Formation Of Compaction Bands Research Articles

A nonlocal kernel-based continuum damage model for compaction band formation in porous sedimentary rock

A nonlocal kernel-based continuum damage model for compaction band formation in porous sedimentary rock

Development of Compaction Localization in Leitha Limestone: Finite Element Modeling Based on Synchrotron X‐Ray Imaging

AbstractThe mechanical behavior and failure mode of porous rocks vary with their microstructures. The formation of compaction bands (CBs) has been captured with high precision via in situ synchrotron CT and kinematic characteristics can be attained by image analysis. However, the stress characteristics cannot be directly evaluated from images, and how porosity heterogeneity triggers local instability and leads to the formation of CBs is not yet fully understood. To address this problem, we established a finite element (FE) model of the solid skeleton of a Leitha limestone sample based on X‐ray μCT data, considering the heterogeneity of pores and plastic hardening, and reproduced the evolution of strain localization and CBs. Our results revealed that the heterogeneity of porosity has a profound influence on the formation and propagation of CBs. Precursory stresses always appear very early around the pores where compaction bands develop, and the stress state of most points in CBs is quasi‐uniaxial compression, which has significantly high maximum principal stress σ1 in a direction subparallel to the sample axis, causing yield then compaction failure. Also, using a simplified FE mesh and ignoring the fracture of particles underestimate the extreme stress and porosity reduction—these can be improved by using fine mesh and involving grain‐scale fracture mechanics. Our study proves the feasibility and reliability of the CT‐FE simulation scheme, which can be extended to investigating the stress distribution and evolution of different rock types with a spectrum of failure modes if in situ CT data of rock deformation is available.

A Thermodynamically Based Modified Cam‐Clay Model for Post‐Bifurcation Behavior of Deformation Bands

AbstractCompaction bands are a type of localized deformation that can occur as diffuse or discrete bands in porous rocks. While modeling of shear bands can replicate discrete and diffusive bands, numerical models of compaction have so far only been able to describe the formation of discrete compaction bands. In this study, we present a new thermodynamic approach to model compaction bands that is able to capture both discrete and diffuse compaction band growth. The approach is based on a reaction‐diffusion formalism that includes an additional entropy flux. This entropic velocity regularizes the solution, by introducing a characteristic diffusion length scale and controlling the mode change from discrete to diffusive post‐localisation growth. The approach is used to model compaction band growth in highly porous carbonates. The model can replicate the areas of material damage exhibiting reduced porosity which are often observed as nuclei for the growth of compaction bands in experiments. The model also has the versatility to predict the formation of diffuse compaction bands, which is a significant advance in the field of compaction band modeling. The method can potentially be used for investigating the effect of material heterogeneities on compaction band growth and is heuristic for developing new methodologies for forecasting compaction band formation.

Acoustic monitoring of compaction in cohesive granular materials.

We study the transition from cohesive to noncohesive states of cemented granular materials (synthetic rocks) under oedometric loading, combining simultaneous measurements of ultrasound velocity and acoustic emission (AE: microseosmicity). Our samples are agglomerates made of glass beads bonded with a few percent of cement, either ductile or brittle. These cemented granular samples exhibit an inelastic compaction beyond certain axial stresses likely due to the formation of compaction bands, which is accompanied by a significant decrease of compressional wave velocity. Upon subsequent cyclic unloading-reloading with constant consolidation stress, we found the mechanical and acoustic responses like those in noncohesive granular materials, which can be interpreted within the effective medium theory based on the Digby's bonding model. Moreover, this model allows P-wave velocity measured at vanishing pressure to be interpreted as an indicator of the debonding on the scale of grain contact. During the inelastic compaction, stick-slip-like stress drops were observed in brittle cement-bonded granular samples accompanied by the instantaneous decrease of the P-wave velocity and AEs which display an Omori-like law for foreshocks, i.e., precursors. By contrast, mechanical responses of ductile cement-bonded granular samples are smooth (without visible stick-slip-like stress drops) and mostly aseismic. By applying a cyclic loading-unloading with increasing consolidation stress, we observed a Kaiser-like memory effect in the brittle cement-bonded sample in the weakly damaged state which tends to disappear when the bonds are mostly broken in the noncohesive granular state after large-amplitude loading. In this paper, we show that the macroscopic ductile and brittle behavior of cemented granular media is controlled by the local processes on the scale of the bonds between grains.

