Offshore energy island based on decommissioned oil and gas platform and construction method thereof

Abstract

The application discloses an offshore energy island based on a decommissioned oil and gas platform and a construction method thereof, relates to the technical field of comprehensive utilization of marine energy and development of green fuel, and aims to solve the problems of high disposal cost of decommissioned marine engineering assets, great volatility of renewable energy in deep sea and difficulty in green fuel delivery. In the application, the decommissioned oil and gas platform is adaptively modified, offshore renewable electric energy is obtained by using an energy supply unit, the electric energy is converted into hydrogen by using an electrolytic hydrogen production unit, and hydrogen-based fuels such as liquid ammonia and methanol are synthesized by using the hydrogen, the hydrogen-based fuels are stored, and are injected into the modified original oil and gas pipeline to be delivered to a land terminal or used for ship refueling, and a smart operation and dispatching system is built to integrally manage and optimize energy flow, material flow and equipment operation of the offshore energy island.

Description

Technical Field

[0001] This invention relates to the field of marine energy comprehensive utilization and green fuel development technology, specifically to an offshore energy island based on a decommissioned oil and gas platform and its construction method. Background Technology

[0002] Offshore wind power, electrolytic hydrogen production, and hydrogen-based fuel synthesis technologies have developed rapidly in recent years, and deep-sea energy development has become an important direction for global energy transition. At the system level, existing technical solutions integrate and model multiple energy forms such as electricity, heat, cooling, gas, carbon, hydrogen, ammonia, and alcohols across the entire industry chain, and employ multi-entity collaborative optimization scheduling methods to achieve low-carbon and economical system operation. For example, there is a Chinese patent with publication number CN121787674A, which relates to a multi-entity collaborative optimization scheduling method and system for island energy systems. However, such solutions are mainly geared towards nearshore island scenarios, relying on grid interaction and natural gas input, and do not address the physical construction of independent energy hubs in deep-sea areas, nor do they solve the problem of reusing decommissioned marine engineering assets.

[0003] At the physical platform level, existing technologies mostly rely on newly built offshore platforms or single-function devices for offshore wind power, hydrogen production, or fuel synthesis, failing to fully utilize the original structural strength, space bearing capacity, subsea pipelines, and supporting facilities of decommissioned oil and gas platforms. Furthermore, existing solutions typically isolate power generation, hydrogen production, fuel synthesis, and storage and transportation, lacking a closed-loop integration from "source" to "load" to "storage." This results in high costs for transporting deep-sea green fuels after production and insufficient supply chain coordination, limiting the construction of a large-scale green fuel supply system. Summary of the Invention

[0004] This invention proposes an offshore energy island based on a decommissioned oil and gas platform and its construction method. By transforming marine engineering assets to be dismantled into a deep-sea green energy hub, it achieves high-value reuse of resources and reduces costs. By constructing a closed-loop system for on-site consumption and stable conversion of renewable energy, it effectively mitigates wind power fluctuations and improves system operational reliability. By modifying existing submarine pipelines to transport green fuel, it breaks through the technical bottleneck of large-scale external transmission of deep-sea green fuel.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for constructing an offshore energy island based on a decommissioned oil and gas platform, comprising: S1 involves adapting decommissioned oil and gas platforms; utilizing energy supply units to obtain renewable offshore electricity. S2, the electrical energy is converted into hydrogen through an electrolysis hydrogen production unit, and the hydrogen is used to synthesize hydrogen-based fuels, including liquid ammonia and methanol; S3, the hydrogen-based fuel is stored and injected into the modified existing oil and gas pipeline for transport to land terminals or ship refueling; S4 establishes an intelligent operation and scheduling system to integrate, schedule, and optimize the energy flow, material flow, and equipment operation of offshore energy islands.

