Carbon dioxide hydrate form carbon sequestration method and storage warehouse thereof at deep sea bottom

Abstract

The invention belongs to the technical field of storage of carbon dioxide hydrates in the deep sea bottom, and discloses a carbon dioxide hydrate form carbon sequestration method and a storage warehouse of the carbon dioxide hydrate form carbon sequestration method in the deep sea bottom. Carbon dioxide is converted into high-density hydrate in advance through an efficient process and packaged in a module meeting the stable temperature and pressure conditions of the carbon dioxide, the generation quality is ensured, and the technical and environmental risks of deep sea injection and reaction are fundamentally eliminated. The prefabricated sealing module is transported to a site selection area and put down to the seabed of the deep sea, and permanent sealing and storage are achieved through the natural low-temperature and high-pressure environment of the sealing module. Firstly, a proper work area is evaluated and selected according to the water depth, temperature, pressure and seabed geological conditions of a target sea area; and then, transporting the standardized sealed cabin module on which carbon dioxide hydrate filling and sealing detection are completed ashore to a work area, and putting and assembling the standardized sealed cabin module.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture, utilization and storage (CCUS) technology, specifically relating to a method for carbon fixation in the form of carbon dioxide hydrates and its storage warehouse on the deep seabed. Background Technology

[0002] Climate change is a severe challenge to global sustainable development. The continuous rise in atmospheric carbon dioxide concentration has led to a series of catastrophic impacts, including global warming, sea-level rise, and frequent extreme weather events. With countries approaching their 2030 nationally determined emission reduction targets, carbon capture, utilization, and storage (CCLS) technologies are increasingly becoming a global focus, highlighting their importance and urgency. Currently, efficient carbon dioxide sequestration technology is a key pathway to achieving deep emission reduction. Mainstream carbon dioxide sequestration technologies include geological structure sequestration, marine dissolution sequestration, mineral solidification sequestration, and industrial recycling. However, these technologies still face many challenges in large-scale practical application: geological sequestration relies on specific geological structures, limiting site selection and making long-term leakage risks difficult to monitor and control effectively; marine dissolution sequestration may cause local ocean acidification, posing a potential threat to ecosystems; and mineral solidification technology is limited by slow reaction rates, high energy consumption, and difficulties in scaling up. Overall, existing technologies struggle to balance long-term safety, environmental compatibility, carbon storage durability, and economic feasibility, necessitating the development of new technologies to achieve large-scale, long-term, and stable carbon dioxide sequestration.

[0003] Against this backdrop, carbon sequestration based on carbon dioxide hydrates has attracted widespread attention as an emerging geological sequestration approach. This technology utilizes the low temperature and high pressure conditions of the deep-sea environment to convert carbon dioxide into a solid hydrate form for storage. Carbon dioxide hydrates possess characteristics such as high gas density (1 volume of hydrate can store 120-180 volumes of carbon dioxide gas under standard conditions), good thermodynamic stability, and relatively mild formation conditions. Especially in the deep seabed, the high hydrostatic pressure and low temperature provide a naturally suitable environment for the formation and long-term stable preservation of carbon dioxide hydrates. In seawater, due to the density of carbon dioxide hydrates (1.10 - 1.12 g / cm³),... 3 Its density is higher than that of seawater (1.025 - 1.030 g / cm³). 3 Once formed, these hydrates sink to the seabed and exist stably in a quasi-solid state, greatly reducing the risk of carbon dioxide migration or leakage. In addition, in deep-sea sediments, when the hydrate saturation in the reservoir is higher than 25%, the formation permeability can drop to an extremely low level (relative permeability < 0.05), theoretically allowing for a storage time of more than 100,000 years, demonstrating excellent long-term storage potential.

[0004] Despite the significant theoretical advantages of deep-sea carbon dioxide hydrate sequestration, its technological implementation faces a series of engineering challenges. First, the deep-sea environment is typically far from continental shorelines, making the transportation and injection of carbon dioxide extremely costly, directly hindering the feasibility and economic viability of the project. Second, if carbon dioxide is directly injected, the process of hydrate formation under the low temperature and high pressure conditions of the deep sea is extremely slow and the reaction is uncontrollable, making efficient carbon sequestration difficult. Furthermore, the formed hydrates are susceptible to decomposition due to environmental temperature and pressure fluctuations or disturbances, compromising the permanence and safety of the sequestration. In summary, there is currently a lack of systematic, integrable, and large-scale engineering technologies and implementation plans suitable for deep-sea environments in this field.

[0005] Currently, the mainstream technologies for deep-sea carbon dioxide sequestration are mainly based on the principle of geological sequestration, injecting carbon dioxide into seafloor geological reservoirs (such as saline aquifers or depleted oil and gas reservoirs). This method is highly dependent on the integrity of the geological caprock and the reservoir itself, and carries the risk of leakage due to unknown faults or wellbore corrosion. The injection process relies on the complex natural pore structure of the reservoir, making the carbon dioxide plume transport path difficult to predict and control, resulting in uncertainty in sequestration efficiency and capacity. Once a leak occurs, high concentrations of carbon dioxide will acidify the local seawater, harming the benthic ecosystem. Furthermore, leak monitoring and engineering remediation measures in the deep-sea environment are extremely limited and costly.

[0006] Furthermore, existing methods for sequestration in seabed waters require on-site synthesis of carbon dioxide hydrates, removal of any remaining unreacted carbon dioxide, and even on-site grouting and sealing of the storage tanks. This method is cumbersome, carries certain environmental risks (due to the removal of remaining unreacted carbon dioxide), and necessitates transporting the sealing grout to the deep-sea operation area, relying on large high-pressure reactors and long-distance towing, thus resulting in high operating costs. From a system perspective, existing technologies have not yet formed a standardized, scalable, and easily integrated modular sequestration system, making large-scale, engineered deployment difficult and hindering subsequent monitoring, maintenance, and resource utilization.

[0007] Therefore, there is an urgent need to develop a new carbon sequestration technology that does not rely on finding effective mass traps, can actively control the sequestration morphology, and significantly reduce long-term leakage and environmental risks.

