Exploring reservoir heterogeneity effects on halite precipitation during CO2 storage

Abstract

Carbon dioxide (CO2) storage in geological reservoirs is an effective approach to mitigate greenhouse gas emissions. However, salt precipitation induced by dry CO2 injection can reduce injectivity, thereby affecting storage efficiency and operational stability. This study investigates the impact of rock permeability on halite precipitation patterns and their influence on CO2 injectivity through core-flooding experiments. Using four distinct cores, three homogeneous and one heterogeneous under controlled conditions, we analyse the dynamic processes of brine displacement, water evaporation, salt accumulation, and permeability evolution with real-time computed tomography (CT) imaging and multiple fluid pressure sensors. Results indicate that permeability contrast redistributes brine and changes the location of salt deposition. Permeability impairment is not governed by initial permeability alone; instead, it reflects the combined influence of permeability, porosity, mineral heterogeneity, capillary retention, and local flow-path blockage. Salt precipitation is more dispersed in heterogeneous cores compared to homogeneous cores, where under our experimental conditions, it predominantly accumulates near the injection point. Furthermore, permeability impairment varies with initial rock properties, with higher-permeability cores experiencing more severe injectivity reduction due to increased pore clogging. These findings highlight the importance of incorporating reservoir heterogeneity in predictive models for CO2 storage operations. Understanding the dynamic interplay between brine migration, salt crystallization, and permeability evolution is crucial for optimizing long-term injectivity and ensuring the viability of geological carbon storage.