[0006] Preferably, step S1 includes: S11, the adaptive modification includes utilizing the deck space, load-bearing structure and utilities of the decommissioned oil and gas platform to support energy conversion equipment and fuel storage units, and modifying the original pipeline interfaces to adapt to hydrogen-based fuel transportation; S12 deploys floating wind turbines to generate electricity, which is then transmitted to the platform via dynamic submarine cables.

[0007] Preferably, step S12 includes: using the power output of at least one floating wind turbine to transmit the power to the power dispatch and distribution unit of the decommissioned oil and gas platform via a dynamic submarine cable for preliminary stabilization and dispatch.

[0008] Preferably, step S2 includes: S21, high-purity green hydrogen is prepared using a proton exchange membrane electrolyzer or an alkaline electrolyzer, wherein the operating temperature of the electrolyzer is controlled at approximately 70°C and the current density is controlled at approximately 200 mA cm⁻¹. -2 Within this range, the system energy efficiency is higher than 80%; S22 is an integrated hydrogen-based fuel synthesis system that synthesizes liquid ammonia from hydrogen and nitrogen, and methanol from syngas synthesized from biomass feedstock and hydrogen.

[0009] Preferably, step S22 includes: obtaining nitrogen from the air using air separation technology, reacting the hydrogen with the nitrogen in a synthesis tower to generate liquid ammonia, wherein the operating pressure of the synthesis tower is 15.0 MPa to 25.0 MPa, the operating temperature is 170°C to 200°C, and the ammonia-to-carbon ratio of the reactants is maintained between 4.0 and 4.1.

[0010] Preferably, step S22 includes: synthesizing methanol from hydrogen and carbon dioxide in a methanol synthesis reactor, wherein the reactor operates at a pressure of 2.0 MPa to 5.0 MPa, an operating temperature of 250°C to 320°C, and a reaction space velocity controlled at 400 to 1600 mL g. -1 h -1 Within the range.

[0011] Preferably, in step S3, a fuel storage and delivery system is constructed, including a fuel storage module, a ship refueling module, and a pipeline delivery module. The fuel storage module stores the hydrogen-based fuel in a cryogenic storage tank; the ship refueling module provides refueling services to passing ships; and the pipeline delivery module injects the hydrogen-based fuel into existing oil and gas pipelines that have undergone adaptability assessment and modification, and delivers it to onshore terminals in the form of pure material or mixed with natural gas.

[0012] Preferably, step S4 includes: S41 collects real-time data from the entire system, including fan power, electrolyzer operating status, storage tank level, pipeline pressure, and environmental data. S42 integrates wind farm power prediction models, electrolysis hydrogen production load regulation models, energy storage optimization configuration models, and intelligent planning and simulation models to dynamically adjust and support the operation of the energy island. S43 receives instructions and performs precise control of the physical unit through the field control system.

[0013] This invention also adopts the following technical solution: a marine energy island based on a decommissioned oil and gas platform, comprising: a decommissioned oil and gas platform, which, after adaptive modification, carries energy conversion equipment and a fuel storage unit; equipped with: an energy supply unit to obtain renewable offshore electricity; an electrolysis hydrogen production unit to convert electricity into hydrogen; an auxiliary raw material preparation unit to obtain auxiliary raw materials; a hydrogen-based fuel synthesis system to synthesize hydrogen-based fuel from hydrogen and auxiliary raw materials; a fuel storage and delivery system to store hydrogen-based fuel and deliver it externally via pipeline or ship refueling; and an intelligent operation and scheduling system to integrate, schedule, and optimize the energy flow, material flow, and equipment operation of the marine energy island.

[0014] Preferably, the auxiliary raw material preparation unit includes a nitrogen preparation unit and a syngas preparation unit. The nitrogen preparation unit obtains nitrogen from the air through air separation technology, and the syngas preparation unit sends the pretreated biomass raw material into the gasifier to generate syngas including H2, CO, and CO2.

