation, there are distributed multiple slurry mixer temperature and pressure sensors (69), and at the lower part of the outside, there is a slurry mixer support (76) for leaving enough space at the bottom to enable the connection between the horizontal straight pipe (96) for mixed slurry output and the bottom of the inner wall on the right side of the slurry output function area (64); the described core bearing and moving sub-module (21) includes a core system crawler wheel (22), a core system bearing base (23), and a dragging hook (24), at the bottom of the core system bearing base (23), there are multiple groups of core system crawler wheels (22), and at both ends of the core system bearing base (23), there are respectively dragging hooks (24).

4. The equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir according to claim 3, characterized in that: The described surfactant injection sub-module (17) consists of a surfactant stirring storage tank (77), a surfactant delivery straight pipe (78), and a surfactant delivery pump (79), at the top of the surfactant stirring storage tank (77), there is a surfactant riser injection port (80) connected to the surfactant injection riser (7); inside the wall of the surfactant stirring storage tank (77), there is a surfactant stirring device (81), on the inner wall of the surfactant stirring storage tank (77), there is installed a storage tank temperature and pressure sensor (82), and the bottom is connected to the subsea slurry mixer (16) for carbon dioxide hydrate formation through the surfactant delivery straight pipe (78) and the surfactant delivery pump (79).

5. The equipment for solidifying and storing carbon dioxide in the undersea artificial hydrate reservoir according to claim 4, wherein: The described sediment slurry injection sub-module (18) consists of a slurry delivery telescopic hose (36), a slurry delivery hose expander (83), a slurry delivery vertical straight pipe (84), a secondary slurry delivery pump support (85), a secondary slurry delivery pump (86), and a slurry delivery horizontal straight pipe (87), the output end of the secondary slurry delivery pump (86) is connected to the subsea slurry mixer (16) for carbon dioxide hydrate formation through the slurry delivery horizontal straight pipe (87); below the secondary slurry delivery pump (86), there are installed the secondary slurry delivery pump support (85), the slurry delivery vertical straight pipe (84), and the slurry delivery hose expander (83), and the control of the distance and relative position between the subsea slurry collection system (9) and the integrated core system (8) of subsea slurry mixing for hydrates is achieved through the slurry delivery telescopic hose (36) and the slurry delivery hose expander (83).

6. The equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir according to claim 5, characterized in that: The seawater injection sub-module (19) consists of a seawater suction inlet (88), a solid filter device (90), a filter device support (91), a horizontal seawater suction straight pipe (92), a seawater suction pump (93), and a seawater suction pump support (94). The output end of the seawater suction pump (93) is connected to the subsea slurry mixer (16) for carbon dioxide hydrate formation. The input end of the seawater suction pump (93) is connected to the seawater suction inlet (88) through the horizontal seawater suction straight pipe (92) and the solid filter device (90). The filter device support (91) is installed on the lower side of the solid filter device (90), and the seawater suction pump support (94) is installed on the lower side of the seawater suction pump (93).

7. The equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir according to claim 6, characterized in that: The mixed slurry output sub-module (20) consists of a horizontal mixed slurry output straight pipe (96), a primary mixed slurry output pump (98), a telescopic device for the mixed slurry output hose (99), and a telescopic mixed slurry output hose (42). The input end of the primary mixed slurry output pump (98) is connected to the subsea slurry mixer (16) for carbon dioxide hydrate formation through the horizontal mixed slurry output straight pipe (96). The output end of the primary mixed slurry output pump (98) is connected to the mixed slurry output system (10) through the telescopic device for the mixed slurry output hose (99) and the telescopic mixed slurry output hose (42).

