Prediction of permeability for porous media reconstructed using multiple-point statistics

TLDR

Predicting multiphase flow in realistic porous media requires 3D pore‑space representations, which can be derived from thin‑section images that provide multiple‑point statistics describing spatial pattern probabilities. The study aims to generate geologically realistic 3D pore‑space representations using multiple‑point statistics derived from 2D thin sections. The method generates isotropic 3D images from 2D thin‑section multiple‑point statistics, reconstructs carbonate reservoir structures, and computes permeabilities with the lattice‑Boltzmann method. On Berea sandstone, the method preserves long‑range connectivity better than two‑point statistics and yields permeabilities comparable to micro‑CT measurements and effective‑medium predictions.

Abstract

To predict multiphase flow through geologically realistic porous media, it is necessary to have a three-dimensional (3D) representation of the pore space. We use multiple-point statistics based on two-dimensional (2D) thin sections as training images to generate geologically realistic 3D pore-space representations. Thin-section images can provide multiple-point statistics, which describe the statistical relation between multiple spatial locations and use the probability of occurrence of particular patterns. Assuming that the medium is isotropic, a 3D image can be generated that preserves typical patterns of the void space seen in the thin sections. The method is tested on Berea sandstone for which a 3D image from micro-CT (Computerized Tomography) scanning is available and shows that the use of multiple-point statistics allows the long-range connectivity of the structure to be preserved, in contrast to two-point statistics methods that tend to underestimate the connectivity. Furthermore, a high-resolution 2D thin-section image of a carbonate reservoir rock is used to reconstruct 3D structures by the proposed method. The permeabilities of the statistical images are computed using the lattice-Boltzmann method (LBM). The results are similar to the measured values, to the permeability directly computed on the micro-CT image for Berea and to predictions using analysis of the 2D images and the effective medium approximation.