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Characterization of Fracture Activation During EGS Stimulation Using Waveform Cross-Correlation: An Example Application at Utah Forge

Description: 

One of the many technical challenges in the safe stimulation of Enhanced Geothermal Systems (EGS) is the control of induced seismicity. Fluid injections during simulation may cause induced earthquakes. Microseismicity analysis provides real-time risk management, and detailed knowledge of activated fracture size, orientation, stress state and seismogenic potential. Due to subsurface heterogeneity within the reservoir, analysis of microseismicity is strongly influenced by the surrounding medium. Waveform cross-correlation utilizing the full wavefield of microseismic events, and can significantly improve the fracture characterization. Here, we apply waveform cross-correlation analysis to microseismic events during stage 3 of 2022 stimulation at the FORGE site to detect similar event clusters, and asperities with nearly identical waveforms, and obtain improved in-situ seismic parameters. The Frontier Observatory for Research in Geothermal Energy (FORGE) is a geothermal project located at Milford, Utah, providing pioneer research and insights in EGS with a comprehensive microseismic monitoring network including nodal arrays, borehole arrays and DAS fibers. The 2022 stimulation features over 20,000 microseismic events over three stages. We identify ten similar clusters from cross-correlated waveforms with a minimum CC coefficient of 0.65 from at least 8 stations. Analysis of cluster propagation and orientation reveals fracture planes with low b values being activated first, suggesting the activation of a planar structure with similar orientation to natural fractures at this site. We identify successive activation of different clusters, in particular, some clusters with larger events were activated post shut-in. To characterize the seismogenic potentials of different fractures, and their relationship with injection history, we obtain improved magnitudes based on precise relative magnitude measured from principal component analysis of aligned waveforms, and characterize magnitude-frequency for different fractures

Session: Seismic Monitoring, Modelling and Management Needed for Geothermal Energy and Geologic Carbon Storage - II

Type: Oral

Date: 5/2/2024

Presentation Time: 11:15 AM (local time)

Presenting Author: Richard

Student Presenter: Yes

Invited Presentation: 

Authors