[0015] The beneficial effects of this invention are: (1) By adapting and modifying decommissioned oil and gas platforms, the resources of decommissioned platforms can be reused, reducing the initial investment in deep-sea energy development and avoiding the high costs and secondary impacts on the marine ecosystem caused by platform dismantling. (2) An integrated system with floating wind power as the source, covering hydrogen production, hydrogen-based fuel synthesis, storage and transportation and ship refueling, has been built, which has improved the efficiency of energy conversion and utilization and promoted the green and low-carbon transformation of the marine economy. (3) By utilizing the stability and load-bearing capacity of decommissioned oil and gas platforms, a stable energy supply platform is provided for fluctuating energy sources such as offshore wind power, thereby reducing the instability of energy supply; (4) An innovative adaptive environmental restoration device was proposed, which can intelligently match and dynamically adjust restoration strategies based on real-time ecological risk assessment results, significantly improving the accuracy and effectiveness of ecological restoration. Attached Figure Description

[0016] Figure 1This is a flowchart of a method for constructing an offshore energy island based on a decommissioned oil and gas platform, according to the present invention.

[0017] Figure 2 This is a flowchart illustrating the adaptive modification in Embodiment 2 of the present invention.

[0018] Figure 3 This is a structural diagram of the marine energy island in Embodiment 5 of the present invention. Detailed Implementation

[0019] Example 1

[0020] This embodiment provides a method for constructing an offshore energy island based on a decommissioned oil and gas platform. This method systematically repurposes and integrates the functions of the decommissioned oil and gas platform, transforming it from a soon-to-be-abandoned fossil energy extraction facility into a comprehensive offshore energy hub integrating deep-sea renewable energy capture, green hydrogen-based fuel production, storage, and transmission.

[0021] refer to Figure 1 The method specifically includes the following steps.

[0022] Step S1: Adapt the decommissioned oil and gas platform; utilize the energy supply unit to obtain offshore renewable electricity.

[0023] This step is crucial for realizing the physical foundation of the entire offshore energy island. It abandons the traditional, high-cost, and environmentally impactful approach of completely dismantling decommissioned platforms. Instead, through scientific assessment and modification, it maximizes the potential value of decommissioned oil and gas platforms, providing a stable, reliable, and economical physical carrier for the integration of new functions. Simultaneously, this step deploys energy supply units, injecting initial, clean primary energy into the subsequent energy conversion chain.

[0024] Step S2: The electrical energy is converted into hydrogen through an electrolysis hydrogen production unit, and the hydrogen is used to synthesize hydrogen-based fuels, including liquid ammonia and methanol.

[0025] This step is the core of energy conversion. Through a multi-energy coupling path of "electricity-hydrogen-liquid fuel," it transforms offshore wind power—a low-density, discontinuous energy source characterized by high volatility and difficulties in grid connection and transmission—into hydrogen-based fuels such as liquid ammonia and methanol, which offer high energy density, convenient storage and transportation, and wide applicability. This conversion process not only solves the problem of on-site consumption of deep-sea wind power but also provides diversified commercial exports, greatly enhancing the economic feasibility of the project and the flexibility of the energy system.

[0026] Step S3: Store the hydrogen-based fuel and inject it into the modified existing oil and gas pipeline for delivery to land-based terminals or ship refueling.

[0027] This step establishes an export channel for energy products. It innovatively reintegrates another core legacy asset of the decommissioned platform—the subsea oil and gas pipeline—into the new energy logistics system. Through adaptive assessment and modification, the pipeline has been transformed into a major artery for transporting green fuels, thereby achieving a physical connection between the deep-sea energy base and the onshore energy consumption market at extremely low marginal cost. Simultaneously, it retains the function of providing direct refueling services to shipping vessels, forming a dual-mode export system of "pipeline transportation + offshore refueling."

[0028] Step S4: Build an intelligent operation and scheduling system to integrate, schedule and optimize the energy flow, material flow and equipment operation of the offshore energy island.

