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The lack of publicly available data on the UK's onshore oil and gas drilling means there are significant "unknowns" about the safety of future fracking wells, according to a new study. The research also found that public data from the US showed that hundreds of recent shale gas wells in Pennsylvania have suffered failures that could cause water or air pollution.
"The research confirms that well failure in hydrocarbon wells is an issue and that publicly available data in Europe on this seems to be sparse," said Professor Richard Davies of Durham University, and who led the team of academics who undertook the work. "In the UK, wells are monitored by well inspectors but there is no information in the public domain, so we don't really know the full extent of well failures. There were unknowns we couldn't get to the bottom of."
The research analysed every reliable dataset on the 4m onshore hydrocarbon wells that have been drilled around the world since the industry began a century ago, in order to assess the implications for unconventional oil and gas exploitation, including shale gas. The study focused on well failures, in which the cement, steel casing or valves failed to contain the oil, gas and drilling fluids. It noted the difference between internal failures, where gas, oil or other chemicals did not leak into the wider environment and external failures, where leaks did enter rocks, water acquifers or the air.
While a lot of well data is made public in the US, it was not detailed enough for the researchers to distinguish serious and minor well failures. "But in the UK we don't even have that," said Davies.
The study, published on Tuesday in the journal Marine and Petroleum Geology, reported that 2,152 wells have been drilled onshore in the UK since 1902. But no producing shale gas wells exist yet in the UK and, for a comparison, Davies said: "It is sensible to look at the data from Pennsylvania." One dataset highlighed found that 8,030 fracking wells targetting the Marcellus shale in Pennsylvania were inspected between 2005-2013 and 6.3% (506 wells) were reported for internal or external well barrier failures.
Analysis of another Pennsylvania dataset of 3,533 wells between 2008-2011 found that one-third were issued with environmental violation notices. These were mostly for surface water contamination, land spills or problems with site restoration. But 2.6% (91 wells) suffered some internal or external well barrier failures, including four blowouts. "Measurable concentrations of gas we present at the surface for most wells with casing or cementing violations," the researchers wrote.
In the UK, data provided to the researchers by the Department of Energy and Climate Change (Decc), the Environment Agency and operating companies showed 143 onshore oil and gas wells were producing in 2000. Of nine recorded oil spills, two (at the same site) were linked to well barrier problems. "But that may be an underestimate," said Davies. "The intuition is that it is not a problem, but intuition is not good enough." The study also noted that the ownership of over half the wells drilled in the UK since 1902 was now unclear and that no monitoring was now taking place for at least two-thirds of the wells ever drilled.
Davies said: "The data from the monitoring of active wells and the carrying out of periodic surveys of abandoned wells would help assess the impact of shale exploitation and it is important that the public should have access to this information." The study was funded by the UK taxpayers via the Natural Environment Research Council and by Total, Shell and Chevron and was commissioned by an independent academic board.
A Decc spokesman said: "The report highlights just how important well construction is as part of safe and environmentally sound exploration. Decc and the industry are working together to put in place a robust scheme that would cover monitoring and liabilities even in the event that the relevant operator is no longer in business. Experts will also consider all aspects of the design and construction of wells, including how they will be made safe after they are no longer in use."
But Tony Bosworth, energy campaigner at Friends of the Earth, said: "Going after these risky sources of energy threatens our natural world as regulation can only go so far in protecting people, our water supplies and the wider environment. This report highlights that oil and gas well failure is widespread and the best way to avoid the risk this brings is not to frack or go after other hard to reach and polluting fossil fuels."
Previously, the Guardian revealed that fracking company Cuadrilla was chastised in 2012 by ministers for "failing to recognise the significance" of deformation of a well casing at its Preese Hall drill site in Lancashire. The "failure" exposed "weaknesses in Cuadrilla's performance as a licensee" but the integrity of the well was not compromised and there were no leaks.
The UK Onshore Operators Group (UKOOG), the trade body for the onshore oil and gas industry, said its guidelines state that monitoring data should be publicly available and it welcomed the recommendation to monitor abandoned wells. Ken Cronin, UKOOG chief executive, said: "It is important to note that the research focuses on historical records and studies. The industry and its practices are constantly improving with experience and technology as required by regulation."
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