Forty per cent of remaining gas may be `unconventional`

18th June 2013 -- According to new research, which builds on a recent report by UKERC on 'unconventional' gas for the European Commission, 40 per cent of the world's remaining gas resources could come from unconventional sources such as shale gas.

However, the study warns that there are huge uncertainties about exactly how much unconventional gas will be available in the future, particularly given the relative absence of peer-review and insufficient information on data, assumptions and methodology.

The review “Unconventional gas – A review of regional and global resource estimates” is published in the journal Energy and looks at over sixty studies on unconventional gas resources (shale gas, tight gas and coal bed methane). The paper finds that using ‘best’ estimates around 286 trillion cubic metres of unconventional gas could be feasibly recovered.

There is growing interest in unconventional gas across the globe; between 2006 and 2010 shale gas production in the United States increased ten-fold, sharply reducing US gas prices and leading to an oversupply of liquefied natural gas on world markets.

“Making predictions on the availability of unconventional sources of gas is hugely important to world commodity markets as well as in determining the future direction of energy policy,” said lead author of the paper Christophe McGlade from University College London.

“But making predictions on the recoverable resource of the unconventional gases is notoriously difficult, being sensitive to numerous assumptions over geology and extraction rates. Without a detailed description of the methodology used to generate resource figures, it is hard to have much confidence in many of the estimates quoted.” he added.

More than two thirds of the unconventional gas and a quarter of the total amount of gas available globally is likely to come from shale deposits. Nevertheless, even in the United States, the country with by far the best characterised resource, estimates of shale gas availability vary hugely, ranging from 64 per cent to 230 per cent of the central estimate.

US experience suggests that shale gas deposits are very heterogeneous meaning that estimates simply assuming uniform productivity across a deposit are likely to significantly overestimate the true potential. Coupled with the inadequate treatment of uncertainty and inconsistencies in terminology and definitions, this means that the range of uncertainty remains extremely wide.

The review concludes that while the unconventional gas resource is potentially very large, the uncertainty in estimates is underappreciated, while the extent to which these technically recoverable resources will ultimately become economically recoverable is also far from clear.