Abstract
BP has been operating gas injection projects in a variety of challenging environments throughout the world for more than three decades. Numerous innovative techniques have been used to optimize oil recovery and the results have been reported in a series of publications.
The focus of this paper is the North Sea, where BP operates offshore miscible gas floods in the Magnus and Ula fields and an immiscible gas flood in the Harding field. Tertiary miscible WAG in Magnus began in 2002 and its impact on reservoir performance is significant and well understood. More than 112 Bscf of gas have been injected into three mature panels, yielding 11.5 mmstb of oil at a very high net efficiency of 3.5 mscf/stb. The contribution of EOR to total field production has increased to 40% by 2010. In Ula, tertiary miscible WAG started in 1998 and has played a key role in arresting production decline. More than 23 mmstb of oil has been recovered by gas injection, which accounted for 60 – 70% of total field production in 2010. Key to the success of both projects has been securing a source of miscible gas and pursuing an active surveillance and reservoir management programme to monitor and optimize the flood.
The success of the North Sea projects is partly based on the experience of operating the world's largest miscible gas flood at Prudhoe Bay (Alaska), where conventional and unconventional techniques have been successfully applied in a variety of different settings. The knowledge acquired in Prudhoe Bay has been shared with other assets, including the North Sea, through a series of managed moves and master classes.
Miscible gas injection has generated considerable benefits for BP over the past three decades and will continue to do so in the future. The potential availability of large sources of CO2 in the future, through carbon capture, could help maintain a leading role for miscible gas injection for years to come.