[0029] This step equips the entire offshore energy island with a "smart brain." Faced with a complex "source-grid-load-storage" system, the coupling and coordination of various heterogeneous energy and material flows, and the harsh and variable environmental conditions of the deep sea, relying on human experience for scheduling is impossible. Therefore, it is essential to establish a smart operation and scheduling system encompassing data perception, analysis, decision-making, and command execution to ensure the safe, stable, efficient, and economical operation of the entire energy island under various conditions.

[0030] Through the steps S1 to S4 described above, the present invention provides a complete and closed-loop technical solution, realizing the entire chain connection from asset revitalization, energy conversion, product delivery to intelligent management and control.

[0031] Example 2

[0032] This embodiment further refines the adaptive modification and energy acquisition methods in step S1 based on embodiment 1.

[0033] Step S1 includes the following sub-steps, such as... Figure 2 As shown.

[0034] Step S11, the adaptive modification includes utilizing the deck space, load-bearing structure and utilities of the decommissioned oil and gas platform to support energy conversion equipment and fuel storage units, and modifying the original pipeline interfaces to adapt to hydrogen-based fuel transportation.

[0035] Specifically, this step follows the principle of "minimizing new construction and maximizing utilization." First, a comprehensive structural safety assessment and life extension analysis are conducted on the decommissioned oil and gas platform; this is the prerequisite for all modification work. Based on the confirmation of the platform's structural safety and reliability, physical modifications are then carried out. The platform's deck space, originally used for drilling equipment, oil and gas processing equipment, and living quarters, is now cleared, reinforced, and redesigned to accommodate modular, skid-mounted electrolysis hydrogen production units, hydrogen-based fuel synthesis units, air separation units, and other core energy conversion equipment. These units typically employ a compact layout to reduce land occupation and adapt to the limited but valuable deck space of the offshore platform. The platform's load-bearing structure, especially the beam-column system of the main deck and lower decks, has sufficient design margin to support new fuel storage units, such as large cryogenic liquid ammonia or methanol storage tanks. These tanks are enormous when fully loaded and require robust load-bearing foundations. Utilizing existing utilities is a key aspect of cost reduction. The platform's existing seawater pumping system provides ample cooling water for the electrolytic hydrogen production and synthesis reaction processes. The existing fire protection system has been upgraded to cover the newly added hydrogen and hydrogen-based fuel production and storage areas, meeting higher safety protection standards. The existing power dispatching system can be expanded and upgraded to accommodate new demands for wind power input and internal power dispatching. Finally, the platform's existing pipeline interfaces used for oil and gas transportation will be completely overhauled, including material replacement, updated sealing methods, pressure level adjustments, and the addition of necessary safety isolation valve assemblies, enabling them to reliably adapt to the transportation requirements of new media such as hydrogen, ammonia, and methanol.

[0036] Step S12: Deploy floating wind turbine generators to obtain electrical energy and transmit the power to the platform via dynamic submarine cables.

[0037] This step specifically defines the composition of the energy supply unit. In deep-sea areas, the economic and technical feasibility of traditional fixed-foundation wind turbines decreases, making floating wind turbines an ideal choice. These turbines, semi-submerged or suspended on the sea surface via mooring systems, can capture the abundant and stable wind energy resources of the deep sea. The electricity generated by each turbine or turbine group is boosted at the turbine end and then transmitted to the decommissioned oil and gas platform via a dynamic submarine cable. The dynamic submarine cable is a key component connecting the floating wind turbine to the fixed or floating platform. Its design must be able to withstand the continuous relative motion between the turbine and the platform caused by wind, waves, and currents, ensuring the safety and stability of power transmission. After the submarine cable lands on the platform, it connects to the platform's power dispatch and distribution unit, thus completing the first step from wind energy capture to power aggregation.

[0038] Example 3

[0039] This embodiment, based on embodiment 2, provides more specific limitations on the power transmission and preliminary scheduling stage in step S12. Step S12 includes: using the power output of at least one floating wind turbine, transmitting it via a dynamic submarine cable to the power scheduling and distribution unit of the decommissioned oil and gas platform for preliminary stabilization and scheduling.

