The British Geological Survey, commissioned by the Department of Energy and Climate Change, has studied the shales of the Midland Valley of Scotland. The total volume of prospective shale in the Midland Valley of Scotland was estimated based using a regional 3D geological model generated using seismic mapping, integrated with borehole, coal mining and outcrop information.
The results of the analysis show resources of shale gas and shale oil in place. The range of total in-place oil resources for the Carboniferous shale is 3.2 – 6.0 – 11.2 billion bbl (421-793-1497 million tonnes) and range of total in-place gas estimate is 49.4 – 80.3 – 134.6 tcf (1.40 – 2.27 – 3.81 tcm).
The report emphasises that these ‘oil-in-place’ and ‘gas-in-place’ figures refer to an estimate for the entire volumes of hydrocarbons contained in the rock formation, the resource, not how much can be recovered. This methodology is similar to that used in the resource assessment for the previous BGS reports of the Bowland and Weald shales, but the uncertainty in the Midland Valley of Scotland is compounded as there are fewer historic wells and seismic lines to provide data. Further, the geology of the basin includes thinner shale packages mixed in with volcanic rocks, faults and abandoned deep coal mine workings which make it more complex and are likely to limit where wells can be drilled.
In simple terms, the resource estimate for any shale gas or shale oil play is the amount of gas or oil in the ground (some or all of which might never be produced), while the reserve estimate is a more speculative measure which describes the amount of gas or oil that might be able to be extracted. It takes into account non-geological constraints including technology, economics and the commercial risk operators are prepared to take.
Without substantive data from drilling and production rates, figures for reserves cannot be reliably estimated. In time, the drilling and testing of new wells in the Midland Valley of Scotland will give an understanding of achievable, sustained production rates.
You can read the report in full here.