Coupled Modeling of Reactive Rock-Fluid Interactions and Impurity-Tolerant CO2 Injection for Geological CCS

Abstract

Geological carbon capture and storage requires both tailored CO? stream designs and robust prediction of subsurface rock-fluid behavior to ensure secure, enduring sequestration. We introduce an integrated, high-performance modeling framework that links thermodynamic evaluation of multicomponent CO2 mixtures with fully coupled hydro-mechanical-chemical simulations. Our approach employs accelerated solvers to represent fluid flow, rock deformation, and reactive transport in a unified system, capturing processes from mineral alterations to dynamic changes in porosity, permeability, and stress fields. Our model addresses CO2 stream tolerance by evaluating how the relative proportions of various impurities influence phase behavior and reactivity in carbonate formations. This impurity-focused strategy guides the design of injection fluids that mitigate corrosive reactions while preserving key trapping mechanisms. We demonstrate that mineral trapping occurs within a narrowly defined reaction front, whose propagation is dictated by the interaction of permeability and pressure gradients. As CO2 dissolves into formation water, it forms acid that lowers fluid pH. Additional acidification arises from common impurities, yet the native mineral assemblage exerts a strong buffering effect that stabilizes pH well above unphysical lows predicted by earlier simplified models. Capturing this buffering demands explicit treatment of all aqueous species and comprehensive fluid chemistry. We emphasize that only high spatial and chemical resolution can faithfully reproduce rock-fluid equilibria and pH distributions. Coarse or oversimplified grids blur steep concentration, leading to significant mispredictions. Validation against illustrative field and laboratory analogs confirms that our GPU-accelerated, fully coupled framework is essential for resolving extreme localization in both time and space. Together, these findings underscore that prioritizing impurity ratios and embracing detailed, high-resolution coupling are critical for optimizing CO2 injection designs and reliably forecasting complex rock-fluid interactions, thereby advancing the safe implementation of large-scale geological CCS.