Network Simulations of Flow Processes in Strongly Wetting and Mixed-Wet Porous Media

The main objective of this work is to derive two phase flow parameters, such as relative permeability and capillary pressure, from microscopic considerations using a network modelling approach. A steady-state network method is used in order to elucidate the most important factors affecting these flow parameters under various imbibition and drainage cycles and for porous media which are either strongly wetting or mixed wet in character. The network model is used to examine how phenomena such as phase-trapping, saturation history and film-flow affect relative permeability and capillary pressure curves. Both primary and secondary displacements have been simulated and results demonstrate that the accepted way in which relative permeability curves are constructed and presented tends to disguise the underlying dynamics of the process under investigation. There is some disagreement in the literature regarding the effects of wettability on waterflood recovery efficiency. Recent studies have indicated that this may be optimal at close to neutral conditions in mixed wet porous media. By explicitly incorporating pore wettability effects into the network model, it has been possible to explain these experimental observations from a microscopic standpoint. Results are presented which show how a (the fraction of pores which are assigned oil wet characteristics) affects the calculated relative permeability curves. These relative penneabilitites have been used to calculate waterflood displacement efficiencies for a range of wettability conditions, and have been shown to be in very good qualitative agreement with related experimental results. This appears to be the first time that a network model has been used in the study of both fractionally- and mixed-wet media in order to explain waterflood perfonnancc. The implication is, therefore, that the essential physics underlying the relative permeability concept is included in our rule based steady-state simulator.