Modeling heterogeneity and permeability evolution in a compaction band using a phase-field approach

Compaction bands are tabular zones of localized compressive deformation associated with porosity and permeability reduction. Depending on their orientation, compaction bands can act as barriers to fluid flow, and can be detrimental to fluid production in oil and gas reservoirs, as well as in CO2 sequestration. The process of permeability reduction and the development of excess pore pressures during compaction band formation in a heterogeneous rock mass are not fully understood. Furthermore, few studies have modeled compaction band formation considering coupled hydromechanical processes. In this study, we propose a coupled hydromechanical, phase-field approach for capturing the formation and propagation of compaction bands in heterogeneous porous media. Breakage mechanics is adopted to characterize the free energy function in the intact and damaged material. The resulting phase-field variable provides a measure of the degree of grain crushing. Permeability reduction in the zone of compaction localization is modeled using the Kozeny–Carman equation accounting for microstructural evolution. Numerical simulations demonstrate the ability of the model to capture compaction band formation, porosity reduction, and permeability evolution under drained and undrained conditions. The results highlight the role of effective confining pressure, drainage conditions, and material parameters on the styles of compaction bands that form.

A phase‐field approach for compaction band formation due to grain crushing

AbstractCompaction bands are tabular regions of localized compressive deformation with little or no shear offset. Often observed in high‐porosity rocks, they can be classified into several subtypes based on their pattern and orientation with respect to the maximum principal stress. The combined effects of material properties and loading conditions on the type of compaction bands that develop are not fully understood, and realistic simulations of their formation are not always successful. In this study, a phase‐field approach for capturing the formation and propagation of compaction bands is proposed. The fracture energy utilized in classic phase‐field formulations is interpreted to be driven by grain crushing and is herein characterized by breakage mechanics theory. A new decomposition of the free energy function is introduced in which the energy stored by plastic compactive flow drives grain crushing. Depending on the value of the energy release rate, the model predicts different styles of compaction bands that are remarkably consistent with those observed in the field. Numerical simulations demonstrate the role of confining pressure, plasticity, and critical breakage energy on the styles of the predicted compaction bands.

The Brittle–Ductile Transition and the Formation of Compaction Bands in the Savonnières Limestone: Impact of the Stress and Pore Fluid

Carbonate sediments play a prominent role on the global geological stage as they store more than 60% of world’s oil and 40% of world’s gas reserves. Prediction of the deformation and failure of porous carbonates is, therefore, essential to minimise reservoir compaction, fault reactivation, or wellbore instability. This relies on our understanding of the mechanisms underlying the observed inelastic response to fluid injection or deviatoric stress perturbations. Understanding the impact of deformation/failure on the hydraulic properties of the rock is also essential as injection/production rates will be affected. In this work, we present new experimental results from triaxial deformation experiments carried out to elucidate the behaviour of a porous limestone reservoir analogue (Savonnières limestone). Drained triaxial and isotropic compression tests were conducted at five different confining pressures in dry and water-saturated conditions. Stress–strain data and X-ray tomography images of the rock indicate two distinct types of deformation and failure regimes: at low confinement (10 MPa) brittle failure in the form of dilatant shear banding was dominant; whereas at higher confinement compaction bands orthogonal to the maximum principal stress formed. In addition to the pore pressure effect, the presence of water in the pore space significantly weakened the rock, thereby shrinking the yield envelope compared to the dry conditions, and shifted the brittle–ductile transition to lower effective confining pressures (from 35 MPa to 29 MPa). Finally, permeability measurements during deformation show a reduction of an order of magnitude in the ductile regime due to the formation of the compaction bands. These results highlight the importance of considering the role of the saturating fluid in the brittle–ductile response of porous rocks and elucidate some of the microstructural processes taking place during this transition.

