This paper combines the knowledge and experience accumulated in IRIS over a number of years from several case studies involving Tjelbergodden CO2 value chain, modelling of CO2 injection at the Ekofisk field and Gullfaks CO2 injection compositional simulations. The paper will discuss the importance of correctly representing the physical effects when modelling miscible or immiscible CO2 injection in sandstone and carbonate reservoirs. The following aspects will be evaluated: Transfer of CO2 from fractures to matrix involving diffusion and gravity segregation;Viscous effects;Formation of low and high concentration liquid hydrocarbon phases;Compositional effects and oil swelling;Chemical interaction between CO2, formation or injection water and reservoir rock. The sensitivity and importance of these effects were studied on several simplified mechanistic models and later applied to actual field cases. The overview of viscous fingering effect will be presented. Results from mechanistic studies of the CO2 matrix-fracture transfer and physical effects will be shown. The paper will also discuss critical aspects of Equation-Of-State (EOS) modelling and PVT studies necessary for CO2 flooding. From our experience we will suggest recommendations and "cooking recipes" for building reservoir simulation models for CO2 based IOR process evaluations. Case studies of the CO2 and CO2-WAG IOR methods for reservoirs on the Norwegian Continental Shelf (NCS) will be presented. Oil recovery potential of these IOR processes will be discussed.
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