Abstract: The CO₂content in the associated gas produced in the H Oilfield in the eastern South China Sea is as high as 19.67%, and it cannot be directly used as fuel gas for power generation. To address this, in light of the engineering conditions of offshore oilfields, the decarbonization technology was selected. Based on the sealing properties of the geological cover strata, the physical properties of reservoirs, and the integrity of the structure, the geological suitability for CO₂ storage and the feasibility of injection and production in the same well were evaluated. Numerical simulation research on CO₂ storage was carried out, ultimately forming an integrated technology of membrane decarbonization and storage for associated gas, and on-site experiments were conducted in the H Oilfield in the eastern of South China Sea. The results show that the CO₂ content in the associated gas has decreased to 4.68%, meeting the fuel gas standard (CO₂<5%), and the hydrocarbon recovery rate was greater than 90%. The concentration of CO₂ in the gas after decarbonization reached 70%. The application results show that the integrated technology of membrane decarbonization and storage for associated gas in H Oilfield operates stably and can solving the problem of effective utilization of associated gas with high CO₂ content in offshore oilfields, providing a new paradigm for the large-scale application of CCS in offshore oilfields.