Once upon a time when we talked about oil, the presumption was we were talking about crude oil (or perhaps crude oil plus condensate if you were a petroleum wonk). Nowadays, when BP, the Energy Information Administration (EIA) or the International Energy Agency (IEA) publish their flagship yearly reports (see here, here and here) the lead-in charts highlight ‘All Liquids’ (click for larger image).
I’ve taken the numbers below from Table 3.4 in the IEA’s World Energy Outlook 2012 (click for larger image). Apologies for the lack of a link since the report needs to be ordered and is not freely available on the web.
As can easily be seen, traditional conventional crude oil is making up an ever smaller share of total liquids in percentage terms, falling from 88.8% in 1990 to 63.1% in 2035 under the IEA’s Current Policies scenario (basically business as usual).
This would be irrelevant if all liquids are perfectly substitutable amongst themselves; i.e., they are fungible. Unfortunately, they are not. The EIA released a great graphic yesterday showing two key determinants of fungibility (there are others): energy content per unit volume and energy content per unit weight here (click for larger image):
Risk and Well-Being 