A review of the uncertainties in estimates of global oil resources

▸ We examine the individual categories within 'conventional' and 'unconventional' oil. ▸ Intrinsic uncertainties are found within every category of oil. ▸ Methods are suggested for mitigating or reducing these in future assessments. ▸ Future assessments should acknowledge these issues and assess their impacts. ▸ We estimate recoverable light tight oil resources to be between 150 and 508 billion barrels.