Prof Richard Davies, BSc, PhD, FGS
Dean of Knowledge Exchange and Impact in the Department of Earth Sciences
Durham University
Lecture presented by Professor Davies to an audience of around 150 U3A members and Sixth Formers in the Torch Theatre. The event organised by the Pembrokeshire Earth Science Schools Trust (PESST) on Thursday 13th March..
Fracking is a topic which may fill many with fear and loathing of yet another attempt by man to destroy the environment and all that is pleasant on our planet. On the other hand many consider that it will enable us to provide ourselves with our own viable energy supply for industry and our homes and tax revenues to pay for our ever growing needs and services in the 21st Century.
Professor Davies emphasised that his Department were unbiased in their assessment of Fracking, its development and impact and to provide advice to the Government and other agencies as well as to inform the public. Research papers are in continuous production and some can be accessed on line.
The potential resources of oil and gas that could be obtained from oil shales in northern England from the 1000 ft thick Bowland Shales and from Jurassic shales in south east England are enormous. They are estimated to be far greater than those obtained from the North Sea basin although possibly about 10% of this can be easily recovered. Being beneath the land they are more easily assessable by means of vertical drilling and then horizontal bores so that fracking, the use of high pressure water injection at a depth of around 3 km. can fracture the impermeable shales to release the oil and gas. These have been formed from algae and other organic remains which by deep burial, pressure and heat over millions of years have been converted to hydrocarbons. The injection of water, sand and chemicals in each bore would only be for about 2 hours to fracture the shale at depth. The fractures are confined to around the bores at a depth of over 3 km.
Drilling of 1000s of bore holes would be necessary but would occupy limited spaces and when completed the features left would not be unsightly towers or ‘nodding donkeys’ but only a 6ft high valve system connected to underground pipes. Each would be operative for up to 10 years and would then be sealed off and buried with concrete. Fracking on a limited scale has been used in the UK since before WW2.
Does Fracking cause Earthquakes? Earthquakes naturally occur with great frequency in the UK but the vast majority are very small and are only detectable by sensitive seismographs. Fracking would cause some of these very minor quakes. One quake of 2-3 on the Richter Scale was the cause of a recent minor quake in Lancashire which Geologists diagnosed as high pressure fracking water lubricating an ancient fault. Fracking should therefore avoid faulted strata.
Possible pollution of ground water held in aquifers can be avoided by only Fracking below 3km. since aquifers are only tapped at shallow depths of less than 1km. so they are isolated from Fracking. Water used in Fracking is ejected from boreholes by the escaping gas. This is treated to remove chemicals including any radioactive material and may be reused in Fracking.
To ensure Fracking operations are safe and within the limitations indicated thorough and carefully monitored systems must be imposed on the industry. These are being designed to safeguard all aspects of the operations. One essential aspect of this control system must address the long term monitoring of possible leakages from sealed boreholes.
The Government policy for Energy favours the development of Fracking to fill our future Energy Gap but it is up to us as voters to appreciate the potential benefits and environmental impacts of Fracking and respond accordingly.
The Science and Technology Groups of the U3As who attended this lecture very much appreciated the clarity and excellence of Professor Davies’s presentation and have expressed their appreciation of being invited by Chris Evans and the Pembrokeshire Earth Science Study Trust to this event.
dur.ac.uk/earth.sciences/research/themes/
Graham Goodeve 14th March 2014.