The report noted that while heavy oil, tar sands, shale gas, shale oil, tight sands gas, coalbed methane, and other unconventional oil and gas resources were not included, their volumes can be significant. ???For example, the mean estimate for recoverable heavy oil from the Orinoco oil belt in Venezuela alone is 513 billion bbl [a 2009 USGS Orinoco oil belt team assessment], compared to mean conve