Fracking is a technique involving pumping water and chemicals into shale rock at high pressure to extract gas.

BBC: Lancashire's shale gas estimated at ?136bn by Cuadrilla

The drilling technique, which uses sand, water and chemicals under high pressure to extract oil and natural gas from rock formations, has helped Eagle Ford oil production grow by 184% last year compared with 2011, according to the Railroad Commission of Texas, which regulates the state's oil and gas exploration and production.

WSJ: From Oil, a Land Rush��WSJ Mansion

Fracking is a technique where water and chemicals are pumped into shale rock at high pressure to extract gas.

BBC: Lancashire election candidates asked to oppose fracking

Fracking is a technique of shale gas extraction that involves pumping water and chemicals into shale rock at high pressure to extract gas.

BBC: Lancashire shale gas 'could be worth billions'