[0008] Based on the above problems, this invention proposes a method for marine carbon dioxide hydrate sequestration that differs from current domestic and international practices. Taking into account the high hydrostatic pressure and low temperature of the deep-sea seabed, and the higher density of carbon dioxide hydrate compared to seawater, this invention proposes for the first time a method for carbon sequestration in the form of carbon dioxide hydrate and its storage warehouse on the deep-sea seabed, thus inventing a novel method for deep-sea seabed carbon dioxide hydrate sequestration. This method is innovative and a powerful supplement to traditional carbon dioxide sequestration methods, and is of significant importance. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a method for carbon fixation in the form of carbon dioxide hydrate and its storage warehouse on the deep seabed.

[0010] This invention is implemented as follows: a method for carbon fixation in the form of carbon dioxide hydrate, the method comprising:

[0011] S1: Based on deep-sea geophysical exploration data, suitable work areas within the deep-sea seabed carbon dioxide hydrate stability zone are identified. The carbon dioxide hydrate phase diagram shows that the intersection of the carbon dioxide hydrate phase equilibrium line and the seawater temperature change curve represents the upper boundary of the carbon dioxide hydrate stability zone, approximately 400m. This means that seabed areas at depths greater than 400m belong to the carbon dioxide hydrate stability zone; the upper boundary of the methane hydrate stability zone is approximately 700m. Therefore, it can be considered that the area where carbon dioxide hydrate can stably exist on the seabed is more extensive. This invention proposes selecting areas with water depths ≥600m as deep-sea seabed storage depots for carbon dioxide hydrate. This area not only currently meets the temperature and pressure conditions for carbon dioxide hydrate storage, but also, even with a 3-degree Celsius increase in global warming (which could cause the upper boundary of the carbon dioxide hydrate stability zone to shift downwards by 50-100 degrees Celsius), it is still feasible to store carbon dioxide hydrates. The selected site for the storage facility is located within the carbon dioxide stability zone, ensuring stable conditions for carbon dioxide hydrates and preventing their decomposition. Additionally, the site requires a flat seabed topography; a thick layer of sediments with sufficient bearing capacity; stable regional geological structure, far from known active faults, volcanoes, and landslides; calm bottom seawater with low current velocity; and avoidance of sensitive marine ecosystems and important human-made underwater engineering facilities. At the selected deep-sea storage site, its storage capacity and long-term safety will be assessed to determine project feasibility. If the assessment is deemed feasible, the selected sea area will be leveled and pre-treated. The prefabricated complete modules, which have already undergone hydrate filling and sealing testing on shore, will be lowered as a whole and precisely placed on the leveled sediments. Using in-situ detection equipment onboard the ROV, parameters such as seabed sediment type, porosity, permeability, and seawater salinity will be obtained. Combined with indicators such as carbon dioxide storage capacity, the storage potential and long-term geological safety will be comprehensively assessed to select the final work area.

[0012] S2: At the shore-based factory, the sealed chamber body, constructed of super duplex stainless steel, is manufactured, and a composite geomembrane is continuously laid on its inner wall. Subsequently, in an adjacent dedicated preparation workshop, the captured carbon dioxide is efficiently converted into high-density solid hydrate by optimizing reaction conditions. Each sealed chamber module is designed with a side length of 1m and a height of 2m, and the total internal volume of the sealed chamber is approximately 5.2m³. 3 Considering an actual storage volume of 0.85, meaning one volume storage tank can store 0.85 volume of carbon dioxide hydrate, the solid volume of carbon dioxide hydrate that can be stored in one unit module sealed chamber is approximately 4.4 m³.3 The volume of carbon dioxide gas that can be stored, calculated at a minimum multiplication factor of 120, is 4.4 m³. 3 ×120=528 m 3 Calculated at the maximum magnification of 180: 4.4 m 3 ×180=792 m 3 A sealed chamber module contains carbon dioxide hydrate, with a corresponding carbon dioxide gas volume of approximately 528 m³. 3 up to 792m 3 Between; fill the pre-made hydrate into the sealed chamber, and install the removable sealed chamber cover to complete the final seal; all monitoring components such as pressure sensors and fiber optic temperature sensors are integrated and calibrated in the factory; each complete unit module sealed chamber must pass a rigorous airtightness pressure test and functional test before leaving the factory;

[0013] S3: Use ROV to level and pre-treat the selected sea area to ensure that the fixed base of the sealed cabin can be supported stably;

[0014] S4: The sealed compartments of each unit module, which have been filled and tested on shore, are lowered to the selected work area using the lifting system of the offshore platform; the standard interconnection interfaces on the side of each module are driven by the ROV to complete mechanical locking and sealing docking to form a large-scale storage array; after docking, an underwater pressure test is immediately carried out to verify the initial sealing integrity of the entire array.

[0015] S5: Start the monitoring system; verify the stability of the pressure sensor readings, with an error ≤ ±0.1MPa; verify the full-cabin temperature field monitoring function of the fiber optic temperature sensor and confirm that there are no signal blind spots; check the transmission stability of all data through the submarine network to the land control center; after the system integration and debugging are qualified, switch to long-term automatic monitoring mode.

[0016] S6: During the storage period, the monitoring system continues to operate; pressure sensor 4 and fiber optic temperature sensor 8 collect temperature and pressure data every 10 days, referencing the sampling interval of 10 days for data from 3,800 global ocean temperature monitoring Argo buoys. All data is transmitted to the land control center in real time; a regular maintenance system is established, with an external inspection of the sealed compartment and standard interconnection interfaces conducted every 6 months via ROV, and an underwater sealing performance retest conducted annually to promptly address potential sealing hazards; if an abnormal pressure drop is detected, indicating a suspected leak, the emergency response procedure is immediately initiated, and an ROV is dispatched to locate and repair the leak. If repair is not possible, the unit module is recovered to the offshore platform;

[0017] S7: This step is initiated when a specific carbon sequestration module needs to be recycled. The target sealed module is precisely located using the offshore platform operation system, and the entire module is recovered and transported to a shore-based factory. In a dedicated processing workshop at the shore-based factory, the module undergoes controlled heating or depressurization to safely and completely decompose the carbon dioxide hydrate within the sequestered material, releasing high-purity carbon dioxide gas. After collection and purification, this gas can become an industrial-grade carbon dioxide product, used in food processing, welding protection, chemical synthesis, or as a raw material for carbon-neutral fuels, thus achieving a closed loop from carbon sequestration to recycling. This process not only verifies the reversibility of sequestered assets but also provides a key technological interface for the future carbon circular economy.