8. The equipment for solidifying and storing carbon dioxide in an artificial hydrate reservoir on the seabed according to claim 7, characterized in that: The described mud seabed collection system (9) consists of a sediment impactor (25), a mud collector (26), a mud suction pipe (27), a mud suction pump and a solid filtration device (28), a mud suction port (29), a mud stirring storage tank (30), a mud stirring device (31), a mud storage tank temperature and pressure sensor (32), a small seawater suction pump and a solid filtration device (33), a mud conveying straight pipe (34), a primary mud conveying pump (35), a mud conveying telescopic hose (36), a collection system crawler wheel (37), a collection system bearing base (38), a collection system mobile controller (39), and a small seawater suction port (40). The bottom of the collection system bearing base (38) is provided with a collection system crawler wheel (37), and a mud stirring storage tank (30) is installed on the upper side of the collection system bearing base (38). The top of the mud stirring storage tank (30) is connected to the small seawater suction port (40) through a small seawater suction pump and a solid filtration device (33). On the left side of the mud stirring storage tank (30), there are a mud suction pump and a solid filtration device (28) and a collection system mobile controller (39). The outside of the mud suction pump and a solid filtration device (28) is connected to the mud collector (26) through a mud suction pipe (27), and a sediment impactor (25) is installed under the mud collector (26); on the right side of the mud stirring storage tank (30), it is connected to a primary mud conveying pump (35) through a mud conveying straight pipe (34), and the outer end of the primary mud conveying pump (35) is connected to the carbon dioxide hydrate - sediment slurry injection sub-module (18) through a mud conveying telescopic hose (36); a mud stirring device (31) is installed in the inner cavity of the mud stirring storage tank (30).

9. The equipment for solidifying and storing carbon dioxide in the artificial hydrate reservoir on the seabed according to claim 8, characterized in that: The described mixed slurry output system (10) includes a mixed slurry output telescopic hose (42), a secondary mixed slurry output pump (43), an extendable hose in front of the mixed slurry discharge pipe (44), a mixed slurry discharge pipe lifter (45), a mixed slurry discharge pipe (46), a mixed slurry discharge deflector (47), an output system crawler wheel (48), an output system bearing base (49), and an output system mobile controller (50). The bottom of the output system bearing base (49) is provided with an output system crawler wheel (48), and a secondary mixed slurry output pump (43) and an output system mobile controller (50) are installed on the upper side. The left end of the secondary mixed slurry output pump (43) is connected to the mixed slurry output telescopic hose (42), and the right end is connected to the mixed slurry discharge pipe (46) through an extendable hose in front of the mixed slurry discharge pipe (44). A mixed slurry discharge deflector (47) is provided under the mixed slurry discharge pipe (46), and the carbon dioxide hydrate - sediment mixed slurry is transported to the seabed depression area (13) through the mixed slurry discharge pipe (46) and the mixed slurry discharge deflector (47).

