Explainer: What is fracking?

Fracking comes from the term hydraulic fracturing and is a process used to extract natural gas from the ground.

The controversial method involves drilling down at least a mile into layers of shale into deposits of national gas. The gas is extracted by pumping in millions of gallons of high pressure water, sand and chemicals into a well to fracture the rock, allowing the gas to escape through to the cracks to the surface.

A significant number of wells are needed in order to produce a high volume of gas.

STAGE ONE - EXPLORATION

Exploratory drilling to identify if oil or gas can be produced profitably. The operator may do tests or take samples of the shale rock, conduct one or more fracks and flow testing.

A 'pad' is built and a 30m tall drilling rig is installed. The operator may need to transport equipment, water and chemicals to and from the site. This part of the process takes approximately two to six months.

In order to be given permission to drill in areas of potential tracking, companies need the following:

• Landowner(s) agreement

• Planning permission

• Environment Agency permit

• Examination from the Health and Safety Executive

• Consent from the Department of Energy and Climate Change

STAGE TWO - MOVING INTO PRODUCTION

If a site is suitable for production, more wells will be drilled and tracked. Water, chemicals, equipment and material is brought on and off site, while waste water is removed for treatment and disposal. It can take up to two years to move into production.

STAGE THREE - PRODUCTION

Maintenance activity will take place and more wells could be drilled, but the overall level activity is likely to decline over a 20 year period of production.

STAGE FOUR - DECOMMISSIONING AND RESTORATION

Restoring a stie to its original conditions includes making the wells safe for abandonment and the removing surface installations.

Decommissioning and restoration can happen at any time in the process.