Experimental Insights into the Dynamics of Salt Precipitation During CO₂ Injection in Saline Aquifers: A Micromodel Study

The CO₂ storage in deep saline aquifers is recognized as a key strategy for mitigating greenhouse gas emissions. However, the evaporation of water into the injected dry CO₂ could lead to salt precipitation, which subsequently reduces CO₂ injectivity. This study employs a heterogenous, layered glass micromodel with permeability contrast, designed with a realistic pore space pattern, to enhance the visualization of CO₂ flow and also provide further insights into salt precipitation and its negative impact on the CO₂ flow behavior. Also, this study aims to address the possible pore-blocking phenomena induced by salt precipitation during CO₂ injection in a saline aquifer. To this end, a series of microfluidic experiments, aided by direct microscopic observation and image processing, was performed to elucidate the dynamics of salt precipitation. The obtaining results were further analyzed in terms of permeability and porosity impairment by injecting CO₂ into the glass micromodel saturated with ۲۰ wt.% NaCl brine. All experiments were conducted at ambient conditions with CO۲ injection flow at five, and ۱۰ mL/min. The results indicated that as gas injection flow rate increased from five to ۱۰ mL/min, the amount of overall salt precipitation decreased from ۱۶.۵۹۵% to ۱۴.۳۸۴%, respectively. Additionally, the presence of the crystal structure was more evident at lower flow rates. At high injection rates, densely clustered structures formed near the injection side, while salt precipitation was observed to initiate through high permeable region of the micromodel and then propagate diagonally from high- to low-permeable zone. Importantly, this progression deviated from a piston-like displacement behavior. These microscopic findings could provide valuable insights into the mechanisms of salt precipitation and its impact on the CO₂ flow behavior, contributing to the optimization of CO₂ storage operations and the mitigation of possible formation damage in deep saline aquifers.

کلیدواژه ها:

CO₂ Storage ، Saline Aquifers ، Salt Precipitation ، Permeability Impairment ، Micromodel Study