Estimation of permeability of sedimentary rocks by applying water-expulsion porosimetry to Katz and Thompson model

The pore-size distribution of a rock is one of the important factors controlling permeability. The Katz and Thompson model (KT model) can predict permeability using only pore-size distribution and porosity. Previous studies have conventionally used those of open pores measured by mercury intrusion porosimetry. However, open pores usually include pores unavailable for flow such as dead ends and dents. In contrast, water-expulsion porosimetry (WEP) yields information of transport pores directly serving as flow paths. The size distributions and porosities of transport pores of twelve sedimentary rocks were measured by WEP, and the permeabilities calculated by the KT model were compared with those measured using a gas permeameter. Permeabilities are shown to be better calculated by using transport porosity rather than by open porosity. Application to estimating the permeability–saturation degree relation by combining WEP, the KT model, and a relative permeability model is also discussed.