[0018] Another object of the present invention is to provide a deep-sea seabed storage warehouse based on the aforementioned carbon sequestration method using carbon dioxide hydrate, the warehouse comprising:

[0019] The sealed chamber has a hexagonal prism structure and is made of super duplex stainless steel. It is the core sealed container for carbon dioxide hydrates on the deep seabed, providing a closed space for hydrate formation. As an integrated carrier, it carries monitoring and other system components, ensuring the stability and airtightness of the internal environment.

[0020] The standard interconnection interface is located on the side edge of the sealed chamber and is used for interconnection between sealed chamber modules. Different numbers of modules can be flexibly assembled according to the amount of carbon dioxide hydrate to be sealed. The interface has a built-in sealing structure to ensure the overall impermeability after the modules are connected, while improving the stability of the combined structure.

[0021] The fixed base is installed at the bottom of the sealed cabin and can be inserted into the deep-sea seabed sediment to provide stable support for the sealed cabin, ensuring that the cabin remains vertical in the deep-sea environment and preventing displacement due to terrain fluctuations.

[0022] The pressure sensor is installed at the center of the top of the sealed chamber and is fixed by a base. The main body is external and the probe extends through the top of the chamber into the chamber. It is used to monitor the pressure changes inside the sealed chamber in real time and provide data support for the safe operation of the chamber and process adjustment.

[0023] The fixed base is the mounting base for the pressure sensor, which is arranged to fit the outer surface of the cabin roof; it is used to enhance the stability of the pressure sensor in the high-pressure environment of the deep sea, prevent the sensor from shifting due to water flow, vibration and other factors, and ensure the accuracy of pressure monitoring data.

[0024] The detachable sealed hatch cover, with a hexagonal plate structure that matches the hatch body, is made of the same super duplex stainless steel material as the main body and is the key openable sealing interface of the sealed hatch; it provides a reliable access channel for the interior of the hatch during hydrate filling, maintenance, and resource recovery.

[0025] The composite geomembrane uses reinforced HDPE (High-Density Polyethylene) material as a continuous sealing and seepage-proof layer laid on the inner wall of the entire compartment, closely attached to the inner surface of the sealed compartment; it provides secondary sealing protection to prevent the decomposition or leakage of carbon dioxide hydrate inside the compartment, while blocking the infiltration of external seawater and ensuring the stability of hydrate inside the compartment.

[0026] Fiber optic temperature sensors are continuously laid on the inner surface of the composite geomembrane, extending from the bottom to the top of the chamber, to monitor the temperature field distribution and changes inside the sealed chamber, providing key data for the long-term safe and stable state of the chamber.

[0027] The modular sealed chamber is a modular hexagonal prism sealed unit that can operate independently. Each unit integrates core components such as the sealed chamber body, sealed chamber cover, composite geomembrane, monitoring system, and fixed base; the number can be flexibly combined through standard interconnection interfaces.

[0028] Offshore platforms are movable floating mobile platforms, truss structures that rise above the sea surface and have a water platform surface; deep-sea carbon dioxide hydrate storage arrays can cover a wide sea area. The platform can move along the array layout to perform full-cycle offshore operations such as transporting sealed cabin modules, precise deployment, long-term condition inspection, and overall recovery of modules requiring maintenance or resource utilization.

[0029] The horizontal boom is adjusted to bring the hoisting wire rope to the working position.

[0030] The lifting steel wire rope is used to send the sealed cabin module to the seabed or lift it to the sea surface.

[0031] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0032] First, this invention proposes a novel method for deep-sea carbon dioxide sequestration: "shore-based prefabrication and deep-sea storage," namely, establishing a deep-sea seabed carbon dioxide hydrate warehouse. This method is a powerful supplement to current carbon dioxide sequestration methods and possesses certain innovative features.

[0033] Inspired by natural and engineering structures, this invention, for the first time, combines the honeycomb biomimetic reinforcement principle with high-performance sealing materials (reinforced HDPE geomembrane and super duplex stainless steel) for deep-sea carbon dioxide sequestration, constructing an active, engineered seabed hydrate storage warehouse. Through modular design and active environmental monitoring, this system upgrades the passive process of uncontrollable carbon dioxide migration after injection in seabed geological sequestration into a simple, actively regulated, morphologically stable, and recyclable industrial carbon sequestration process. This method transfers the difficult-to-control deep-sea in-situ generation process to a shore-based factory with optimal conditions. Through efficient processes, carbon dioxide is pre-converted into high-density hydrates and encapsulated within modules that meet stable temperature and pressure conditions for carbon dioxide, ensuring generation quality and fundamentally eliminating the technical and environmental risks of deep-sea injection and reaction. The prefabricated sealing modules are transported to the selected site and lowered into the deep-sea seabed, utilizing its natural low-temperature and high-pressure environment for permanent storage. First, a suitable work area is assessed and selected based on the water depth, temperature, pressure, and seabed geological conditions of the target sea area. Subsequently, standardized sealed chamber modules, which had already undergone carbon dioxide hydrate filling and sealing testing onshore, were transported to the work area for deployment and assembly. Each sealed chamber module is constructed of super duplex stainless steel and lined with a reinforced HDPE geomembrane, forming a series of independently stable, double-protected sealed chambers. During storage, the pressure, temperature, and structural integrity within the chambers can be monitored in real-time via a sensor system embedded in the structure and membrane. When maintenance or resource utilization is required, a recovery or maintenance mechanism connected to the offshore platform can be activated to lift specific modules to the offshore platform or transport them back to the shore-based plant for processing, realizing the reversible management and recycling potential of carbon sequestration assets.

[0034] The system provided by this invention, on the one hand, enables long-term, safe, and monitorable sequestration of carbon dioxide in the form of high-density hydrates through actively constructed rigid containment structures and flexible sealing barriers, significantly reducing the absolute dependence on caprock integrity and the risk of unknown leakage inherent in traditional geological sequestration. On the other hand, its modular and standardized engineering structure avoids large-scale deep-sea drilling and formation fracturing, significantly reducing construction costs and engineering complexity, and minimizing disturbance to the original deep-sea geological structure and ecosystem. Therefore, this system achieves large-scale carbon dioxide sequestration while possessing engineering reliability, environmental friendliness, and operational economics. Furthermore, as a reservoir, the carbon dioxide hydrates can be recovered from the seabed for subsequent industrial applications such as food processing, welding protection, chemical synthesis, or as a raw material for carbon-neutral fuels. In conclusion, if this method can be widely applied, it will open up a new, engineered artificial marine carbon sequestration technology pathway for addressing climate change, possessing significant scientific and practical implications.

