Research

Beware of fracking in UK mining areas, says earthquake expert

 fracking KM Eddie Thornton

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.

Peter Styles

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

traffic light system

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 Harthill 170627 Richard How HAF2

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?

Blackpool earthquake BGS

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.”

44 replies »

  1. I am sorry but this much heralded Traffic Light system is not worth a jot. Once a seismic event is triggered it will go on to its natural conclusion, the cessation of the injection at high pressure will not miraculously stop it, it is about time people realised this!

  2. Peter Styles should already have known that we receive less than 1% of our gas from Russia ( Govt. figures )

    • He should, but since he was an advisor to David Cameron he’s most likely a Tory and we all know they love to spread misinformation about where we get our gas from and bring the Russia word in whenever they can.

      • Pauline

        A bit of virtue signalling there I think. In my experience spreading misinformation is not limited to any particular political party or indeed any human or group. Should Peter ever advise a different party, would that make him a saint?p in your eyes?

  3. https://www.britishgas.co.uk/the-source/our-world-of-energy/energys-grand-journey/where-does-uk-gas-come-from

    44% of UK Gas comes from European pipelines and of that 35% comes from Russia. The molecules don’t have their name on them but these are statistics from British Gas. How the mix between Norwegian and Russian gas works out will vary but Belgium isn’t producing the gas we import from there!

    13% comes from LNG ( Algeria, Quatar and others) .

    My politics is none of your business!!

      • Baroness, Lady Neville-Rolfe, written answer, September 2016:
        “There are no pipelines that allow Russian gas to flow from Norway (our biggest source of imports) or via shipped Liquefied Natural Gas (which comes mainly from Qatar).”
        “Some gas of Russian origin may enter via pipelines from Belgium and the Netherlands. However, Belgium has reported virtually no Russian gas imports over the past three years.”
        “The Netherlands does report some Russian imports, but we estimate Russian gas via this route would account for less than 1% of the UK’s gas imports and, therefore, much less than 1% of our total gas supply”.

      • John
        I agree. Plus it does seem that ‘not a lot of people know that’, though I am not sure BG knew they were going to cause so much angst re Russian Gas when they put the information together.

    • Published data from Juan-Reyes Montes of the University of Liverpool demonstrates the relationship between microseismic events and pump rate/pressure. Other studies show there might be a relationship between proppant volumes and induced seismicity. Fracture propagation is also likely to be stopped by a change in formation lithology, ie a thin bed of different rock type.

      • Al

        The good news is that we should find out soon when Cuadrilla frack.
        However for the ex mining areas we will have to wait a bit longer as only wells are planned to be drilled sans fracking, so fracking in mined areas still seems way off.

        Maybe Misson and Tinkers Lane will frack first … on the edge of or not bothered by old workings, leaving INEOS to work out what to do in the heavily mined areas.

        Bye the bye, the Ollerton Earthquakes were interesting, the plates rattled from time to time and the dog looked worried. There were few prior to the ‘swarm’ and few since. Thoresby Colliery was in action when they hapenned, and oodles of collieries prior to that ( Bevercotes, Ollerton, Bilsthorpe, Clipstone and Welbeck within shouting distance), but all since shut.

  4. What’s the basis for using a distance of 850m from a fault? Is there any way of examining the calculations?

    How much research has actually been done on this in the field to demonstrate that the modelling is backed up?

  5. Prof Styles, would I be correct in assuming you have communicated the concerns expressed in the article directly to the relevant people in the companies involved?

    If so, it would be good to hear what kind of responses they elicited.

    • Not as yet but I will be. This has all followed on from a talk I only gave last Saturday!

      They do know about the 850m respect distance.

      • Peter

        I would hope there is no knee jerk reaction from INEOS or Igas.
        Neither company has applied for planning permission to frack yet, and IGas, being on the fringe of the worked coalfield may well avoid mined areas.

        Cuadrilla are not in such an area, of course, so I would presume they have no need to respond in a hurry.

        It is interesting stuff.

        Maybe 0.5 is too parsimonius for fracking in old mining areas.

      • Several companies offer real time detection, processing, and display of micro-seismic events. Prior to fracking a maximum allowable fracture length can be determined to avoid intersecting faults, and the job can then be terminated when this length is reached. There are papers (sandstones) which show how fractures grow; a maximum height and length is reached, and all further micro seismic events are then located within this envelope. While 895m might be necessary for operations with no real time monitoring, it should certainly not be a constraint for those operations that do have real time monitoring.
        Regarding your paper, drilling horizontal wells non perpendicular to SHmax is operationally bad for two reasons: first, it can make initiating the fracture extremely difficult, if not impossible. Second, if you do manage to frac, often the fracture will parallel the borehole before turning to parallel SHmax. These bends in the fracture seriously impact fluid flow and greatly reduce rates.

        • I have monitored microseismicity for more than 40 years and some of my graduate students populate the very capable companies you mention but the trick is knowing where the faults you might stimulate are and that is the issue when the ones capable of producing a 0.5 ML event are so small.

