Pore Structure and Permeability of Tight-Pore Sandstones: Quantitative Test of the Lattice–Boltzmann Method

Abstract

This paper presents a characterization of the pore structure of tight-pore sandstones of the Achimov suite and examines the application of Lattice–Boltzmann method (LBM) simulations to estimate the permeabilities of rock formations with a single-scale porosity. Porosity is characterized by pore volume distribution, pore throat connectivity, and tortuosity, which are calculated from 3D computer tomography pore network maps. The tight sandstones are poorly permeable, with permeabilities from 0.7 to 13 mD. For comparison, sandstones and carbonates with higher porosity and permeability from the existing database are also considered. For the more permeable reference samples with wider pores (250 µm), LBM simulations show good agreement with the experiments and somewhat outperform the selected state-of-the-art direct simulations from the literature. For samples with the tightest pores and lowest porosity, LBM simulations tend to somewhat overestimate the permeability in comparison with the direct simulation methods, whereas for samples of higher porosity, a slight underestimation is obtained. We explain the inconsistencies by an interplay between the compressibility effects neglected by our LBM simulations in wider pores and the friction at the pore-wall interface, which is underestimated due to the use of the bounce-back conditions. However, the general agreement with experimental and direct simulation methods is very reasonable and suitable for practical use, which means that LBM is fast, highly parallel, and computationally sound even in tight pores.