Two-phase flow behavior in CO2 geological storage considering spatial parameter heterogeneity

Abstract

Saline aquifer rocks exhibit significant spatial randomness due to geological sedimentation processes. To address the issue of the heterogeneity of rock formations in numerical simulations, it is common practice to homogenize rock layers with similar lithologies. However, the acceptability of the errors generated during homogenized computations is a major concern and should be investigated. Therefore, to study the influence of heterogeneity at the storage site on the CO₂ migration behavior, the Monte Carlo simulation–random finite element method (MCS-RFEM) was combined with a CO₂ two-phase flow model to compare the effects of the coefficient of variation (C_v) and correlation length (λ_x) of random reservoir permeability fields on the migration distance and extent of CO₂ storage under the same mean conditions. The results showed that higher C_v and λ_x values significantly reduced the CO₂ migration distance while increasing the spread extent. Compared to the homogeneous model, at a λ_x value of 100 m, the CO₂ migration distance decreased by 5.05%, while the profile sweep area increased by 6.20%. Concurrently, with increasing C_v, the area with a CO₂ volume fraction higher than 0.75 decreased by 20.22%, while an increase in λ_x resulted in a 42.35% increase in the area with a CO₂ volume fraction higher than 0.75. Therefore, reservoirs with high C_v and low λ_x values are more suitable for safely storing CO₂. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.