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Predicting Ongoing Induced Seismicity in the Groningen Gas Field After Shut-in Using Rate-Dependent Compaction

Description: 

Annual production in the Groningen gas field has been decreasing over the last years towards full cessation and shut-in planned in 2023/2024, motivated by safety risk and societal unrest from production-induced earthquakes. The shut-in is associated with an increase in reservoir pressure, which already occurs locally in the field . The current seismic source model (SSM), used as part of the seismic hazard and risk analysis (SHRA), formulates that directly induced earthquakes (i.e., main shocks) occur as a function of compaction, where compaction is a linear elastic function of reservoir pressure – suggesting an arrest of main shocks after shut-in. However, subsidence measurements and laboratory deformation experiments suggest that reservoir compaction, and thus generation of main shocks, continues after shut-in. Hence, the current SSM requires an update to be able to provide SHRA predictions after shut-in.
Here, such a future-proofing exercise is carried out by reformulating the function relating pressure to compaction – assuming that total compaction (elastic and permanent) causes reservoir-hosted fault loading. The empirical Rate Type isotach Compaction Model (RTiCM) is used to describe reservoir compaction as the sum of the instantaneous elastic compaction and delayed rate-dependent creep. The model has been shown to accurately match experimental data as well as subsidence data. The RTiCM model parameters have recently been calibrated on Groningen field subsidence data. The results of the RTiCM-based SSM and elastic compaction-based SSM are compared. The earthquake event counts of the most recent years, where field production was strongly reduced, are reproduced better by the RTiCM-based SSM. In particular, the model can simulate seismic events in areas of limited pressure increase . The performance between the two models is further quantified using the CSEP testing framework. The RTiCM-based SSM is a viable option for a post shut-in SHRA.

Session: Opportunities and Challenges in Source Modeling for Seismic Hazard Analysis [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Frans M. Aben

Student Presenter: No

Invited Presentation: 

Authors