Finite-difference method is widely used for solving large-scale multiphase displacement problems, e.g., displacement of oil by water/gas in heterogeneous petroleum reservoirs. Drawbacks of finite difference methods are numerical dispersion, grid orientation, small time step size (limited by the CFL condition), and large computation time. To overcome these problems, streamline methods are being developed in which fluid is transported along the streamlines instead of the finite difference grid. Larger time steps and higher spatial resolution can be achieved in these simulations.; In this work, a three-dimensional black oil and compositional streamline module is developed and integrated with an existing finite difference simulator to study water flooding and gas injections in a quarter five spot pattern. The 3-D multi-component material balance equation is decomposed into 1-D equations along the streamlines using the streamline time of flight as the spatial coordinate. Pressure field is solved in the conventional finite difference manner and streamlines are traced from injector to producer. Gravity effects are added using operator splitting technique to account for the gravity segregation due to density differences. This simulator can handle the formation and flow of the fourth phase (third hydrocarbon phase) which is observed in CO2 injections into certain types of oils under specific conditions. Different forms of higher order TVD schemes are implemented to construct an accurate numerical solution along the streamlines by reducing the impact of numerical dispersion.; A parallelized version of compositional streamline simulator is also developed to run large scale simulations using multiple processors. The streamline module is parallelized by distributing streamlines among different processors because computations along any streamline are independent of other streamlines and no communication is required. Flux calculation along streamlines is computationally expensive primarily due to flash calculations that are performed to distribute components among the hydrocarbon phases. Simultaneous solution of this time consuming step results in reduction of total CPU time.; Predictions from streamline simulator are in good agreement with the finite difference simulation results. Streamline method is faster than conventional finite difference method. Gravity segregation is observed in gas injection and water flood simulations. Use of lower order schemes produced more error in miscible displacement problems due to alteration of composition path than in immiscible displacement problems. Gas injection simulation of the reservoir oil indicates that three hydrocarbon phases exist near the gas-oil displacement front. The influence of horizontal well length on the breakthrough sweep efficiency is observed. As the length of the horizontal well is increased, streamlines tend to bend towards the toe of the well thereby resulting in lower volumetric sweep.
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