Environmental Engineering Reference
In-Depth Information
2 Potential Shale Gas Resources and Aquifers in the UK
2.1 Potential Shale Gas Source Rocks
The establishment of a successful shale gas industry in the United States has
led to many other countries considering the potential within their own ter-
ritories. The UK is one of these and, with support from the current Gov-
ernment and the introduction of economic incentives, a significant amount
of exploration is expected over the coming decade. This exploration is nee-
ded ahead of any commercial development, as very little is currently known
about how much shale gas can be extracted and whether it can be produced
economically.
It was over 20 years ago that it was suggested that the UK may have
abundant shale gas reserves, but at that time there was little interest as
North Sea gas was still plentiful and the technology to extract the gas was in
its infancy. There is now significant interest, with growing recognition that
there may be considerable on-shore shale gas potential. Originally it was
assumed that this potential was restricted to locations where there had
been thermal maturation of organic-rich shales to produce (thermogenic)
gas. However, it is now known that (biogenic) shale gas can also be formed
by microbiological degradation of organic material irrespective of geo-
logical age and burial depth.
2
This finding enhances the UK shale gas
resource potential dramatically, making many more rocks potentially
prospective.
Potential shale gas source rocks occur in many areas of the UK,
including the Carboniferous shales in the Midland Valley of Scotland
and across Northern England (Pennine Basin, Stainmore and Northumber-
land Basin system and Widmerpool Trough), the Jurassic shales in the
Wessex and Weald Basins and Lower Palaeozoic shales associates with the
Midland Microcraton that extends from Wales in the west to the Thames
Estuary in the east.
3
Whilst the UK has an abundance of shale, there is
considerable variation in the depth and thickness of each of the shale
formations and their full extent is not yet known. The potential shale gas
source rocks that are currently being considered in the UK are shown in
Table 1.
The first of a series of detailed shale gas resource estimates for UK shales
was published in 2013.
1
This focussed on the Carboniferous Bowland-
Hodder unit (Bowland Shale) across Northern England. A total 'gas-in-place'
resource estimate was made using a 3D-geological model based on over
15 000 miles of seismic profile data integrated with outcrop mapping and
information from 64 deep boreholes. The study showed that the Bowland
Shale can be divided into an upper and lower unit. The lower unit is struc-
turally more complex than the upper unit, which is considered to be more
similar to the Barnett Shale in the United States. The relatively complex
lower unit is unlike anything encountered in the United States and it is in-
ferred that there will be unique challenges for the shale gas industry in the
UK if it is to be successfully developed.
