Fracking realities

The government department Energy and Climate Change (DECC) commissioned three reports on the potential extraction of oil and gas from shales by the British Geological Survey (BGS), on the Bowland, Weald Jurassic and Midland Valley of Scotland shales.

The aim of the reports is to use all available geological information to provide, if sufficient data are available, in-place shale oil and shale gas resource estimates

Resources vs. reserves  

Unfortunately the results of the surveys have been misinterpreted by a misunderstanding of the distinction between (in-place) resources and (recoverable) reserves. 

A resource is an estimate of the entire content of the field considered, while the reserves are those likely to be recovered. In the particular circumstances of the oil and gas shales surveyed the recovery factor (i.e. recoverable oil or gas/oil or gas in-place) is probably only around 5%.

Recovery factors, and hence recoverable reserves, are not discussed in the reports. However in media interviews when presenting the reports, BGS warned that recovery factors would be poor.

A recovery factor of 5% is assumed for the analysis in this article. Extracts from the respective BGS reports are in italics.

BGS findings on the Bowland shale

"The total range for estimated gas in place is 822 – 1329 – 2281 tcf (23.3 – 37.6 – 64.6 tcm) ... for the combined upper and lower parts of the Bowland-Hodder unit.

This large volume of gas has been identified in the shales beneath central Britain, but not enough is yet known to estimate a recovery factor, nor to estimate potential reserves (how much gas may be ultimately produced). An estimate was made in a previous DECC-commissioned BGS report that the Carboniferous Upper Bowland Shale, if equivalent to the Barnett Shale of Texas, could potentially yield up to 4.7 tcf (133 bcm) of shale gas."

This is a recovery factor of only 0.35% (4.7/1329 = 0.00354).

In 2013 the UK’s consumption of natural gas was 2.59 tcf (73.1 bcm). It means that at this recovery factor, the amount of gas that could be recovered from the entire Bowland shale would last for less than 2 years at the current level of consumption. However, at a recovery factor of 5%, a yield of 66.5 tcf would last for 27 years. With an average Estimated Ultimate Recovery (EUR) of 1.3 bcf/well this would require the drilling of 51,000 wells.

BGS findings on the Weald Jurassic shale

"This study offers a range of total in-place oil resource estimates for the various Jurassic shales of the Weald Basin of 2.2 – 4.4 – 8.6 billion bbl (0.29 – 0.59 – 1.14 billion tonnes). It should be emphasised that these ‘oil-in-place’ figures refer to an estimate for the entire volume of oil contained in the rock formation, not how much can be recovered.

Indeed, there is a chance that there may be little or no ‘free oil’, given that the ‘oil saturation index’ is considerably less than 100 and what oil there is could be located entirely within the kerogen particles and would thus require heating/retorting to extract it. In these circumstances, the resource could no longer be categorised in terms of ‘shale oil’.

The study concludes that there is no significant Jurassic shale gas potential in the Weald Basin."

In 2013 the UK’s consumption of crude oil was 549 million barrels (69.8 million tonnes). It means that with an oil recovery of 5% from the entire Weald Jurassic shale, it would last for less than 6 months at the current level of the UK’s consumption. With an average EUR of 340,000 bbls/well this would require the drilling of 650 wells. If it turns out to be mainly kerogen it would make no contribution.

BGS findings on the Midland Valley of Scotland

"This study offers a range of total in-place oil resource estimates for the Carboniferous shale of the Midland Valley of Scotland of 3.2 - 6.0 - 11.2 billion bbl (421-793-1497 million tonnes). Total in-place gas resource estimates are 49.4 – 80.3 – 134.6 tcf (1.40 – 2.27 – 3.81 tcm). The West Lothian Oil-Shale unit makes the largest contribution to this estimated resource.

It should be emphasised that these ‘oil-in-place’ and ‘gas-in-place’ figures refer to an estimate for the entire volumes of hydrocarbons contained in the rock formations, not how much can be recovered."

In 2013 the UK’s consumption of crude oil was 549 million barrels (69.8 million tonnes). It means that with and oil recovery of 5% from the entire Midland Valley shale would last for just over a year at the UK’s current level of consumption. With an average EUR of 340,000 bbls/well this would require the drilling of 880 wells

In 2013 the UK’s consumption of natural gas was 2.59 tcf (73.1 bcm). It means that with a recovery of 5% gas from the entire Midland Valley shale would last for 18 months at the UK’s current level of consumption, but might last an independent Scotland for 15 years. With an average EUR of 1.3 bcf/well this would require the drilling of 3,000 wells.

Summary - if entire field drilled

Bowland                  27 years of gas; no oil

Weald Jurassic         6 months of oil; no gas

Midland Valley        1 year of oil; 18 months of gas

Conclusions

BGS comments:- "In time, the drilling, fracturing and testing of shale wells will demonstrate if commercially viable production rates can be achieved. These, combined with other non-geological factors such as engineering design, operating costs and the scale of development agreed by the local planning system, will allow estimates of the UK's producible shale oil and shale gas reserves to be made in the future." 

Even so the likelihood of drilling thousands of wells over the entire shale oil and gas fields nominated is poor. Given the uncertainties highlighted by the three BGS reports it appears that with the catastrophic impact fracking will have on the UK’s countryside the initiative should be aborted.

© John Busby 30 July 2014

bbl = barrels Tcf = Trillion cubic feet

Bcm = billion cubic metres

BGS comments are in italics