Waterflood calculations for hand-held computers. Part 7. Evaluating flood performance using the Stiles technique

Many reservoirs contain layers of markedly different permeabilities that are found to exhibit lateral continuity throughout the reservoir. Where such permeability stratification exists, the displacing water sweeps faster through the more permeable zones so that much of the oil in the less permeable zones must be produced over a long period of time at high water-oil ratios, whether the water is from natural influx or from injection systems. The Stiles method is one approach to the calculation of recovery and water cut from such a stratified system. A computer program for determining recovery and water cut from a stratified system using the Stiles method is presented. The program, step-by-step instructions for its use, and an example calculation are included.