Abstract: Natural gas hydrates in sea areas are clean energy with abundant reserves, which can meet the great demands from national and regional energy and economic development. Hydrate reservoirs in the sea areas occur under high temperature and pressure conditions (12 ℃-16 ℃), low argillaceous permeability, leading to a great difficulty in hydrocarbon development. Conventional mining methods such as depressurization, heat/inhibitor injection, and carbon dioxide replacement should be integrated and collaboratively optimized to form the safe and efficient exploitation technologies for natural gas hydrate resources in special geological environments in sea areas. By introducing the current research progress of existing combined mining technologies for natural gas hydrates, in accordance with the idea of "safe mining, being green and efficient", with the goal of improving natural gas recovery efficiency and CO₂ storage efficiency, and remediating hydrate reservoirs, a new generation of triple mining technology of production, carbon sequestration, and geological restoration for natural gas hydrates in sea areas is proposed by combining depressurization and CO₂ injection. Specifically, hydrates are exploited by depressurization method at first, then CO₂ mixture is injected to assist in stimulating hydrate production and displacing natural gas to improve recovery efficiency, and finally the high-pressure and high CO₂ component gas mixture is injected to re-form mixed hydrates in the pores. This aims to achieve energy exploitation, carbon storage, and formation remediation. The paper elaborates the background, technical principle, thermodynamic feasibility analysis, verification results of medium- and small-scale tests, and future development direction of the new technology, aiming to provide reference for the production of natural gas hydrates in sea areas.