The 330 bbo value is considerably greater than the 95 bbo value indicated above as the remaining resource - the difference in these numbers reflects the difference in the costs of extraction. The estimate above is 1400 bbo for the remaining resource, assuming reasonable cost of extraction. 15 bbo is ultimately recoverable by enhanced recovery. This oil is a target for high cost enhanced recovery. Resources of Unconventional Oil Shale oil is a huge potential resource.
Questions are recoverability and environmental impact.
Tar sands and heavy oil are a large resource, though not as great as the shale oil. There is a lot of oil in the earth, especially if shale oil is included. Natural Gas Resources Use of gas began later than the use of oil. The gas resource may be greater than previously estimated. Although gas produces less air pollution and greeenhouse gases than other fossil fuels, there still are significant environmental impacts from large-scale use of gas.