The DF1-1 gas field is located in the west of the South China Sea, which is associated with a high concentration of CO2 Currently CO2 separated from a natural gas stream is disposed in a way that doesn't consider environmental effects In this study, a demonstrative project of a CO2 capture and storage (CCS) technique is considered, proposing to inject CO2 separated on the platform back into the original gas reservoir. The CO2 storage site considered is a nearly abandoned gas block in the DF1-1 gas field, which was reassessed for the safety of CO2 storage A membrane separation technique will be used on the platform for the separation. CO2 is compressed at supercritical state and injected through a single well (that used to be a producer) Into the gas formation A new platform auxiliary to the main platform will be built to accommodate the compressor and separation equipment CO2 will be injected at the rate of 0.14x10(6) Sm-3/d for 10 years over the field development period At the end of the project, the pressure of the CO2 storage reservoir will be increased to its original pressure Scoping economic analysis shows that the CO2 storage cost of the project is approximately USD 20 per ton CO2, in which the auxiliary platform is the main cost factor