Challenging the claims about leaky wells
It is often claimed that 6% of all oil and gas wells leak, with shale gas opponents citing a paper by Schlumberger. But this is taken out of context.
It is true that Schlumberger, one of the world’s largest oilfield services companies, did produce a document in 2003 stating that 6% of wells experience something called Sustained Casing Pressure (SCP), but it is wrong to conclude that this means 6% of all wells leak.
Firstly, the document in question related specifically and only to operations conducted on the US Offhsore Continental Shelf (OCS) in the Gulf of Mexico, where deepwater drilling is used; the environmental and operating conditions are self-evidently very different to land-based drilling.
Secondly, the Schlumberger document, and other references, make it clear that SCP does not necessarily indicate a failure of well integrity and loss of fluid or gas to soil, air or water.
Thirdly, and crucially, the Schlumberger document makes it clear that whilst conducting repairs to OCS wells is difficult because of the operating environment, is does not make this same observation of onshore wells. It also discusses the improvements that have been made to borehole construction, drilling fluids and cementing techniques that have been developed specifically to reduce the prevalence of SCP problems.
No evidence of leaky wells in the UK
The UK has a proud tradition of safely exploring for and then exploiting oil and gas onshore that dates back over 70 years, including in Lancashire, the current focus of the shale gas debate.
For instance, D’Arcy Exploration Company drilled a well at Scarisbrick in 1938 – a well that has long since been plugged and abandoned.
These activities of drilling boreholes, constructing wells and testing for the presence and flow of oil and gas have been carried out without incident at thousands of locations across the UK since, including 19 just in 2014.
If leaking wells were genuinely so prevalent, then we could expect those drilled in the last 70 years to be showing evidence of that, but we can find no such evidence.
Regulations, standards and practices are protecting us
Britain has a complex but very robust regulatory structure that, for decades, has driven improvements in the standards and practices employed to protect workers, the public and the environment from harm.
There is no reason to suspect that modern-day shale gas extraction will pose any greater risk or that the existing system of regulations, standards and practices won’t continue to safeguard us.
Keeping risks in proportion
There are undoubtedly some risks associated with shale gas, and other forms of onshore energy extraction and it would be inappropriate to claim otherwise.
But those risks are well known and understood, meaning that appropriate measures already exist to reduce and mitigate them.
It’s important to keep those risks in proportion. Under or over-stating them helps nobody.
One thing is certain: the risks of leaking wells is regularly over-stated in some quarters.