Computational estimation of compaction band permeability in sandstone

Abstract

Permeability measurements are difficult to obtain when sample availability is restricted, dimensions limited, or materials poorly consolidated. With subsurface cores of sandstone containing thin, tabular compaction bands (CBs), all three challenges can arise. Computational methods for estimating permeability from thin section provide an alternative. We evaluate a new physics-based technique in which lattice-Boltzmann flow simulations are conducted on stochastic realizations of 3D pore structure generated from thin-section images. Applied to the Aztec sandstone of southeastern Nevada, and exhumed analog for CB-rich sandstone aquifers and reservoirs, the estimates agree well with available data—a few millidarcys (CB) to a few Darcys (matrix)—capturing the range of both matrix and CB permeability from a single, representative thin-section. The technique also gives us a tool for estimating permeability anisotropy due to bed types in sandstone. For a subsurface with Aztec equivalent, this result can be invaluable, since pervasive arrays of compaction bands in sandstone have been shown capable of exerting substantial fluid flow effects at scales relevant to aquifer and reservoir management.