10. The method of using the equipment for solidifying and storing carbon dioxide in a submarine artificial hydrate reservoir according to claim 9, characterized in that: It is mainly divided into four stages: the continuous injection stage, the hydrate formation and slurry mixing stage, the mixed slurry discharge stage, and the sediment layer covering stage; First, in the continuous injection stage, it is necessary to inject the liquid carbon dioxide on the transport ship (1), the sediment slurry formed by the surfactant and the seabed formation (14), and the low-temperature seawater near the seabed into the carbon dioxide hydrate generating subsea slurry mixer (16) in sequence, mainly including the following steps: a1. Preparation before system layout: Before arranging all equipment on the seabed formation (14), make the pressures in the carbon dioxide hydrate generating subsea slurry mixer (16), the mud stirring storage tank (30), and the surfactant stirring storage tank (77) be 0 MPa and keep them in a completely sealed state; a2. System layout on the seabed: Lower the hydrate subsea slurry integration core system (8), the mud subsea collection system (9), and the mixed slurry output system (10) to the seabed formation (14) at a water depth of 800 to 2000 meters according to the positions of different seabed depression areas (13); Insert the subsea anchoring device (100) installed on the core system crawler wheel (22) into the seabed formation (14), and connect the carbon dioxide injection pump (4) and the surfactant injection pump (6) on the transport ship (1) to the carbon dioxide injection port (65) and the surfactant riser injection port (80) respectively through the carbon dioxide injection riser (5) and the surfactant injection riser (7); Move the mud subsea collection system (9) to a position near the hydrate subsea slurry integration core system (8) through the collection system mobile controller (39), and insert the subsea anchoring device (100) installed on the collection system crawler wheel (37) into the seabed formation (14); Move the mixed slurry output system (10) to a position near the seabed depression area (13) through the output system mobile controller (50), and insert the subsea anchoring device (100) installed on the output system crawler wheel (48) into the seabed formation (14); a3. Injection and cooling of the surfactant: Open the ball valve in the surfactant riser injection port (80), inject the surfactant into the surfactant stirring storage tank (77), and at the same time start the surfactant stirring device (81). When the pressure in the surfactant stirring storage tank (77) is close to the pressure at the seabed position, stop injecting and close the ball valve in the surfactant riser injection port (80), and continuously stir to accelerate the heat exchange process of the surfactant through the outer wall of the surfactant stirring storage tank (77) and the low-temperature seawater; a4. Collection and dilution of subsea sediment slurry: While the surfactant is being injected and cooled, the sediment impactor (25) in the subsea sediment collection system (9) is used to disperse and lift the sediment in the subsea formation (14), initially forming slurry with seawater. At the same time, the ball valve, slurry suction pump, solid filtration device (28), small seawater suction pump and solid filtration device (33), and slurry stirring device (31) inside the slurry suction port (29) are turned on. The initially formed subsea slurry and seawater are pumped into the slurry stirring storage tank (30) and continuously stirred. The pressure is monitored through the pressure sensor (32) of the slurry storage tank. When the pressure inside the slurry stirring storage tank (30) reaches the pressure value at the subsea position, all pumps and ball valves in the subsea sediment collection system (9) are closed; a5. Injection of carbon dioxide: When the temperature of the surfactant in the surfactant stirring storage tank (77) drops below the carbon dioxide hydrate phase equilibrium temperature corresponding to the subsea pressure, the ball valve inside the carbon dioxide injection port (65) is opened, and liquid carbon dioxide is injected into the subsea carbon dioxide hydrate generating slurry mixer (16). At the same time, the slurry mixing stirring device (70) is turned on. When the internal pressure reaches 0.8 times the pressure value at the subsea position, the injection is stopped and the ball valve inside the carbon dioxide injection port (65) is closed; a6. Injection of low-temperature surfactant: Start the surfactant delivery pump (79), open the ball valve inside the surfactant injection port (67), and inject the surfactant into the subsea carbon dioxide hydrate generating slurry mixer (16). At the same time, keep the surfactant stirring device (81) and the slurry mixing stirring device (70) turned on. When the injection amount reaches the design standard, stop the injection, and close the ball valve inside the surfactant injection port (67) and the surfactant delivery pump (79); a7. Injection of sediment slurry: Start the primary slurry delivery pump (35) and the secondary slurry delivery pump (86), open the ball valve inside the slurry injection port (66), and transport the sediment slurry with a reduced sediment concentration after dilution with seawater into the subsea carbon dioxide hydrate generating slurry mixer (16). At the same time, keep the slurry stirring device (31) and the slurry mixing stirring device (70) turned on to avoid sediment deposition. When