Oil supply projections for individual countries are developed by a bottom-up approach using monthly information on over 700 fields, areas or other elements for over 90 countries. The contribution of individual fields is projected, taking into account growth and decline rates, maintenance schedules and start-up dates for new fields. Information provided by field operators is taken into consideration, but judgement is used if there is evidence of conservatism or optimism based on past experience. The current and expected upstream operating environment is also taken into account. For fields where production is traditionally affected by the weather, or weather-related seasonal fluctuations (e.g. the North Sea, Alaska and the US Gulf of Mexico), typical seasonal supply fluctuation is assumed. Downward revisions to supply projections are caused by new field delays and unanticipated decreases in output from mature fields due to their coming off plateau early or due to higher-than-expected rates of decline. Random events also add to downside risk. These events can include accidents, unplanned or unannounced maintenance, technical problems, labour strikes, guerrilla activity, wars and extreme weather-related supply losses, and may cause supply losses of perhaps 0.4 mb/d for non-OPEC supply each year. With effect from July 2007, forecast non-OPEC supply contains a net adjustment of -410 kb/d to reflect these factors, based on historical experience. Individual adjustments are applied at a national, but not a field-specific, level. This ‘reliability’ factor will be adjusted over time depending on actual performance.

Related Links if available:

© OECD/IEA 2009. All rights reserved.