  6. Hi Peter,

    If we’re talking about the 0.5 ML cut off then are we talking about any fracking company attempting to frack in such an area just constantly hitting the regulatory barrier and having to stop for a period, rather than felt events or the types of environmental risks that many in the public have been led to think about (such as fault conductivity to above aquifers)?

    I.e. any company trying to do this will be potentially hitting an economic barrier whereby they cannot successfully frack an horizon within an economic timeframe and instead are having to just inject very low volumes, with each stage being stopped short due to 0.5ML events?

    I just want to clear up in my own mind as even here the headlines and 1st paragraph read as if fracking in any faulted area leads to ‘earthquakes’ and its easy for people to read that and imagine large earthquakes.

    I’m in complete agreement with you that the 0.5ML cut off could impact the economics of sites. That is pretty obvious. The 850m value is then being picked to do what? Stop 99% of 0.5ML events? Is the purpose of the 0.5ML barrier here to prevent larger quakes, or to prevent companies working? Honest question, since this can be interpreted as the frequency of 0.5ML events being an issue of economics rather than public safety, or felt activity on surface? I.e. if a company needed to frack a well over 2 weeks for the program to be economic and the setback distance was 850 (or 895m as per your paper) giving a 1% chance of a 0.5ML event and that happened and the company stopped fracking for say 1 day then what we have is an economic question. If the setback distance was 500m and gave have a 20% chance of a 0.5ML event and that resulted in a shutdown of 1 day then can it still be achieved in the 2-week timeframe, etc.

    Otherwise what needs to be said is that 0.5ML events occurring should ban fracking in an area, which I don’t think anyone is saying are they? I thought the 0.5ML cutoff was there to act as a point whereby injection is stopped and later injections reduced so as to reduce the risk of larger events?

    • There are two (?3?) aspects Garry

      1.How should we manage the process?: and what we (Reporting Group) originally suggested was that 0.5ML (which does seem to be a transitional point from ‘normal’ hydrofracking microseismicity and ‘induced seismicity’) was the point at which the process was temporarily stopped, flow back established and then decisions made on how to proceed and if the maximum magnitude stayed beneath 1.5 the operation could proceed cautiously. DECC decided that this was too complex ( and what did we know?) I suspect and stipulated that all should cease at 0.5ML and hence the Traffic Light System as it is presently. In previously undermined areas, this might be difficult anyway because of the shallow disturbed and subsided ground above longwall mines, existing mining-induced seismicity and fault rejuvenation and that needs careful examination which is what I have pointed out. The statistical probability of events happening in the context of their societal vs economic acceptability again is a subject which hasn’t been explored.

      2 Faults which produce 0.5ML Earthquakes cannot be resolved from surface seismic surveys and can probably only be detected from the microseismicity occurring on them which is often at extremely low levels (-ve magnitudes) but easily detectable with the right monitoring but is that already too late (see above?). Work needs to be done here.

      The other option, which I have suggested many times in public lectures, is, in these still very early days of this industry, to first access the near offshore ( many of these major Carboniferous Basins run straight into the North Sea, Irish Sea, etc.,) using deviated wells a la Wytch Farm, where many of the impact issues might be better managed, but I guess the regulatory regimes have a disjoint here as no-one either from operators or regulators has ever asked me to take this thought further!!

      • Thanks very much for your reply Peter.

        1) Pausing in the event of 0.5ML events, shutting the pumps off, establishing flowback, monitoring and then trying again with reduced parameters has always seemed sensible to me. However, I had accepted this only on the premise that 0.5ML events were below what might impact the surface. Obviously, if a 0.5ML event may disturb mine workings then there is an issue. Is there any data on what these mine workings can tolerate, seismicity wise? How to manage the process? The standard I would try and use is of any induced seismicity not affecting the surface / not being noticed on surface. So I suppose the question becomes whether different localities would benefit from different regulatory cut offs? Previously undermined areas having a cut off of 0.4ML or 0.3ML etc.

        2) If 0.5ML is actually a point whereby surface risks escalate then yes. Being unable to determine 1m faults that may result in 0.5ML events on seismic poses a problem. However, if the seismic resolution defines the upper magnitude of possible events.. I.e. if the seismic can determine faults of 5m and above then this leaves a gap of faults of <5m in our knowledge of an area. The obvious question then is what ML can we get from say a 4.5m fault, and what impact might this have in an area with no mining / 'undermined' areas, and one with mining etc.

        I think the main aim must surely be for any induced seismic activity to be below the threshold of affecting the surface, either directly, or indirectly.

        I would imagine that if the first few shale wells do not go without pretty much a hitch then it will kill the industry. In that sense if the first few wells result in seismicity that leaves the 0.5ML cutoff pointless, i.e if a few events come in at 2.5 straight away etc then that will be that.

        • Garry

          In the Nottinghamshire and Derbyshire coal fields we were not affected underground by the seismic events we created (as noted mining causes seismic events ) nor by those events which were visited upon us. Old long wall mine workings are resilient to seismic events as are existing workings. Our workings were more affected by what we did and the interaction of us working either above old workings or below them.

          The old workings consist primarily of collapsed workings ( which collapse behind the coal face ) and the remaining roadways which comprise less than 5% of the take and are well distributed.

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