Regulation

Amber-level tremor while fracking at Cuadrilla’s shale site

181023 pnr Eddie Thornton

Fence art at Cuadrilla’s Preston New Road fracking site near Blackpool, 23 October 2018. Photo: Eddie Thornton

Cuadrilla has confirmed there was a 0.4 magnitude earth tremor while it was fracking at its Preston New Road shale gas site this afternoon.


This is an amber event under the seismic regulations, known as the traffic light system. At this level, operators should proceed at caution.

The company said it had stopped fracking for the day.

The tremor is the sixth in a week reported by the British Geological Survey in a series of seismic events near the fracking site.

181023 BGS chart

Extract of British Geological Survey list of seismic activity in the UK showing most recent event in Blackpool

The tremor measured only 0.4 magnitude and was too small to be felt at the surface. But it is the largest of the tremors so far. And it is the first that we know happened while fracking was taking place.

Under the seismic rules, fracturing should stop immediately if there is seismic activity measure 0.5M or more.

Cuadrilla told DrillOrDrop:

“The highly sensitive monitoring systems at and around Cuadrilla’s shale gas exploration site in Preston New Road have detected a seismic event within the company’s operational area (approx. 4.8km²) of 0.4 ML (Local Magnitude) this afternoon while hydraulic fracturing operations were ongoing.

“This is an extremely low level of seismicity, far below what could possibly be felt at the surface but classed as an amber event as part of the Traffic Light System (TLS) in place for monitoring operational activity. As such we are required to reduce the rate we are pumping fracturing fluid once it has been detected. In fact we have adopted extra caution and have stopped pumping for the day.

“Seismicity will, as always, continue to be monitored closely around the clock by ourselves and others and we plan to continue hydraulic fracturing again in the morning. Local residents should be reassured that the monitoring systems in place are working as they should. These are tiny seismic events that are being detected by our monitors as we fracture the shale rock and are not capable of being felt much less cause damage or harm.”

According to the BGS, six of the past eight seismic events reported in the UK have now been in the area around the end of the well where fracking began on 15 October 2018.

Today’s event was at 3.45pm (BST) in an area between the A583 and Peel Road. It follows a gap in recorded seismic activity in the area since 4.44am (BST) on Saturday (20 October 2018), when there was a 0.0M event.

181023 location map

Yellow rings mark location of six tremors up to the afternoon of 23 October 2018. Source: Googlemaps

The activity began last week on 18 October, when there were -0.2, -0.8 and -0.3 events. There was a single event on 19 October which measured 0.3.

Previous events had not been shown on the Cuadrilla online portal. The company said events at an amber level that occurred outside the fracturing operations were regarded as “trailing events” and would not be shown.

A spokesperson for Frack Free Lancashire said:

“Frack Free Lancashire is greatly concerned about these seismic events. It is most alarming for residents. Considering this is only the exploratory phase and only one frack a day imagine how much worse it could be.

“Who knows what is happening under our feet? This is the earth giving out a warning, as predicted by geologists following the previous failures of fracking in Lancashire. “The increased risk of larger magnitude quakes is serious. Cuadrilla must stop now, for all our sakes.”

A spokesperson for the campaign network Frack Free United said:

“To continue risks a larger ‘industry wrecking event’ , like Preese Hall 2.0. To stop just admits that they couldn’t see the fault before they started fracking. Its lose, lose, but experts have tried to mention the risks and safeguards.

“Permitted Development were to be allowed, with the present planning avoidance of seismic risk, there would be no way to stop these tremors before they happen. Yet it was only a week ago that we were told by Claire Perry, Natascha Engel and UKOOG that earthquakes are a non issue.”

A spokesperson for the pro-fracking campaign group, Lancashire For Shale, said:

“A 0.4 magnitude event like this is so small it is only possible to detect it using very sensitive instruments like those deployed locally by Cuadrilla and the British Geological Survey.

“The very open manner in which this event has been reported, and Cuadrilla’s reaction to it, demonstrates just how robust the new controls are and that the Traffic Light System is working effectively.”

59 replies »

  1. Certainly not smooth sailing for Cuadrilla. Surely fracking will cause some microseismic events because the rock is being splitting apart. But these does limit their progress. Not sure what they are testing.

    So the question is are they pushing the maximum pump rate and pressure when they trigger amber alert or this is just minimal mini frack.

          • Sherwulfe – 10 is fake news, like a lot of stuff on this website. Simple maths at one frack per day starting last Monday and Sunday off = 8 so far excluding today. I assumed from your post you already knew the number so I was testing you?

            This assumes all the sleeves operate as planned and there were no other operational issues. I have no idea how many really.

            But your anti’s at the gate should easily be able to figure the numbers out based on the frack pumps running – each frack should be continuous pump running time of 3 -5 hours. Unless of course Cuadrilla’s sound proofing is working better than expected?

            I can come down and monitor for you, using the drone will also help, but my day rate is pretty high?

            For Richard – I don’t think (but not 100% sure) they leave the pressure on when they close the sleeve. I would expect them to bleed back the pumped volume (approx) to surface pressure zero before closing the sleeve – makes sleeve closing easier as well. Makes it a lot simpler and I read somewhere in the Cuadrilla documents that they are flowing back a limited amount after each frack. The other option is to leave the pressure on and let it bleed off into the shale thereby extending the frack minutely (water is pretty uncompressible). But I think they bleed back through the well.

            • So the gate antis don’t know? This is shocking. They are not very observant. What are they there for if not to monitor the operations (other than checking if the lorry wheels are clean or not)? Are you going to take me up on my monitoring offer?

