Production from highly stratified reservoirs can result in significant crossflow between layers through wellbores. This paper describes a new, relatively simple superposition method to represent this, crossflow in a numerical simulator. The method calculates vertical wellbore saturation variations throughout the wellbore and gives more accurate results than a fully mixed wellbore method. Equations are given for the new method, a fully mixed wellbore method, and the exact solution for crossflow in a well completed in a column of gridblocks. Three examples, including a field-scale depletion, are given comparing exact results with those from the superposition and fully mixed wellbore methods.

creasing production rate can adversely affect ultimate recovery. This rationale With the world wide high demand for oil, is in turn, partly derived from observathe rate of oil production from Alberta pools tions that counter-current imbibition and has dramatically increased over the last few gravity drainage are time-dependent reyears. This investigation was undertaken covery mechanisms and can more effectively "to determine if reservoirs, typical of the contribute to ultimate recovery at lower more important Alberta pools, are sensitive reservoir withdrawal rates.

A reservoir simulator has been developed to solve gas~water reservoir problems where the gas may be treated as a two component miscible mixture. It is specifically designed to study gas~storage problems where an inert gas such as nitrogen, may be used as a displacing fluid during cycling operations. The model includes both the convective transport of components within the gas phase plus the diffusion or dispersion of components. The solution to the multicomponent gas problem is accomplished using the method of characteristics, so that numerical dispersion is eliminated or minimized.A description of the model is included along with several example problems. The example problems include comparisons of calculated results with analytical solutions and experimental laboratory data in one and two dimensional models. The experimental data were measured on both liquid-liquid and gas-gas miscible systems.