Updated: Fracking earthquakes are unpredictable and could damage buildings – new research

The government is standing by its moratorium on fracking in England after new research concluded that induced earthquakes were hard to predict and manage.

Chart showing a 2.9ML earthquake induced by fracking at Cuadrilla’s Preston New Road site on 26 August 2019

Studies commissioned by the regulator, the Oil & Gas Authority (OGA), found it was not possible to predict accurately how and when fracking would cause earthquakes. The OGA concluded:

“there remain significant uncertainties and challenges related to the prediction and management of induced seismicity from hydraulic fracturing.”

A spokesperson for the Department of Business, Energy and Industrial Strategy said in response:

“The government maintains its position that fracking will not be allowed to proceed in England unless compelling new scientific evidence is provided.”

The moratorium on fracking in England has been in force since November 2019, following seismic activity caused by fracking at Cuadrilla’s Preston New Road site near Blackpool.

An earthquake on August bank holiday 2019 measured 2.9 on the local magnitude (ML) scale and was the strongest fracking-induced seismic activity recorded so far in the UK.

At the announcement of the moratorium, the government said fracking would be paused “unless and until further evidence is provided that it can be carried out safely here”.

“Unpredictable and difficult to control”

The studies, published today, were commissioned to help the OGA understand what happened during the Preston New Road earthquakes and to predict how induced seismicity could be controlled.

The research concluded that fracking-induced earthquakes were not predictable. The OGA said:

“whilst recently-identified novel methods offer some potential, it is not yet possible to accurately predict the seismic response to hydraulic fracturing, if any, in relation to variables such as site characteristics, fluid volume, rate or pressure.”

The OGA also said measures to control seismic activity had often not worked.

Cuadrilla used a more viscous fracturing fluid to frack the second well at Preston New Road. It said this would “improve operational performance under the uniquely challenging micro-seismic regulations”. But within a week of the start of fracking there were earthquakes measuring 1.6ML and 0.9ML.

The OGA said:

“Where induced seismicity has occurred, mitigation measures have shown only limited success, and there can only be low confidence in their effectiveness currently.”

Campaigners outside Cuadrilla’s shale gas site at Preston New Road near Blackpool, 26 August 2019. Photo: Used with the owner’s consent

Damage to buildings

One part of the study concluded that a 4.5ML earthquake was “highly likely” to damage buildings in the region around a shale gas site, though not the borehole.

A 4.5ML seismic event caused by fracking was “unlikely”, the research said. But it is at the maximum limit permitted for fracking-induced seismicity in parts of North America. Some UK shale gas companies have argued that a limit of 4.0ML-4.5ML should be allowed here.

Modelling for the research estimated that within 1km of the epicentre, damaging ground motion intensities may occur with a 4.5ML earthquake. Around 3-4km away, there could be intensities resulting in slight or cosmetic damage.

The OGA said:

“Whilst it is important to note that hydraulic fracturing-induced seismicity at this ‘unlikely’ magnitude [4.5ml] has only a few international precedents, it is within the range of UK tectonic events experienced in the past, and should such an event occur, there would be high likelihood of damage to buildings within the region.”

The British Geological Survey received 197 reports of damage from the 2.9ML earthquake at Preston New Road.

Cuadrilla has not disclosed how many properties were damaged by the seismic event but claims are still being pursued.

The research also found that the geomechanical mechanisms for felt seismicity were complex and different for Preston New Road and Cuadrilla’s earlier fracking site at Preese Hall, also near Blackpool.

“This high variability and uncertainty make it challenging to make generalised conclusions of the causal mechanisms.”

The study raises questions over research carried out by the University of Liverpool, which suggested that a tremor of 1.1ML would have an equivalent effect to dropping a 1 kg bag of flour from a table.

Another section of the research found that magnitudes of seismicity recorded downhole at both Preston New Road shale gas wells were lower than the local magnitudes measured at the surface. The research found that recorded downhole magnitudes were significantly less than expected, particularly in the first fracked well at Preston New Road, PNR1z.

“No assurance that fracking can take place safely”

Opponents of fracking welcomed the research findings.

Susan Holliday, chair of Preston New Road Action Group, which campaigns against fracking, said:

“Given the conclusions in this report, it is very difficult to see how fracking at PNR could ever be considered further within the current constraints of technology.

“Our experts always maintained that the geology of the Fylde was complex and not properly understood by Cuadrilla. This report seems to confirm that view.

“If the seismicity cannot be understood or predicted then there is no assurance that fracking can take place safely. Surely this should be the end for the site at PNR. ” 

Steve Mason, of the campaign network Frack Free United, said:

“This report is a vindication of the evidence-based arguments our campaign brought to the fore. Finally it seems the BGS [one of the authors of the research] have listened.”

“The Mining and Fracking report by Professor Peter Styles added real vigour to the narrative around fracking and earthquakes. Professors Smythe, Hazeldine and Styles and all the campaigners that fought so hard to get that message out have finally been proved right.”

Grant Hocking, an American fracking expert whose company GeoSierra, contributed to a review of Cuadrilla’s 2011 Preese Hall frack, said:

“It is clear that this latest OGA research report has had no input from any hydraulic fracturing expert.

“If the OGA and its consultants had even an elementary understanding of hydraulic fracturing, they would have immediately shut down Cuadrilla’s Preston New Road PNR-2 hydraulic fracturing activities upon seeing the mini-frac data of August 13, 2019, two (2) days before Cuadrilla’s start of PNR-2 hydraulic fracturing operations.”

The mini-fracking data from PNR-2 was released to the public in September 2019, and reported by DrillorDrop.

