Shale gas could increase global gas resources by some 50%, according to a recently published report by a team of energy experts funded by the UK Energy Research Centre (UKERC).

The report, to the Energy Security Unit of the Joint Research Centre of the European Commission, has been produced by a team based at University College London’s Energy Institute, the Imperial Centre for Energy Policy and Technology at Imperial College London, and the Sussex Energy Group at the University of Sussex.

The report finds that technically recoverable resources of shale gas may be half as large as those for conventional gas, but there are major uncertainties in resource estimates, even for regions where development is relatively advanced. The majority of studies fail to address this uncertainty, and there are considerable difficulties in comparing and combining estimates from different studies. The report also highlights significant limitations in currently available estimation methodologies.

It is increasingly claimed that we are entering a ‘golden age of gas’, with the exploitation of unconventional resources expected to transform gas markets around the world. Shale gas production has grown extremely rapidly in the US, but the extent to which this growth can be maintained, or reproduced in other areas of the world, remains unclear.

Multiple uncertainties still exist, particularly with regard to the size and recoverability of the physical resource. Even in the US, estimates of recoverable resources are contested and are frequently the subject of radical revisions. But this is eclipsed by the much greater uncertainty surrounding unconventional gas resources in the rest of the world.

The research team assessed the currently available evidence on the size of unconventional gas resources at the regional and global level. Focusing in particular on shale gas, they summarised and compared the estimates that have been produced to date, and assessed the strengths and weaknesses of the methods used to produce those estimates, the range of uncertainty in the results and the factors that are relevant to their interpretation.

Taking the best of currently available estimates, the team found that global shale gas resources may be approximately half the size of conventional gas resources, with the US holding around ten percent of shale gas resources and Europe around eight percent. When other forms of ‘unconventional gas’ are taken into account, the total global gas resource may be 60% larger than was thought a few years ago. However, these figures refer to technically recoverable resources and a range of factors could lead the economically recoverable resource to be substantially less.

The team found numerous weaknesses in the available literature, including the use of imprecise, ambiguous or inappropriate terminology; insufficient transparency with regard to the methods and assumptions used; and the tendency to produce single value estimates rather than a range of estimates that better expressed the inherent uncertainty.

They also found that resource estimates were sensitive to a small number of variables that need to be much better defined. Of particular importance was the rate at which production from shale gas wells may be expected to decline – an issue that has become the focus of controversy in the US. If current assumptions for this variable proving incorrect, resource estimates may need to be significantly downgraded.

The authors commented, “Claims that shale gas will last for decades deserve much more careful scrutiny. While the resource is clearly very large, there is still an enormous amount of uncertainty, even in areas where production is well established. The evolving experience in the US needs to be watched very closely to see if shale gas lives up to expectations.”

Given the absence of production experience in most parts of the world, and the number and magnitude of uncertainties that currently exist, the team conclude that estimates of recoverable, shale gas resources should be treated with considerable caution.