Because of increased speed and accuracy, 3D streamline simulation can model a wide range of reservoirs. Large reservoirs with hundreds or thousands of wells, several hundred thousand grid blocks, and an extensive production history are a challenge for finite-difference simulation, The size and complexity of these reservoirs generally have limited simulation to sections or well patterns, The streamline technique enables simulation of these reservoirs by reducing the 3D domain to a series of 1D streamlines, along which the fluid-flow computations are performed, offering computational benefits orders of magnitude greater Maintaining the sharp flood fronts from the displacement processes and reducing grid-orientation effects increases accuracy. The streamline-simulation results have additional value as a reservoir-management tool when used with traditional reservoir-engineering techniques, such as standard finite-difference simulators.