The British Geological Survey (BGS) in partnership with the Researching Fracking in Europe consortium has published a review of global oil and gas well integrity*. The study covers some 25 on well barrier and integrity failure datasets from the estimated four million onshore hydrocarbon wells drilled globally. The BGS’ Rob Ward said, ‘Hydrocarbon well integrity problems are a real issue. While there has been only one reported incidence of a UK onshore well causing pollution due to integrity failure, there is a lack of information for the many hundreds of other abandoned wells.’
Abandoned wells in the UK are sealed with cement, cut below the surface and buried, but are not subsequently monitored. The reported numbers are likely to underestimate the number of wells that have failed. Knowledge of the risks would be better if systematic, long-term monitoring data from both active and abandoned wells were in the public domain. It is also probable that some wells in the UK and Europe will become orphaned and it is important that the appropriate financial and monitoring processes are in place so that legacy issues associated with the drilling of wells for shale gas and oil are minimised.
The risks associated with well integrity failure need to be taken very seriously. Wells drilled onshore in the future (including those for shale gas) will be subject to strict regulatory controls that require a detailed environmental risk assessment to be carried out, approval of well design by an independent inspector, well integrity testing and effective groundwater monitoring.
* Oil and gas wells and their integrity: Implications for shale and unconventional resource exploitation. March 2014 Journal of Marine and Petroleum Geology.
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