Fracking near geological faults in former coal mining areas could trigger earthquakes and should not take place without careful assessment of all available geological data, according to one of the UK’s leading experts on the subject.
Photo: Keele University
Professor Peter Styles, a former adviser to David Cameron, said the fracking process could lead to seismic activity by stimulating faults in geology that was already stressed by mining.
The retired academic, who linked Cuadrilla’s fracking in Lancashire with the 2011 Blackpool earthquakes, believes this could jeopardise the shale gas industry.
He said fracking should not be carried out within 850m of a fault in any area. But in mining regions he suggested the risk could be greater:
“We have already changed the stress in these areas by removing the coal and allowing the ground above to subside.
“We have already preconditioned the faults. Even when mining stops it is still possible to have seismicity, as we have seen recently around Ollerton and Thoresby in Nottinghamshire.”
He told DrillOrDrop there could be hundreds of faults near shale gas sites that companies may not know about.
He said some faults were too small to be identified on geological maps or seismic surveys but were still big enough to cause the 0.5 magnitude earthquakes that under UK regulations would stop fracking.
His comments would appear to raise questions about fracking in large parts of the Bowland Shale, which lies under the Coal Measures from the East Midlands and Yorkshire to parts of Lancashire and Cheshire. They could also have implications for the seismic surveys being carried out across shale gas areas.
Professor Styles is a former President of the Geological Society of London, a project leader with the ReFine fracking research project and previous Head of Geology at Keele University.
He said he had identified faults close to proposed shale gas sites using detailed underground mining records. He called for these records to be taken into account when decisions were made about fracking sites.
Traffic light warning
Source: Department for Business, Energy and Industrial Strategy
The UK’s regulation on induced earthquakes – known as the traffic light system – requires shale gas companies to stop fracking if they detect seismic activity at a magnitude of 0.5.
Professor Styles said:
“There are 10s, perhaps 100s, of small faults, measuring 25-50m long, to which a 0.5M earthquake corresponds. They have not been mapped on the surface or by the British Geological Survey.
“There are faults present near some of the proposed boreholes – 10s of metres away.
“There are faults that have experienced seismicity which are much closer to the boreholes than the companies possibly understand.
“I already have evidence that these faults have caused seismic activity.”
Asked by DrillOrDrop if he thought fracking in mining areas near pre-existing faults should be banned, he said “Yes”.
“If you wanted to establish a secure future for shale gas wells in the UK, I probably wouldn’t advise doing it in areas that have already been undermined.”
He added:
“If you could be 850m away from a fault, you would probably be ok. If you can’t be 850m away from that fault then there could be problems.”
Seismic surveys not fit for purpose?
Seismic survey trucks in south Yorkshire. Photo: Harthill Against Fracking
Professor Styles suggested that the seismic surveys currently being carried out across Northern England would not identify small faults that could lead to a 0.5ML earthquake.
An earthquake of this size could be induced by a fault displaced vertically by as little as 1m, he said. But seismic surveys detected displacement – known as the throw – down to only 5m or 10m.
He said:
“Seismic surveys are adequate to define the big faults. Faults with throws of 100m are a problem. But faults that are much smaller than that are also a problem.”
Professor Styles said:
“The faults that are going to stop fracking are five times less than the resolution of the [seismic survey] tool we are looking for them with.
“That means that seismic reflections will give you the bigger faults but below that level there are faults that are capable of giving you earthquakes that would stop fracking.”
Inducing a ban?
Map of the 2011 Blackpool earthquake linked to fracking by Cuadrilla at Preese Hall. Source: BGS
Professor Styles said he feared the government would stop fracking in England if the industry activated a fault and induced an earthquake bigger than 0.5 magnitude.
This is much smaller than the fracking-induced earthquake in Blackpool in 2011, which measured 2.3ML.
Professor Styles said:
“If the industry carries on with this, there is a good chance they will affect one of these faults capable of inducing an earthquake of 0.5 ML. They would be forced to stop fracking.
“That is not a very sensible approach to moving this forward towards energy security.
“What I would hate is for this to go ahead and for it to go catastrophically wrong.
“These will not be big earthquakes, and may not be discernible by the population. But we have regulated to say that if a certain magnitude happens then fracking will stop.”
He added:
“I’m an advocate of us stabilising our energy supply sustainably and not offshoring our environmental responsibilities to Russia, Qatar and Algeria. But it has to be done right.
“I do not want this to go ahead willy-nilly without a proper appraisal of what might happen.
“In these mining areas, which cover a lot of the areas identified by BGS [British Geological Survey] as a prospective source for the Bowland Shale, there is a lot of information that should be taken into account before we charge too deeply into this.”
He said that it may also be difficult to distinguish between earthquakes induced by fracking and those by mining:
“Earthquakes happen after mining has stopped”.
He said he had advised the government that all available information should be considered as part of the planning process.
Coal Board engineers and surveyors had recorded faults as small as a few centimetres, he said. These records had been analysed by Liverpool University researchers and can now be used to overlay proposed and actual shale gas sites.
