How much oil remains for the world to produce? Comparing assessment methods, and separating fact from fiction

This paper assesses how much oil remains to be produced, and whether this poses a significant constraint to global development. We describe the different categories of oil and related liquid fuels, and show that public-domain by-country and global proved (1P) oil reserves data, such as from the EIA or BP Statistical Review, are very misleading and should not be used. Better data are oil consultancy proved-plus-probable (2P) reserves. These data are generally backdated, i.e. with later changes in a field's estimated volume being attributed to the date of field discovery. Even some of these data, we suggest, need reduction by some 300 Gb for probable overstatement of Middle East OPEC reserves, and likewise by 100 Gb for overstatement of FSU reserves. The statistic that best assesses ‘how much oil is left to produce’ is a region's estimated ultimately recoverable resource (URR) for each of its various categories of oil, from which production to-date needs to be subtracted. We use Hubbert linearization to estimate the global URR for four aggregate classes of oil, and show that these range from 2500 Gb for conventional oil to 5000 Gb for ‘all-liquids’. Subtracting oil produced to-date gives estimates of global reserves of conventional oil at about half the EIA estimate. We then use our estimated URR values, combined with the observation that oil production in a region usually reaches one or more maxima when roughly half its URR has been produced, to forecast the expected dates of global resource-limited production maxima of these classes of oil. These dates range from 2019 (i.e., already past) for conventional oil to around 2040 for ‘all-liquids’. These oil production maxima are likely to have significant economic, political and sustainability consequences. Our forecasts differ sharply from those of the EIA, but our resource-limited production maxima roughly match the mainly demand-driven maxima envisaged in the IEA's 2021 ‘Stated Policies’ scenario. Finally, in agreement with others, our forecasts indicate that the IPCC's ‘high-CO2’ scenarios appear infeasible by assuming unrealistically high rates of oil production, but also indicate that considerable oil must be left in the ground if climate change targets are to be met. As the world seeks to move towards sustainability, these perspectives on the future availability of oil are important to take into account.