Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Unconventional oil is petroleum produced or extracted using techniques other than the traditional oil well method. Unconventional oil production is less efficient and has more environmental impacts than conventional oil production. Oil Industries and governments are investing in unconventional oil sources due to the increasing scarcity of conventional oil reserves.Unconventional sources of oil will be increasingly relied upon as motor fuel for transportation when conventional oil becomes "economically non-viable" due to depletion. Conventional sources of oil are currently preferred because they provide a much higher ratio of extracted energy over energy used in extraction and refining processes. Technology, such as using steam injection in oil sands deposits, is being developed to increase the efficiency of unconventional oil production.