the injection amount reaches the design standard, stop the injection, and close the ball valve inside the slurry injection port (66), the primary slurry delivery pump (35), and the secondary slurry delivery pump (86); a8. Injection of low-temperature seawater: Confirm that the ball valve at the end of the liquid recovery retractable hose (95) is closed, open the ball valve of the seawater suction vertical pipe (89), start the seawater suction pump (93), open the ball valve inside the seawater injection port (68), and inject the low-temperature seawater filtered by solids near the seabed into the subsea carbon dioxide hydrate generating slurry mixer (16). At the same time, the slurry mixing stirring device (70) is turned on. When the injection amount reaches the design standard, stop the injection, and close the ball valve inside the seawater injection port (68), the seawater suction pump (93), and the ball valve of the seawater suction vertical pipe (89); Second, in the hydrate formation and slurry mixing stage, the main steps are as follows: b1. Hydrate formation: Increase the rotation speed of the slurry mixing and stirring device (70) in the subsea slurry mixer (16) for carbon dioxide hydrate formation, so that carbon dioxide in the sediment slurry agitation system with high seawater content rapidly forms carbon dioxide hydrate with seawater under the action of subsea high pressure, the driving force of low seawater temperature, and surfactant. Monitor the temperature and pressure in different areas of the subsea slurry mixer (16) for carbon dioxide hydrate formation through multiple slurry mixer temperature and pressure sensors (69), and assist the observation with the pressure-resistant high-definition camera lens (75) installed inside. When there is an obvious sudden increase in temperature, it indicates the start of carbon dioxide hydrate formation, and calculate the hydrate formation amount based on the real-time changes of temperature and pressure; b2. Formation of carbon dioxide hydrate-sediment mixed slurry: When the temperature and pressure in each area of the subsea slurry mixer (16) for carbon dioxide hydrate formation no longer change significantly, reduce the rotation speed of the slurry mixing and stirring device (70). Under the influence of surfactant, make the hydrate particles and small hydrate aggregates gradually form a carbon dioxide hydrate-sediment mixed slurry with good fluidity with sediment and seawater during the agitation process. By monitoring the feedback torque power of the slurry mixing and stirring device (70), when the torque power no longer fluctuates significantly, it indicates that the properties and agitation state of the carbon dioxide hydrate-sediment mixed slurry formed by carbon dioxide hydrate and sediment have tended to be stable; Third, in the stage of discharging the mixed slurry, the main steps are as follows: c1. Discharge of the mixed slurry: Keep the slurry mixing and stirring device (70) rotating at a constant speed to avoid sedimentation of the carbon dioxide hydrate-sediment mixed slurry; Adjust the mixed slurry discharge pipe lifter (45) to the lowest position, open the ball valve (97) of the mixed slurry output pipe, turn on the primary mixed slurry output pump (98) and the secondary mixed slurry output pump (43), and discharge the carbon dioxide hydrate-sediment mixed slurry to the lowest water level of the subsea depression area (13). While discharging, adjust the mixed slurry discharge deflector (47) to ensure the uniform sedimentation of the solid aggregates in the carbon dioxide hydrate-sediment mixed slurry on the lowest water level of the subsea depression area (13); When the sediment is close to uniformly filling the lowest water level of the subsea depression area (13), raise the mixed slurry discharge pipe lifter (45) so that it starts to discharge to a higher water level of the subsea depression area (13), and cycle in turn until the subsea depression area (13) is close to being filled; Fourth, in the stage of sediment layer covering, the main steps are as follows: d1. Injection of sediment slurry: Repeat the steps of collecting and diluting the subsea sediment slurry, injecting the low-temperature surfactant, injecting the sediment slurry, and injecting seawater in the continuous injection stage, so that the pressure in the subsea slurry mixer (16) for carbon dioxide hydrate formation is close to the pressure before discharging the mixed slurry, and at the same time keep the slurry mixing and stirring device (70) rotating at a constant speed; d2. Discharge of sediment slurry: Pull out the seabed anchoring device (100) on the crawler wheel (48) of the output system, and discharge the sediment slurry by repeating the steps of discharging the mixed slurry, but without performing the liquid recovery step. While discharging the sediment slurry, adjust the position of the mixed slurry output system (10), the hoist (45) of the mixed slurry discharge pipe, and the state of the mixed slurry discharge guide plate (47) in real time, so that the sediment is evenly deposited on all the carbon dioxide hydrate-sediment mixed solid sediments in the seabed depression area (13). When the thickness of the overlying sediment layer formed reaches the coverage requirement of the hydrate-sediment mixed solid sediments in the depression area, stop all operations, close all pumps and ball valves in the system, and move the entire system to the vicinity of the next seabed depression area (13).

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