[0035] Secondly, as supporting evidence of the inventiveness of this invention, it is also reflected in the following important aspects:

[0036] (1) The expected benefits and commercial value of the technical solution of this invention after transformation are as follows:

[0037] Carbon trading and carbon tax revenue: Assuming each module stores approximately 660 cubic meters of CO2 (taking a midpoint) and occupies 2.6 square meters, about 385,000 modules can be deployed per square kilometer, storing approximately 250 million cubic meters of carbon dioxide, equivalent to about 500,000 tons. Based on current global carbon market prices (approximately US$50-100 / ton), the potential carbon credit revenue for a 1 square kilometer storage scale is estimated at approximately US$24.9 million to US$49.8 million.

[0038] Reduce deep-sea engineering costs: By adopting the "shore-based prefabrication and modular assembly" model, the complex in-situ reaction is transferred to the factory, avoiding the on-site construction difficulties in the high-pressure environment of the deep sea. Compared with traditional geological storage, it can reduce the engineering cost of CO2 storage per ton.

[0039] Value of carbon resource recycling: The scheme has reversible recycling characteristics. The stored CO2 hydrate can be decomposed back into high-purity industrial-grade CO2 products, which can be used for food processing (about 1,000 yuan / ton), welding shielding gas (about 800 yuan / ton), or synthetic fuels (such as green methanol, about 3,000-5,000 yuan / ton), forming a closed loop of carbon circular economy from storage to utilization.

[0040] Marine ecological compensation and its value in Environmental, Social and Governance Investing (ESG): This plan does not damage the seabed geological structure, complies with ESG investment guidelines, can attract investment from global green funds, and can obtain policy subsidies related to marine ecological protection.

[0041] (2) The technical solution of this invention fills a technical gap in the industry both domestically and internationally:

[0042] This invention proposes and systematically constructs a carbon dioxide hydrate sequestration technology system for the first time, encompassing "shore-based prefabrication - modular packaging - deep-sea storage - reversible recovery," filling the following technological gaps:

[0043] This invention fills a gap in "actively constructed" marine carbon sequestration technology: While existing technologies have attempted seabed carbon sequestration using concrete structures, these methods still require on-site synthesis of carbon dioxide hydrates in the deep sea, removal of any remaining unreacted carbon dioxide, and on-site grouting to seal the storage tanks. This process is cumbersome, carries environmental risks due to residual carbon dioxide emissions, and necessitates long-distance transportation of the sealing grout to the deep-sea operation area, relying on large high-pressure reactors and long-distance towing, resulting in high operating costs. In contrast, this invention actively constructs a closed space using an artificial sealed chamber (super duplex stainless steel + composite geomembrane), completing hydrate generation, filling, and sealing entirely at an onshore factory. This completely eliminates dependence on natural geological structures and avoids the complex procedures and environmental risks of on-site synthesis and grouting in the deep sea, achieving truly active construction and large-scale engineering deployment.

[0044] It fills the technological gap in "reversible recycling and resource utilization" of carbon sequestration: For the first time, a standardized recycling interface and process have been designed in a deep-sea sequestration scheme, transforming CO2 from "permanent waste" into "storable strategic carbon resource", providing a raw material interface for the future carbon neutral fuel industry.

[0045] It fills the gap in modular and large-scale deep-sea carbon sequestration engineering standards: it proposes a standardized unit module with a side length of 1 meter hexagonal prism (honeycomb biomimetic), interconnection interface and offshore platform operation system, providing the first systematic engineering technology solution for the industrialization and large-scale replication of carbon sequestration.

[0046] It fills the gap in the in-situ real-time monitoring system of multi-physics field: it integrates pressure sensors (error ≤ ±0.1MPa) and distributed fiber optic temperature sensors throughout the chamber, realizing long-term, continuous and accurate monitoring of the internal state of deep-sea storage bodies, and solving the monitoring problem of traditional geological storage "black box" operation.

[0047] (3) The technical solution of the present invention solves a technical problem that people have long wanted to solve but have never been able to solve successfully:

[0048] The problem of "slow and uncontrollable process of CO2 hydrate formation by direct injection into the deep sea" has been solved: by moving the formation process to an onshore plant, CO2 can be converted into solid hydrate quickly, efficiently and completely under optimal reaction conditions, fundamentally avoiding the reaction lag and conversion rate uncertainty problems of in-situ injection into the deep sea.

[0049] This solves the economic challenge of high transportation and injection costs due to distance from the base shore: A standardized modular design is adopted, with each module capable of storing approximately 528-792 m³. 3 (Standard conditions) CO2 gas, maximizing CO2 storage and transportation efficiency per unit volume. Mechanized operations using offshore platforms and ROVs significantly reduce the manpower and time costs of a single deep-sea operation.

[0050] (4) The technical solution of the present invention overcomes technical bias:

[0051] This invention overcomes the prejudice that "carbon sequestration mainly relies on natural geological traps": For a long time, the industry has generally believed that CO2 sequestration requires finding natural saline aquifers or depleted oil and gas reservoirs and depends on effective caprocks. This invention demonstrates that through artificially constructed sealed warehouses, safe and even more controllable sequestration can be achieved on the deep seabed where there are no natural caprocks, changing the site selection process from "passive searching" to "active construction".

[0052] This invention overcomes the prejudice that "deep-sea carbon sequestration is a one-way, irreversible end-of-life disposal": in traditional methods, once CO2 is injected into the deep sea or underground, the process is irreversible. However, this invention, through a modular recycling design, demonstrates that deep-sea carbon sequestration can be "reversible." The sequestered CO2 hydrates can serve as a strategic reserve resource, safely recovered and reused when future technologies mature or market demands arise, upgrading carbon sequestration from "end-of-life disposal" to "dynamic inventory management." Attached Figure Description

[0053] Figure 1 This is a flowchart of a carbon fixation method using carbon dioxide hydrate provided in an embodiment of the present invention;

[0054] Figure 2 Here are two examples of the present invention: a) a schematic diagram of the stability region and distribution boundary of carbon dioxide / methane hydrate in the sea area; b) a phase equilibrium curve of carbon dioxide / methane hydrate in the sea area.

[0055] Figure 3 This is a schematic diagram of the overall structure of the deep-sea seabed carbon dioxide hydrate warehouse module provided in an embodiment of the present invention;

[0056] Figure 4 This is a partial frontal cross-sectional view of the deep-sea seabed carbon dioxide hydrate storage module provided in an embodiment of the present invention.