“We only know about these small faults because we have the mining records. Everywhere that was mined by the National Coal Board, there are maps of underground faults.
“There is information that the companies may be unaware of. I would hate to think that I failed to point out what I do know.”
Rejecting the idea of a blanket moratorium on fracking, he said:
“I am interested in us having information to hand and informed planning with the information that is available.
“We have forgotten about mining. Mining has not forgotten about us.”
Categories: Research
DRILL OR DROP? 
I’m just a complete amateur but it seems to me that the government setting the shut-down barrier at an immutable 0.5 (at micro-seismic levels ie below perception level except using instrumentation) is setting up fracking to fail.
I’m really puzzled why Cuadrilla and Igas haven’t made more of an issue of this. Surely they have invested so much money they’re not going to risk another event which would be headlined as an”earthquake” by opponents and set shale exploration back another five years. It seems to me that fracking has the potential to be massively important to the UK’s energy security and for it to be delayed again would be tragic.
By the way does anyone know what’s the experience is in Pennsylvania where there must also be fracking taking place near old mine workings.
Also by the way, just semi humourously I did read somewhere that attempts to make seismic recordings at Balcombe in Sussex were hampered by the ground vibration (not noise) from the London to Brighton train running about 200metres away. Does that say something about the levels we are talking about.
This is where fracking beneath mining has happened in Pennsylvania. They have only recently (Last year) experienced seismicity from shale gas operation in Pennsylvania but not as far as I can tell in this area. It depends of course on the nature of faulting and the historic mining induced seismicity which has not generally been a feature of Pennsylvanian coal ming
http://www.gracelinks.org/blog/4313/fracking-in-the-pennsylvania-coalfields-a-talk-with-the-cen
Some very interesting points raised there Peter … eg “Unconventional is another word for extreme and unproven. No one has any idea how these two industries will interact with each other. The state agency in charge of regulating the industries doesn’t know if this can be done safely but continue to issue permits in rapid succession. A common tact with unconventional fossil fuel extraction is the relentless pursuit of profits. They want to get their coal and gas and get out, hopefully before anyone can hold them accountable for the destruction left in their wake. I think unconventional is code for prioritizing profits over people. ”
… the two kinds of unconventional he’s referring to is fracking (for gas and oil) and long-wall coal mining. As for here the industry keeps spinning the story that certainty will only come with the test results and further drilling (as Martin does), but of course that will only apply to the local spot that they are mining – which may or may not be a sweet spot for productivity. It’s all a gamble and a risk, a bit like Russian Roulette. On average the commercial interests come out on top and the communities suffer, and dare not challenge. They are easily intimidated.
[Typo corrected at poster’s request]
Phil P
Longwall mining is not extreme or unconventional.
When I joined the NCB in 1974 over 90% of coal extracted was by longwall mining.
A few mines used continuous miners ( Point of Ayr ) as did Easington where they were keen to control subsidence, being close to the seabed! Maybe Haig, which is what the proposed new mine up there will do.
For America it is more unusual. America ( outwith the massive opencast operations in the powder river basin et al ) preferred continuous miner operations. These are cheaper to establish ( in many cases just cutting into the side of a hill ) and run. But the objective is the same, to remove all the coal. So, unusual for that county in the USA, but not unusual globally and certainly not extreme.
Longwall costs more to establish but then is more productive if you get it right. However, long runs of unfaulted coal, 8 ft thick and not too deep, competent roof and floor, relatively flat ( and not too gassy ) are perfect, and these conditions seem to be what they have.
You cannot tease coal out with sweet words, and the days of pick and shovel have gone.
If any coal mining is extreme then souritage mining of 8m thick plus seams on a 1 in 1.5 gradient would fit the bill ( cut 2.5 m by machine and get the rest from behind the supports as it caves. Very expensive to set up.
More later on this, it’s interesting stuff. Especially interactions and the effects of fracking induced seismic activity on disused longwall workings ( which I suspect is none but more on that in a bit ).
The big longwall mining company in USA is Catepillar followed by Komatsu ( who took over Joy, who swallowed Dowty ). Dowty we’re British. Joy had trouble in China, which is another country now wedded to longwall, as is Mongolia etc etc.
Plus, coal mines that lose money shut unless the gov subsidises them ( see the Spanish coal industry and EU bungs ). So for coal, it is not big profits, but a reasonable rate of return that is required.
Good points. The unconventional may have been just referencing the fracking but there seemed to be an implication of the long-wall mining had been going beyond safe limits. Therefore extreme
Phil P
For the workforce longwall can be as safe as it gets for underground mining.
The issue is subsidence which is new for them, but not for the UK.
It lowers the land, it an cause problems with your house it alters streams (the river Meden running though Clumber Park is an example of a river well affected by subsidence – including lowering the man lake dam and giving a few more areas of marshy ground for the birds ).
