oa One-Dimensional Analytical Solution for CO2 Injection in the Presence of Multiple Impurities

This article employs the theory of miscible gas injection to address the compositional mass transport equation for the propagation of gaseous components during underground CO2 storage. It uses an analytical approach to predict the propagation patterns of multiple components and their velocities. The method integrates Yan et al.’s approach for identifying crossover tie-lines with an improved method of characteristics (MOC) to generate saturation and composition profiles for CO2-impurities systems. This involves determining intersecting key tie-lines and intersection points using negative flash calculations, identifying the primary tie-line using the location of intersection points, identifying tangent points, calculating shock velocities, and constructing tie-line paths.

The presented analytical method can handle complex flow models and initial conditions. It was shown that the composition of intersecting tie-lines indicates that each jump comes with an inconsistency in the composition of at least one component between the two tie-lines, which can be used to analytically and systematically describe the propagation pattern and depth of invasion for each component. The results also reveal that impurities can accumulate due to the separation in porous media, forming a bank with a higher concentration of the more volatile components.