Induced earthquake potential in geothermal reservoirs: Insights from The Geysers, California

Abstract

Geothermal reservoir production and associated induced seismicity may experience pronounced attention in the near future, given the ambitious plans for reducing greenhouse gas emissions toward a carbon-neutral economy and society. At some geothermal sites, the occurrence of hazard- and risk-prone induced earthquakes caused by or associated with reservoir stimulation has resulted in project shutdown (e.g., Pohang, South Korea, and Basel Deep Heat Mining, Switzerland). At other geothermal sites, the maximum event magnitudes were successfully maintained below a threshold defined by local authorities (e.g., Helsinki St1 Deep Heat project in Helsinki, Finland). In this study, we review some of our results from seismological and geomechanical reservoir characterization at The Geysers geothermal reservoir in California, USA, the largest producing geothermal field worldwide. We relate our findings to other geothermal sites to better understand the variability of reservoir behavior. In particular, we obtain a constant and relatively low seismic injection efficiency at The Geysers, which is interpreted to be related to the large energy dissipation through thermal processes and additional dissipation through aseismic slip, the latter now being considered to play a fundamental role in earthquake nucleation. We discuss some characteristics of the seismicity from The Geysers that suggest stable reservoir seismic injection efficiency and possibly low potential to rupture into large induced earthquakes, reducing the associated seismic hazard.

Limited Earthquake Interaction During a Geothermal Hydraulic Stimulation in Helsinki, Finland

“…Activation and growth of a small-scale network of randomly distributed fractures and joints may be less prone to host larger seismic events (cf. discussion in Martínez-Garzón et al, 2020). Therefore, near-realtime assessment of spatio-temporal behavior of seismic event locations, focal mechanisms, and temporal evolution of statistical properties such as b-value, c-value, and d-value (Dresen et al, 2020;Eaton & Igonin, 2018;Goebel et al, 2017;Schoenball et al, 2015) is key to identify the existence/emergence of large fault structures.…”

“…For example, McGarr (2014) proposed that total seismic moment release (the static deformation caused by earthquakes) and maximum event magnitude increase linearly with total volume of fluid injected, 𝐴𝐴 𝐴𝐴 max 0 ∝ 𝑉𝑉 1 , 𝐴𝐴 ∑ 𝑀𝑀0 ∝ 𝑉𝑉 1 , or alternatively to the volume of rock mass perturbed by fluid injection 𝐴𝐴 𝐴𝐴 perturbed and average pore pressure increase in that volume, 𝐴𝐴 𝐴𝐴 max 0 ∝ 𝑉𝑉 perturbed Δ𝑃𝑃 (cf. Kwiatek et al, 2015;Martínez-Garzón et al, 2020). The fracture mechanics-based model of Galis et al (2017) provided estimates of the maximum magnitude of self-arrested ruptures increasing nonlinearly with total fluid volume, 𝐴𝐴 𝐴𝐴 max 0 ∝ 𝑉𝑉 3∕2 .…”

Detecting the Preparatory Phase of Induced Earthquakes at The Geysers (California) Using K‐Means Clustering

“…This area is a well-known, very active geothermal area, being one of the largest geothermal IACCARINO AND PICOZZI 10.1029/2023JB026429 4 of 18 fields in the world (Bentz et al, 2019). The area is characterized by the occurrence of induced and triggered seismicity due to the human activities related to the geothermal field exploitation for energy production (Majer & Peterson, 2007;Martínez-Garzón et al, 2020).…”

“…In this work, we consider The Geysers geothermal area in Northern California, where the seismicity is mainly caused by energy‐related anthropic activities (Majer & Peterson, 2007). Due to its complex geological structure, the industrial operations for energy production and the existence of a dense seismic network, The Geysers area represents a natural laboratory for seismicity studies (among others; Bentz et al., 2019; Holtzman et al., 2018; Kwiatek et al., 2015; Martínez‐Garzón et al., 2020; Picozzi et al., 2017; Trugman et al., 2016).…”