The oil reserves in the Statfjord field’s reservoirs are declining. So far, well over 60% of the stock tank oil originally in place has been extracted. In the coming years recovery is expected to increase to 66%.
Injecting gas and water to maintain reservoir pressure has been an important element in the present production strategy for the field.
Combined with an extensive programme of drilling wells to tap remaining oil pockets, injection has helped to push the recovery factor much higher than expected when development began.
By reducing pressure in the reservoirs and on the platforms, large volumes of previously-injected gas can be recovered. Gas will also be released from the remaining non-recoverable oil.
This change of strategy will increase the recovery factor for natural gas from 54 per cent of recoverable reserves to almost 71 per cent.
Statfjord is currently an oil field with associated gas, but the late life project will convert it to a gas field with associated oil.
The total investment in the Statfjord late life project is estimated at around NOK 23 billion, including the Tampen Link pipeline and the submersible pumps for Statfjord B and C.
About 52 per cent of the investment relates to modification of the installations, 38 per cent to the drilling and well programme and 10 per cent to the pipeline.
Improving recovery from Statfjord will enhance revenues. The project will also boost activity and create opportunities for further business development.
Converting existing platforms will be significantly cheaper than building new installations. Modifying them during production avoids loss of revenue from long shutdowns.
The overall value creation of the Statfjord late life project is estimated at around NOK 60 billion. This is a sixfold value increase since the project plan was submitted to the authorities in 2004.
The modified operating solution for Statfjord will reduce annual emissions of carbon dioxide and nitrogen oxides.
Produced water volumes will remain unchanged from today’s levels. Technology for water treatment has been installed to meet the official requirement for zero harmful discharges to the sea.
Oil-based drilling mud and drill cuttings will be injected below ground.
The modified plan for development and operation (PDO) for Statfjord and the plan for installation and operation (PIO) for Tampen Link were submitted to the government on 25 February 2005 and given the green light by the Norwegian Storting (parliament) on 8 June.
The construction contracts were awarded in the spring of 2005 and conversion of the platforms started in the autumn of the same year.
Gas export to St Fergus, Scotland, from the Norwegian sector of the Statfjord field began on 12 October 2007.
The facilities are being prepared for low-pressure production from the autumn of 2009 on Statfjord B and from spring 2010 on Statfjord C.
Statfjord is expected to produce beyond 2020 from Statfjord B and Statfjord C. Plans call for Statfjord A to be shut down from 2013.