Closed-form Analytical Approaches to Constrain Fraction of Injected CO2 Dissolving in Brine During CO2 Storage in Saline Aquifers

Document Type

Conference Proceeding

Publication Date

1-1-2025

Abstract

CO2 dissolution in the storage aquifer’s brine is one of the main CO2 immobilization mechanisms in the subsurface. During injection, CO2 dissolution is primarily governed by the contact area between the CO2 and brine. Accordingly, when using finite-difference numerical simulation tools to model the CO2-brine displacement, the model discretization size affects the level of dissolution given that it controls the contact area. Grid size should be carefully selected to avoid unrealistic dissolution estimations. It is important to obtain an independent estimate of the dissolution using discretization-free analytical approaches. In this study, the author presents two analytical approaches to estimate the range of CO2 dissolution. The first method assumes gravity-dominated flow, with a limited role for the capillary force in the vertical direction, resulting in vertical equilibrium modeling approach. The second assumes viscous-dominated flow with no role for gravity force, maximizing the CO2-brine contact area and dissolution rate through the fractional flow modeling approach. The two approaches are applied to an example CO2 injection case and their resulting ranges are compared with estimates from numerical simulations considering different spatial discretizations. Numerical simulations show that large discretizations can result in unrealistic dissolution rates outside the analytically-driven range.

Publication Source (Journal or Book title)

Society of Petroleum Engineers SPE AAPG Seg Carbon Capture Utilization and Storage Conference and Exhibition Ccus 2025

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