Engineering Visual Presentation E08: Impact of heterogeneity on CO2-brine displacement: hybrid analytical-numerical modelling accounting for velocity dependent relative permeability

Engineering Visual Presentation E08 Subsurface storage of CO2 introduces a series of new technical challenges that require the development of new mathematical models. One such challenge is that the balance of viscous, capillary and gravitational forces results in velocity-dependent mixing and thus relative permeabilities. The substantial variation between near-wellbore and far-field velocities necessitates including these velocity-dependent relative permeability functions to accurately predict reservoir and well behaviour. Analytical models are an efficient option for predicting reservoir behaviour in CO2 geosequestration; however, they often require limiting assumptions. Numerical modelling can provide detailed spatial and time dependent changes in fluid properties, with the drawbacks of long computation times and large input data requirements. In this work, we use a hybrid approach: numerical modelling in Petrel is used to resolve the velocity dependence of relative permeabilities, and a novel analytical model is used to calculate sweep efficiency and injectivity at the reservoir scale. The model introduces a new analytical framework for Buckley–Leverett CO2-water displacement that includes spatially dependent fractional flow. This study focuses on heterogenous reservoirs initially saturated with water. The novelty of this new hybrid model is: (1) a set of velocity-dependent relative permeability functions covering a range from viscous to gravity dominant flow and (2) a solution for upscaled CO2-water displacement processes. Sensitivity analysis shows that heterogeneity highly influences the vertical redistribution of CO2 in the reservoir. This has significant consequences for solubility and residual trapping of CO2 during geosequestration. To access the Visual Presentation click on 'Supplementary data' below. To read the full paper click here