[0040] A specific operational scenario involves an offshore wind farm comprised of multiple floating wind turbines. The output cables of each turbine are connected at a convergence point on the seabed or surface, and the centralized power is transmitted to the energy island platform via one or more main dynamic submarine cables. On the platform, the power dispatch and distribution unit is the first line of defense for the power flow; it is not merely a physical connection point but a fully functional system. This unit integrates transformers, converters, and intelligent switching equipment. Transformers convert the medium- or high-voltage electricity from the wind turbines to the voltage levels required by the various process units within the platform. Converters handle AC / DC conversion and power quality regulation; for example, they convert the unstable AC power from the wind turbines into DC power, and then invert it into stable DC or AC power that meets the requirements of the electrolyzers. Intelligent switching equipment is responsible for precisely distributing power to different loads such as the electrolysis hydrogen production unit, auxiliary equipment, and living facilities according to instructions from the intelligent operation and dispatch system, and for rapid isolation and protection in case of faults. This initial stabilization and dispatch at this level provides a high-quality power supply for subsequent sensitive electrochemical processes.

[0041] Example 4

[0042] This embodiment is a further optimization based on any one of embodiments 1 to 3, and elaborates in detail the specific process path and key parameters from hydrogen production to fuel synthesis in step S2. Step S2 includes: S21, high-purity green hydrogen is prepared using a proton exchange membrane electrolyzer or an alkaline electrolyzer, wherein the operating temperature of the electrolyzer is controlled at approximately 70°C and the current density is controlled at approximately 200 mA cm⁻¹. -2 Within the specified range, the system energy efficiency is higher than 80%.

[0043] To achieve the highest system efficiency and widest load regulation range, a proton exchange membrane (PEM) electrolyzer is preferred. The PEM electrolyzer is particularly suitable for the application scenarios of this invention due to its compact structure, fast response characteristics, and good adaptability to fluctuating power sources (such as wind power). Maintaining the operating temperature at approximately 70°C is a critical operating window, at which the proton exchange membrane maintains optimal proton conductivity and chemical stability, and the electrode reaction kinetics are sufficiently fast. The current density is controlled at approximately 200 mA cm⁻¹. -2The optimal balance between hydrogen production rate and electrolyzer energy consumption and lifespan is achieved within this range. Excessively high current density leads to increased ohmic polarization losses, reduced energy efficiency, and accelerated membrane and catalyst degradation; conversely, excessively low current density results in low equipment utilization and untapped hydrogen production capacity. A system energy efficiency exceeding 80% means that over 80% of the input electrical energy is effectively converted into the chemical energy (low calorific value) of hydrogen. This metric ensures the economic viability of converting wind power to hydrogen energy. Achieving this efficiency relies on a highly efficient electrolyzer stack design, optimized operating conditions, and low-loss power electronic conversion devices.

[0044] S22 is an integrated hydrogen-based fuel synthesis system that synthesizes liquid ammonia from hydrogen and nitrogen, and methanol from syngas synthesized from biomass feedstock and hydrogen.

[0045] This step integrates two parallel or switchable liquid fuel synthesis routes to address different market demands and enhance system flexibility.

[0046] For the liquid ammonia synthesis route, the feedstocks are hydrogen produced in step S21 and nitrogen obtained from the air separation unit. The hydrogen and nitrogen are mixed in a molar ratio of approximately 3:1 and then enter the ammonia synthesis loop.

[0047] For the methanol synthesis route, an innovative process coupled with biomass utilization is employed. First, biomass feedstocks (such as energy plants transported by sea, agricultural and forestry waste pellets, etc.) are pretreated and fed into a gasifier to generate crude syngas rich in H2, CO, and CO2. Then, this crude syngas is mixed and modulated with a portion of the hydrogen produced in step S21 to precisely control the proportions of each component in the syngas, ensuring it reaches the optimal operating range for the methanol synthesis catalyst. This coupled process not only produces green methanol but also provides a pathway for non-target components generated during biomass gasification (such as excess CO2) to react with green hydrogen and be fixed, thus achieving the recycling of carbon resources.

