Towards coupling fluid flow and rate-and-state friction in compacting visco-poro-elasto-plastic reservoirs

Abstract:

Induced seismicity as a result of natural gas production is a major challenge from a scientific, industrial and societal perspective. The compaction caused by gas production leads to changes of the effective stress fields in the reservoir and stress redistributions are particularly large on faults that off-set the reservoir. In addition, the strong coupling between fluid flow and solid rock deformations and the role of fluid flow regarding the frictional properties of the faults necessitate a coupled and comprehensive modeling framework. A general and fully coupled thermo-hydro-mechanical finite difference formulation is developed herein and the results are verified against numerical benchmarks. A poro-visco-elasto-plastic rheological behavior is assumed for the bulk material and a return-mapping algorithm is implemented for accurate simulation of the stress evolution. The geometrical features of the faults are incorporated into a regularized continuum framework, while the response of the fault zone is governed by a rate-and-state-dependent friction formulation. Efficiency of the numerical simulations is assured through the evaluation of the consistently linearized systems of equations. The proposed framework is a step towards the modeling of earthquake sequences for induced seismicity applications, but we will first simulate laboratory experimental setups to better understand the thermo-hydro-mechanical feedbacks in this fully coupled system. The improved understanding of these feedback mechanisms will also be important for understanding the role of fluids in relation to natural earthquakes and aseismic and slow slip.