Abstract
The DF1-1 gas field, located in the western South China Sea, contains a high concentration of CO
2
, thus there is great concern about the need to reduce the CO
2
emissions. Many options have been considered in recent years to dispose of the CO
2
separated from the natural gas stream on the Hainan Island. In this study, the feasibility of CO
2
storage in the lateral saline aquifer of the DF1-1 gas field is assessed, including aquifer selection and geological assessment, CO
2
migration and storage safety, project design, and economic analysis. Six offshore aquifers have been investigated for CO
2
geological storage. The lateral aquifer of the DF1-1 gas field has been selected as the best target for CO
2
injection and storage because of its proven sealing ability, and the large storage capacity of the combined aquifer and hydrocarbon reservoir geological structure. The separated CO
2
will be dehydrated on the Hainan Island and transported by a long-distance subsea pipeline in supercritical or liquid state to the central platform of the DF1-1 gas field for pressure adjustment. The CO
2
will then be injected into the lateral aquifer via a subsea well-head through a horizontal well. Reservoir simulations suggest that the injected CO
2
will migrate slowly upwards in the aquifer without disturbing the natural gas production. The scoping economic analysis shows that the unit storage cost of the project is approximately US$26-31/ton CO
2
with the subsea pipeline as the main contributor to capital expenditure (CAPEX), and the dehydration system as the main factor of operating expenditure (OPEX).