SCIENCE BRIEFING 2013

Q: What exactly is Shale Gas?A: Shale gas is mostly methane. Methane is natural gas and is the gas used to generate electricity, and for domestic heating and cooking. Shale gas is produced using technologies developed since the 1980s that enable gas to be recovered from rocks (mostly shale) which were previously considered to be unsuitable for extracting gas.

Q: How does it differ from conventional gas?A: Conventional gas comes from a source rock that was buried and heated at considerable depth (up to thousands of metres below the surface). Temperature increases with depth, and hydrocarbons, such as oil and gas, are released from the source rocks at different rates depending on how fast the rocks are heated. These hydrocarbons migrate upwards and may find their way into a porous reservoir rock. If this is overlain by an impermeable cap (or

seal) rock the hydrocarbons become trapped. The hydrocarbons are extracted by drilling through the cap rock into the reservoir. These hydrocarbons, which can be relatively easily recovered, are known as conventional hydrocarbons and have been exploited for more than 100 years. North Sea gas is a conventional hydrocarbon. With unconventional hydrocarbons, and shale gas in particular, the rock which contains the hydrocarbons is virtually impermeable and so acts as hydrocarbon source rock, reservoir and seal. The gas is both produced and trapped within the shale. It is only when the shale is drilled and artificially fractured that the gas is released from the rock and can be extracted. The process of artificially fracturing the rock is called fracking.

Q: Theres been a lot of interest within the UK on shale gas prospectively, with lots of activity in the North West of England what other main areas of interest are there within the UK?A: There are several different rock units within the geological sequence of the UK that have the potential to produce shale gas. The main interest is in the Carboniferous units, particularly the Bowland Shale Formation which occurs throughout parts of north west and Central and Eastern England. Other units of interest occur in the Jurassic rocks of the Weald Basin, parts of southern and north eastern England, and County Fermanagh, Northern Ireland. There is a possibility that much older Lower Palaeozoic rocks in Wales and central England may be prospective for shale gas (although this remains to be confirmed as it has not been fully evaluated by exploration companies or BGS).

Q: How do we get the gas out of the Shale?A: Advances in technology, developed principally in the USA, have meant that gas can now be extracted from shales and other low permeability rocks. Transferring these technologies from the USA to the UK could give rise to shale gas production if gas occurs in the rocks in commercial quantities. After initial exploration of the shale deposits, a borehole is drilled into the shale horizon at a carefully selected site. It may be drilled horizontally to increase the volume of rock that can be accessed by the borehole. A process called hydraulic fracturing (fracking) is undertaken. This involves pumping water into isolated sections of the borehole at pressures high enough to fracture the surrounding rock. Sand entrained in the water helps to prop open the fractures, create permeability in the rock and allow the gas to flow into the borehole. Chemicals are also added to improve the efficiency of the fracking operation.

The BGS provides independent, expert and impartial geological advice to both industry and government

Shale Gas: BGS research

Factfile Shaleisaveryfine-grainedsedimentaryrockformedfromclay,siltormudandisoneofthemostabundantsedimentaryrocktypesintheEarthsshallowcrust

Shalegasismostlycomposedofmethane(CH4)otherwiseknownasnaturalgasandcanberecoveredfromshaleusinghydraulicfracturingi.e.fracking

TheBGSwillplayitspartinprovidingup-to-dateandaccurateinformationonresourcesandtheenvironmenttothepublic,industryandgovernment

A shale outcrop in the UK.

Q: Are there any risks associated with fracking?A: Shale gas extraction and fracking has received a huge amount of media interest. Just like any other industrial process there will be associated risks. Some of those relevant to shale gas include induced seismicity, such as the low magnitude earthquakes experienced in Lancashire in 2011. There is also the potential for groundwater and surface water contamination. This may arise from surface activities that may lead to spills associated with the storage and mixing chemicals at the drill/ fracking site or the storage/ management of fluids that return to the surface from the borehole, the so-called flowback and produced waters. Other potential pathways for contamination of groundwater include poor well-design and well construction, and the migration of contaminants along natural pathways into overlying aquifers. Understanding the risks is a very important step in the design and approval process and very strict controls and regulations are in place to reduce the risks to an acceptable level.

Q: How dangerous are the induced earthquakes caused by fracking?A: The two main induced earthquakes in Lancashire in 2011 were very small. To put them into context, they were smaller than most of the earth tremors that have been associated with coal mining in the 1950s and 60s and that occur today.

Q: What do you think the likely impact will be on groundwater?A: There are two potential impacts on groundwater. The first is associated with the supply and consumption of water for fracking as groundwater may be considered as a source of this water. The second is contamination of groundwater. In both cases the regulations that apply

to shale gas extraction will require a detailed risk assessment before any authorisation or permit is granted. Before granting a permit the relevant regulatory authority (e.g. the Environment Agency in England) will need to be satisfied that the activity will not cause pollution of groundwater or lead to unsustainable abstraction. Once approved, monitoring of the environment will be required as part of permit conditions to demonstrate that no impact is occurring. To provide an independent environmental baseline against which this compliance monitoring can be compared, BGS is undertaking a baseline survey of methane concentrations in groundwater ahead of any shale gas development as there is currently no UK baseline. The baseline study is not only restricted to methane. A wider range of chemical indicator parameters are also being measured and the results will supplement the data already published by the BGS and used to set groundwater threshold values (standards) for the EU Water Framework Directive.

Q: Can shale gas meet the UKs energy needs?A: Estimates of the amount of recoverable gas and the gas resources are variable. It is possible that the shale gas resources in UK are very large. However, despite the size of the

resource, the proportion that can be recovered is the critical factor. A better understanding of the shale gas resource, and the amount of gas that is potentially recoverable, will come from further geological research, such as that carried out by the BGS.

Q: What role does BGS play in shale gas research?A: BGSs main role is to evaluate the amount of shale gas present and how safe it is to extract. BGS is taking a central role in shale gas research in the UK and also across Europe as follows:

Undertakingabaselinegroundwatersurvey of methane concentrations and other relevant chemical indicators in ground waters across Great Britain;

Evaluatingthespatialrelationshipbetween different potential shale gas source rocks and the principal aquifers in England and Wales;

Researchingtheinducedseismicitythat may be related to fracking; studies of the organic content and the organic make-up of the shales to improve understanding of how much shale gas they might produce and how the gas is stored within the rocks;

Understandingthedistributionandcorrelation of shale and how the shale layers behave in response to depositional and tectonic controls;

Adviceandguidanceforgovernmentin trying to understand the amount of gas that may be both in place and possibly recoverable within the shales in the UK.

SCIENCE BRIEFING 2013

Shale Gas: BGS research

www.bgs.ac.uk

More information: www.bgs.ac.uk/shalegas

Contact Prof Mike Stephenson, Director of Science and Technology: mhste@bgs.ac.uk

Shale gas clearly has potential in Britain but it will require geological and engineering expertise, investment and protection of the environment.Prof Mike Stephenson, Director of Science and Technology, BGS