[0048] Example 5

[0049] This embodiment, based on Embodiment 4, specifically limits the process parameters for liquid ammonia synthesis in step S22 to achieve optimal synthesis efficiency and system stability. Step S22 includes: obtaining nitrogen from the air using air separation technology, reacting the hydrogen and nitrogen in a synthesis tower to generate liquid ammonia, wherein the operating pressure of the synthesis tower is 15.0 MPa to 25.0 MPa, the operating temperature is 170°C to 200°C, and the ammonia-to-carbon ratio of the reactants is maintained between 4.0 and 4.1.

[0050] Air separation units typically employ cryogenic separation or pressure swing adsorption (PSA) technology to extract high-purity nitrogen from the endless air in situ, serving as the second major feedstock for ammonia synthesis. The core equipment of the reaction is the ammonia synthesis tower, which is filled with iron-based or ruthenium-based catalysts. The operating pressure of the synthesis tower is set between 15.0 MPa and 25.0 MPa, an optimized range that balances synthesis conversion rate, equipment investment cost, and compression energy consumption. Higher pressure results in a higher equilibrium conversion rate for ammonia synthesis, but also a sharp increase in compressor energy consumption and pressure requirements. The operating temperature is set between 170°C and 200°C, matching the high-activity temperature range of the selected catalyst. Too low a temperature results in a slow reaction rate; too high a temperature not only accelerates catalyst sintering and deactivation but also reduces the equilibrium ammonia content due to reaction equilibrium limitations. The ammonia-to-carbon ratio (NH3 / CO2 molar ratio) of the reactants is maintained between 4.0 and 4.1. It should be noted that in the ammonia synthesis section, this parameter usually refers to the hydrogen-to-nitrogen ratio, maintained at approximately 3:1. However, considering that if downstream products such as urea are involved, there will be a description of the ammonia-to-carbon ratio, the above method will be used for construction and operation.

[0051] The offshore energy island comprises decommissioned oil and gas platforms, which, after adaptive modifications, house energy conversion equipment and fuel storage units. It includes: an energy supply unit to obtain renewable offshore electricity; an electrolysis hydrogen production unit to convert the electricity into hydrogen; an auxiliary feedstock preparation unit to obtain auxiliary feedstocks; a hydrogen-based fuel synthesis system to synthesize hydrogen with the auxiliary feedstocks to produce hydrogen-based fuel; a fuel storage and delivery system to store the hydrogen-based fuel and deliver it externally via pipeline or ship refueling; and an intelligent operation and scheduling system to integrate, schedule, and optimize the energy flow, material flow, and equipment operation of the offshore energy island.

[0052] Specifically, this energy island is a highly integrated and complex system, referencing Figure 3The decommissioned oil and gas platform forms the physical framework of the entire system. After adaptive modifications such as structural reinforcement, spatial rezoning, and interface alteration, it physically supports all newly added functional units. The energy supply unit is the system's energy source, preferably a floating wind turbine generator, which delivers clean electricity to the platform via a dynamic submarine cable. The electrolysis hydrogen production unit is the starting point for energy conversion, transforming electrical energy into hydrogen energy that is easy to store and further convert. The auxiliary feedstock preparation unit is the material replenishment end for the synthesis reaction, providing essential auxiliary feedstocks such as nitrogen and carbon sources (e.g., CO2 or biomass syngas) for the synthesis of hydrogen-based fuels. The hydrogen-based fuel synthesis system is the core reactor for material conversion. Here, hydrogen reacts chemically with auxiliary feedstocks to generate liquid fuels with higher energy density, namely liquid ammonia and methanol. The fuel storage and delivery system serves as a product warehouse and logistics center, ensuring stable buffering and safe output of energy products. Green fuels are delivered to end users through both the modified existing subsea pipelines and offshore refueling facilities. Finally, as... Figure 3 As shown, the intelligent operation and scheduling system is like the central nervous system, consisting of a data perception and acquisition layer, a core analysis and decision-making layer, and a scheduling instruction execution layer. It runs through and controls all the above physical units. By integrating multiple optimization models, it dynamically schedules the information flow, energy flow, and material flow of the entire process from wind energy capture to fuel delivery in real time, achieving overall system synergy and optimization.

