SCOTLAND could have enough shale oil and gas to meet its energy needs for decades, it has been claimed, but old mineworks could make it difficult to access.
Geologists have estimated the area between Glasgow and Edinburgh known as the Midland Valley could store up to 80 trillion cubic feet of shale gas and six billion barrels of shale oil.
However, they caution that only a fraction of this could be recovered. Part of the difficulty lies in disused mines that litter the region.
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The British Geological Survey report states: "The complex geology of the area and historic mine workings mean exploratory drilling and testing is even more important to determine how much can be recovered."
The study describes the potential haul from fracking as a "modest amount", but its significance has split opinion.
Andrew Aplin, Professor of Unconventional Petroleum at Durham University, said: "The key issue is the proportion of the oil and gas that might be recoverable, which is likely to be low as a result of the complex geology of the region, plus the fact neither the rocks nor the oil appear to be of optimal quality.
"For gas, if five per cent could be recovered, that equates to about one year's UK consumption.
"(For oil) since neither the rock nor the oil is of optimal quality in the Midland Valley, we might estimate one per cent of the Midland Valley oil resource might be recoverable.
"This would equate to 0.06 billion barrels, which is about two months UK consumption. It could be a lot of effort for not very much reward."
However, a spokesman for the UK Onshore Oil Operators Group, which represents drilling com- panies, said it believed the geologists' estimates on the quantity of shale were overly modest. He added the group believed at least 10 per cent of the shale gas could be extracted - equivalent to eight trillion cubic feet on the BGS estimate - which would be enough to heat Scottish homes for 46 years.
Ken Cronin, the group's chief executive, said: "This report will give reassurance to investors who wish to explore for oil and gas onshore in Scotland and adds to the estimates of significant onshore resources, which can help replace the UK's growing dependency on imports and balance the decline of the North Sea."
However, the industry body believes the outcome of the Dart Energy public inquiry is likely to play a crucial role in luring investors, who will only be attracted north of the Border if they believe planning permission is likely.
The Australian firm has outlined plans to drill for coalbed methane at 22 wells in the Forth Valley area, but has faced local opposition. A public inquiry was held in Falkirk in March but the outcome has yet to be decided.
Scotland's Energy Minister Fergus Ewing said: "At this time there are no proposals that involve the use of hydraulic fracturing (fracking) techniques in Scotland, and proposals for coalbed methane or shale gas production will be studied on their merits, and considered through the normal planning process.
"Our responsible approach to the development of unconventional gas was confirmed in the Scottish Planning Policy published last week, which introduces rules to ensure no operator can undertake hydraulic fracturing unless they first gain explicit planning consent for that activity."