An expert report on the seismic events experienced in the UK Blackpool area last year during hydraulic fracturing operations at Preese Hall was published by the UK Department of Energy and Climate Change (DECC) on 17. April 2012 (see DECC website for background information). The report reviews earlier reports commissioned by the operator Cuadrilla on the seismic events and recommends mitigation measures. The report is open to public comments until 25 May 2012.

Accordance and differences

The DECC report agrees with Cuadrilla-commissioned reports that the 2011 seismic activity was caused by hydraulic fracturing operations. But the DECC report questiones the projected low probability of other earthquakes during future treatments due to the lack of detailed knowledge of faulting in the basin. The DECC report supports the "traffic light system" proposed in the Cuadrilla-commissioned reports, but recommends a lower maximum magnitude threshold of 0.5 ML instead of 1.7 ML.

Recommendations

To mitigate the risk of future earthquakes in the Bowland Basin, the following recommendations are made:

1. Hydraulic fracturing procedure should invariably include a smaller pre-injection and monitoring stage before the main injection.
2. Hydraulic fracture growth and direction should be monitored during future treatments.
3. Future HF operations in this area should be subject to an effective monitoring system that can provide automatic locations and magnitudes of any seismic events in near realtime.
4. Operations should be halted and remedial action instituted, if events of magnitude 0.5 ML or above are detected.

Future hydraulic fracturing operations

The authors conclude about future hydraulic fracturing operations that "based on the induced seismicity analysis done by Cuadrilla and ourselves, together with the agreement to use more sensitive fracture monitoring equipment and a DECC agreed induced seismic protocol for future operations, the authors of this report see no reason why Cuadrilla Resources Ltd. should not be allowed to proceed with their shale gas exploration activities and recommend cautious continuation of hydraulic fracture operations, at the Preese Hall site."