Keele’s research on fracking has guided UK government policy for shale gas extraction over the past decade, informing stakeholders on causes of fracking-related seismicity and identifying high-risk regions and procedures to mitigate risk. Recommendations from Keele’s research led to the ‘traffic light’ system of magnitude limits, enforcing operators to conduct detailed surveys. Based on Keele’s research, The Oil and Gas Authority placed a moratorium on fracking in England from November 2019.
Issue
Fracking generates networks of small fractures in impermeable rock, injecting a mix of water, sand and chemicals under high pressure, creating pathways along which hydrocarbons flow. This generates microseismic activity with magnitudes too small to be felt. However, if the injected fluid encounters a pre-stressed pre-existing geological fault, the change in fluid pressure can cause the fault to fail, inducing larger seismic events that can potentially damage surface infrastructure. Given that not all locations of natural faults are known in advance, currently it is not possible to accurately predict the probability of fracking-associated tremors.
Approach
The Keele Applied and Environmental Geophysics (KAEG) group, in collaboration with the British Geological Survey (BGS), led research into ‘induced’ seismicity related to hydraulic fracturing (fracking).
KAEG’s work, with Durham and Newcastle universities, established a national baseline for human induced earthquakes in the UK. The research found that from the mid-1980s to the 2000s such earthquakes declined per year.
KAEG has applied its expertise in geomechanical modelling to understand the level of stress changes caused by fracking and the influences these have upon geological structures, including faults.
Impact
Over the past decade, KAEG has advised the UK government on how fracking-related earthquakes are caused, high-risk areas where fracking should be avoided, and procedures needed to minimise the risk of fracking-induced earthquakes.
Following fracking-related seismic activity at Preese Hall, Lancashire, the UK government reviewed regulations and, in 2012, introduced a traffic light system. Further recommendations have also been implemented, including the requirement of operators to conduct local geological studies, including mapping faults and fully understanding local geology, to assess whether fracking could reactivate existing faults.
In August 2019, fracking began at Preston New Road 2, Lancashire, after agreeing a Hydraulic Fracture Plan with fracking operator Cuadrilla. The plan proposed mitigation measures including the traffic light system. A series of seismic events were recorded including red-light events, which led to suspension of fracking operations.
More information
Institution: Keele University
Researchers: Professor Peter Styles, Dr Ian Stimpson, Dr Nigel Cassidy, Dr Jamie Pringle, Dr Glenda Jones, Dr Rachel Westwood, Samuel Toon