Modeling of Solute Transport in a 3D Rough-Walled Fracture–Matrix System

Fluid flow and solute transport in a 3D rough-walled fracture–matrix system were simulated by directly solving the Navier–Stokes equations for fracture flow and solving the transport equation for the whole domain of fracture and matrix with considering matrix diffusion. The rough-walled fracture–matrix model was built from laser-scanned surface tomography of a real rock sample, by considering realistic features of surfaces roughness and asperity contacts. The numerical modeling results were compared with both analytical solutions based on simplified fracture surface geometry and numerical results by particle tracking based on the Reynolds equation. The aim is to investigate impacts of surface roughness on solute transport in natural fracture–matrix systems and to quantify the uncertainties in application of simplified models. The results show that fracture surface roughness significantly increases heterogeneity of velocity field in the rough-walled fractures, which consequently cause complex transport behavior, especially the dispersive distributions of solute concentration in the fracture and complex concentration profiles in the matrix. Such complex transport behaviors caused by surface roughness are important sources of uncertainty that needs to be considered for modeling of solute transport processes in fractured rocks. The presented direct numerical simulations of fluid flow and solute transport serve as efficient numerical experiments that provide reliable results for the analysis of effective transmissivity as well as effective dispersion coefficient in rough-walled fracture–matrix systems. Such analysis is helpful in model verifications, uncertainty quantifications and design of laboratorial experiments.

[1]  Richard A. Ketcham,et al.  Modification of the Local Cubic Law of fracture flow for weak inertia, tortuosity, and roughness , 2015 .

[2]  Richard A. Ketcham,et al.  Effects of inertia and directionality on flow and transport in a rough asymmetric fracture , 2009 .

[3]  C. Chrysikopoulos,et al.  Analytical solutions for one-dimensional colloid transport in saturated fractures , 1994 .

[4]  Christopher C. Pain,et al.  Non-linear regimes of fluid flow in rock fractures , 2004 .

[5]  Stephen R. Brown,et al.  The effect of anisotropic surface roughness on flow and transport in fractures , 1991 .

[6]  N. Thomson,et al.  Two-phase flow and transport in a single fracture-porous medium system , 1999 .

[7]  Vladimir Cvetkovic,et al.  Transport of reactive tracers in rock fractures , 1999, Journal of Fluid Mechanics.

[8]  Richard A. Ketcham,et al.  Navier‐Stokes flow and transport simulations using real fractures shows heavy tailing due to eddies , 2007 .

[9]  I. Neretnieks.  Stress‐mediated closing of fractures: Impact of matrix diffusion , 2014 .

[10]  D. Crandall,et al.  Numerical simulations examining the relationship between wall-roughness and fluid flow in rock fractures , 2010 .

[11]  J. Pickens,et al.  Modeling of scale-dependent dispersion in hydrogeologic systems , 1981 .

[12]  Tomofumi Koyama,et al.  A numerical study on differences in using Navier-Stokes and Reynolds equations for modeling the fluid flow and particle transport in single rock fractures with shear , 2008 .

[13]  Guanhua Huang,et al.  Analytical solution of two-dimensional solute transport in an aquifer-aquitard system. , 2009, Journal of contaminant hydrology.

[14]  Chin-Fu Tsang,et al.  Flow and tracer transport in a single fracture: A stochastic model and its relation to some field observations , 1988 .

[15]  E. A. Sudicky,et al.  Contaminant transport in fractured porous media: Analytical solution for a single fracture , 1981 .

[16]  John F. Pickens,et al.  Solute transport through fractured media: 1. The effect of matrix diffusion , 1980 .

[17]  L. Jing,et al.  Stress Effects on Solute Transport in Fractured rocks , 2011 .

[18]  Ivars Neretnieks,et al.  Diffusion in the rock matrix: An important factor in radionuclide retardation? , 1980 .

[19]  L. Jing,et al.  Evaluation of hydrodynamic dispersion parameters in fractured rocks , 2010 .

[20]  C. Tsang,et al.  Flow channeling in heterogeneous fractured rocks , 1998 .

[21]  Emil O. Frind,et al.  Contaminant transport in fractured porous media: Analytical solutions for a system of parallel fractures , 1982 .

