Geologists say Horse Hill oil site likely to blame for earthquakes

Press release from the Weald Action Group

As an earthquake rocked the Charlwood area this morning [1], scientists from Edinburgh University have made a submission to Surrey County Council [2] which points the finger at the Horse Hill oil site for 13 quakes in Surrey in 2018.

In December the Oil and Gas Authority ruled out a human cause for the shallow quakes, which were without precedent in the region. It said nothing was going on at Horse Hill, so it excluded it from its analysis. But the Edinburgh team said one possible cause could be release of pressure at Horse Hill well site: “We infer that management of this pressure (probably by bleeding the well annulus prior to testing) likely altered the Horse Hill fault stress balance, which then impacted on the Newdigate fault, causing the earthquakes”.

The Edinburgh University team’s research shows that there was work on the site before the quakes started in April and “the earthquakes in August and September coincide exactly with the deployment of a perforation gun downhole to improve flow”. They have produced a timeline of activity.

They conclude: “our assessment supports the concern that Horse Hill oil exploration triggered the earthquakes. We infer that future oil exploration and production close to critically stressed faults in the Weald is likely to result in similar earthquake events”.

The Weald Action Group [3] says the company behind the drilling should provide its well and site engineering logs for the relevant period. So far Horse Hill Developments Ltd has not provided any information.

James Knapp of the Weald Action Group said: “The Oil and Gas Authority appears to have been less than rigorous in researching what caused these quakes. Horse Hill Developments Ltd hasn’t provided the information that’s needed for a proper assessment and what information there is available clearly points the finger at their well site.

With plans afoot for a massive increase in oil extraction at this site, this matter needs to be thoroughly investigated before any decisions are made. We support calls for a moratorium on drilling and on decisions on planning applications which might cause quakes. They have caused a lot of concern locally and the process of analysing the cause of the quakes has been far from transparent”.


[1] Magnitude 2.4

Felt in the Charlwood area – residents report a large bang and it being “scary”

[2] Further Potential for Earthquakes from Oil Exploration in the Weald, by Dr Andrew Cavanagh, Dr Stuart Gilfillan and Professor Stuart Haszeldine, School of GeoSciences, The University of Edinburgh, 5 Feb 2019

Submitted to Surrey County Council with reference to the current planning application.

[3] The Weald Action Group is an umbrella organisation for community groups across the South East opposing extreme oil and gas extraction.

One Response

  1. j morrow says:

    The company which has been fracturing the earth under our homes in the Fylde have admitted to causing earthquakes round here. People/media and all the confusing information streams tell me that the the drillers think that the limit on the size of earthquakes that people are allowed to cause is too low. John McDonell visited Preston New Road drilling site and he told our Labour candidate Jed Sullivan that Labour would ban Fracking like many other countries already have done and are doing. Local democracy voted against fracking in Lancashire and central government’s Sajid Javid MP overturned the local vote. At the end of the day ordinary people get to vote every now and then. We have to balance out the confusing messages and the lies from what we think the truth might be. Do your best to sort it all out with your own brain and vote. Meanwhile the nations school children strike to ask us to think about their future. As I write this note of support to the terrified folk living near earthquakes in Surrey. I still don’t know what our local frackers are up to apart from the fact that we were told recent earth tremors above the limit may have been caused by them as the injection of all the stuff they were pumping was susspended and the drilling rig has been moved but now there is a big fence there looking like it is hiding something. Locals have been told nothing. I notice that my tap water pressure still seems variable but there are thousands of new houses going up round here as well. Yup you guessed and not a single sign of any renewable power schools or doctors or much forward thinking beyond how Amy how much. Of course its all part of the same dinosaur thinking this is what our children are trying to tell us when they’re not being brainwashed.

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