The ‘unconventional’ oil & gas extraction industry (often referred to as the fracking industry) is regulated by the Oil and Gas Authority (OGA), who have set low limits on induced seismicity and require the developers to operate a ‘traffic light’ system to manage their activities.

They must halt activity if an event of magnitude 0.5 is detected, irrespective of its effect at the surface. Geothermal developers are not regulated by the OGA and are not required to adhere to their limits or their methodology. This does not mean that geothermal projects are unregulated; just that they are regulated in a different way.

The most important difference as far as GEL projects are concerned is that our seismicity management protocol is based on ground vibration at the surface, not on event magnitude at the source. We believe that this is a more appropriate methodology since it relates directly to the impact on people and property and it is consistent with planning regulations already in force in Cornwall for other industries that could cause ground vibrations, such as mining, quarrying and construction.

GEL operates at very conservative vibration limits. Cornwall Council set a maximum PGV of 8.5mm/s for a single event in their daytime blasting regulations, and previous research suggests that humans cannot generally feel movements with a PGV of less than 2mm/s. However, at United Downs a maximum PGV of 0.8 mm/s was felt by some individuals. Therefore, operations at all GEL sites will enter a ‘caution’ state if events with a PGV greater than 0.5mm/s are detected during the day. Above this, operations will be closely monitored and if further significant events are detected, operations will cease until the reservoir stabilises.