[0053] Example 10

[0054] This embodiment, based on Embodiment 9, specifically defines the internal structure of the auxiliary raw material preparation unit. The auxiliary raw material preparation unit includes a nitrogen preparation unit and a syngas preparation unit. The nitrogen preparation unit obtains nitrogen from the air using air separation technology. The syngas preparation unit feeds pretreated biomass raw materials into a gasifier to generate syngas comprising H2, CO, and CO2.

[0055] The nitrogen production unit is specifically designed for the liquid ammonia synthesis route. In a preferred configuration, this unit employs a skid-mounted pressure swing adsorption (PSA) nitrogen generator, directly adsorbing oxygen, carbon dioxide, and water from the atmosphere to produce nitrogen with a purity exceeding 99.9%. Its flexible start-up and shutdown capabilities allow it to effectively match the fluctuating conditions of wind-powered electrolytic hydrogen production, ensuring a stable and on-demand supply of both hydrogen and nitrogen feedstocks. The syngas production unit is the core component providing the carbon source for the methanol synthesis route. It receives biomass feedstock particles transported to the platform periodically by ship. The feedstock first undergoes a pretreatment process, including drying, crushing, and screening, to ensure its particle size and moisture content meet the feed requirements of the gasifier. Subsequently, the treated biomass powder is continuously fed into a fluidized bed or entrained gasifier. Inside the gasifier, under precisely controlled temperature and an oxygen / water vapor atmosphere, the biomass undergoes a series of complex reactions including pyrolysis, oxidation, and reduction, ultimately producing crude syngas primarily composed of hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2). After undergoing purification processes such as cooling, dust removal, and desulfurization, the crude syngas becomes clean syngas and is sent to the downstream methanol synthesis reactor. There, it serves as a carbon source and part of the hydrogen source, merging with external green hydrogen to synthesize green methanol. This integrated approach achieves the organic unity of renewable energy, biomass energy, and the carbon cycle.

Claims

1. A method for constructing an offshore energy island based on a decommissioned oil and gas platform, characterized in that, include: S1 involves adapting decommissioned oil and gas platforms; utilizing energy supply units to obtain renewable offshore electricity. S2, the electrical energy is converted into hydrogen through an electrolysis hydrogen production unit, and the hydrogen is used to synthesize hydrogen-based fuels, including liquid ammonia and methanol; S3, the hydrogen-based fuel is stored and injected into the modified existing oil and gas pipeline for transport to land terminals or ship refueling; S4 establishes an intelligent operation and scheduling system to integrate, schedule, and optimize the energy flow, material flow, and equipment operation of offshore energy islands.

2. The method for constructing an offshore energy island based on a decommissioned oil and gas platform according to claim 1, characterized in that, Step S1 includes: S11, the adaptive modification includes utilizing the deck space, load-bearing structure and utilities of the decommissioned oil and gas platform to support energy conversion equipment and fuel storage units, and modifying the original pipeline interfaces to adapt to hydrogen-based fuel transportation; S12 deploys floating wind turbines to generate electricity, which is then transmitted to the platform via dynamic submarine cables.

3. The method for constructing an offshore energy island based on a decommissioned oil and gas platform according to claim 2, characterized in that, Step S12 includes: using the power output of at least one floating wind turbine to transmit the power to the power dispatch and distribution unit of the decommissioned oil and gas platform via a dynamic submarine cable for preliminary stabilization and dispatch.

