The determination of big energy companies to make significant investments in shale gas exploration seems to be showing no signs of abating despite environmental concerns across the globe.

Bloomberg’s Julie Hyman reported from the US that overseas deals involving shale exploration added up to $51bn last year.

She said the hunt for new shale gas opportunities seemed unaffected by the fact that natural gas prices had plummeted and she attributed this partly to the fact that shale exploration also taps into reserves of ethane, butane and methane which have not seen prices fall to the same degree.

The controversial fracking method used in shale gas extraction involves pumping water, sand and chemicals into fissures in the ground to allow the release of oil and gas. Some environmentalists have questioned whether the process leads to chemical seepage in ground water and the presence of chemicals in water has been confirmed during tests in the US Mid West.

Some observers have also blamed earthquakes and tremors in Blackpool, England, and Ohio in the USA on shale gas exploration.

However, energy companies continue to explore large parts of the US including Pennsylvania, Ohio, Texas and Oklahoma and the Financial Times reported in November that the UK has “significant” shale gas reserves.