            • You may be able check by looking at the daily BGS seismographs for the nearest station to PNR – which I think is AQ05 Staining?

              http://www.earthquakes.bgs.ac.uk/helicorder/heli.html

              Sunday – nothing going on:

              Monday – something going on:

              Someone can check the daily graphs and work out how many fracks? Perhaps Prof Smythe can comment on the relevance of this technique?

            • Dear Paul and Sherwulfe
              I have asked Cuadrilla how many fracks it has carried out and when. I will let you know when, or if, I get a reply.
              Best wishes, Ruth

  2. Ermm-did anyone look at the wider stock market situation yesterday??? Certainly tremors-but nothing to do with PNR! Try Italy.

    Apologies to Ruth. It appears you spend your time reporting the information but some can’t read that. Cuadrilla decided to finish for the day when this tremor occurred late in the afternoon. All there. Nothing to get excited about.

    Who knows if this was a late in the day attempt to “push the revs” to see what resulted? Whatever, the result was some shale fracturing, hardly earth shattering.

    • Move along please, nothing to see here. Not so much as a ‘told you so’. Just miniscule tremors in invisible faults that can’t possibly get any worse because we stopped irritating them at massive pressure. Oh, and invester confidence hopefully won’t notice anything because they’re too small to even notice.

  3. I suppose if a magnitude 4.0 now occurs on the Wakepark fault over the fracturing of the well, Cuadrilla can’t really be held to be culpable. They’re following the rules as signed off by the EA & OGA. The EA and OGA have accepted and ‘signed off’ all interpretations, frack plans …

    The geology is being stressed by lots of frack fluid, presumably there’s some indication of where it’s going from the microseismic geophones array in well 2. Some of the seismic events may not be on the fracture lines, but on faults away from this activity. But Cuadrilla aren’t breaking any rules, even if all these events are on faults away from the direct fracturing lines.

    There isn’t any stipulation in the hydraulic fracture plan about when to close the frack sleeves after a frack. I assume the idea is to let the gas build up behind, ready for good flow results. So shut in straight away after a frack. But this is of course stresses the geology more and more as nothing can flow back.

    So, the Wakepark fault at this depth is about 1km away to the west? But dozens of faults probably link it all directly to the rocks Cuadrilla are fracking. So the gas and fluid is free to migrate and lubricate this nice big fault that goes all the way to the surface. How critically stressed is this fault?

    But remember, this is not the responsibility of Cuadrilla. It is the OGA and EA to apply the cautionary approach to this activity. So really, the first red event should signify a final stop to proceedings.

    • Last time a 4.4 event happened in Wales, it was met by howls of laughter from the locals. Of course that would be 10,000x more powerful than that experienced at PNR.

      • Last time a 2.5ml event occurred on the Fylde it caused wellbore ovalisation quickly followed by a fracking moratorium. Oh and that was preceded by lots of ‘tiny’ and ‘insignificant’ and ‘not felt at the surface’ tremors too.

        • So, wellbores are engineered to ovalize. Absolutely didn’t impact the integrity of the well anywhere near the surface. But who cares about facts when there is the opportunity to sensationalize, right Crembrule?

          • Mmmmmkay Bob, that’s a new one on me and if that was the case why would a design feature working within parameters lead to a shut down of all activity on national scale? That said I am no expert and would be glad to look at any information you might be able to point me too on this deformation being a designed in.

    • Richard
      Or …

      If a magnitude 4 fault occurs on the Wakepark fault while fracking, or not, Cuadrilla will, very likely be in the frame as while the EA etc have accepted the frack plans, they have not accepted a magnitude 4 event on that fault. A bit like the HSEx accepting a safety case does not mean that they accept anything going wrong on the platform is OK.

      Then .. on no evidence …

      The well raddled ground ( riddled by dozens of small faults ) is allowing fracking to proceed in an enhanced way as each fault, conveniently running N/S is allowing more fractures with less effort. No doubt someone will say the ground is naturally fractured, but unfortunately well compressed by the horizontal stresses, such that it has to be pried apart by fracturing it.

      No faults are being lubricated as if they were, all the water would have disappeared up them, a bit like trying to inflate a tyre when it has a hole in it.

      But ….

      The responsibility to follow the frack sits with Cuadrilla, although the first red event will show how well the system works, compared to working without such a system, and whether 0.5 is a suitable level to stop while things cool,off, or a higher number is ok. A point which will exercise the minds of critically stressed observers for a few months I suspect.

      Just whiling away the time to the next event.

  4. Bad taste humour alert .. all this reminds me of the joke about God not minding (too much) about America going to war – because it teaches them geography. Here we’ve got Cuadrilla going to frack because it teaches them geology. Pretty soon they might catch up with the (old) knowledge that UK strata are highly warped and faulted, and that pre-stressed faults will release seismic events. Duh.

    No vast, neatly stacked Permian basin to be found here.

  5. Crembule refers to the Preese Hall-1 earthquakes of 2011. These provide a good lesson.

    Scientifically Cuadrilla’s current slice-and-dice approach to the overall fracking job in a well is untenable, because there is often a delay between the end of an injection stage and the onset of a triggered event caused by the injection. For example, the Cuadrilla-commissioned report into the earthquakes triggered by fracking of shale in the vertical Preese Hall-1 well notes that the two strongest tremors (of magnitudes 2.3 and 1.5) each occurred about 10 hours after the cessation of injection in stages 2 and 4 respectively. The injection fluid needs time to seep along a fault zone until such time as enough of the fault has thereby been lubricated. If the shale is critically stressed – that is, it is ready to crack – the fault will slip, causing the earthquake.

    Cuadrilla was eventually forced to admit that these earthquakes were caused by fracking at Preese Hall-1, although initially it denied any link. Unfortunately for Cuadrilla, all the shale in the Bowland Basin seems to be critically stressed, so the problem won’t simply disappear.

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