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Assessing the Potential Bias of Observations From a Single Monitoring Well Within a Local-scale Seismic Array

Description: 

The continued advancement of Enhanced Geothermal Systems (EGS) and Carbon Capture and Storage (CCS) relies in part on the ability to provide comprehensive characterizations of microseismicity. High quality seismic catalogs are a crucial component of seismic risk management strategies, yet the financial viability of these projects also depends on the cost-effectiveness of the seismic monitoring approach. Downhole instrumentation approaches such as distributed acoustic sensing (DAS) can be particularly effective due to low noise levels and improved depth constraint, but the costs associated with drilling monitoring wells and maintaining downhole instruments can be multiple orders of magnitude larger than those of a surface network. As a result, some operators have opted to use a surface network of seismometers in tandem with a single downhole DAS cable in an attempt to provide affordable and effective microseismic monitoring. However, this approach relies on the assumption that downhole observations can be easily integrated into traditional detection and location workflows, a process that is made difficult by the large volumes of data produced by DAS. One way to address this issue is to limit the number of channels outputted by the DAS cable, either through downsampling or aggregation. In this study, we seek to determine the optimal number of observations at reservoir depth from a single monitoring well to be included in a traditional location workflow. To do so, we forward model arrival times from a grid of synthetic sources to a set of receivers on the surface and an increasingly large number of receivers within a single monitoring well. We then generate locations from the synthetic arrival times using NonLinLoc (Lomax et al., 2000) and compare them to the original locations to assess the ability of a wide range of monitoring scenarios to accurately characterize seismicity throughout the study area. Preliminary results indicate that including large numbers of observations from the monitoring well can bias event locations. This effect is exacerbated by the quality of the earth model used in earthquake locations.

Session: From Drilling to Ground Shaking: Mechanisms, Monitoring and Mitigation of Induced Earthquakes [Poster]

Type: Poster

Date: 4/17/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Alex J. Dzubay

Student Presenter: No

Invited Presentation: 

Poster Number: 94

Authors