[0057] Figure 5 This is a macroscopic top view of the deep-sea seabed carbon dioxide hydrate warehouse provided in an embodiment of the present invention;

[0058] Figure 6 This is a schematic diagram of an offshore platform system provided in an embodiment of the present invention;

[0059] In the diagram: 1. Sealed chamber body; 2. Standard interconnection interface; 3. Fixed base; 4. Pressure sensor;

[0060] 5. Fixed base; 6. Removable sealed hatch cover; 7. Composite geomembrane; 8. Fiber optic temperature sensor; 9. Unit module sealed cabin; 10. Offshore platform; 11. Horizontal boom; 12. Lifting wire rope. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0062] like Figure 1 As shown, an embodiment of the present invention provides a method for carbon fixation in the form of carbon dioxide hydrate, comprising the following steps:

[0063] S1. Select a deep-sea seabed area located within the carbon dioxide hydrate stability domain as the storage area. The water depth of the area is not less than 600m, and the area remains within the stability domain even after the top boundary of the stability domain shifts down by 200m under the condition of global warming of 3°C.

[0064] S2, in a shore-based environment, carbon dioxide is converted into solid hydrate, and the solid hydrate is filled into a prefabricated sealed chamber to form a unit module;

[0065] S3, the entire unit module is lowered to the work area and placed on the seabed sediment;

[0066] S4, through the module side interconnection structure, completes the mechanical locking and sealing docking of multiple unit modules to form a sealing array;

[0067] S5 performs long-term pressure and temperature monitoring of the sealing array;

[0068] S6, when an abnormal pressure change is detected, execute the emergency response procedure;

[0069] S7 recycles the unit module and performs controlled decomposition of hydrates when resource utilization is required.

[0070] The actual sealing volume coefficient inside the unit module provided in this embodiment of the invention is 0.85, the hydrate volume inside a single module is 4.4 m3, and the sealed carbon dioxide gas volume is calculated by multiplying the hydrate volume by the sealing ratio, which is 120 to 180.

[0071] The pressure and temperature data provided in this embodiment of the invention are collected once every 10 days and transmitted to the land control center via an underwater communication network.

[0072] This invention provides a modular sealed chamber for deep-sea carbon dioxide hydrate storage, the structure of which is as follows: Figures 3 to 6As shown, the device uses a hexagonal prism-structured sealed chamber 1 as its main frame, employing a multi-faceted splicing design to improve pressure uniformity and modular layout efficiency. Standard interconnecting interfaces 2 are located on the sides of chamber 1 for mechanical locking and sealing between adjacent unit module sealed chambers 9, achieving a honeycomb array structure and improving seabed deployment stability and space utilization. A fixed base 3 is located at the bottom of the chamber, its structure capable of being inserted into seabed sediment to form a solid support, thereby enhancing overall anti-buoyancy and resistance to lateral disturbances. A removable sealed cover 6 is installed at the top of the chamber; the cover and the fixed base 5 constitute a reliable sealing assembly, facilitating later maintenance and resource recovery operations.

[0073] A composite geomembrane 7 is continuously laid on the inner wall of the chamber 1. This composite geomembrane is made of reinforced high-density polyethylene material, which has excellent corrosion resistance and impermeability, effectively isolating the risk of seawater erosion and gas leakage. Simultaneously, a pressure sensor 4 is installed on the top of the chamber, with a sensing structure penetrating the interior of the chamber. The measurement error is no greater than 0.1 MPa, enabling real-time monitoring of the temperature and pressure status within the sealed space. Fiber optic temperature sensors 8 are laid along the inner wall of the chamber, forming a distributed temperature monitoring network for dynamically sensing thermal changes during the formation and decomposition of hydrates, achieving multi-parameter coupled monitoring and safety early warning.

[0074] Its working principle is as follows: In the deep sea area, multiple unit module sealed chambers 9 are assembled into an array structure through standard interconnection interfaces 2 and deployed on the seabed, with fixed bases 3 embedded in the sediment layer to form stable support. Utilizing the low temperature and high pressure environment of the deep sea, in-situ sealing and long-term stable storage of carbon dioxide hydrates are achieved inside the chamber 1. During the sealing process, pressure sensors 4 and fiber optic temperature sensors 8 continuously collect internal parameters to ensure that the operating conditions are within the hydrate stability range.

[0075] When resource recovery is required, the target unit module is precisely lifted and recovered using the lifting system of the offshore platform 10, employing a horizontal boom 11 and lifting wire ropes 12. After the module is recovered to the shore-based facility, the temperature or pressure is controlled to move it out of the hydrate stability region, causing the hydrate to decompose into gaseous carbon dioxide. The released gas is then collected and purified, achieving an integrated cycle of storage and resource utilization. The overall structure is highly modular, with comprehensive safety monitoring, making it suitable for long-term storage and controlled recovery applications in the deep sea.

[0076] The heating or depressurization operations provided in this embodiment of the invention are controlled within a temperature and pressure range outside the hydrate stability region.

[0077] The recovery operation provided in this embodiment of the invention completes the vertical lifting and precise positioning of the module through the lifting system and horizontal boom of the offshore platform.

