Obstacles to the storage of CO₂ through EOR operations in the North Sea

Forties is a giant offshore oil field situated on the edge of the South Viking Graben in the UK sector of the North Sea. It has been on production since the mid 1970’s using seawater injection for pressure support. This has proved exceptionally productive with a forecast recovery factor of 62%. Gas injection has been investigated as a future option to increase the recovery factor in excess of 70%. Screening studies have shown that CO₂ injection has potential advantages over either hydrocarbon gas or air. The screening studies were followed up with detailed evaluation of CO₂ injection including PVT studies to look at Minimum Miscibility Pressure (MMP), coreflood studies to confirm displacement mechanisms, reservoir simulation to model sweep and a review of the modifications needed to surface facilities and infrastructure. CO₂ injection is predicted to have the potential to produce an additional 150 – 200 million barrels of oil from Forties whilst 40 – 80 million tonnes CO₂ would be permanently trapped in the subsurface. Despite the significant production benefits, the project is currently not economically attractive as a stand-alone EOR project as a consequence of the large capital expenditure that would be required for adaptation of wells, flowlines and surface facilities to make them compatible with wet CO₂ operation. That economic picture could change if storage Of CO₂ were to generate additional project value through a carbon trading system. However, there is considerable uncertainty over the potential value Of CO₂ credits and the role that they may have in justifying future oilfield projects.