A multi-scale, image-based pore network modeling approach to simulate two-phase flow in heterogeneous rocks

Despite the large interest in the multi-phase flow properties of rocks with broad pore size distributions, most digital rock physics approaches struggle with the presence of multiple pore scales. In this work, we present a method to estimate relative permeability (Kr) and resistivity index (RI) curves of such heterogeneous rocks during drainage. In our dual pore network model (DPNM), macropores are represented as pores and throats , while unresolved microporosity is treated as a continuous porous medium. The scales are coupled by including microporosity as symbolic network elements in the DPNM, based on 3D image analysis. The validity of the method is investigated by treating two carbonate rocks (Estaillades and Savonnières limestone). We present a sensitivity analysis of the drainage behaviour of these networks on the microporosity's petrophysical properties, which are provided as input. While a number of challenges persist, the presented examples show how DPNM can help increase the understanding of two-phase flow in complex carbonate rocks.