Abstract
In this study, we apply control theory to mitigate earthquake hazards to a stress-based model of 14 enhanced geothermal stimulation. The model considers pore pressure diffusion as the main stressing 15 mechanism and rate-and-state friction as the shear failure mechanism. The controller is designed to follow
16 a given average pressure and the probability of exceedance of a red-light earthquake (the magnitude at 17 which the stimulation would have to stop by regulation) within chosen volumes surrounding the injection 18 source and within a target time. We rigorously prove that the proposed controller can effectively force
19 two output types within the system to given references, despite the presence of model uncertainties, and 20 with minimal system information, using a continuous control signal. This framework is applied to a 21 validated model of the 2018 Otaniemi geothermal stimulation. We use a suite of simulations to identify 22 injection scenarios that outperform the 2018 Otaniemi stimulation. The optimal stimulation achieves 23 higher average pressure in a shorter time with lower seismic hazard. The controller can help determine 24 whether a combination of safety thresholds and optimization targets is feasible and economical. The
25 control framework could be used to design stimulation schedules for enhanced geothermal systems.
16 a given average pressure and the probability of exceedance of a red-light earthquake (the magnitude at 17 which the stimulation would have to stop by regulation) within chosen volumes surrounding the injection 18 source and within a target time. We rigorously prove that the proposed controller can effectively force
19 two output types within the system to given references, despite the presence of model uncertainties, and 20 with minimal system information, using a continuous control signal. This framework is applied to a 21 validated model of the 2018 Otaniemi geothermal stimulation. We use a suite of simulations to identify 22 injection scenarios that outperform the 2018 Otaniemi stimulation. The optimal stimulation achieves 23 higher average pressure in a shorter time with lower seismic hazard. The controller can help determine 24 whether a combination of safety thresholds and optimization targets is feasible and economical. The
25 control framework could be used to design stimulation schedules for enhanced geothermal systems.
| Original language | English |
|---|---|
| Journal | Geothermics |
| Publication status | Accepted/In press - 16 May 2025 |