Investigating the relative permeability behavior of microporosity-rich carbonates and tight sandstones with multiscale pore network models

The relative permeability behavior of rocks with wide ranges of pore sizes is in many cases still poorly understood, and is difficult to model at the pore scale. In this work, we investigate the capillary pressure and relative permeability behavior of three outcrop carbonates and two tight reservoir sandstones with wide, multi-modal pore size distributions. To examine how the drainage and imbibition properties of these complex rock types are influenced by the connectivity of macropores to each other and to zones with unresolved small-scale porosity, we apply a previously presented micro-computed-tomography-based multi-scale pore network model Bultreys et al. [2015b, 2016b] to these samples. The sensitivity to the properties of the small-scale porosity is studied by performing simulations with different artificial sphere-packing-based networks as a proxy for these pores. Finally, the mixed-wet water flooding behavior of the samples is investigated, assuming different wettability distributions for the micro-and macroporosity. While this work is not an attempt to perform predictive modeling, it seeks to qualitatively explain the behavior of the investigated samples and illustrates some of the most recent developments in multi-scale pore network modeling.