4. A method for constructing an offshore energy island based on a decommissioned oil and gas platform according to any one of claims 1-3, characterized in that, Step S2 includes: S21, high-purity green hydrogen is prepared using a proton exchange membrane electrolyzer or an alkaline electrolyzer, wherein the operating temperature of the electrolyzer is controlled at approximately 70°C and the current density is controlled at approximately 200 mA cm⁻¹. -2 Within this range, the system energy efficiency is higher than 80%; S22 is an integrated hydrogen-based fuel synthesis system that synthesizes liquid ammonia from hydrogen and nitrogen, and methanol from syngas synthesized from biomass feedstock and hydrogen.

5. A method for constructing an offshore energy island based on a decommissioned oil and gas platform according to claim 4, characterized in that, Step S22 includes: obtaining nitrogen from the air using air separation technology, reacting the hydrogen and the nitrogen in a synthesis tower to generate liquid ammonia, wherein the operating pressure of the synthesis tower is 15.0 MPa to 25.0 MPa, the operating temperature is 170°C to 200°C, and the ammonia-to-carbon ratio of the reactants is maintained between 4.0 and 4.

1.

6. A method for constructing an offshore energy island based on a decommissioned oil and gas platform according to claim 4, characterized in that, Step S22 includes: synthesizing methanol from hydrogen and carbon dioxide in a methanol synthesis reactor, wherein the reactor operates at a pressure of 2.0 MPa to 5.0 MPa, an operating temperature of 250°C to 320°C, and a reaction space velocity controlled at 400 to 1600 mL g. -1 h -1 Within the range.

7. A method for constructing an offshore energy island based on a decommissioned oil and gas platform according to any one of claims 1-3, characterized in that, In step S3, a fuel storage and delivery system is constructed, including a fuel storage module, a ship refueling module, and a pipeline delivery module. The fuel storage module stores the hydrogen-based fuel in a cryogenic storage tank; the ship refueling module provides refueling services to passing ships; and the pipeline delivery module injects the hydrogen-based fuel into existing oil and gas pipelines that have undergone adaptive assessment and modification, and delivers it to onshore terminals in the form of pure material or mixed with natural gas.

8. A method for constructing an offshore energy island based on a decommissioned oil and gas platform according to claim 1, characterized in that, Step S4 includes: S41 collects real-time data from the entire system, including fan power, electrolyzer operating status, storage tank level, pipeline pressure, and environmental data. S42 integrates wind farm power prediction models, electrolysis hydrogen production load regulation models, energy storage optimization configuration models, and intelligent planning and simulation models to dynamically adjust and support the operation of the energy island. S43 receives instructions and performs precise control of the physical unit through the field control system.

9. A marine energy island based on a decommissioned oil and gas platform, realizing the method for constructing a marine energy island based on a decommissioned oil and gas platform as described in any one of claims 1-8, characterized in that, include: Decommissioned oil and gas platforms, after adaptive modifications, can house energy conversion equipment and fuel storage units; on top of them... The system includes: an energy supply unit that acquires renewable electricity from the sea; an electrolysis hydrogen production unit that converts electricity into hydrogen; an auxiliary feedstock preparation unit that acquires auxiliary feedstocks; a hydrogen-based fuel synthesis system that synthesizes hydrogen-based fuels from hydrogen and auxiliary feedstocks; a fuel storage and delivery system that stores hydrogen-based fuels and delivers them via pipelines or ship refueling; and an intelligent operation and scheduling system that integrates, schedules, and optimizes the energy flow, material flow, and equipment operation of the offshore energy island.

10. A marine energy island based on a decommissioned oil and gas platform according to claim 9, characterized in that, The auxiliary raw material preparation unit includes a nitrogen preparation unit and a syngas preparation unit. The nitrogen preparation unit obtains nitrogen from the air through air separation technology. The syngas preparation unit feeds the pretreated biomass raw material into a gasifier to generate syngas including H2, CO, and CO2.

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