The modelling methodology is the same as in my previous analyses, which started 20 years ago, namely the use of a multi-cycle logistic curve (and its derivatives) to extrapolate the future. The ultimate reserves are those extrapolated from the creaming curve. In a creaming curve, the cumulative backdated 2P reserves (proved plus probable, with the mean value assumed) is plotted versus the cumulative number of discovered fields (or of the new field wildcats). The reserves in the creaming curve incorporate all past revisions and reserve hikes, attributed to the year of original discovery. Very few countries report production and reserves by field: the UK (DECC), Norway (NPD) and the US for the Federal offshore. Therefore, one has to rely on expensive scouting and scout databases, which are not available to the general public. But even then, the scout databases need to be corrected to estimate the actual “2P” reserves.

via The Oil Drum | World Oil and Gas Production Forecasts Up to 2100.