*NOTE: VIDEO NOT AVAILABLE PER SPEAKER REQUEST—Check back later for PowerPoint slides. High-Fidelity Simulations of Induced Earthquakes Inform Operational Management Strategies (In-Person Presentation)

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Kayla Kroll

Lawrence Livermore National Lab

Date & Time
In-person presentation (online via Microsoft Teams)
Evan Hirakawa

As carbon storage technologies advance globally, methods to understand and mitigate induced earthquakes become increasingly important. While the fundamental relationship between pore-pressure and induced earthquakes has long been known, surefire methods to control or mitigate such seismic events remain elusive. Reservoir engineering strategies for mitigating induced earthquakes typically involve modulation of the injection rate. In some cases, operators are injecting consistent fluid volumes over time which allows for nearly constant injection rate (e.g., Illinois Basin Decatur Project), while other operations have more variable injection rates/volumes with time to accommodate the changing influx of waste fluids (e.g., oil and gas operators in variable markets). Both approaches can lead to high rates of induced earthquakes. To mitigate induced earthquakes, some sites have implemented periodic episodes shut-in (i.e., effective cycling of injection rates) to allow reservoir pressures to equilibrate (e.g., Paradox Valley) or shut-in wells after the occurrence of an event of concern (e.g., Basel, Switzerland). Other proposed strategies include ramping up or down of injection rates, actively managing pressures through co-production of fluids, and pre-injection brine extraction. Note that, while the latter two strategies may be more reasonable for geothermal or carbon storage than for wastewater disposal, they may apply in situations where formation brine is more readily treatable than waste fluids from oil and gas operations. In this work, we use 3D physics-based earthquake simulations to understand the impact of variable injection strategies under the condition that the same total volume of fluid has to be injected within a given time period on induced earthquake rates, maximum event magnitudes, and post-injection seismicity. In general, we find that higher-rate injection, even given the same total injection volume, leads to more frequent and larger events. Further, we find that cycling injection rates tends to have a significant portion of the events during the shut-in periods and those event rates decay more slowly when compared to constant rate injection. Finally, we find that ramping down injection rates slowly is most effective at reducing post-shut in seismicity rates.

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