Numerical modelling of gas flow in a compact clay barrier for DECOVALEX-2019

The mechanisms controlling the movement of gases through geological disposal facilities can be described by models accounting for (i) diffusion, (ii) two-phase flow, (iii) localised flow pathways and (iv) gas fracturing of the rock. It is therefore necessary to consider all these phenomena for a better understanding of the processes governing the movement of gases in low permeability materials. The purpose of Task A in the current phase of the DEvelopment of COupled models and their VALidation against Experiments (DECOVALEX) project is to better understand the processes governing the advective movement of gas. In this paper, a synthesis of the ongoing work of eight participating modelling teams is presented. A wide range of 2D and 3D approaches including (i) continuous strategies assuming different mechanical deformation behaviors, (ii) continuous models with distinct phases or embedded fractures and (iii) discrete models with different formulations are validated against a gas flow test on pre-compacted bentonite undertaken by the British Geological Survey. The results of the ongoing work show that after a calibration process, plausible descriptions of the laboratory experiment can be achieved.