[22]  W. Lennox,et al.  A Control Volume Model of Solute Transport in a Single Fracture , 1995 .

[23]  Shemin Ge,et al.  A governing equation for fluid flow in rough fractures , 1997 .

[24]  Seung Hyun Lee,et al.  Tail shortening with developing eddies in a rough‐walled rock fracture , 2015 .

[25]  G. Marsily,et al.  Solute transport in a single fracture with negligible matrix permeability: 2. mathematical formalism , 2003 .

[26]  Zhihong Zhao.  Gouge Particle Evolution in a Rock Fracture Undergoing Shear: a Microscopic DEM Study , 2013, Rock Mechanics and Rock Engineering.

[27]  Gudmundur S. Bodvarsson,et al.  Hydraulic conductivity of rock fractures , 1996 .

[28]  G. Kumar.  Effect of sorption intensities on dispersivity and macro-dispersion coefficient in a single fracture with matrix diffusion , 2008 .

[29]  Giovanni Grasselli,et al.  Trapping zones: The effect of fracture roughness on the directional anisotropy of fluid flow and colloid transport in a single fracture , 2006 .

[30]  L. Smith,et al.  Influence of Specific Surface Area on Transport of Sorbing Solutes in Fractures: An Experimental Analysis , 1996 .

[31]  C. Chrysikopoulos,et al.  Transport of Neutrally Buoyant and Dense Variably Sized Colloids in a Two-Dimensional Fracture with Anisotropic Aperture , 2003 .

[32]  L. Jing,et al.  Roughness decomposition and nonlinear fluid flow in a single rock fracture , 2015 .

[33]  M. Cardenas,et al.  Non‐Fickian transport through two‐dimensional rough fractures: Assessment and prediction , 2014 .

[34]  Emil O. Frind,et al.  Contaminant Transport in Fractured Porous Media: Analytical Solution for a Two‐Member Decay Chain in a Single Fracture , 1984 .

[35]  Pascale Royer,et al.  Contaminant transport in fractured porous media , 2003 .

[36]  Quanlin Zhou,et al.  Field-scale effective matrix diffusion coefficient for fractured rock: results from literature survey. , 2007, Journal of contaminant hydrology.

[37]  Wookhyun Yeo.  Effect of fracture roughness on solute transport , 2001 .

[38]  Frederick Delay,et al.  Solute transport in a single fracture with negligible matrix permeability: 1. fundamental mechanisms , 2003 .

[39]  L. Jing,et al.  Shear enhanced nonlinear flow in rough-walled rock fractures , 2017 .

[40]  Ivars Neretnieks,et al.  Flow and nuclide transport in fractured media: the importance of the flow-wetted surface for radionuclide migration , 1993 .

[41]  Harihar Rajaram,et al.  Saturated flow in a single fracture: evaluation of the Reynolds Equation in measured aperture fields , 1999 .

[42]  Seung Hyun Lee,et al.  Assessment of the validity of Stokes and Reynolds equations for fluid flow through a rough‐walled fracture with flow imaging , 2014 .

[43]  G. Suresh Kumar,et al.  Numerical Modeling and Spatial Moment Analysis of Solute Mobility and Spreading in a Coupled Fracture-Skin-Matrix System , 2012, Geotechnical and Geological Engineering.

[44]  Chuhan H. Zhang,et al.  Experimental and numerical study of the geometrical and hydraulic characteristics of a single rock fracture during shear , 2011 .

[45]  Chin-Fu Tsang,et al.  A variable aperture fracture network model for flow and transport in fractured rocks , 1992 .

[46]  Daniel M. Tartakovsky,et al.  Semi‐analytical solutions for solute transport and exchange in fractured porous media , 2012 .

[47]  H. Kimura,et al.  Particle-tracking technique for nuclide decay chain transport in fractured porous media. , 1990 .

[48]  Constantinos V. Chrysikopoulos,et al.  Modeling of colloid and colloid-facilitated contaminant transport in a two-dimensional fracture with spatially variable aperture , 1995 .

[49]  Sumit Mukhopadhyay,et al.  Analytical solutions of tracer transport in fractured rock associated with precipitation-dissolution reactions , 2011 .

[50]  L. Jing,et al.  Assumptions of the analytical solution for solute transport in a fracture–matrix system , 2016 .