The impact of spatial variation and correlation length of wettability on scCO2-brine immiscible displacement in 3D porous media

Surface wettability plays a significant role in multiphase flow in porous medium. This study is to investigate the impact of the spatial variation and correlation length of surface wettability on the scCO₂-brine immiscible displacement in 3D porous medium. In-situ measurements of contact angles (CAs), which is employed to describe the surface wettability of a rock sample in this study, were conducted on a Bentheimer sandstone sample which was constructed using computed tomography (micro-CT) after a supercritical CO₂ (scCO₂) flooding. The distribution of the CAs was model by a log-normal distribution and associated standard deviation and correlation length were calculated. The distribution of wettability of a realistic rock was assumed as a continuously distributed fractional wettability model. Based on the measured statistical information, the standard deviation and correlation length will be shifted within a certain range of values to investigate the sensitivity of scCO₂-brine displacement on the CA spatial distribution. The wettability models of rock samples were constructed by generating random wettability fields with different standard deviation and correlation length and projecting them onto the Benthermer sandstone. A Lattice Boltzmann model accelerated by a hybrid, multicore CPU/GPU parallel computing algorithm was used to conduct the large-scale simulation on a 800×800×600-pixel Bentheimer sandstone sample. The impact of standard deviation and correlation length of the CA distribution on the scCO₂-brine displacement, especially on relative permeability, will be discussed. The Corey model was used to fit the simulated relative permeabilities to quantitatively evaluate the impact of wettability heterogeneity.