Research highlights

• Provided critical analysis that informed the UK government’s decision to pause fracking in 2019.
• Improved monitoring array design and processing methods that produced significant savings for operators in monitoring costs.
• Created magnitude scales and forecasting systems that operators and regulators used to guide real-time safety decisions.

The shale gas extraction (or fracking) industry is valued globally at over $40 billion a year. However, fracking remains controversial with high levels of public concern surrounding the potential for the practice to cause earthquakes.

Bristol’s research into small earthquakes generated by industrial activities in the subsurface, known as microseismicity, has played a major role guiding the debate, shaping regulatory and industry practices and ultimately providing critical analysis that informed the UK government’s decision to introduce a moratorium on fracking in 2019.

Breaking new ground

Many human activities in the subsurface create microseismicity – earthquakes that are too small to feel. However, occasionally these activities create larger seismic events that can be felt and could potentially cause damage. It is these larger ‘induced’ seismic events that have raised safety concerns for the shale gas industry.

Established in 2004, Bristol University’s Microseismicity ProjectS (BUMPS) leads the way in measuring and analysing patterns of microseismicity caused by human activities and, since 2013, has responded to concerns around fracking by generating the tools and science needed to inform safety decisions.

Research breakthroughs have included new monitoring techniques, including full-waveform methods, Fiber-Optic Distributed Acoustic Sensing and machine learning to detect and locate microseismic events generated by subsurface activities.

The combination of these methods has dramatically improved the industry’s ability to detect small-magnitude microseismic events. Improvements to monitoring efficiency and accuracy have also significantly reduced the projected costs of monitoring deployments for operators by several million pounds.

In addition, the team has created new magnitude scales for the accurate calculation of event magnitudes, which is critical for assessing induced seismicity hazard.

New forecasting tools developed by BUMPS have also empowered real-time operational decision-making to mitigate induced seismicity during hydraulic fracturing, enabling operators and regulators to ask the question, “what event magnitudes might be reached if operations continue as planned?”

Informing government decision making

Since 2013, BUMPS researchers have worked closely with the North Sea Transition Authority (NSTA) and the Environment Agency (the regulators of the shale gas industry in the UK) to reach significant safety decisions.

All three major hydraulic fracturing companies in the UK (Third Energy, IGas and Cuadrilla) have also worked with BUMPS to help ensure safe conduct related to both induced seismicity and the potential for shallow groundwater contamination.

This triangular collaboration between our scientists, fracking operators and the regulatory authorities ultimately led to the UK pausing fracking. In 2019, an M 2.9 scale event occurred at the Cuadrilla Preston New Road site in Lancashire. The event had been predicted as ‘likely’ by the BUMPS system without mitigative measures, but were not prevented by operational adjustments made.

BUMPS’ updated forecasts showed that events with magnitudes larger than M 3 might be expected if operations were to continue. The NSTA (then known as the Oil and Gas Authority) subsequently halted all hydraulic fracturing activities at the Preston New Road site.

Following the incident, the NSTA commissioned BUMPS researchers to draft reports that directly informed the UK government’s decision to impose a moratorium on fracking that is still In place today.

The government stated that “ministers took the decision on the basis of the report by the Oil and Gas Authority”, confirming BUMPS’ prominent role in influencing this highly significant government decision.

Wider impact

Beyond its influence on the fracking industry, BUMPS expertise in microseismicity has also brought economic and efficiency benefits for the construction industry.

In 2017, for example, BUMPS provided quantitative assessment methods for the construction of Hinkley Point C nuclear power station which allowed Kier BAM to measure rock disturbance more precisely.

The results of these geophysical surveys culminated in a reduction in the construction programme of around four weeks, saving labour and material costs of approximately £225,000.  

BUMPS’ reputation for microseismic monitoring has also led to the creation of a profitable spin-off consultancy company, Outer Limits Geophysics, which was formed in 2014 and now has global reach.

Among other many projects, the consultancy has provided seismic monitoring services in Saskatchewan, monitored for induced seismicity for a hydraulic fracturing operator in Türkiye and designed geophysical arrays for monitoring geomechanical deformation in the North Sea.