“…6 For this reason, the industry is seeking unconventional oil supplies, such as heavy oil deposits, tar sands, and oil shales, which may require novel extraction technologies and involve higher costs. 7 Natural gas consists primarily of methane, alkenes, and other impurities, and is used for heating, cooking, and electricity production, but it is also slowly replacing oil because the cost of liquefaction and transportation is diminishing. Unconventional gas reservoirs such as coal beds and shales are a quickly growing component of the U.S. gas supply, due mainly to the development of hydraulic fracturing (fracking) and horizontal drilling.…”