But it is not something you would want unless you were suitably recompensed. Note that tens of thousands of houses were undermined by the NCB, still stand and new owners only find out from the searches.
The link below gives an overview of Appalachian mining history and the move from stall and pillar without subsidence to stall and pillar with retreat and longwall mining.
http://www.dep.pa.gov/Business/Land/Mining/Pages/PA-Mining-History.aspx
Note that there is nothing especially difficult about the coal they are mining – indeed compared to the UK its easy.
The issue of interaction between fracking for gas and active coal mining is an interesting one for them.
The main issue is that, thanks to Coal Board Surveyors and Mining Engineers who noted all discontinuities as part of roof control and seam tracking, we can map the faults in underground workings at a far higher resolution(orders of magnitude better) than can be done from the surface and I have already demonstrated that some of these mapped faults have had induced seismic events on them at levels of 1.5 ML far higher than the regulations permit at 0.5ML. So any activities beneath these worked seams are likely to encounter more or less the same fault pattern (may vary depending on lithology and the 3D nature of faults, but statistically similar. It is then tricky to choose a borehole site which is more than 850 metres away from a fault noting that a 0.5 Ml seismic event only requires a fault of length less than c 40 metres with a displacement of less than a metre. If mining-stimulated seismic events have already occurred on such faults it may be difficult to avoid rejuvenating them. These faults cannot be resolved by surface seismic reflection.
The issue of whether or not you can feel seismicity in a mine isn’t really the point. Longwall mining can cause seismic events due to movement on pre-existing faults as we showed in 1993 around Thoresby and then in 1998 at Asfordby where the mine was abandoned after one face due to the inability to control the roof. We were monitoring this with underground seismometers in boreholes distributed around the mine with geophones in the seam and recorded the progressive failure.
Comment posted on behalf of Simon Parker:
Just a quick thought on this story as it seems like the headline might be misleading.
You’ve got to admit ‘Beware of fracking in UK mining areas, says earthquake expert’ certainly says ‘something’. Beware, says expert etc. Earthquake Expert. Beware earthquakes.
Fair enough, but then when you read the article there is nothing on felt earthquakes or risk to anything due to earthquakes. I don’t think the article even proposes risks to something as small as a teapot or pencil rolling off of someone’s table.
All I can see in it is a repeated reference to the 0.5ML regulatory limit and the chance that small undetected faults below the seismic threshold, which in your story you quote at 5m-10m.
You’ve then got a quote that faults of as little as 1m can cause events of 0.5ML. 1m obviously being less than the 5-10m resolution. Again, fine.
But what does that mean for anything? The 0.5ML limit in regulation is there to stop the injection process and re-evaluate. It isn’t there as a new limit by which people should inform the public they must panic. If a 1m fault slips at 3500m depth and isn’t felt by anyone, other than sensitive equipment that is what now? Cause for banning?
Again, that wasn’t the purpose of the 0.5ML limit in the regulations. It isn’t there as a safety limit. It is set well well below a safety limit to indicate when the pumps should be turned off…
So, the headline.. ‘BEWARE OF FRACKING.. says expert’
Really? Seriously? Is there not just the slight chance that the language here is incendiary?
With any process or activity, there is the potential for multiple people to shoulder the costs. There are numerous activities in the oil and gas sector that result in extra costs for companies, ranging from not ordering something in time to maybe running the wrong tool in the well and having to spend time pulling it out and putting the right one in. Basic stuff of the normal human error type. My point is that some things hit a companies bottom line rather than causing events that seriously impact people and the two are not the same.
If a fracking company drills a well in an area with a high risk of 0.5ML events then what is going to happen is that when it comes to fracking the well they are going to end up either unable to, or spending alot of time/money doing so.
It doesn’t necessarily translate into environmental impact.
Is there anything in your article that warrants the ‘BEWARE OF FRACKING’ headline? I cannot find it.. I can find a cautionary advise by a leading geologist to the companies as to be cautious about fracking in areas where there is a risk that the regulations will prevent them fracking. That I can see. But that is no reason for the public to ‘BEWARE’. That is an economic issue for the companies that might mean they drill a well and are unable to do anything with it.
I see this exact question has been asked in the comments too. I just thought I’d point it out. The title might well be ‘Fracking companies need to be cautious of trying to frack in areas where the 0.5ML limit might prevent them doing so either at all, or in an economic manner’. Not catchy or clickbaity but maybe more accurate given the text of the article.
The get out might be if there are larger faults of course, but then they’d be in the resolution of the seismic surveys? Either way, just looking at the article ‘as is’ it discusses the 0.5ML limit, for which the earthquake frequency risk might be higher/much higher with distances much less than 850m, but does this translate to risk of larger earthquakes if the discussion is about the lower limits of the seismic survey thresholds and their impacts on fault detection, and of sub 5m or even 1m faults. Even if they’re capable of creating 0.5ML events. All that will do is shut down the companies operations and cost them money. That isn’t a reason for the public to ‘BEWARE’, etc.