Compaction localization and anisotropic permeability evolution

The oedometric compaction of materials with collapsible structure is investigated from a numerical point of view. Such materials form planar zones of localized volumetric deformation that may or may not be accompanied by grain crushing. The purpose of the present work is to investigate the evolution of the permeability and its anisotropy as the result of the formation of compaction bands. The finite element method is used for the simulations with the commercial software ABAQUS. The mechanical response is calibrated on experimental results from the literature. Due to the localization of the deformation, the problem is not numerically stable and shows mesh dependence when a simple material model is used. To resolve the issue a nonlocal formulation is implemented. Drained oedometric tests are simulated. For the permeability different formulations are used, either ignoring the anisotropic evolution of the pore network or accounting for it. The results show that permeability anisotropy at the microscale needs to be considered, because otherwise the predicted reduction in permeability is qualitatively not in agreement with experimental results. On the whole, it is concluded that the permeability reduction following the formation of compaction bands can be highly anisotropic both at the micro and the macro scale.

Compaction Banding in High‐Porosity Carbonate Rocks: 1. Experimental Observations

AbstractIdentifying the mechanisms that control the formation of compaction bands is of high interest in reservoir mechanics since these structures may drastically affect the performance of geosystems operations. Considering the difficulty to identify compaction bands in carbonate samples tested in the laboratory, the Digital Volume Correlation technique is applied here and proves to be a relevant method. X‐Ray Computed Tomography (XRCT) images of Saint‐Maximin limestone centimetric samples are recorded before and after several triaxial loading stages and deformation maps are built. A new postprocessing method based on the analysis of the kinematics throughout the observed localization bands is proposed to identify their type. Compaction bands are identified at relatively high‐confining pressures, while shear bands are observed at lower confinements. The brittle‐ductile transitional regime reveals the formation of compactive shear bands, while a diffuse compaction is observed under hydrostatic loading. The effect of porosity heterogeneities on strain localization is explored by computing 3D porosity maps from calibrated XRCT images. Compaction bands are found to dominantly lay inside high‐porosity zones, while shear bands can cross both high‐ and low‐porosity zones. The band orientation is found to be controlled primarily by the confining pressure. Moreover, the porosity heterogeneity strongly affects the volumetric behavior inside the deformation bands, with a dilatant behavior identified in low‐porosity zones in contrast to a compactive behavior observed in high‐porosity zones. Finally, Scanning Electron Microscopy observations reveal that calcite grain crushing is dominant in high‐porosity zones, while intergranular cement cracking occurs in denser zones.

Compaction Banding in High‐Porosity Carbonate Rocks: 2. A Gradient‐Dependent Plasticity Model

AbstractBased on the experimental study on Saint‐Maximin limestone presented in a companion paper (Abdallah et al., 2020), a gradient‐dependent plasticity model is developed to account for the key role of porosity heterogeneity in the formation and propagation of compaction bands. The constitutive law, developed in the frame of a micromorphic continuum theory, contains two hardening variables: the porosity and its second gradient. A calibration method for the additional micromechanical parameters is proposed. Data from the companion paper are used in a four‐step calibration procedure. First, the standard Cauchy component is calibrated by means of the macroscopic stress‐strain curves. An Asymmetric Cam‐Clay (ACC) model is adopted for the yield surface. The dominant wavelength of the porosity heterogeneity of the material is evaluated by applying the fast Fourier transformation (FFT) on several porosity profiles obtained on samples before loading. This wavelength is interpreted as the material length that appears in the model. In addition to the deformation maps computed from digital volume correlation (DVC), a method that evaluates the second gradient of porosity is developed to calibrate the hardening laws. A linear stability analysis (LSA) is performed to calibrate the higher‐order elastic modulus. The constitutive model is implemented in a finite element code, and triaxial loading experiments are simulated. The numerical results are consistent with the experimental data in terms of the onset of compaction bands, their thickness, and plastic strain. The size effect of the sample is explored, and a regular band spacing, comparable to the band thickness, is obtained.