[0078] This invention provides a novel method for carbon sequestration using carbon dioxide hydrates on the deep-sea seabed, namely, a method for establishing a carbon dioxide hydrate storage facility. Inspired by efficient structures found in nature and modern anti-seepage engineering, this method leverages the advantages of the low-temperature, high-pressure conditions on the deep-sea seabed for the long-term stable preservation of carbon dioxide hydrates. It establishes an engineered, modular, and prefabricated seabed active storage system that integrates shore-based prefabrication and deep-sea storage. The storage system employs a modular prefabrication approach. At the shore-based factory, the honeycomb support structure and reinforced HDPE geomembrane sealing liner are integrated, and all pipes, valves, and monitoring sensors are installed, forming a complete empty sealed chamber module. In an adjacent dedicated carbon dioxide hydrate preparation workshop, by optimizing reaction conditions, the captured and purified carbon dioxide is efficiently converted into high-density, uniformly sized solid hydrate blocks. These prefabricated carbon dioxide hydrate blocks are directly filled into the aforementioned empty sealed chamber modules under stable conditions, and after sealing, form a complete functional module containing stable carbon-fixing matter. All sealed chamber modules undergo rigorous airtightness pressure tests and functional tests before leaving the factory. First, the site selection for this deep-sea subsea warehouse should ideally be located in a deep-sea seabed area with the following characteristics: water depth not less than 600m; flat seabed topography; a thick layer of sediment with sufficient bearing capacity; stable regional geological structure, far from known active faults, volcanoes, and landslides; calm bottom water with low current velocity; and avoidance of sensitive marine ecosystems and important human-made subsea engineering facilities. At the selected deep-sea storage site, its storage capacity and long-term safety will be assessed to determine the feasibility of the project. If the assessment results indicate feasibility, the selected sea area will be leveled and pre-treated. The prefabricated complete modules, which have already undergone hydrate filling and sealing testing on shore, will be lowered as a whole and precisely placed on the treated and leveled sediment. The carbon dioxide hydrate warehouse deployment uses a standardized honeycomb support structure made of super duplex stainless steel as the load-bearing skeleton of the system. Each independent sealed compartment module is lined with a reinforced HDPE geomembrane, forming a series of clearly defined and well-sealed reaction and storage compartments. Multiple modules can be quickly interconnected and integrated on the seabed via standard interfaces to form a large-scale storage array. During the storage period, the pre-embedded monitoring system inside the cabin operates in real time, providing real-time online monitoring of the cabin's pressure, temperature, and structural integrity. When a module is detected to require maintenance or resource utilization, a recovery or maintenance mechanism connected to the offshore platform can be activated to lift the specific module as a whole to the offshore platform or transport it back to a shore-based factory for processing. The specific structure of the sealed cabin module of this deep-sea seabed carbon dioxide hydrate warehouse is shown in the overall structural diagram of the deep-sea seabed carbon dioxide hydrate warehouse module (…). Figure 3 A partial frontal cross-sectional view of the deep-sea seabed carbon dioxide hydrate storage module. Figure 4 ), Macroscopic top view of the carbon dioxide hydrate warehouse ( Figure 5 As shown in the diagram, the structures are explained below:

[0079] 1: The sealed chamber has a hexagonal prism structure and is made of super duplex stainless steel. It is the core sealed container for carbon dioxide hydrates on the deep seabed, providing a closed space for hydrate formation. As an integrated carrier, it carries monitoring and other system components, ensuring the stability and airtightness of the internal environment.

[0080] 2: Standard interconnection interface, located on the side edge of the sealed chamber, is used for interconnection between sealed chamber modules 11. Different numbers of modules can be flexibly assembled according to the amount of carbon dioxide hydrate sealed. The interface has a built-in sealing structure to ensure the overall impermeability after the modules are connected, while improving the stability of the combined structure.

[0081] 3: Fixed base, installed at the bottom of the sealed cabin, can be inserted into the seabed sediment to provide stable support for the sealed cabin, ensuring that the cabin remains vertical in the deep-sea environment and avoiding displacement due to terrain fluctuations.

[0082] 4: Pressure sensor, installed at the center of the top of the sealed chamber, fixed by the base 5, with the main body external and the probe extending through the top of the chamber into the chamber; used to monitor the pressure changes inside the sealed chamber in real time, providing data support for the safe operation of the chamber and process adjustment.

[0083] 5: Fixed base, which is the mounting base of pressure sensor 4, is arranged to fit the outer surface of the cabin top; it is used to enhance the stability of the pressure sensor in the high pressure environment of the deep sea, prevent the sensor from shifting due to water flow, vibration and other factors, and ensure the accuracy of pressure monitoring data.

[0084] 6: The detachable sealed hatch cover has a hexagonal plate structure that matches the hatch body. It is made of the same super duplex stainless steel material as the main body and is the key openable sealing interface of the sealed hatch. It provides a reliable access channel for the interior of the hatch during hydrate filling, maintenance and resource recovery.

[0085] 7: Composite geomembrane, made of reinforced HDPE (high-density polyethylene) material, serves as a continuous sealing and seepage-proof layer covering the entire inner wall of the chamber, closely adhering to the inner surface of the sealed chamber; providing secondary sealing protection to prevent the decomposition or leakage of carbon dioxide hydrate inside the chamber, while also blocking external seawater infiltration and ensuring the stability of hydrate inside the chamber.

[0086] 8: Fiber optic temperature sensor, continuously laid on the inner surface of the composite geomembrane 7, extending from the bottom to the top of the chamber, is used to monitor the temperature field distribution and changes inside the sealed chamber, providing key data for the long-term safe and stable state of the chamber.

[0087] 9: The unit module sealed chamber is a modular hexagonal prism sealed unit that can operate independently. Each unit integrates core components such as the sealed chamber body 1, the sealed chamber cover 6, the composite geomembrane 7, the monitoring systems 4, 5, and 8, and the fixed base 3. The number can be flexibly combined through the standard interconnection interface 2.

[0088] like Figure 6 10: Offshore platform, a movable floating mobile platform, a truss structure that is above the sea surface and has a water platform surface; the carbon dioxide hydrate storage array on the deep seabed can cover a wide sea area. The platform can move along the array layout line to perform full-cycle offshore operations such as transporting sealed cabin modules, precise deployment, long-term condition inspection, and overall recovery of modules requiring maintenance or resource utilization.

[0089] 11: Horizontal boom, adjust its position in the horizontal direction so that the hoisting wire rope reaches the working position.

[0090] 12: Use the hoisting steel wire rope to send the sealed cabin module to the seabed or lift it to the sea surface.

[0091] The specific steps of this method are as follows:

[0092] Step 1: Based on deep-sea geophysical exploration data, identify suitable work areas within the deep-sea seabed carbon dioxide hydrate stability domain. The carbon dioxide hydrate phase diagram shows that the intersection of the carbon dioxide hydrate equilibrium line and the seawater temperature change curve represents the top boundary of the carbon dioxide hydrate stability domain. Figure 2 The selection process prioritizes areas with a water depth of ≥600m, meeting the temperature and pressure conditions for carbon dioxide hydrate sequestration. Even with a 3°C increase in global temperature due to global warming, and the current upper boundary of the carbon dioxide hydrate stability zone shifting 200m downwards, this location will still be within the carbon dioxide stability zone, preventing hydrate decomposition. Additionally, the seabed topography must be flat; the seabed foundation must be a thick layer of sediment with sufficient bearing capacity; the regional geological structure must be stable, far from known active faults, volcanoes, and landslides; the bottom seawater must be calm with low current velocity; and sensitive marine ecosystems and important human-made underwater engineering facilities should be avoided. At the selected deep-sea sequestration sites, their sequestration capacity and long-term safety are assessed to determine project feasibility. If the assessment concludes that the site is feasible, the selected sea area is leveled and pre-treated. The prefabricated complete modules, which have already undergone hydrate filling and sealing testing onshore, are then lowered as a whole and precisely placed on the treated and leveled sediment. Using the in-situ detection equipment carried by the ROV, parameters such as seabed sediment type, porosity, permeability and seawater salinity in the work area are obtained. Combined with indicators such as carbon dioxide sequestration capacity, the sequestration potential and long-term geological safety are comprehensively evaluated, and the final work area is selected.

