A coupled discrete element and finite element model for multiscale simulation of geological carbon sequestration

摘要

We present a numerical study using a discrete element method (DEM) coupled with a finite element method (FEM) at the boundary to simulate the fluid flow, geomechanical deformation, and dynamic fracturing together to enhance the sustainability analysis for geological sequestration of CO2. The fluid flow, geomechanical deformation, and fracturing due to the injection of fluid are all modeled by the bonded DEM (bonded-DEM), where fluid flow is modeled by solving the Darcy flow directly on the Lagrangian particles. Because of the high computational expense, the bonded-DEM is only used in the domain where fracturing is highly possible, namely the area near to the injection well and around the pre-existing fault. For the area far away from the high risky domain, the deformation and pressure solutions are obtained by a standard finite element method (FEM). The stress, deformation, and pressure obtained from FEM are fed back into the bonded-DEM simulations as boundary conditions that were applied to the DEM boundary particles. The proposed model has the potential to be used to evaluate the safety and sustainability of a sequestration site. By predicting the critical time when the fault is reactivated and the time when CO2 breaks through the caprock through the reactivated fault. The model also shows that the ground surface displacement can be used as an effective monitoring indicator for fracturing, fault reactivation, and CO2 breakthrough in aquifer and caprock, implying a very useful monitoring method for the safety of any sequestration site. (C) 2015 Society of Chemical Industry and John Wiley & Sons, Ltd