The dynamic evolution of compaction bands in highly porous carbonates: the role of local heterogeneity for nucleation and propagation

The formation of compaction bands in porous brittle rocks such as sandstones and carbonates has a significant impact on the localization mechanisms preceding earth and planetary surface instabilities such as earthquakes, landslides, and plate boundary faults. The micromechanics underpinning the dynamics of the formation of compaction bands and its effect on alteration of pore fluid pathways are not yet fully understood. The current study seeks to understand the mechanical properties of compaction in highly porous carbonate at micro- and macro-scale using time-lapse triaxial experiments in an X-ray transparent flow and deformation cell. Images were obtained with increasing axial strain levels using X-ray computed tomography allowing mapping of the evolution of internal structures. In addition to the X-ray analysis, digital image correlation (DIC) was used to quantify the evolution of strain and precisely identify the nucleation mechanism of compaction bands and its dynamics. The effect of friction on the boundary platens was shown to be minimal as evidenced by shear strain obtained from DIC analysis. This comprehensive analysis allowed assessment of the role of heterogeneity for the initiation of compaction bands. Local regions with high porosity provide the initial seeds for discrete compaction followed by the nucleation of traveling waves that lead to diffuse growth of the compaction zone. This interesting phenomenon is expected to be a fundamental mode of compressional deformation in porous brittle media where discrete, often periodic, deformation bands are observed on compaction.

Compaction bands in Tuffeau de Maastricht: insights from X-ray tomography and multiscale modeling

We present a study on compaction band in a high-porosity limestone (Tuffeau de Maastricht) based on comparison and analysis of X-ray tomography observations and computational multiscale simulations. We employ a hierarchical multiscale approach coupling the finite element method (FEM) with the discrete element method (DEM) to simulate the formation of compaction bands in Tuffeau de Maastricht. A high-porosity RVE is prepared according to X-ray tomography observations of material microstructure, and its grain-scale parameters are calibrated by data from laboratory isotropic compression and triaxial compression tests. Triaxial compression tests are simulated by FEM as a boundary value problem to observe compaction bands. The generated RVE is embedded into each integration point of the FE mesh, receiving displacement gradient as DEM boundary conditions, and is solved accordingly to produce the required mechanical responses for FEM computation without assuming phenomenological constitutive relations. The simulated global mechanical responses of the triaxial tests are found to show qualitative agreement with the experimental data. The evolution of compaction band patterns in the simulation matches remarkably well with the experimental observations in terms of fields of porosity and incremental strains. Both show two compaction fronts initiating from the two ends of the specimen and propagating toward the middle. By virtue of the multiscale approach, useful microstructural information is further extracted from the simulations to offer cross-scale insights into compaction bands. The study confirms that significant debonding accompanied by collapse of macropores and grain rearrangements is the major microstructural mechanisms causing the formation of compaction bands in high-porosity Tuffeau de Maastricht.

