Hydraulic fracturing — or ‘fracking’, as it is popularly known — presents a “very low risk” of contaminating drinking water or triggering forceful earthquakes in the United Kingdom, and can safely be performed as long as companies engage in different practices from those that have produced concern in the United States.
This was the conclusion of an independent review of the controversial practice — in which a mixture of water, sand and proprietary chemicals are injected under high pressure into wells — published by the Royal Society and the Royal Academy of Engineering today. The method fractures shale, creating fissures that allow previously inaccessible natural gas to flow more easily out of the well.
“The most common areas of concern, such as the causation of earthquakes with any significant impact or fractures reaching and contaminating drinking water were very low risk,” said Robert Mair, the chairman of the review’s working group.
Recent controversy over the practice was highlighted by the 2011 release of Gasland, a North American documentary notable for its clips of people lighting running tap water on fire. The director argued that fracking was contaminating drinking water with methane.
In June last year, France banned le fracking, and last month, Vermont became the first US state to outlaw the practice. Moratoria have been imposed in Pennsylvania, New York, Quebec, South Africa and Bulgaria.
However shocking images of fireballs in kitchen sinks may be, the UK report said that none of the claims of contaminated water have shown evidence of chemicals found in hydraulic-fracturing fluids and that water wells in areas of shale-gas extraction have historically shown high levels of naturally occurring methane. This methane already in water wells may, however, be “mobilized by vibrations and pressure pulses associated with the drilling”.
Earth tremors caused by the practice are also likely to be of smaller magnitudes than England normally experiences or those related to coal-mining activities.
Last November, a report commissioned by energy firm Cuadrilla Resources based in Staffordshire, UK, concluded that it was highly probably that shale-gas drilling triggered two small tremors in Lancashire, but that this was caused by the unusual geology of the well site. The report from the Royal Society and Royal Academy of Engineering advised that seismic-risk assessments should be carried out at every site and real-time seismic monitoring employed so that operators can shut down activities promptly.
The investigators suggested that most environmental concerns springs from “improper operational practices” in the United States.
“There has been much speculation around the safety of shale-gas extraction following examples of poor practice in the US,” Mair continued. The review highlights a case of contaminated drinking water in Wyoming, in which the well casing was poorly constructed and the shale formations that were fractured were as shallow as 372 metres. Fracking normally enables the production of natural gas from rock formations between 2,000 and 6,000 metres below the Earth’s surface.
So long as shale-gas extraction occurs at depths of many hundreds of metres or kilometres, the risk of fractures reaching overlying aquifers is very low.
“This is not to say hydraulic fracturing is completely risk-free,” Mair said. “Strong regulation and robust monitoring systems must be put in place and best practice strictly enforced.”
The report calls for mandatory risk assessment for all such operations, adding that risks should be assessed across the entire life cycle of gas extraction, including the disposal of waste water and the abandonment of wells. Methane and other contaminants in groundwater should be monitored before, during and after operations.
Critics of the practice in the United States have demanded that energy companies disclose the mix of chemicals added to slurry injections, but some firms maintain that this information is proprietary. In the United Kingdom, disclosure of the constituents of fracturing fluid is mandatory. Nonetheless, the reviewers suggested that the use of non-hazardous chemical additives, where possible, would help to mitigate the impact of any leak or spill.
The report was also sympathetic to concerns over stresses to local water resources caused by the vast volumes of water involved in the practice, and said that waste water should be recycled and salt water used instead of fresh water.
The authors restricted themselves to health and safety risks and immediate environmental threats, and did not consider the consequences for climate change from the use of the gas resources that are extracted.
The working group was led by chair Robert Mair, a civil engineer who advised on the construction of a London Underground extension and the construction of the Channel Tunnel. He was joined by seven geologists and civil engineers, including one fault-zone structure expert, who have variously been involved in oil exploration, underground gas storage, coal-gas extraction and carbon capture and storage for employers such as BP, Conoco and StatoilHydro, all of which engage in fracking. Conoco, for its part, has called on the industry to use less water in fracking, and StatoilHydro backs public disclosure of fracking-fluid additives.