Dr. Wenzhuo Cao

Biography

Wenzhuo Cao is an Assistant Professor of Coupled Subsurface Processes in the Department of Earth Sciences at Utrecht University, the Netherlands. He holds a PhD from Imperial College London, where he worked as a Research Associate and then a LKAB Research Fellow before joining Utrecht University. His research focuses on elucidating the physical mechanisms driving induced seismicity and the role of fracture systems and fault structures within coupled thermo-hydro-mechanical-frictional (THMF) processes. By integrating field observations, fundamental mechanics, and advanced predictive modelling, his research advances sustainable geo-energy development, geo-storage, and risk mitigation. He leads research projects funded by the European Commission and the Dutch Research Council.

Chin-Fu Tsang Coupled Processes Award Lecture

Understanding and mitigating induced seismicity through coupled hydro-mechanical-frictional dynamics

Fluid injection-induced seismicity present a significant challenge for geo-energy and geo-storage applications. The rich thermo-hydro-mechanical-frictional (THMF) physics involved, together with highly nonlinear coupled dynamics, makes induced seismicity notoriously difficult to predict and manage. Recent research on coupled THM processes, including our own work, has improved our understanding of the causal mechanisms underlying induced seismicity. However, it remains unclear how the interplay among these processes controls earthquake magnitude and frequency, and how this understanding can be used to mitigate induced seismicity. Here, I will present our recent research on coupled HMF dynamics addressing these questions.

Injection-induced seismicity arises from three key processes: fluid pressurisation, hydraulic diffusion, and frictional nucleation, each characterised by a distinct timescale. Using a coupled HMF model of injection-induced fault slip, we investigated how the three processes interact to control earthquake magnitude and frequency. The results show that, while earthquake magnitude and frequency are primarily governed by fault frictional properties, they are modulated by fluid pressure rate and reservoir hydraulic diffusivity. This highlights injection-rate management as an effective means of mitigating induced seismicity by controlling the fluid pressurisation timescale.

Building on this mechanistic understanding, we further developed an injection schedule optimisation framework for a coupled HMF fault system under a prescribed total injection volume. The optimisation is formulated as a constrained variational problem to minimise maximum fault slip velocity. Using an adjoint approach, the injection schedule is iteratively optimised based on the objective gradient with respect to the injection rate. The optimised results reveal that the coupled system favours a short period of high-rate injection followed by a longer period of low-rate injection, allowing the system to stabilise. This gradient-based optimisation framework provides a new approach for understanding and controlling the response of complex fault systems to fluid injection.