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

Abstract

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 1Dsimulation 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.