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Characterization of wettability in porous media using the lattice boltzmann method

Takashi Akai, Japan Oil, Gas And Metals National Corporation (JOGMEC), Branko Bijeljic, Martin Blunt
This thesis is concerned with multiphase flow in porous media, focusing primarily on applications to oil recovery from subsurface rocks. The wettability of crude oil-brine-rock systems in petroleum reservoirs often exhibits mixed-wet states where effective contact angle varies locally, because surface active components such as asphaltenes in the crude oil can alter the wettability from its original water-wet to more oil-wet states. Furthermore, when a lower salinity brine than that of formation
more » ... n that of formation brine is injected to displace oil, which is known as low salinity water flooding, wettability alteration from a mixed-wet state to more water-wet condition can occur, resulting in an improvement of oil recovery. We use direct numerical simulation to study the impact of wettability and its alteration on multiphase flow in porous media at the pore-scale. A numerical model is constructed based on the lattice Boltzmann method with two newly developed numerical methods: a wetting boundary condition which precisely models contact angle, and a model to capture wettability alteration which changes contact angle depending on the computed local salinity. The numerical model is validated using several test cases where analytical solutions are available. In particular, the new wetting boundary condition is extensively validated using the static test cases of a flat, curved and staircase solid surfaces, and a dynamic test case of capillary rise. Water flooding in mixed-wet media is studied using the numerical model. Water flooding experiments imaged with a micro-CT by Alhammadi et al. are used in which hundreds of thousands of geometrically measured in situ contact angles are available using the method of AlRatrout et al. We show that a good agreement in both the fluid configurations and effective water permeability is obtained when we model the spatial distribution of contact angle on a pore-by-pore basis, but using higher contact angles than those measured in oil-wet regions of the pore space. This physically makes sense because the [...]
doi:10.25560/80977 fatcat:jn4saq4nnbgprmapaflr7v3ezm