Proved reserves

In 2011, Shell added 1,205 million boe of SEC proved oil and gas reserves before accounting for the year’s production. At the end of the year, total proved oil and gas reserves excluding non-controlling interest were 14,250 million boe (10,304 million boe for Shell subsidiaries and 3,946 million boe for equity-accounted investments). Reserve life (an estimate of how many years it would take to exhaust the current proved reserves at the current level of production) has increased from 10 years at the end of 2007 to approximately 12 years at the end of 2011.

The Reserves Replacement Ratio for Shell subsidiaries and equity-accounted investments was 99% in 2011 (and 165% over the last three years). Excluding acquisitions, divestments and price effects, the ratio was 127% in 2011 and 175% in the period 2009–2011.

The largest crude-oil proved reserves additions in 2011 were from field performance studies for development activities in Europe (140 million barrels, primarily Italy and the UK) and Africa (128 million barrels). An extension of mining operations in Alberta, Canada also added significantly to proved reserves (116 million barrels). The main increase in natural gas reserves came from: field extensions and discoveries associated with LNG integrated projects in Australia (1,471 billion scf); revisions and reclassifications in Denmark, Norway, Ireland and the UK that resulted from better production performance and development activities (990 billion scf); and extensions and discoveries related to development drilling in Canada (816 billion scf).

Proved reserves can be either developed or undeveloped. Subsidiaries’ proved oil-equivalent reserves at the end of 2011 were divided into 63% developed and 37% undeveloped. For the Shell share of equity-accounted investments the proved oil-equivalent reserves were divided into 76% developed and 24% undeveloped.