[0093] Step 2: At the shore-based factory, the sealed chamber 1, constructed of super duplex stainless steel, is manufactured, and a composite geomembrane 7 is continuously laid on its inner wall. Subsequently, in an adjacent dedicated preparation workshop, the captured carbon dioxide is efficiently converted into high-density solid hydrate by optimizing reaction conditions. Each sealed chamber module is designed with a side length of 1m and a height of 2m, resulting in a total internal volume of approximately 5.2m³. 3Considering an actual storage volume of 0.85, meaning that 1 volume storage tank can store 0.85 volume of carbon dioxide hydrate, the solid volume of carbon dioxide hydrate that can be stored in one unit module sealed chamber is approximately 4.4 m³. 3 The volume of carbon dioxide gas that can be stored, calculated at the minimum multiplication factor (120 times), is 4.4 m³. 3 ×120=528 m 3 Calculated at the maximum magnification (180x): 4.4 m 3 ×180=792 m 3 A sealed chamber module contains carbon dioxide hydrate, with a corresponding carbon dioxide gas volume of approximately 528 m³. 3 up to 792m 3 Between. This pre-formed hydrate is filled into the sealed chamber, and the removable sealed chamber cover 6 is installed to complete the final seal. All monitoring components, such as pressure sensors 4 and fiber optic temperature sensors 8, are integrated and calibrated in the factory. Each complete unit module sealed chamber 9 must undergo rigorous airtightness pressure tests and functional tests before leaving the factory.

[0094] Step 3: Use ROV to level and pre-treat the selected sea area to ensure that the fixed base of the sealed cabin can be stably supported;

[0095] Step 4: Using the lifting systems 11 and 12 of the offshore platform 10, the sealed compartments 9 of each unit module, which have been filled and tested on shore, are lowered as a whole to the selected work area. By operating the ROV, the standard interconnection interfaces 2 on the sides of each module are driven to complete mechanical locking and sealing docking, forming a large-scale sealing array. After docking, an underwater pressure test is immediately conducted to verify the initial sealing integrity of the entire array.

[0096] Step 5: Start the monitoring system. Verify the reading stability of pressure sensor 4 (error ≤ ±0.1MPa), verify the whole-cabin temperature field monitoring function of fiber optic temperature sensor 8, and confirm there are no signal blind spots; check the transmission stability of all data through the subsea network to the land control center. After the system integration and debugging are successful, switch to long-term automatic monitoring mode.

[0097] Step 6: During the storage period, the monitoring system continues to operate. Pressure sensor 4 and fiber optic temperature sensor 8 collect temperature and pressure data every 10 days (referencing the 10-day sampling interval of data from 3800 global ocean temperature monitoring Argo buoys). All data is transmitted to the land-based control center in real time. A regular maintenance system is established, with an external inspection of the sealed compartment 1 and standard interconnection interface 2 conducted every 6 months via ROV, and an underwater sealing performance retest performed annually to promptly address potential sealing hazards. If an abnormal pressure drop is detected (suspected leakage), the emergency response procedure is immediately initiated, and an ROV is dispatched to locate and repair the leak. If repair is not possible, the unit module is recovered to the offshore platform 10.

[0098] Step 7: This step is initiated when a specific carbon sequestration module needs to be recycled. The target sealed module is precisely located using the offshore platform operation system, and the entire module is recovered and transported to an onshore facility. In a dedicated processing workshop at the onshore facility, the module undergoes controlled heating or depressurization to safely and completely decompose the carbon dioxide hydrate within the sequestered material, releasing high-purity carbon dioxide gas. This gas, after collection and purification, can become an industrial-grade carbon dioxide product used in food processing, welding protection, chemical synthesis, or as a raw material for carbon-neutral fuels, thus achieving a closed loop from carbon sequestration to recycling. This process not only verifies the reversibility of sequestered assets but also provides a crucial technological interface for the future carbon circular economy.

[0099] Example 1: Sealing project in a flat continental slope area at a water depth of 1200m in the South China Sea. The location of the top boundary of the stable zone was determined using seismic reflection data and seafloor temperature, salinity, and structure data. Calculations showed that even after a 3°C temperature rise and a 200m downward shift of the top boundary, the target stratum would still be within the stable zone. A silty muddy bottom area with a sediment thickness greater than 30m was selected for seafloor leveling. In the onshore facility, captured carbon dioxide was converted into high-density hydrates at 4MPa and 4°C and then filled into unit modules. The hydrate volume of a single module is 4.4m³. 3 The corresponding volume of gaseous carbon dioxide is 528 m³. 3 up to 792m 3 A large-scale storage unit is formed by arraying 100 modules.

[0100] Example 2: Array deployment in a deep-sea sedimentary basin in the western Pacific Ocean. In-situ testing of sediment porosity and permeability was conducted using an ROV. The porosity was 45%, and the permeability was less than 1×10⁻¹⁵ m², meeting the stability requirements. The modules were arranged in a hexagonal honeycomb pattern, forming a planar array structure. Initial underwater pressure testing was completed, and the pressure deviation of all modules did not exceed 0.05 MPa, verifying the overall sealing and collaborative stability mechanism.

[0101] Example 3: Safety Verification under Extreme Temperature Disturbance. A simulated temperature rise test was conducted on the deployed array, and the internal pressure response was observed by changing the local seawater temperature by 1.5°C. Monitoring data showed that the pressure change was less than 0.02 MPa, and the temperature field distribution was uniform, proving that the deep-water environment and the sealed structure together constitute a dual stabilization mechanism, which is significantly better than the simple formation injection mode.

[0102] Example 4: Verification of Long-Term Operation Monitoring Mechanism. After 36 months of sealed operation, data was collected every 10 days from the pressure sensing structure, totaling 108 sets of data. All data were stable with no abnormal fluctuations. ROV visual inspections were conducted every 6 months, and no interface corrosion or sediment erosion instability was found, indicating that the structure, materials, and environment work synergistically to form a long-term safe storage system.

