Shale gas is natural gas – Shale gas is natural gas extracted from sedimentary shale rock composed of organically rich mud and clay. Geologists have known about these resources for a long time but they were not developed because of cost and productivity issues. The situation changed in the late-1990s, when a combination of two existing, proven technologies (horizontal drilling and hydraulic fracturing) and rising prices made shale gas commercially viable in the US and Canada. Since then, production has consistently increased, as have the estimates of total global shale resources. According to the US Energy Information Administration (EIA), 32% of the total global estimated natural gas resources are in shale formations. Although aglobal gas production has doubled over the past thirty years, proven resources continue to increase: the new global shale gas resource estimate (EIA 2013) – 7,299 trillion cubic feet – is 10% higher than the EIA’s 2011 estimate.