Multiscale modeling of compaction bands in saturated high-porosity sandstones

We propose a hierarchical multiscale modeling approach to simulate the hydro-mechanical coupling behavior in saturated high-porosity sandstone, with a particular focus on the occurrence and transition of compaction bands. In this multiscale approach, we use the finite element method (FEM) to solve the global boundary value problem for a sandstone, and the discrete element method (DEM) to solve the local representative volume elements (RVEs) embedded at the Gauss integration points of the FE mesh to provide the effective material constitutive responses required for FEM. The global governing equations for a coupled hydro-mechanical problem are solved with the standard u–p formulation, where the total stress is decomposed into the pore pressure and the effective stress which is directly derivable from the DEM solution of the RVEs, according to the seminal Terzaghi's effective stress principle. By choosing proper RVEs to represent the typical microstructure of high-porosity sandstone, we perform both drained and undrained simulations on saturated sandstone specimens to examine localized compactive failures developed therein. We identify that both mean effective stress and porosity control critically the initiation and development of failure modes in sandstone. Under undrained shear, our simulations show that a sandstone specimen may first develop a compaction band followed by a gradual transition to a shear-enhanced compaction band and even shear band, with the build-up of excessive pore pressure and hence drop of mean effective stress. In the specimen, regions experiencing localized volumetric contraction show relatively higher pore pressure than other regions and act as the source of flux flow. The Darcy flux peaks during the formation of compaction band and decreases gradually in the following stages. To distinguish the different failure stages with distinct physical attributes, the ratio of deviatoric strain to volumetric strain is adopted as a useful indicator signifying the underlying microstructural mechanisms for different deformation bands. This study signifies the importance of considering pore pressure and mean effective stress in fluid-involved engineering operations, e.g. aquifer management, hydrocarbon extraction and CO2 geological sequestration.

Simulation of localized compaction in Tuffeau de Maastricht based on evidence from X-ray tomography

Deformation experiments with concurrent X-ray microtomography are used to characterize the mechanical properties of a high-porosity carbonate rock from Central Europe (the Tuffeau de Maastricht). Evidence of deformation behavior and pressure-dependent strain localization for this rock are taken into account to define the parameters of an elastoplastic constitutive law with competing hardening and softening mechanisms. Full-field data regarding the compaction localization regime have been used to identify a compromise between compaction hardening and structure deterioration. It was shown that by placing emphasis on the destructuration behavior it was possible to reproduce features such as the elongation of the deformation plateau emerging during compaction band formation, as well as the pressure-dependent inclination of the ensuing compaction bands. Most notably, the comparison between measurements and simulations showed that the strategy here used to constrain the model parameters allows a satisfactory depiction of both the macroscopic deformations and the portion of sample volume across which the compaction zones develop and propagate. These results point out the major benefits of parameter calibration strategies accounting synergistically for global measurements and spatially-distributed deformations, especially in the presence of constitutive laws meant to replicate compaction localization.

Can mechanical failure in unconsolidated sands during hydrocarbon production result in flow barriers?

Water injectors in unconsolidated sands often experience severe injectivity decline and premature failure. The formation of shear bands and compaction bands is a possible mechanism which can cause a flow barrier. Herein, we exploit an elasto-plastic bifurcation analysis in order to assess whether shear bands and compaction bands can form under realistic reservoir conditions. Since injection favors the formation of dilatant shear bands, we focus on the possible formation of compactant deformation bands during a preceding depletion period with the potential to severely impede flow during subsequent injection. A set of conditions is elaborated, and they indicate a low risk of localization as a consequence of hydrocarbon production. In fact, the possibility of localization reduces upon progressive depletion. An extensive sensitivity analysis shows that this conclusion continues to hold when varying the material parameters and initial stress conditions within a realistic range for subsurface conditions. This renders the sketched scenario of deformation bands acting as flow barriers unlikely under conditions typical of deepwater reservoirs in the Gulf of Mexico. The conclusion that localized deformation bands probably do not cause injectivity loss is reinforced since only compaction bands can reduce the permeability sufficiently to create effective flow barriers. They would form perpendicular to the major compressive principal stress, and in a normal faulting regime, this would result in bands with a low inclination angle to the horizontal plane. They would not adversely affect flow from or towards (vertical) wells in a reservoir.