[0103] Example 5: Single-Module Emergency Recovery Verification. A simulated abnormal pressure drop of 0.15 MPa was used to initiate the recovery procedure. The offshore platform located the target module and lifted it as a whole. A controlled depressurization operation was implemented in a shore-based environment. The hydrate completely decomposed when the pressure dropped below the stable range, releasing carbon dioxide gas with a purity of over 99%. This process verified the reversibility and industrial reuse value of the sealed assets.

[0104] Example 6: Closed-Loop Demonstration Project for Recycling. The recovery module decomposes carbon dioxide gas, which is then transported to the chemical synthesis system for methanol production. The entire process of storage, recovery, and reuse is demonstrated. Data shows no carbon dioxide leakage recorded throughout the entire cycle, proving that this technology forms a synergistic technical system encompassing geologically stable domain utilization, engineering structure isolation, intelligent monitoring and control, and resource regeneration.

[0105] Evidence related to the technical effects obtained by the embodiments of the present invention.

[0106] Based on a comprehensive analysis of existing geophysical data, the deep-water area of ​​the Pearl River Estuary Basin in the South China Sea is the preferred and optimal region for implementing the technical solution of this invention, and its core advantages are reflected in the following aspects:

[0107] The water depth in this area is generally between 800 and 2000 meters, fully meeting the patented technology's requirement of a water depth ≥600 meters. Even considering the downward shift of the top boundary of the carbon dioxide hydrate stability domain due to a 3°C increase in global warming, this area can still guarantee the long-term thermodynamic stability of carbon dioxide hydrates. In terms of geological and engineering conditions, the Pearl River Estuary Basin, as the core area for offshore oil and gas exploration in my country, has accumulated a large amount of high-precision geological data. Its flat seabed topography, thick sedimentary layers, and tectonic stability have been proven by long-term exploration practice, providing reliable load-bearing capacity for the fixed base of the sealed module and significantly reducing early-stage exploration costs.

[0108] In contrast, while the Okinawa Trough in the East China Sea meets the depth requirements, this area is located at a plate boundary, experiencing active tectonic seismic activity, a high geothermal gradient, and volcanic and hydrothermal activity. Its long-term geological stability is highly uncertain, potentially posing a risk to the permanent safety of seabed storage facilities. In contrast, the deep-water area of ​​the Pearl River Estuary Basin in the South China Sea is tectonically stable and far from active seismic zones and volcanic activity areas, providing a more reliable geological guarantee for the permanent storage of carbon dioxide hydrates.

[0109] Furthermore, the region boasts significant economic and transportation advantages: it is only about 200 to 300 kilometers from major carbon dioxide capture sources along the Guangdong coast (such as coal-fired power plants and petrochemical enterprises). Compared to alternative areas such as the Okinawa Trough in the East China Sea, this significantly shortens the carbon dioxide transportation distance, substantially reducing shipping costs and the time required for offshore operations. Simultaneously, the region already possesses mature oil and gas platform infrastructure, which can be converted and utilized as offshore operation support platforms in the future, further enhancing the feasibility and economic efficiency of engineering deployment.

[0110] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of carbon sequestration in the form of carbon dioxide hydrate, characterized by, The method comprises the following steps: S1, selecting a deep-sea seabed area within the stable domain of carbon dioxide hydrate as a storage work area, the area having a water depth of not less than 600 m and still being within the stable domain after the top boundary of the stable domain moves downward by 200 m under the condition of global warming of 3°C; S2, converting carbon dioxide into solid hydrate in a shore-based environment, and loading the solid hydrate into a prefabricated sealed cabin to form a unit module; S3, lowering the unit module as a whole to the seabed sediment in the work area; S4, completing mechanical locking and sealed docking of a plurality of unit modules through a module side interconnection structure to form a storage array; S5, performing long-term pressure and temperature monitoring on the storage array; S6, performing an emergency treatment program when an abnormal pressure change is monitored; S7, recycling the unit module and implementing controlled decomposition of the hydrate when resource utilization is required.

2. The method according to claim 1, wherein the actual storage volume coefficient inside the unit module is 0.85, the hydrate volume inside a single module is 4.4 m3, the storage carbon dioxide gas volume is calculated according to the product of the hydrate volume and the storage multiple, and the storage multiple is 120 to 180.

3. The method according to claim 1, wherein the collection period of pressure data and temperature data is 10 days, and the data is transmitted to a land-based control center through a submarine communication network. The method comprises: a sealed cabin body in a hexagonal prism structure; 4. A unit module containment vessel for deep-sea carbon dioxide hydrate sequestration implementing the method of carbon dioxide hydrate form sequestration according to any one of claims 1 to 3, characterized in that, a standard interconnection interface arranged on the side of the cabin body; a fixed base arranged at the bottom of the cabin body; a detachable sealed cabin cover arranged at the top of the cabin body; a composite geomembrane continuously laid on the inner wall of the cabin body; a pressure sensing structure installed on the top of the cabin body and penetrating through the cabin body; an optical fiber temperature monitoring structure laid along the inner wall of the cabin body; wherein the standard interconnection interface is used to realize mechanical locking and sealed docking of a plurality of unit modules. The composite geomembrane is a reinforced high-density polyethylene material. The fixed base can be inserted into the seabed sediment to form a support structure.

5. The unit module containment vessel of claim 4, wherein, The measurement error of the pressure sensing structure is not greater than 0.1 MPa.

6. The unit module containment vessel of claim 4, wherein, The method comprises:

7. The unit module containment vessel of claim 4, wherein, locating a target unit module; 8. A method for recovering carbon dioxide hydrate form carbon sequestration resources in deep sea, which implements the method for carbon sequestration of carbon dioxide hydrate form according to any one of claims 1 to 3, characterized in that, recycling the target unit module as a whole to a shore-based facility; performing a temperature raising or pressure reducing operation on the module to decompose the hydrate into gaseous carbon dioxide; collecting the carbon dioxide gas generated by the decomposition; purifying the gas. The temperature raising or pressure reducing operation is controlled to be performed in a temperature and pressure condition range outside the hydrate stable domain. The recycling operation is completed by a vertical lifting and precise positioning of the module through a lifting system and a horizontal boom of a sea platform.

9. The method of claim 8, wherein, ​ 10. The method of claim 8, wherein, ​

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