In April of this year, BBC Scotland will air a programme presenting the debate around shale gas and fracking. The Scottish Government currently has a moratorium in place (as of January 2015) preventing the granting of planning consents related to unconventional oil and gas developments, including fracking, in Scotland. The moratorium will stay in place for an unknown length of time, until evidence gathering and a consultation process has been concluded.
|BBC Scotland film crew debate a wide angle shot|
|Bob gets fitted with a microphone|
|Weathered West Lothian Oil Shales at surface|
Historically, “conventional” oil and gas reservoirs have been exploited by drilling. Conventional reservoirs form when shales have reached maturity under the right temperature and pressure, and the resultant oil or gas has migrated out of the shale into overlying rocks that are more porous (e.g. sandstones). Where these sandstones are covered by a cap or sealing unit, such as a mudstone, further upward migration of the oil or gas is prevented, forming a reservoir. The larger pore spaces of the sandstone make the oil and gas more accessible for extraction as the fluids flow more easily out of the rock. Recently, new technology developed in the USA now means that “unconventional” reservoirs can be accessed and drilled, extracting oil and gas directly from the shales through artificial fracturing, thereby unlocking some of the largest natural gas reserves in the world.
|Bob describes the West Lothian Oil Shales to the BBC presenter|
So what link does that have to a chilly spot on a beach in South Queensferry? Bob took us along the beach a short way to where the West Lothian Oil Shales outcrop at the surface to explain how it formed, and the general principles behind oil and gas formation in shales.
The Midland Valley is a basin that lies between two faults, the Highland Boundary and the Southern Upland faults, both of which span Scotland from east to west, encompassing Glasgow and Edinburgh.
|Midland Valley location|
During the Carboniferous Period (~358.9 ± 0.4 to 298.9 ± 0.15 million years ago), Scotland was located just south of the Equator, with a hot, humid climate, seasonal rains and a large organic source from vegetation. Sediments and organic matter slowly filled the Midland Valley basin, depositing the West Lothian Oil Shales in a perennial lake with adjoining rivers and a shallow marine delta environment. Over the course of time, these sediments were buried at depth and heated, forming shales and providing the perfect conditions for the development of natural oil and gas.
|Pumpherston Oil Works, commercial postcard, c.1922. Copyright Almond Valley Heritage Trust. www.scottishshale.co.uk|
|Bob Gatliff in front of the West Lothian Oil Shale outcrop|
One final question was asked by the BBC team
“Are we reacting before we have got the scientific answers to accurately address this issue?”
I think only time will tell us the answer to that one. But to see the documentary in its entirety, please keep a look out on the BGS website where we will post the date and time that it will be shown once it has been scheduled.
For more detailed information on The Carboniferous Shales of the Midland Valley please see Monaghan, A.A. 2014. The Carboniferous shales of the Midland Valley of Scotland: geology and resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.
Thanks also to the Museum of the Scottish Shale Oil Industry (www.scottishshale.co.uk)
By Carol Cotterill