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 68%.
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 75 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.
Investments
The Statfjord late phase development is costed at NOK 17.9 billion in current money, while Tampen Link – including pipeline-related modifications on Statfjord B – will cost NOK 2.1 billion.
The Statfjord late life project is intended to improve recovery from this StatoilHydro-operated North Sea field and keep it on stream until 2019.
This will be achieved with a very extensive well programme as well as modifications to the platforms. The associated Tampen Link pipeline is also being laid to export increased gas output.
Crude production from Statfjord is in decline, with well over 60 per cent of the stock tank oil originally in place (Stooip) already recovered. This recovery factor is expected to reach 68 per cent over the next few years.
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.
Environment
The modified operating solution for Statfjord will reduce annual emissions of carbon dioxide and nitrogen oxides by 38 and 28 per cent respectively in 2007.
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.
Schedule
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 until 2020 from Statfjord B and Statfjord C. Plans call for Statfjord A to be shut down from 2013.
