Finite-Element Analysis of Phase Transitions in Gas Migration within Clay Rock

This study explores the numerical simulation of gas transport in low-permeable rocks, specifically focusing on clay rock. Utilizing the finite-element method, we examine the transition from single-phase to two-phase flow conditions. Our approach diverges from traditional methods by avoiding persistent primary variables or variable switching. We validate our methodology through two benchmark tests: the first simulates gas injection relevant to radioactive waste disposal, while the second models a core drilling experiment that induces mechanical unloading.

Our findings are significant for understanding gas behavior in geological formations, particularly in the context of nuclear waste disposal and CO2 storage. We offer a novel perspective on managing phase transitions in non-isothermal environments, bolstered by an extensive analysis of secondary variables. The outcomes of this research contribute to the improved modeling of large-scale repository systems, highlighting the intricacies and complexities involved in gas transport within clay rock.

This paper not only provides insights into the physical processes underpinning gas movement in these environments but also proposes a scalable and adaptable framework for future research in similar geological contexts.