Implications of earthquakes triggered by massive injection of produced water in saline aquifers for large-scale geologic storage of CO2

It is well-established that to significantly decrease greenhouse gas emissions, CO₂ capture and storage in subsurface geologic formations (CCS) must occur at an enormous scale. In this context, large-scale injection of supercritical CO₂ into saline aquifers is an analogous process to the disposal of large volumes of saltwater co-produced with oil and gas (SWD). However, large-scale SWD in saline aquifers over the past 15 years in the mid-continent of North America has caused a remarkable increase in intraplate seismicity. Since 2010, nearly 4 billion m³ of produced water has been injected into sedimentary layers that are in hydraulic communication with seismogenic geologic basement in Oklahoma and Texas alone, triggering earthquakes as large as magnitude 5.8 and more than 200 M ≥ 4.0 earthquakes that were widely felt. Every case of large-scale SWD in the mid-continent in deep saline aquifers in hydrologic communication with basement has caused significant induced seismicity. If CO₂ storage projects are associated with induced seismicity, they could be perceived by the public as a hazardous activity which should not be allowed to continue, generally regardless of the magnitudes of the induced events. Thus, among many challenges (operational, geologic and economic), large-scale CCS projects will face, they also will need to minimize the occurrence of injection-induced seismicity. In this paper, we review the extensive research carried out in four regions of the central U.S. with abundant seismicity induced by large-scale SWD in central U.S. as an analogous process to large-scale CO₂ injection. Our primary purpose is to inform non-experts of the key findings of the large body of scientific evidence now available in these areas that help guide decision making related to finding viable options for long-term, large-scale CO₂ storage in geologic formations.