The Influence of Aquifer Geochemistry on Salt Precipitation During CO₂ Injection: Insights From 1D Simulations Using The Rand Algorithm

CO₂ storage in saline aquifers is deemed as a feasible way to control the atmospheric levels of greenhouse gases. When CO₂ is injected in saline aquifers, several phenomena take place, such as multiphase fluid flow, adsorption and chemical reactions, which can in turn produce mineral phases that might risk the whole process. Thus, mathematical modelling of CO₂ storage in saline aquifers is a very complex task. In this work, we resort to the RAND algorithm for chemical and phase equilibrium (CPE), coupled with 1D material balance equations for multiphase fluid flow in porous media, to simulate the injection of CO₂ in saline aquifers. Two types of aquifers were studied: one with NaCl and water; and another one involving a more complex brine containing Na⁺, Mg²⁺, K⁺, Cl^-, SO₄^2-. We focused the analysis on salt precipitation, a phenomenon that takes place when dry CO₂ is injected into an aquifer. From the 1D-simulation and from phase equilibrium diagrams, we produced insights on the thermodynamic conditions that allow for salt precipitation, the typical flow patterns observed, and the precipitation of multiple salts. The analysis performed is intended as a systematic evaluation of the interplay between geochemistry and fluid flow, with a special focus on salt clogging. Furthermore, we have shown the applicability of the RAND algorithm to challenging conditions involving fluid flow and several reactions and mineral phases.