This chapter is divided into three main parts: (1) governing processes in multiphase multicomponent flow and reactive transport (MMF&RT), (2) mathematical and numerical approaches of MMF&RT modeling, and (3) applications with respect to CO 2 storage. Thereafter, discussion of other applications that illustrate the ability of existing methods to represent general non-ideal multicomponent gaseous systems within a wide range of temperature and pressure conditions, in addition to their possible interactions with water/brine/rock, are presented. GOVERNING PROCESSES The governing processes and present issues of multiphase flow and geochemical modeling are introduced in this section. The definition of wettability is first presented, which is difficult for several systems; followed by the definitions of capillary pressure, residual and capillary trapping, and heterogeneity. In addition, the relative permeability is introduced, which is a characteristic property of multiphase flow. Recently, novel experimental and numerical technologies have provided further insight into different concepts such as residual nonwetting saturation, maximum relative permeability, governing forces, hysteresis, the impact of heterogeneity, and upscaling from pore-and core-scales. The different regimes of gas diffusion are then discussed in conjunction with corresponding modeling methods. Thereafter, basic formulations of multiphase flow are presented, from immiscible to compositional flows.

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International audienceThis work aims to incorporate compressible multiphase flow into the conventional reactive transport framework using an operator splitting approach. This new approach would allow us to retain the general paradigm of the flow module independent of the geochemical processes and to model complex multiphase chemical systems, conserving the versatile structure of conventional reactive transport. The phase flow formulation is employed to minimize the number of mass conservation nonlinear equations arising from the flow module. Applying appropriate equations of state facilitated precise descriptions of the compressible multicomponent phases, their thermodynamic properties and relevant fluxes. The proposed flow coupling method was implemented in the reactive transport software HYTEC. The entire framework preserves its flexibility for further numerical developments. The verification of the coupling was achieved by modeling a problem with a self-similar solution. The simulation of a 2D CO2-injection problem demonstrates the pertinent physical results and computational efficiency of this method. The coupling method was employed for modeling injection of acid gas mixture in carbonated reservoir