Unconventional oil is petroleum produced or extracted using techniques other than the conventional method (oil well). Industry and governments across the globe are investing in unconventional oil sources due to the increasing scarcity of conventional oil reserves. Unconventional oil and gas have already made a dent in international energy linkages by reducing US energy import dependency. Sources According to the International Energy Agency's (IEA) World Energy Outlook 2001 unconventional oil included "oil shales, oil sands-based synthetic crudes and derivative products, (heavy oil, Orimulsion®), coal-based liquid supplies, biomass-based liquid supplies, gas to liquid (GTL) - liquids arising from chemical processing of gas." In the IEA's World Energy Outlook 2011 report, "[u]nconventional oil include[d] extra-heavy oil, natural bitumen (oil sands), kerogen oil, liquids and gases arising from chemical processing of natural gas (GTL), coal-to-liquids (CTL) and additives." Definition In their 2013 webpage jointly published with the Organisation for Economic Co-operation and Development (OECD), the IEA observed that as technologies and economies change, definitions for unconventional and conventional oils also change. According to the US Department of Energy (DOE), "unconventional oils have yet to be strictly defined." In a communication to the UK entitled Oil Sands Crude in the series The Global Range of Crude Oils, it was argued that commonly used definitions of unconventional oil based on production techniques are imprecise and time-dependent. They noted that the International Energy Agency does not recognize any universally accepted definition for "conventional" or "unconventional" oil. Extraction techniques that are categorized as "conventional" use "unconventional means" such as gas re-injection or the use of heat" not traditional oil extraction methods. As the use of newer technologies increase, "unconventional" oil recovery has become the norm not the exception. They noted that the Canadian oil sands production "pre-dates oil production from areas such as the North Sea (the source of a benchmark crude oil known as "Brent"). Under revised definitions, petroleum products, such as Western Canadian Select, a heavy crude benchmark blend produced in Hardisty, Alberta may migrate from its categorization as unconventional oil to conventional oil because of its density, even though the oil sands are an unconventional resource. Oil sands Oil sands generally consist of extra heavy crude oil or crude bitumen trapped in unconsolidated sandstone. These hydrocarbons are forms of crude oil that are extremely dense and viscous, with a consistency ranging from that of molasses for some extra-heavy oil to as solid as peanut