Analytical and Numerical Analysis of EOR process in Stratified Reservoirs

Abstract

Summary We develop analytical tools to predict the flow behaviour and solute transport during advanced EOR processes in stratified models as an extension to simpler waterflood models based on fractional flow theory. We also derive an extended set of dimensionless numbers that are particularly designed to quantify the flow behaviour in EOR processes. These analyses are essential for upscaling and improve the accuracy of predictions. We consider EOR flow conditions in which layered models are affected by retardation and dispersion of flow and include variations in wettability and relative permeability as well as other petrophysical properties. We developed our analysis using the principles of the fractional flow theory, applied to EOR processes. A revised model corrects for the effects of numerical and physical dispersion. By grouping and rearranging the derived formulae, we obtain dimensionless numbers and scaling groups to evaluate the effect of various scenarios of properties contrast between layers. We investigated the impact of various parameters on the recovery factor and the water cut from the production data. The scaling groups can be utilized to identify properties of the model that should be changed so we can reproduce flow behaviour from small scale (e.g. core scale) to larger scale (e.g. reservoir scale). The new analytical model was validated against numerical solution of low salinity waterflooding with varying degrees of heterogeneity and mobility ratio, where a very good match was obtained. These analytical tools enable us to obtain ultra-fast predictions complex flow during EOR processes without a need to run a numerical simulator and with better accuracy. The approach can potentially be applied in streamline simulators and used as flow diagnostics to improve analysis of EOR methods where retardation and dispersion occur.