Hydraulic fracturing, or “fracking”, has been used since the 1950s to stimulate oil and gas wells. The process involves pumping a sand-laden slurry into a well and subjecting it to enough pressure that the rocks in the productive formation fracture, or break. The purpose of the sand is to prop open the fracture, so it stays in place. The carrying fluid can then flow back out of the well, along with oil and gas if it’s been a successful frac.
The technique of hydraulic fracturing is used to increase or restore the rate at which fluids, such as oil, gas or water, can be produced from a reservoir, including unconventional reservoirs such as shale rock or coal beds.
Hydraulic fracturing enables the production of natural gas and oil from rock formations deep below the earth's surface (generally 5,000-20,000 feet or 1,500-6,100 m). At such depth, there may not be sufficient porosity and permeability to allow natural gas and oil to flow from the rock into the wellbore at economic rates. For example, creating conductive fractures in the rock is essential to produce gas from shale reservoirs because of the extremely low natural permeability of shale. The fracture provides a conductive path connecting a larger area of the reservoir to the well, thereby increasing the area from which natural gas and liquids can be recovered from the targeted formation.