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Source Characteristics of Microseismicity Occurring During Operational Shut-in Periods at the Coso Geothermal Field, California

Description: 

Throughout its 30+ years of energy production, the Coso Geothermal Field (CGF) in California has regularly experienced both tectonic and induced microseismicity. While distinguishing between these two types of earthquakes can be difficult, knowledge of the interplay between operational parameters and the reservoir’s seismic response can shed light on key factors affecting the stress field and the reservoir’s productivity.

In this study, we examine daily production and microseismicity data from the CGF between 1996 and 2010 to gain insight into the evolution of its stress field and how it has been affected by long-term production. Using 27 seismic stations from a local network, we analyse the source characteristics of 60,000+ earthquakes with moment magnitudes between -1 and 3.3. We find that most of the seismicity occurs towards the southern and eastern sections of the field, coinciding with the regions of the CGF where most of the fluids are reinjected. Additionally, these regions with higher seismicity rates tend to experience an abrupt increase in seismicity rates during the yearly power plant maintenance periods and wellbore shut-ins. Increased seismicity during shut-in periods has been observed previously at other geothermal fields and spatially linked to production wellbores. Through waveform cross-correlation and seismic event relocation, we identify distinct clusters of microseismicity re-occurring during these shut-ins. These observations may suggest that certain fracture and fault sections respond quicker to changes in pore pressure and poroelastic stresses within the geothermal system. Better understanding of these relationships can de-risk geothermal operations and optimize productivity of the field.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards - III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Joanna

Student Presenter: No

Invited Presentation: 

Authors