Multiscale pore system reconstruction and integration

Better understanding of single-/multi-phase flow through reservoir rocks largely relies on the characterisation of the pore system. For homogeneous rock materials, a complete description of the real pore structure can be obtained from the network extracted from a rock image at a single resolution. However, for complex rocks (e.g., carbonates, heterogeneous sandstones, deformed rocks etc.), a comprehensive description of the real pore structure may involve many decades of length-scales (e.g., from sub-micron to cm), which cannot be captured by a single-resolution image. Hence, the creation of a 3D multiple-scale model of a porous medium is an important step in quantitatively characterising such heterogeneous rocks and predicting their multi-phase flow properties using pore –scale network modelling.

In this paper, we describe a series of pore architecture models (PAMs) to reconstruct 3D reservoir rocks from 2D thin section images along with a set of pore analysis tools (PATs) to extract the corres onding pore network systems. Specifically, we created the multiple scale pore structure through “multiple scale reconstruction”. We present a methodology to construct multi-scale (or combined) networks based on the statistical description of pore-networks of 3D rock images at multiple resolutions. Using such networks, two-phase network modeling results are presented for carbonate samples to illustrate the importance of topology in the hierarchical pore structure. We show examples where isolated large-scale pores (e.g. vugs) are connected by small-scale pores, thus determining the combined effective petrophysical properties (capillary pressure, absolute and relative permeability). Finally, we indicate how the stochastic network generation method can be used to combine information from multiple images at the same resolution but obtained at different locations.