Companies seek “level playing field” on seismicity

In response to the research findings, Cuadrilla Resources issued a statement :

“Cuadrilla Resources welcomes the publication today by the OGA of four detailed technical reports analysing various aspects of seismicity induced during the hydraulic fracturing of the Preston New Road 2 well, along with an OGA summary of those four technical studies.

“The studies were commissioned in March 2020 some four months after a moratorium on hydraulic fracturing in England was announced by the UK Govt citing disturbance caused to residents local to the PNR site. Their release today, 13 months after that moratorium announcement, will, we believe, allow that decision to be considered and reviewed in a new light.

“We note in particular the finding that the maximum induced seismic event at PNR2 of 2.9Ml “may cause sparse cases of low superficial damage”. This is consistent with our own data of the low level impact of the 2.9Ml event. The data also confirms that the levels of ground vibration generated during hydraulic fracturing at PNR were typically below levels frequently encountered and safely managed in other UK onshore industry such as quarrying, construction and geothermal (ref ongoing Cornwall geothermal well).

“We will now fully assess the detailed reports and discuss further with other industry players, with Regulators and with the Govt. Our focus will be on how shale can be put on a level regulatory playing field with comparable industries already managing the risk of induced ground vibrations and operating safely and responsibly in the UK.”

On the damage risk from a 4.5ML induced earthquake, the company said:

“Induced seismicity of this magnitude is not something that we or other experts in the field have considered a credible scenario. We will fully assess the detailed report to better understand the scientific rationale for its inclusion.”

Ken Cronin, chief executive of the industry body, UK Onshore Oil and Gas, said:

“We note the release of four studies regarding seismicity around Preston New Road. Due to the nature of the reports, our technical teams will need time to study them in detail. During this process we will continue to work with Government and our regulators in regards to the hydraulic fracturing moratorium.”

“More work needed”

The OGA said the performance of tools used to predict the likelihood and magnitude of earthquakes should be improved.

It said there were limitations with reflection seismic surveys when used to identify sub-surface faults. Alternative methods were needed, it said, to predict and avoid faults and fracture networks that lead to seismic events

Further work could look at whether certain geologies contributed to fracking-induced seismicity, the OGA added.

The OGA said the research could help other industries, such as geothermal heat and underground storage or disposal of methane, waster water or carbon dioxide.

Updated on 15 December 2020 to include comment from BEIS and UK Onshore Oil and Gas and an additional statement from Cuadrilla

  • Professor Stuart Haszeldine, of Edinburgh University, has reviewed the four studies in a guest post for DrillOrDrop

6 replies »

  1. All interesting stuff

    I am not sure that the study raises questions as to the surface effects of a 1.1ML event (at the surface) as noted in the DOD report ….

    The study raises questions over research carried out by the University of Liverpool, which suggested that a tremor of 1.1ML would have an equivalent effect to dropping a 1 kg bag of flour from a table.

    ie – is that right?

    But comparisons with the relevant report on DOD re bags of flour show some interesting comparisons.

    From above ……..

    Another section of the research found that magnitudes of seismicity recorded downhole at both Preston New Road shale gas wells were lower than the local magnitudes measured at the surface. The research found that recorded downhole magnitudes were significantly less than expected, particularly in the first fracked well at Preston New Road, PNR1z.

    From DOD report re bags of flour –

    In a guest post published by DrillOrDrop yesterday, engineer Michael Hill said:

    “The industry is endeavouring to focus the media and public’s eyes on “felt” seismicity. It is talking about the level of earthquakes that actually shake our houses.

    “But the risk at the moment is not to construction above the ground but to what lies below: the wellbore itself.

    “We do not know the intensity of the ground movement at the borehole but it is immediately clear that the intensity at the wellbore must be greater than at the surface.

    So, the report would raise questions over the comments in the guest post by Engineer Michael Hill, in that the OGA report does not find that the intensity at the wellbore must be greater than at the surface.

    I am sure the report raises many questions in relation to past assertions here on DOD?

  2. Hi Hewes 62

    I added the line on bags of flour – the OGA report suggests that felt seismicity is complex and the effect might vary from site to site. So how a 1.1ML tremor might feel can’t be easily forecast.

    As you pointed out, other assertions are also challenged by the report – I guess this all goes to reinforce the idea that fracking-induced seismicity is not predictable given our present tools and state of knowledge.

    • Paul

      Thanks – I did not get the impression from reading the report that a 1.1ML at the surface in the Fylde would be felt any different from that envisaged by the people at Liverpool university.

      Just as a 1.1ML felt by people in Ollerton (or in the Weald say) would be able to determine much difference in a 1.1ML event.

      The report does note that fracking induced seismicity is not predictable in terms of when it will happen during fracking, or how bad it will be when it does happen (within certain bounds), but not that its affects in the surface would challenge the seismic affect information given in articles, books and by the BGS as to likely damage from seismic events. ie is a fracking induced 1.1ML at the surface more unpredictable in its affects than coal mining induced seismicity or natural events?

      It was a quick read though – so maybe a more detailed read will lead me to a different conclusion.

  3. The bit that continues to confuse me, hewes62, is how such seismic events can cause such widespread damage, but focused, it seems, upon the unbelievers! The sort of biblical event last seen by Moses in Egypt.

    But, back to more standard maths.:

    4.5ML is VERY different to 2.9ML.

    Wonder which would be required to blast the granite out of the Lizard to build the Swansea Lagoon? (Which the locals at St. Keverne have said NO to, but some of the antis would like to conveniently ignore their local democracy.)


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