According to the International Energy Agency's (IEA) World Energy Outlook 2001 unconventional oil included "oil shales, oil sands-based synthetic crudes and derivative products, (heavy oil, Orimulsion®), coal-based liquid supplies, biomass-based liquid supplies, gas to liquid (GTL) - liquids arising from chemical processing of gas." .
In the IEA's World Energy Outlook 2011 report, "[u]nconventional oil include[d] extra-heavy oil, natural bitumen (oil sands), kerogen oil, liquids and gases arising from chemical processing of natural gas (GTL), coal-to-liquids (CTL) and additives." .