Fracking continues through series of tremors

The warning system for seismic events at fracking sites has been criticised by one of the experts who advised the government on creating it.

The warning came on a day when there were four tremors within a few hours at Cuadrilla’s Preston New Road fracking site near Blackpool.

Peter Styles, emeritus professor of geophysics at Keele University, was one of a committee of three experts who advised the Department of Energy and Climate Change (DECC) on the traffic light system for tremors in 2011.

Under the system, seismic events of less than zero earn a green light, meaning fracking can continue unimpeded. Tremors of between zero and 0.5ML magnitude trigger an amber warning, meaning fracking can proceed “with caution, possibly at reduced rates. Monitoring is intensified”. More than 0.5ML means a red light and an immediate halt to fracking.

On Tuesday 23 October a 0.4ML event in the afternoon brought an amber warning. Cuadrilla says it exceeded its regulatory requirements by halting fracking and only resuming the morning after.

According to Styles, that restriction “was never our intention”. He advocated a monitoring system that was not confined only to the time when fracking was actually taking place.

But, on resumption, a larger tremor – of 0.48ML at 1.02pm on Wednesday afternoon – did not fall under the traffic light system because Cuadrilla was not actually pumping fluids at the time.

According to Styles, that restriction “was never our intention”. He advocated a monitoring system that was not confined only to the time when fracking was actually taking place.

Styles said the process by which fracking led to tremors was complex and not fully understood. Some are caused by the vibrations caused by fracking, but more occur when liquid from fracking enters a geological fault and causes it to move.

As there is a delay in this, Styles said the traffic light system should extend beyond the end of fracking operations.

“The actual definition of how Cuadrilla responds to this has been agreed partly by Cuadrilla and partly by the Oil and Gas Authority now DECC doesn’t exist,” he said. “I have discussed this with the OGA.”

There have now been 10 seismic events recorded by the British Geological Survey since last Thursday, only days after Cuadrilla started fracking at Preston New Road.

It had been forced to stop fracking at nearby Preese Hall in 2011 after earthquakes of 2.3ML, and only started again after a protracted planning battle, the introduction of a new regulatory regime and determined, widespread protest.

In a statement on Wednesday evening, a Cuadrilla spokesperson said: “Following on from hydraulic fracturing operations today Cuadrilla has detected micro seismic activity of 0.48ML. This is within operating expectations and the sophisticated system of monitoring in place is working as it should.

“Local residents should be reassured that the monitoring systems in place are working as they should.”

“We understand that the British Geological Survey has rounded this up to a 0.5ML. Regulators have been advised and we anticipate we will continue work at Preston New Road tomorrow as planned.

“As we have said before, 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 2km underground and are many hundreds of orders of magnitude below what is capable of being felt, much less cause damage or harm at surface.”

Styles has warned previously that fracking on top of previous coal mining sites could be dangerous. That included other areas in the north where companies are hoping to drill.

He said the seismic events of recent days threaten Cuadrilla’s operations but, along with other experts, emphasised that they were too small to threaten the public. He said he actually recommended a higher threshold of magnitude before fracking was halted but DECC decided to use 0.5ML as the cut-off point.

He added that experts only have UK fracking data from Preese Hall, and a 1988 experimental drill by BP – which he monitored. “It may be that we learn that this is OK, that it’s not something we need to worry about, but softly softly catchy monkey,” he said.

This “scant piece of legislation has been poorly drafted, since it appears to permit tremors occurring after the end of a period of injection to be discounted”.

He has today urged Cuadrilla to try to differentiate between different types of tremor.

“What I have suggested to Cuadrilla is that you can tell the difference between these types of events, because they have different seismic signatures,” he said. “You can tell whether it’s a fault moving or you are forcing the rock apart with fluid. One is a sliding motion along a fault and one is like a tearing motion.”

David Smythe, emeritus professor of geophysics at Glasgow University, also criticised the traffic light system, saying this “scant piece of legislation has been poorly drafted, since it appears to permit tremors occurring after the end of a period of injection to be discounted”.

He added: “Unfortunately for Cuadrilla, all the shale in the Bowland Basin seems to be critically stressed, so the problem won’t simply disappear.”

The OGA has been contacted for comment.

UPDATE, 26.10.18

An OGA spokesperson said it had no plans to alter the traffic light system in response to criticism.

The spokesperson said: “The OGA has strict controls in place to ensure that operators manage the risk of induced seismicity. This includes a requirement for operators to undertake detailed geological studies, and submit a hydraulic fracture plan setting out how they will control and monitor seismicity throughout the fracturing process and assess the risk of induced seismic events.

“The OGA is satisfied that Cuadrilla is acting in accordance with the strict controls in the hydraulic fracture plan.”

Asked whether Cuadrilla’s hydraulic fracture plan ought to be revised in light of the series of tremors that had taken place, the spokesperson said: “The low-level seismic activity that has been detected at the Preston New Road site is within the range expected for fracturing operations, of a magnitude that can only be detected with specialist equipment and cannot be felt at the surface.

“The strict controls in the hydraulic fracture plan, which has been approved by the OGA and the Environment Agency, remain robust.”

Photo: Stewart Kirby/Getty Images

Read more of our fracking coverage at https://www.bigissuenorth.com/search/fracking/