Fracking and fluid-induced microseismicity: a toll for our energy thirst?

AXA Postdoctoral Fellowand BGSMath Faculty member Jordi Baró i Urbea is developing stochastic models that will distinguish between natural seismicity and human-induced seismicity. In this article, he explains how he hopes to detect, predict, and prevent the seismic hazard related to human activities and minimise their risks.

During the last decades, we have witnessed an unprecedented increase in earthquakes related to human activities. Most of them involve the injection of highly pressurized fluids into deep layers within the Earth’s crust, in a quest to squeeze our almost-depleted hydrocarbon reserves or to harness the power of geothermal heat. As a paradigmatic example, the number of earthquakes in the state of Oklahoma has increased by a factor of five between 2000 and 2012 and by almost 300 by 2015, to become the most seismically active region in the USA. This increase in seismic activity seems to be related to the massive increase in the number of operations of stimulation of gas and hydrocarbon reservoir through hydraulic fracturing, or ‘fracking’, and the underground disposal of its residual wastewater. The artificial enhancement of geothermal systems (also called EGS) provides an energy source much more sustainable than fossil fuels, but also relies on the injection of fluids to deep layers of the Earth crust. The problem is that EGS can also activate dormant faults and trigger strong earthquakes. This happened in the case of the 5.5-magnitude earthquake that struck Pohang, a densely populated region of South Korea on 15 November 2017. The seismic event and its aftershocks, causing $52 million in damage, were allegedly triggered by a state-of-the-art EGS operation. Other human activities involving injection of fluids have also been related to seismic activity. A local example of this phenomenon is the alarming earthquake swarm activated offshore Tarragona and Castelló, in September and October 2013, during the preliminary tests of the Castor project using a depleted natural gas reservoir for storage. The concern about this problem is growing worldwide, and collaborations between research institutions, public and private companies and policy makers are sprouting worldwide. We all have a clear goal: to understand, predict and prevent anthropogenic fluid-induced seismicity. Projects such as GEISER in the EU, SCITS in the USA, the RING-GOCAD Consortium in France or the MIC in Canada are good examples of these collaborations.  

Industry partners are usually able to provide detailed geomechanical data of actual reservoirs and share the injection protocols used during their operations. Interdisciplinary research teams formed by geophysicists, seismologists, engineers, physicist and applied mathematicians use this data to develop and improve mathematical models of fluid-induced microseismicity based on their knowledge on fluid and wave propagation, material and fault mechanics and poromechanics.

The models are tested against the available seismic information of the area and catalogues obtained through ad-hoc seismometer and geophone arrays active during and way after the operation. The overall research effort is used to design new hazard assessment techniques and protocols for risk mitigation that are proposed to policy makers.

Part of my current research is in collaboration with several labs in the University of Calgary associated to the MIC of Canada. As I have explained, human-induced activities are indeed capable of activating tectonic faults. But statistics can give us a hand to distinguish between fluid-induced microseismicity and tectonically activated seismicity. I am now studying the statistics and spatio-temporal correlations in microseismic catalogs, and the development of a stochastic model for fluid-induced microseismicity. Our model links together different conceptual paradigms in fracture modelling, such as percolation, fluid diffusion and stick-slip mechanics (the spontaneous jerking motion that can occur while two objects are sliding over each other). Our final goal is to understand how the fundamental features in the geomechanics determine the statistical laws of the microseismic catalogs.

Our hope is that, through our joint efforts, in the future we will be able to detect, predict and prevent the seismic hazard related to human activities, minimize risks and ascert responsibilities in the eventual case of damages and losses. Thanks to our research, fluid-induced microseismicity might, one day, be excluded from the long list of unavoidable tolls and consequences of our thirst for energy and scarce resources. (Jordi Baró i Urbea)




Jordi Baró i Urbea

AXA Postdoctoral Fellow

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