Simulation Study of CO2 EOR and Storage Potential in a North Sea Reservoir

Abstract

A simulation study has been carried out using realistic model of a North Sea oil reservoir to assess the performance of CO2 flood in oil recovery compared to the base case water injection. The development strategy for this reservoir is based on one injector and a single producer. Various CO2 injection strategies were studied to define injection schemes that would outperform water injection. Pure CO2 injection, water flooding followed by CO2 injection, CO2 Water-Alternating-Gas (CO2 WAG) injection, and CO2 Simultaneous-Water-And-Gas (CO2 SWAG) injection are strategies that were studied. The latter one was chosen to study the mitigation of gravity segregation between water and gas. Various well locations and well configurations were also evaluated to determine the optimal arrangement. Simulation results showed that the increased recovery factors by the CO2 flooding varies in the range between 3 to 8 percent and is to a considerable extent dependent on well configuration and injection scheme. The flooding with SWAG (water above gas) shows very promising results due to the increased mobility control achieved. Regarding the storage potential, the analysis indicates that this method would result in highest CO2 retention in the reservoir.