Reservoir heterogeneity was uncovered to perform an important role in the variation of components, as well as the transfer of heat within the reservoir. It was also observed that because convection and di¿usion in non-producing reservoirs are relatively slow processes and the di¿usion terms are small in magnitude, the e¿ect of variable di¿usion coe¿cients was termed negligible. Other observations include a consistency in the results obtained irrespective of the grid size used, for example, the three-dimensional grids produced the same average pressure, temperature, composition and velocity pröles as the 2-dimensional grids for certain reservoir con¿gurations.This study rummage-saled the general mass and energy balance equations to simulate ¿uid movement within a non-producing reservoir with thermal gradients. The con¿guration of ¿uid components and heat within the reservoir is characterized using various metrics such as the Nusselt and Rayleigh numbers, as well as separation and density factors. These metrics are able to show, in a concise manner, the e¿ect of changes in the reservoir and ¿uid properties on compositional variations.