AUTOMATIC TIMESTEP SELECTION SCHEME FOR RESERVOIR SIMULATION.

The literature concerning timestep selectors is reviewed with discussion of applications to reservoir simulation. A first order predictor-corrector method is applied to select automatically the time-step size in a finite difference steam injection reservoir simulator. The step size is estimated from the first neglected term in the series expansion; and a set of rules is developed for accepting new step sizes. Comparisons are made with a commonly used method which limits the time step based on the linear extrapolation of maximum changes of key variables. The comparisons show reductions in the number of time step used; easier usage and to some degree elimination of rapidly oscillating time step.