Multi-Resolution Simulation for Efficient Pressure & Stress Calculation in Large-Scale CO2 Storage Using Pseudosteady State Pressure as Spatial Coordinate

Large-scale CO₂ injection operation causes pressure and stress changes in subsurface with potential geomechanical risks such as ground surface uplift, caprock failure and CO₂ leakage through fractures, or/and reactivation of faults and triggering induced seismicity. Although existing dynamic reservoir and geomechanics simulation tools can assess these operational risks, the excessive computational time remains a major bottleneck for large-scale CCS applications. We propose a rapid coupled flow and geomechanics simulation approach that uses pseudosteady state pressure as spatial coordinate (PSS-SIM), focusing on efficient pressure and mean stress change calculation caused by CO₂ injection. PSS-SIM can speed up the coupled simulation by more than an order-of-magnitude while accounting for model heterogeneity, and allows us for quick evaluation of geomechanical risks of CO₂ injection operation under geologic uncertainty. The proposed simulation workflow accelerates pressure and mean stress change calculation in CO₂ injection simulation by multi-resolution grid coarsening based on PSS pressure contours. PSS-SIM can be seen as generalization of the Fast Marching Method (FMM) based multiresolution coupled flow and geomechanics simulation for unconventional reservoirs (Terada et al., 2023) to CCS applications that replaces Diffusive Time-Of-Flight (DTOF) with PSS pressure solution as the choice of spatial coordinate because of the expected flow patterns in CCS reservoirs. PSS-SIM utilizes one-way coupling scheme to facilitate field-scale applications, and is capable of computing pressure and mean stress change with more than an order-of-magnitude less computational time compared to fine-scale simulation. The validity of pressure change calculation along PSS pressure contours in high permeability reservoirs is validated with a synthetic 3-D fine-scale simulation. The applicability to field-scale problems is demonstrated with simulation of a large-scale CO₂ storage test in saline aquifer for rapid geomechanical risk assessment. Snapshots of simulated pressure change from PSS-SIM showed consistent results with fine-scale simulation with capability to calculate mean stress as additional outputs.