What is shale gas?
Shale gas is a form of unconventional natural gas (mostly methane), which is trapped underground in shale rock; a fine-grained, less permeable rock formation made up of mud, silt and clay deposits, alongside organic matter.
Unconventional gases like shale gas do not flow easily through rock, and so additional intervention is needed to extract these gases for commercial use. Hydraulic fracturing (or fracking) and horizontal drilling are required.
Recovery rates for unconventional gases like shale gas are much lower than conventional gases (which are natural gases found in sandstone, siltstone or limestone). Typically, only 15 to 30 per cent of the gas in place can actually be extracted, compared to around 80 per cent for conventional gas.
