Permeability (earth sciences)

About: Permeability (earth sciences) is a research topic. Over the lifetime, 15424 publications have been published within this topic receiving 288535 citations.

Review: Mathematical expressions for estimating equivalent permeability of rock fracture networks

Abstract: Fracture networks play a more significant role in conducting fluid flow and solute transport in fractured rock masses, comparing with that of the rock matrix. Accurate estimation of the permeability of fracture networks would help researchers and engineers better assess the performance of projects associated with fluid flow in fractured rock masses. This study provides a review of previous works that have focused on the estimation of equivalent permeability of two-dimensional (2-D) discrete fracture networks (DFNs) considering the influences of geometric properties of fractured rock masses. Mathematical expressions for the effects of nine important parameters that significantly impact on the equivalent permeability of DFNs are summarized, including (1) fracture-length distribution, (2) aperture distribution, (3) fracture surface roughness, (4) fracture dead-end, (5) number of intersections, (6) hydraulic gradient, (7) boundary stress, (8) anisotropy, and (9) scale. Recent developments of 3-D fracture networks are briefly reviewed to underline the importance of utilizing 3-D models in future research.

Foam Mobility in Heterogeneous Porous Media

Abstract: Foamed-gas injection is a promising technique for achieving mobility control and diverting fluid to low permeability strata within heterogeneous porous media. However, the factors most important for diversion have not been stated and explored definitively. Gas mobility in the presence of foam depends critically on foam-bubble size; bubble size may vary with permeability, porosity, surfactant type and concentration, and the velocity of liquid and gas. This paper adopts a local equilibrium, scaling perspective to describe quantitatively foamed-gas mobility within heterogeneous porous media. Conventional and percolation network scaling ideas are employed. A new closed form expression for the fraction of mobile gas within a foam is derived using statistical network concepts. Additional equations indicate, for instance, that porosity plays an important role in setting gas mobility because it reflects the relative abundance of foam germination and termination sites per unit volume of porous media. Liquid velocity is also important because gas mobility is inversely proportional to this factor.

Permeability evolution during localized deformation in Bentheim sandstone

Abstract: [1] Strain localization in porous sandstones may significantly impact the regional fluid flow. Previous laboratory studies that investigated permeability evolution with deformation concentrated primarily on shear localization and distributed cataclastic flow. Here we focus on compaction bands, a localized mode of deformation characterized by compaction and negligible shear. In this study we used Bentheim sandstone with porosity 23%, where discrete compaction bands have been observed to develop subperpendicular to the maximum principal stress. To investigate coupling between strain localization and permeability, we conducted permeability measurements during triaxial loading at confining pressures ranging from 10 to 350 MPa and microstructural observation on failed samples. Two types of failure were identified: shear localization and compaction localization at low and high effective pressures, respectively. For both failure modes the bulk permeability decreased with deformation. A dramatic decrease of more than one order of magnitude was associated with compaction localization, where permeability reduction occurred over a relatively narrow range of axial strain with the onset of shear-enhanced compaction. Motivated by our microstructural observations, we modeled the permeability reduction of the failed sample as that of a layered medium with significant permeability contrast between the discrete bands and matrix. The model reproduced the experimental observations of permeability evolution during development of discrete compaction bands, with implications for the amount of localized strain and the permeability contrast. Permeability evolution during development of discrete and diffuse compaction bands suggests two different trends with strain, providing guidance for extrapolation of laboratory measurements to field settings.