In the UK, we have been regulating for gas and oil drilling, both onshore and offshore, for many years and have one of the best track records in the world when it comes to protecting our environment while also developing our industries.
The Oil and Gas Authority (OGA) monitors seismicity as part of their regulatory duties at shale gas sites. Before consent for hydraulic fracturing is granted, a Hydraulic Fracture Plan must be agreed with the OGA. Operators have to evaluate the historical and background seismicity and the in-situ stress regime, and delineate faults in the area of the proposed well to identify the risk of activating any fault by hydraulic fracturing. The fracture plan also includes appropriate plans to monitor seismicity before, during and after the well operations.
The OGA requires certain controls and requirements to be adhered to by an operator including following a real-time traffic light system during hydraulic fracturing. If a seismic event over 0.5ML on the ‘Richter Local Scale’ (a ‘red’ event) is detected and causally linked to the operations, hydraulic fracturing is suspended for a minimum of 18 hours.
Seismic events with a magnitude of 2.0 or below (on the Local Richter Scale) are usually not felt at the surface and a magnitude 0.5 is far below the ground motion caused by a passing vehicle, for context, the British Geological Survey has estimated that in the UK we have, on average, around 166 natural occurring earthquakes of 2.9ML and below per year.