Lean gas injection in reservoirs is more and more frequently encountered. This production strategy induces strong compositional gradients in the field. Accurate compositional simulations with a coarse grid have been obtained through the use of an upscaling technique based on three main features:
the computation of pseudo rel perms upscaling molar, instead of volumetric, fluxes;
the reproduction of the fine grid flow through ‘Dual Scale Simulations’ (DSS) which are an alternative to classical Representative Elements of Volume (REV) simulations;
the correction, within each phase, of the flux of each component, with the ‘alpha-factor’ pseudo-functions.