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

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

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

Date:
08.2014

Key findings:

  • Oil and gas wells that were drilled over the last 100 years reveal highly variable well barrier and well integrity failure rates [see Notes to Editors (1) for definitions] of 1.9%-75%.
  • Between 2005 and 2013, 6.3% of the 8,030 wells drilled in the Marcellus shale have been reported to the authorities for infringements related to well barrier or integrity failure.
  • In the UK, up to 53% of the 2,152 wells, drilled onshore between 1902 and 2013, were drilled by a company that no longer exists or which has been taken over or merged.
  • Public domain data on well barrier and well integrity failure rates for onshore wells in Europe is scarce.

Abstract
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.

Source / Publisher:
Marine and Petroleum Geology
Volume 56, September 2014, Pages 239–254
– Link –

See also:
Damian Carrington, Fracking safety: report warns of ‘significant unknowns’
Sparse public data on onshore oil and gas drilling makes full extent of failures in hydrocarbon wells unknown, experts say.
The Guardian, Mar. 24, 2014

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