Modelling of Fracture Healing due to Creep of Caprock Shale in CO2 Geological Sequestration

We assess long-term creep of shale based on back-analysis of laboratory CO2 exposure tests, where we look at fracture healing potential in a typical caprock shale from the Norwegian Continental Shelf (NCS). Preliminary results from COMSOL Multiphy sics simulations highlight conditions for initial fracture closure or further opening in a caprock shale with creep due to stiffness weakening after CO2 exposure. A material model is tailor-made where use solid mechanics, poroelasticity with Mohr-Coulomb and Darcy flow in porous media. COMSOL also allows for inserting pre-determined fractures or cracks, where the conditions for crack opening and fracture propagation can be checked in the simulation output. We use the in-line equation writing feature to input time-dependent stiffness, as well as fracture wall time-dependent load (as a boundary condition). Initial simulations show that for constant applied stresses and increasing fracture loading, one transitions from fracture healing to opening conditions. For time-decreasing fracture pressure, the opposite is seen, with initial opening followed by fracture closure and healing