Hydraulic fracturing (fracking) is a technique used to extract hydrocarbons trapped in certain types of rock. In particular the widespread use of fracking is being driven by the expansion in shale gas extraction.
How does hydraulic fracturing work?
Hydraulic fracturing uses pressurised fluid to free trapped gas. Wells are drilled and the fracking fluid injected into them under high pressure to crack the rock. The fracking fluid consists of water, sand and a massive amount of chemicals. Millions of gallons of water (and hundreds of tons of chemicals) are used to frack a well.