What is fracking?
Fracking, or hydraulic fracturing, is a technique for extracting shale gas by pumping water and other substances into underground shale rock formations at high pressure.
This high pressure water causes small fractures or cracks in the rock, which allows the gas (or oil) to be extracted. Sand (sometimes called the propant) is included in the injection fluid to hold the fractures open. Otherwise the the fractures could close once the pressure is removed. Other substances are included in the fluid in order to manage how the mixture of water and sand behaves.
Stages of onshore shale gas extraction
A project to extract shale gas through fracking has several stages:
- Exploration – Promoters gather and assess data to determine the availability of shale gas. This work can include seismic testing, exploratory drilling, and test fracking to understand how the rock responds. This can take 2-6 months.
- Moving into production – The site is prepared for full-scale fracking, and more vertical and horizontal boreholes are drilled. Materials including water, sand and chemicals are brought on site. This can take between half a year and two years.
- Production – The wells are fracked to extract shale gas, and waste water is taken away to be treated. This can go on for 20 years.
- Decommissioning and restoration – The site is restored to its original condition. This could happen at any stage. For example, this could happen at the exploration stage if the site is found not to be productive.
In the UK, onshore shale gas fracking operations have so far only reached the exploration phase.