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Oil and gas wells and their integrity: implications for shale and unconventional resource exploitation

Davies, Richard J.; Almond, Sam; Ward, Robert S.; Jackson, Robert B.; Adams, Charlotte; Worrall, Fred; Herringshaw, Liam G.; Gluyas, Jon G.; Whitehead, Mark A.


Richard J. Davies

Sam Almond

Robert S. Ward

Robert B. Jackson

Charlotte Adams

Fred Worrall

Liam G. Herringshaw

Jon G. Gluyas

Mark A. Whitehead


Data from around the world (Australia, Austria, Bahrain, Brazil, Canada, the Netherlands, Poland, the UK and the USA) show that more than four million onshore hydrocarbon wells have been drilled globally. Here we assess all the reliable datasets (25) on well barrier and integrity failure in the published literature and online. These datasets include production, injection, idle and abandoned wells, both onshore and offshore, exploiting both conventional and unconventional reservoirs. The datasets vary considerably in terms of the number of wells examined, their age and their designs. Therefore the percentage of wells that have had some form of well barrier or integrity failure is highly variable (1.9%–75%). Of the 8030 wells targeting the Marcellus shale inspected in Pennsylvania between 2005 and 2013, 6.3% of these have been reported to the authorities for infringements related to well barrier or integrity failure. In a separate study of 3533 Pennsylvanian wells monitored between 2008 and 2011, there were 85 examples of cement or casing failures, 4 blowouts and 2 examples of gas venting. In the UK, 2152 hydrocarbon wells were drilled onshore between 1902 and 2013 mainly targeting conventional reservoirs. UK regulations, like those of other jurisdictions, include reclamation of the well site after well abandonment. As such, there is no visible evidence of 65.2% of these well sites on the land surface today and monitoring is not carried out. The ownership of up to 53% of wells in the UK is unclear; we estimate that between 50 and 100 are orphaned. Of 143 active UK wells that were producing at the end of 2000, one has evidence of a well integrity failure.


Davies, R. J., Almond, S., Ward, R. S., Jackson, R. B., Adams, C., Worrall, F., …Whitehead, M. A. (2014). Oil and gas wells and their integrity: implications for shale and unconventional resource exploitation. Marine and Petroleum Geology, 56, 239-254.

Journal Article Type Review
Acceptance Date Mar 1, 2014
Online Publication Date Mar 25, 2014
Publication Date 2014-09
Deposit Date Mar 21, 2016
Publicly Available Date Mar 21, 2016
Journal Marine and petroleum geology
Print ISSN 0264-8172
Electronic ISSN 1873-4073
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 56
Pages 239-254
Keywords Shale, Fracking, Integrity, Barrier, Integrity, Wells
Public URL
Publisher URL
Additional Information This article is maintained by: Elsevier; Article Title: Oil and gas wells and their integrity: Implications for shale and unconventional resource exploitation; Journal Title: Marine and Petroleum Geology; CrossRef DOI link to publisher maintained version:; Content Type: article; Copyright: Copyright © 2014 The Authors. Published by Elsevier Ltd.


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