Modeling of Reactive Transport in Porous Rock: Influence of Peclet Number

Dissolution and precipitation processes in reactive transport in porous rocks play an important role in many contexts, such as geological CO2 storage, reactive contaminant transport, and acid injection in petroleum reservoirs. They are responsible for wormholing and alteration of the rock and transport characteristics due to feedback between the geochemical and the transport processes. A critical aspect of studying reactive transport is the influence of Peclet number on a coupled reactive process, which aims to understand the contributions of advection and diffusion as the two main transport mechanisms.

Our study investigates the influence of Peclet number on dissolution and precipitation processes in a porous calcite matrix due to reaction with the incoming low-pH flow using a particle tracking (Lagrangian) approach. The coupled reactive process is simulated in a series of computational analyses that capture the subtleties of the multiple scale heterogeneity phenomena, such as anomalous (non-Fickian) transport.

Our results show that reaction is manifested most significantly for small Peclet numbers, thus signifying the importance of diffusion in mixing processes that facilitate the reaction and increase the heterogeneity of the porous media. The evolution of the field heterogeneity due to reaction follows a similar trait, which is indirectly supported by fractal dimension estimation. Related to the field heterogeneity is the Shannon entropy, which is considered as a measure of the self-organization of the flow.