Why we need passive seismic monitoring for CO2 storage 

The context of this project is a wider need to understand the risks of small and large earthquakes in regions where CO2 injection projects are planned or in operation. The potential for induced seismicity has been identified as a key potential showstopper for CO2 storage projects (IEAGHG, 2015, Mission Innovation report 2019). Another reason is the concern of potential ‘false alarms’, when earthquakes are suspected of being caused by CO2 injection when they are in fact due to natural tectonic processes or related to hydrocarbon production.

Over the last decade, several CO2 storage projects have demonstrated the value and importance of passive seismic monitoring designed to quantify natural seismicity and identify the characteristics of induced seismicity (e.g. Goertz-Allmann et al. 2014; White and Foxall, 2016). Seismic monitoring is therefore considered an essential part of monitoring programs for CO2 storage sites (e.g. Bourne et al., 2014), with the overall objectives of: 

  • Understanding natural (background) seismicity 
  • Monitoring and controlling any seismicity that might be induced by injection or other operations. 

So far, passive seismic monitoring for CO2 storage has mainly focused on onshore sites, where costs related to the monitoring networks are relatively low. Applying passive seismic monitoring for offshore CO2 storage is more challenging, both in terms of cost and logistics. However, passive seismic monitoring for offshore oilfield projects is being increasingly used with demonstrable benefits for controlling and optimizing projects (e.g. Barkved & Kristiansen 2005; Oye et al., 2014; Bussat et al., 2016). 
In general, the understanding of seismic hazard for CO2 injection projects is still immature with ongoing work on characterizing the hazard functions (e.g. White and Foxall, 2016) and the nature of potential induced seismicity (e.g. Goertz-Allmann and Wiemer, 2012). Consequently, developing a natural seismicity monitoring plan for offshore CO2 storage sites is a topic requiring further research and development efforts