In the UK, there has been much furore and heated debate about shale gas hydraulic fracturing, or fracking, in recent months and it is quite possible that in the media melee the risks of enduring environmental damage have been over stated or inaccurately reported. Leaving to one side the question of whether or not we should be developing and exploiting unconventional gas sources by fracking at all, it is worth perhaps refocussing on the environmental issues.
All on-shore oil and gas wells are essentially the same and to a very large degree the enduring environmental sensitivities are common in all cases. These can be broadly divided into two: those associated with materials and chemicals brought to site and used in the operation; and those, naturally occurring, encountered at depth and as a result of the well bore either brought to the surface or transferred to other parts of the drilled formation. Clearly, there are other, shorter term environmental concerns common to many industrial activities, such as noise and issues associated with increased traffic.
In addition to water (and depending on the planned depth and geological conditions a typical shale gas fracturing operation requires between 5 and 25 thousand tonnes of water) there are numerous chemical additives brought on site, stored and used in the operation. There are those required for the drilling operation itself (the components of drilling water-based ‘mud’) and then there are those used in the fracking process. The former group traditionally includes a gelling agent such as bentonite clay and a weighting agent such as barium sulphate (barite). Other common additives include thickening agents, deflocculants, lubricating agents and corrosion inhibitors.
The full article, by Robin MacDonald, is available in Issue 4 of Shale Gas International Magazine and can be found on page 43.