Effects of pre-existing faults on compaction localization in porous sandstones

The formation of deformation bands can significantly modify the strength and transport properties of porous sedimentary rocks. Among the different types of deformation bands, compaction bands exhibit porosity reduction with little to no shear displacement. Natural compaction bands have previously been reported and studied in only a few areas. They often coexist with faults and other localized deformation structures. We mapped the geometrical relation between compaction bands, shear bands and faults in Lower Cretaceous porous sandstone at Makhtesh Katan, Israel. To understand the effect of pre-existing faults on the formation of compaction bands, we conducted deformation experiments on pre-faulted Bentheim sandstones. These experiments produced compaction bands consistently intersect the pre-existing fault. To gain better mechanical understanding of the observed band geometry, we also carried out three-dimensional (3D) numerical simulations with the input elastic moduli and yield strength well-constrained from the deformation experiments. We demonstrated that the formation of deformation bands is dictated by stress concentrations associated with the pre-existing fault. Frictional slip along the heterogeneous fault plane can produce a local stress concentration that would be responsible for further localized damage and the development of deformation zones. When fault slip is restricted (a possible result of high confinement), compaction bands initiate at high stress concentration sites resulting from geometrical irregularities of the fault. Finally, using a plane-strain two-dimensional (2D) linear-elastic model with the geometry of the faults mapped in the outcrop, we were able to provide a mechanical explanation of the distribution for deformation bands observed at the Makhtesh Katan study area.

Multiscale modeling and analysis of compaction bands in high-porosity sandstones

We present a multiscale investigation on the initiation and development of compaction bands in high-porosity sandstones based on an innovative hierarchical multiscale approach. This approach couples the finite element method and the discrete element method (DEM) to offer direct, rigorous linking of the microscopic origins and mechanisms with complex macroscopic phenomena observed in granular rocks such as strain localization and failure. To simulate compaction band in granular cementitious sandstone, we adopt a bonded contact model with normal and tangential interparticle cohesions in the DEM and propose a dual-porosity structure consisting of macro-pores and interstitial voids for the representative volume element to mimic the typical meso-structure of high-porosity sandstones. In the absence of particle crushing, our multiscale analyses identify debonding and pore collapses as two major contributors to the formation of compaction bands. The critical pressures predicted by our simulations, corresponding to surges of debonding and pore collapse events, agree well with the estimations from field data. The occurrence patterns of compaction band are found closely related to specimen heterogeneity, porosity and confining pressure. Other deformation band patterns, including shear-enhanced compaction bands and compactive shear bands, were also observed under relatively low confining pressure conditions with a rough threshold at $$0.55P^{*}$$ ( $$P^{*}$$ is the critical pressure) on the failure envelop. Key microscopic characteristics attributable to the occurrence of these various deformation patterns, including fabric anisotropy, particle rotation, debonding and pore collapse, are examined. Shear-enhanced compaction bands and pure compaction bands bear many similarities in terms of these microscopic characteristics, whereas both differ substantially from compactive shear bands.

High strain rate deformation of porous sandstone and the asymmetry of earthquake damage in shallow fault zones

In contrast to coseismic pulverization of crystalline rocks, observations of coseismic pulverization in porous sedimentary rocks in fault damage zones are scarce. Also, juxtaposition of stiff crystalline rocks and compliant porous rocks across a fault often yields an asymmetric damage zone geometry, with less damage in the more compliant side. In this study, we argue that such asymmetry near the sub-surface may occur because of a different response of lithology to similar transient loading conditions. Uniaxial unconfined high strain rate loadings with a split Hopkinson pressure bar were performed on dry and water saturated Rothbach sandstone core samples. Bedding anisotropy was taken into account by coring the samples parallel and perpendicular to the bedding. The results show that pervasive pulverization below the grain scale, such as observed in crystalline rock, does not occur in the sandstone samples for the explored strain rate range (60–150 s−1). Damage is mainly restricted to the scale of the grains, with intragranular deformation occurring only in weaker regions where compaction bands are formed. The presence of water and the bedding anisotropy mitigates the formation of compaction bands and motivates intergranular dilatation. The competition between inter- and intragranular damage during dynamic loading is explained with the geometric parameters of the rock in combination with two classic micromechanical models: the Hertzian contact model and the pore-emanated crack model. In conclusion, the observed microstructures can form in both quasi-static and dynamic loading regimes. Therefore caution is advised when interpreting the mechanism responsible for near-fault damage in sedimentary rock near the surface. Moreover, the results suggest that different responses of lithology to transient loading are responsible for sub-surface damage zone asymmetry.

