(Source: Lloyd’s of London)
Hailed by some as a potential saviour to the energy crisis facing the world, and by others an environmental disaster, hydraulic fracturing or “fracking”, is the process of drilling and injecting fluid into the ground at a high pressure in order to fracture shale rocks to release natural gas inside.
Banned by many governments, it is certainly a controversial topic. More recently it hit the news in the UK after earth tremors in Lancashire in 2011 were linked to shale gas test drilling. One tremor of Magnitude 2.3 hit the Fylde coast on 1 April, followed by a second of M1.4 on 27 May.
However a study of hundreds of thousands of fracking operations has concluded the process only caused earth tremors that could be felt on the surface in three cases. The study was funded by Durham University and Keele University.
“The fracking operations were suspended in 2011 after two relatively small earthquakes – which from the catastrophe modelling point of view can be considered minor tremors, ” says Milan Simic, managing director of AIR Worldwide. “But they happened relatively quickly and there was a genuine concern that on a larger scale fracking could potentially cause stronger events.”
The Durham study found that almost all of the resultant seismic activity from hydraulic fracturing was on such a small scale that only geoscientists would be able to detect it.
“Most fracking-related events release a negligible amount of energy roughly equivalent to or even less than someone jumping off a ladder onto the floor, ” said Richard Davies, from the Durham Energy Institute.
“Of the three fracking-related quakes that could be felt, even the largest ever recorded, in the Horn River Basin in Canada in 2011 had a magnitude of only 3.8. That is at the lower end of the range that could be felt by people. The widely-reported earthquake at Preese Hall near Blackpool in 2011 had a magnitude of 2.3.”
However, the underground injection of oil-drilling waste water has been shown to cause more significant seismic activity. While this practice is banned by EU legislation, recent research in the US linked it to a M5.7 earthquake in Oklahoma in 2011.
Mining and dams trigger quakes
While fracking may not cause significant earthquakes, other forms of mining can. “It is worth bearing in mind that other industrial-scale processes can trigger earthquakes including mining, filling reservoirs with water and the production of oil and gas, ” added Davies. “Earthquakes caused by mining can range from a magnitude of 1.6 to 5.6, reservoir-filling from 2.0 to 7.9 and waste disposal from 2.0 to 5.7.”
Some scientists have hypothesized that the Zipingpu dam and reservoir was responsible for the 2008 Great Sichuan earthquake.
Another reservoir blamed for triggering an earthquake is the Koyna Dam in India, which is thought to have contributed to the 1967 Koynanagar earthquake.
“For tall dams where there is a huge volume of water, that pressure on the slopes of the reservoir could cause events, ” says Simic. “There have been a number of events caused by filling a deep reservoir, several in India and more recently in China when the Three Gorges Dam was created.”
Backing fracking in Europe
Fracking activities in the UK and Europe are ramping up. The technology for shale oil and gas extraction has come along significantly over the past decade and is widely credited for lowering domestic oil prices in the US. It is also thought to have helped lower greenhouse gas emissions because it has encouraged more use of gas than coal.
Europe has several rich basins of shale gas reserves with the UK, France, Spain, Germany, Poland, Romania and Bulgaria thought to have the most potential.
In the UK, fracking was given the green light by the government in December 2012. In June 2012 the Royal Society and the Royal Academy of Engineering concluded that the health, safety and environmental risks associated with the technique can be effectively managed. The British Geological Survey estimates UK shale gas resources may be 50% larger than conventional gas sources.
However, fracking remains a controversial practice. “While the UK government seems quite happy there are still potential unknowns and uncertainties. Until recently fracking was banned in Poland and France so it’s still quite a controversial topic, ” says Neil Smith, Lloyd’s manager of emerging risks and research. “From an emerging risk point of view we’re probably more concerned about the risks of water contamination.”
“As part of the fracking process a mixture of sand, water and chemicals is blasted into the shale, ” adds Simic. “All the chemicals constitute about 1% of the fracking materials, but nevertheless in the huge volumes we’re talking about, there are significant amounts of chemicals being pumped into the ground and there are concerns that it could affect the aquifers and quality of ground water.”