In 2011, Statoil delivered total entitlement liquids and gas production of 1,650 mboe per day, down 3% from 1,705 mboe per day in 2010. Total equity liquids and gas production decreased by 2% from 2010, to 1,850 mboe per day in 2011, mainly caused by reduced water injection at Gullfaks, challenges primarily related to risers, maintenance shut downs and deferral of gas sales. In addition, expected reductions due to natural decline on mature fields and suspended production in Libya contributed to the decrease. This decrease was partly offset by production from start-up of new fields, ramp-up of production on existing fields and increased ownership shares.
Despite reduced production, net operating income was up 54% at NOK 211.8 billion in 2011, compared to NOK 137.3 billion in 2010. The increase was mainly attributable to higher prices for both liquids and gas, reduced net impairment losses, unrealised gains on derivatives and gains on sale of assets mainly related to the sale of interests in Peregrino, the Kai Kos Dehseh oil sands and Gassled in 2011. Lower volumes of both liquids and gas sold, increased operating expenses and net impairment losses partly offset the increase in net operating income.
Statoil's exploration programme for 2011 totalled 41 exploration wells completed before 31 December 2011. Sixteen of them were drilled outside the Norwegian continental shelf (NCS). A total of 22 wells were announced as discoveries during 2011. Seventeen of them are located on the NCS.
In 2011, 599 mmboe of proved reserves were added through revisions, extensions and discoveries, compared to additions of 526 mmboe in 2010, also through revisions, extensions and discoveries.
Statoil achieved a reserve replacement ratio of 117% in 2011, compared to 87% in 2010. The increase in 2011 is related to positive revisions of the proved reserves in several of our producing fields, newly sanctioned field development and increased recovery projects, several new wells in production in the Marcellus and the Eagle Ford shale gas acreage and purchase of the Bakken oil play in North America.
Statoil progressed two new projects into production in 2011: the Peregrino field in Brazil and the Pazflor field in Angola both came on stream.