Includes natural gas from deep wells, coalbed methane, tar, shale, tight sands and other sources that are more difficult and costly to develop than conventional sources. Indeed, tightening global oil supply, regional tightening in gas supply and demand growth have resulted in an ever increasing interest in the exploitation of unconventional hydrocarbons. The development of deepwater offshore fields and tar sands require prices of $60 – $80 a barrel to be viable