| The objective of reservoir simulation is to understand chemical, physical and fluid flow processes occurring in petroleum reservoir sufficiently well to be able to optimize the recovery of hydrocarbon. To do this, one must be able to predict the performance of the reservoir under the various exploitation schemes. In order to predict reservoir performance a series of models of reservoir process is constructed which gives information about the complex phenomena accompanying different recovery methods.;In this thesis, we studied compositional variation model under gravity segregation. In addition, we also focused on instability in the component distribution in a multicomponent system. Reservoir simulation technique applicable to single phase flow in two dimensions was used to explore changes in composition under gravity. Further, numerical experiments were done using field data to demonstrate instability at interface of multicomponent.;Simulation result showed that (a) compositional reservoir takes thousand of years to reach at equilibrium state (b) Rayleigh number is a dominant factor in finding the stability of the mixture in the compositional reservoir (c) we observed, for the first time, multiple unstable interfaces phenomenon in six component simulation when PR EOS and Lohrenz viscosity was used (d) we also noticed that compositional commercial softwares, used to simulate gas injection, do not take into account the effect of unstable displacement caused either by adverse mobility ratios or by multicomponent gravity segregation. |
