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Durham University News

News

Research shows that well leakage is an issue for shale exploitation

(25 March 2014)

Image of Carboniferous shales in Edale, Derbyshire

Carboniferous shales in Edale, Derbyshire

ReFINE (Researching Fracking in Europe), an independent research consortium focusing on the issue of shale gas and oil exploitation using fracking methods, has today published a research paper on well barrier and integrity failure. 

The key findings are:

  • Studies of 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%. This variation in failure rates is probably due to the differences in the number of wells included in each study, their age, design and the geology they penetrate. For example, of 8,030 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 the UK, 2,152 hydrocarbon wells were drilled onshore between 1902 and 2013 mainly targeting conventional reservoirs. Between 50 and 100 of these wells are orphaned. In total, up to 53% of the 2,152 wells were drilled by a company that no longer exists or which has been taken over or merged.

 

  • Of 143 active UK wells that were producing at the end of 2000, one has evidence of a well integrity failure.

 

  • Public domain data on well barrier and well integrity failure rates for onshore wells in Europe is scarce.

 

Published in Marine and Petroleum Geology following a peer review process, the study entitled “Oil and Gas Wells and Their Integrity: Implications for Shale and Unconventional Resource Exploitation” is authored by academics from Durham University (UK), Duke University (USA) and the British Geological Survey.

Through its analysis drawing on a variety of datasets, ReFINE has undertaken one of the most comprehensive studies of its kind on the topic of well barrier and well integrity failure. The paper also sought to determine the categorisation of wells (e.g. production, abandoned, idle, and orphaned) and to review statistics on the number of wells that are known to have had some form of well barrier or well integrity failure.

Analysing data from Australia, Austria, Bahrain, Brazil, Canada, Netherlands, Poland, UK and USA, ReFINE found that at least four million hydrocarbon wells have been drilled onshore globally [see Notes to Editors (2)].

ReFINE also looked at 25 other datasets from published and online sources that report well barrier and well integrity failure [see Notes to Editors (3)]. These datasets were from eight countries published between 1989 and 2013 on onshore and offshore wells drilled in the last 100 years. The datasets vary considerably in terms of the number of wells examined, their age and designs. As such, the percentage of wells published in the 25 datasets that have some form of well barrier or well integrity failure is highly variable, between 1.9% and 75%.

ReFINE also found that up to 53% of the 2,152 hydrocarbon wells which were drilled onshore in the UK between 1902 and 2013 were drilled by companies that no longer exist, or have been taken over or merged.

The paper also made recommendations relevant to future shale exploitation that should be considered for implementation across Europe. These include:

  • Data from the systematic monitoring of active wells across Europe should be in the public domain;
  • Periodic surveys of abandoned well sites across Europe should be initiated and the findings made publicly available.

Professor Richard Davies, of Durham University and ReFINE Project Leader, said:“The findings of this research confirm that well barrier failure and well integrity failure in hydrocarbon wells is an issue and that publicly available data in Europe on this seems to be sparse. 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.”

Notes to Editors

1. Definitions of terms used: 

  • Well barrier failure: failure of cement, valves or steel casing within the well which does not lead to release of fluid into the environment. This term can also be referred to as an internal leak. 
  • Well integrity failure: failure of cement, valves or steel casing within the well which does lead to release of fluid into the environment. This term can also be referred to as an external leak. 
  • Orphaned well: the company that drilled the well has gone out of business or is insolvent, meaning that the company that operated the well is no longer responsible for it.
  • Abandoned well: a well that is no longer in use that has been sealed by using cement plugs, cut and buried according to regulation.

2. Data for set one came from: Australia, Austria, Bahrain, Brazil, Canada, Netherlands, Poland, UK and USA.

3. Data for set two came from: Bahrain, Canada, China, Indonesia, Netherlands, Norway, UK, and USA.

 

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