A unified variational eigen-erosion framework for interacting brittle fractures and compaction bands in fluid-infiltrating porous media

The onset and propagation of the cracks and compaction bands, and the interactions between them in the host matrix, are important for numerous engineering applications, such as hydraulic fracture and CO2 storage. While crack may become flow conduit that leads to leakage, formation of compaction band often accompanies significant porosity reduction that prevents fluid to flow through. The objective of this paper is to present a new unified framework that predicts both the onset, propagation and interactions among cracks and compaction bands via an eigen-deformation approach. By extending the generalized Griffith’s theory, we formulate a unified nonlocal scheme that is capable to predict the fluid-driven fracture and compression-driven anti-crack growth while incorporating the cubic law to replicate the induced anisotropic permeability changes triggered by crack and anti-crack growth. A set of numerical experiments are used to demonstrate the robustness and efficiency of the proposed model.

Fluid-flow effects of compartmentalized distribution of compaction bands in an aeolian sandstone in three dimensions

It is well established that the depositional architecture of dunes (cross-bed orientations and dune boundaries) controls the formation and orientation of compaction bands (CBs) in three dimensions, resulting in a compartmentalized distribution of low-angle bed-parallel CBs and high-angle CBs in the Jurassic aeolian Aztec Sandstone, exposed in the Valley of Fire State Park, Nevada, USA. In this study, we used two idealized configurations to represent the characteristic compartmentalization of CBs in three dimensions and performed flow computations to investigate the fluid-flow effects of these configurations. The results suggest that the upscaled permeability of the compartmentalized compaction-band arrays is influenced significantly by the permeability of the compaction-band sets and their orientations and distributions. In particular, in Configuration A, which represents a combination of both the high-angle and bed-parallel domains, upscaled permeability in the direction normal to the dune trend is controlled primarily by the high-angle CB domain. In contrast, in Configuration B, in which the high-angle CB domain is distributed within a limited portion, upscaled permeability in the direction normal to the dune trend is controlled by both the high-angle CB domain and the bed-parallel CB domain. The upscaled permeability in the direction parallel to the dune trend in Configuration A is controlled by both high-angle CBs and bed-parallel CBs, but in Configuration B it is controlled mainly by bed-parallel CBs. In comparison, in both configurations A and B, upscaled permeability in the vertical direction is controlled primarily by the bed-parallel CB domain. The orientation of the major permeability component in both configurations A and B remains almost unaffected by the variation in permeability of CB sets, presumably because the preferred flow path crosses a minimum number of CBs. In contrast, the plunges of the minor permeability component changes significantly in Configuration A, but remains nearly the same in Configuration B. This suggests that the interplay between the spatial distributions of CB sets and their permeability exerts significant influence on the orientation of the minor permeability component in Configuration A, whereas the permeability of bed-parallel CBs has dominant control on the minor permeability component in Configuration B. The difference between the magnitudes of the major principal permeability component and the minor principal permeability component (permeability anisotropy) is about a factor of 2.5, 2.2 and 1.9 in Configuration A for cases 1, 2 and 3, respectively, and about a factor of 5.1, 3.4 and 1.3 in Configuration B for cases 1, 2 and 3, respectively. The parametric study implies that the range of potential variations in the permeability values in flow models would generally yield similar results for the major permeability component, but may yield different results for the minor permeability component. The results presented in this study clearly demonstrate that the compartmentalized distribution of CBs exerts strong influences on fluid flow through aeolian sandstone.