Pore-scale Modelling Of Oil-Gas-Water Three-phase Flow In Porous Media

Multi-phase flow in porous media are studied based on three-dimensional pore network model (3-DPNM), which can reveal the micro-scale flow mechanisms and provide theoretical basis for the application of macroscopic percolation theory. Three-phase flow in porous media appears in both oil & gas fields development engineering fields and environmental engineering fields, including enhanced oil recovery methods: i.e. gas displacement, dissolved gas drive, steam drive, water alternating gas injection etc. and non-aqueous phase contaminants treatments etc. It is usually difficult to carry out oil-gas-water three-phase flow experiments, and there are obvious inaccuracies and limitations of empirical models to estimate three-phase parameters, which show significant superiority of the 3-DPNM. Based on 3-DPNM, three-phase flow in porous media was studied in this dissertation. First, circular capillary entry pressure of displacement phases during different injection processes were analyzed using three-phase flow interfacial parameters and basic equation (Bartell-Osterhof equation), and oil-gas-water three-phase displacement mechanisms & microcosmic distributions in different wettability systems were obtained. Second, extended two-phase piston-like displacement capillary pressure of non-circular section pores (MS-P method), capillary entry pressure of non-circular pores during three-phase flow was deduced, and the exists conditions of spreading layer of the intermediate wetting phase was obtained. Third, near-miscible three-phase interfacial tension linear model, immiscible and near-miscible three-phase contact angle mathematical model were proposed using experimental data of interfacial tensions varying with pressure. Fourth, 3-DPNM was established, calculating methods of flow transmission was described in detail, and followed with 3-DPNM parameter sensitivity analysis; using orthogonal design method, ideal prediction was obtained comparing the Oak experimental data, which validates reliability of the 3-DPNM. Based on the 3-DPNM, oil-gas-water distributions and development effectiveness of pre and post gas drive were studied in different wetting systems; influence of the following parameters on gas displacement in intermediate-wetting system was specially focused: the proportion of wetting films, displacement path, and the oil wet pore fraction. Pore-scale modelling of oil-gas-water flow in porous media not only reveals the basic flow mechanisms, but also riches the microcosmic theory on multi-phase flow in porous media, which has important scientific and academic value as well as promising application prospect.