Using x-ray tomography in coreflooding experiments allows to characterize the sub-core, mm-scale, multiphase flow properties such as permeability, porosity, relative permeability and capillary pressure. This has been studied previously for CO2-brine drainage experiments and a procedure has been developed for sub-core property estimation, showing that their implementation in numerical models leads to accurate predictions of experimental measurements, such as core saturation distribution. Much less work has been conducted regarding CO2-brine imbibition modeling. In this work we characterize hysteretic sub-core properties using experimental data of CO2-brine imbibition coreflooding conducted on two core samples. We adopt the approach of [1] for sub-core capillary pressure modeling and that of [2] for relative permeability modeling, however, we find that these are not sufficient for accurate modeling of saturation distribution within the core. We improve the models by considering a unique turning point and Land trapping coefficient for each mm-scale grid block in our model and also by calculating new imbibition characteristic relative permeability curves based on a procedure developed in [3]. Results show improvements in matching experimental data. [1] R. Pini, and S.M. Benson. “Capillary pressure heterogeneity and hysteresis for the supercritical CO2/water system in a sandstone.” Advances in Water Resources 108 (2017): 277-292. [2] O. Dury, U. Fischer, and R. Schulin. “A comparison of relative nonwetting‐phase permeability models.” Water Resources Research 35.5 (1999): 1481-1493. [3] E. Anto-Darkwah, S.M. Benson, and A. Rabinovich. “An improved procedure for sub-core property characterization using data from multiple coreflooding experiments.” International Journal of Greenhouse Gas Control 105 (2021): 103226.