Induced seismicity in geologic carbon storage

Abstract

Abstract. Geologic carbon storage, as well as other geo-energy applications, such as geothermal energy, seasonal natural gas storage and subsurface energy storage imply fluid injection and/or extraction that causes changes in rock stress field and may induce (micro)seismicity. If felt, seismicity has a negative effect on public perception and may jeopardize wellbore stability and damage infrastructure. Thus, induced earthquakes should be minimized to successfully deploy geo-energies. However, numerous processes may trigger induced seismicity, which contribute to making it complex and translates into a limited forecast ability of current predictive models. We review the triggering mechanisms of induced seismicity. Specifically, we analyze (1) the impact of pore pressure evolution and the effect that properties of the injected fluid have on fracture and/or fault stability; (2) non-isothermal effects caused by the fact that the injected fluid usually reaches the injection formation at a lower temperature than that of the rock, inducing rock contraction, thermal stress reduction and stress redistribution around the cooled region; (3) local stress changes induced when low-permeability faults cross the injection formation, which may reduce their stability and eventually cause fault reactivation; (4) stress transfer caused by seismic or aseismic slip; and (5) geochemical effects, which may be especially relevant in carbonate-containing formations. We also review characterization techniques developed by the authors to reduce the uncertainty in rock properties and subsurface heterogeneity both for the screening of injection sites and for the operation of projects. Based on the review, we propose a methodology based on proper site characterization, monitoring and pressure management to minimize induced seismicity.

Unraveling the Causes of the Seismicity Induced by Underground Gas Storage at Castor, Spain

“…Apart from pressure buildup, other triggering mechanisms may induce seismicity (Brown & Ge, 2018;Jiang et al, 2020;Vilarrasa et al, 2019). In particular, buoyancy need to be considered when gases are injected because their density is lower than that of water, which generates buoyancy-induced stress redistribution around the storage formation (Figure 2a).…”

Sensitivity Analysis of Geomechanical Constraints in CO2 Storage to Screen Potential Sites in Deep Saline Aquifers

“…The lower the pressure buildup at the caprock, the more the caprock stability and, consequently, the more confidence in the reservoir for storage of carbon dioxide. Vilarrasa et al (2019) studied the stress states in different CO 2 storage sites and concluded that all the sites were far from being critically stressed. Thus, they could sustain a fair amount of pressure buildup due to fluid injection.…”

“…In the case of the longterm injection scenario of 50 years, maximum pressure change was observed to be more than 11 MPa-a 75% increase from the initial pore pressure of 14.7 MPa. Such a substantial pressure buildup could induce significant seismicity and lead to pore pressure exceeding the minimum principal stress, based on stress data by Vilarrasa et al (2019). Thus, CO 2 injection needs to be carefully planned depending on the initial reservoir conditions and duration of the storage project.…”

“…The potential magnitude of a seismic event correlates strongly with the fault rupture area, which, in turn, relates to the magnitude of the pore pressure change and the rock volume in which it exists (Verdon, 2011). The induced seismicity can severely affect reservoir integrity and cause conditions that could lead to caprock failure along with a risk of the generation of new faults (Shukla et al, 2010;Vilarrasa et al, 2019). Thus, the practical storage capacity of the reservoir is not only limited by the empty volume in the rocks but also by the maximum sustainable pressure buildup.…”

Sinking CO2 in Supercritical Reservoirs

“…However, CCS should overcome two main hurdles, namely, the risks of induced seismicity (Vilarrasa & Carrera, 2015;Zoback & Gorelick, 2012) and CO 2 leakage (Lewicki et al, 2007;Nordbotten et al, 2008;Romanak et al, 2012), before its widespread deployment takes place. Proper site characterization, monitoring, and pressure management should allow minimizing the risk of perceivable induced seismicity in Gt-scale CO 2 injection (Celia, 2017;Rutqvist et al, 2016;Vilarrasa et al, 2019). The considered storage formations to date include deep saline aquifers, depleted oil and gas fields, and unmineable coal seams in which CO 2 stays in supercritical conditions with a relatively high density but lower than the one of the resident brines (Hitchon et al, 1999).…”