The Horse Hill oil field was discovered in 2015
Invicta Kent Media/Shutterstock
More than 100 earthquakes that have struck southern England are likely to have been caused by oil extraction, experts say. Previous studies ruled out a link, but new information about the geology of the area has established a likely link.
The relatively small earthquakes, ranging from 1.34 to 3.18 on the Richter scale, occurred near Newdigate in Surrey in 2018 and 2019. Residents reported. houses shaking for a few seconds.
There was speculation at the time that the earthquakes were linked to oil extraction by UK Oil & Gas, although the epicenter was 5 to 10 kilometers from the company. Horse Hill drilling site But previous research The British Geological Survey (BGS) and others determined that the earthquakes, although rare and relatively close to drilling, were natural and random.
now, Matthew Fox and Philip Meredith University College London have taken another look, using the latest understanding of the rock composition in the area, suggesting that the earthquake was triggered by oil extraction.
The pair ran more than a million computer simulations based on the location and magnitude of the oil spill, along with details of the surrounding geology, and found that the earthquake predictions matched the actual events more closely than expected.
When oil comes up from deep underground it changes the pressure on the surface, which can cause rock movements that can cause earthquakes. Fox says there were earlier discrepancies in the dates of the earthquakes and when the oil came out, which can be accounted for by considering the geology of the areas being drilled today.
The pair found that in regions of porous Portland rock, pressure changes and rock movement could occur almost simultaneously, while in areas of dense Kimmeridge Clay there could be a delay as pressure changes take time to propagate.
“To me, that makes it more likely (that oil extraction caused the earthquakes),” Fox says. “The correlation between the two – between oil extraction and seismicity – is quite high, which suggests that there is a connection.”
Fox says there’s still room for the link to be a coincidence, but that’s now more likely than previous research has suggested. He expects further statistical analysis to precisely quantify the likelihood of coincidence, but stopped short of making an estimate with the current data.
Controlled UK oil and gas oil extraction at Horse Hill until last October, when work stopped After planning permission was withdrawn from Surrey County Council following a lawsuit brought by campaigners Supported by Friends of the Earth.
A company spokesman said The New Scientist: “This is an event that was answered and worked on many years ago, when BGS seismologists were confident that it was a natural event associated with movement on a deeper unconnected fault many kilometers deeper and further away from the site.”
But Stuart Haszeldine at the University of Edinburgh, who was not involved in this particular study, but has done his work with colleagues, says it is now very likely that there is a link between oil extraction and earthquakes.
“We have done a detailed study of these small earthquakes in Surrey and the possibility that the tremors may have been linked to activity in the Horse Hill oil field,” says Haszeldin. “In my view, there was a clear connection between the timing of the earthquake and the operational activities to produce oil and gas from the Horse Hill site.”
Topics:
