Hydraulic fracturing is the fracturing of various rock layers by a pressurized liquid. Some hydraulic fractures form naturally—certain veins or dikes are examples—and can create conduits along which gas and petroleum from source rocks may migrate to reservoir rocks. It is a technique used to release petroleum. This type of fracturing creates fractures from a wellbore drilled into reservoir rock formations.

The first experimental use of hydraulic fracturing was in 1947, and the first commercially successful applications in 1949. As of 2010, it was estimated that 60% of all new oil and gas wells worldwide were being hydraulically fractured.[2] As of 2012, 2.5 million hydraulic fracturing jobs have been performed on oil and gas wells worldwide, more than one million of them in the United States.