Upscaling of Flow, Transport, and Stress-effects in Fractured Rock

One of many applications of geohydraulic modelling is assessing the suitability of a site to host a nuclear waste repository. This modelling task is complicated by scale-dependent heterogeneity and coupled thermo-hydro-mechanical (THM) processes. The objective here was to develop methods for (i) upscaling flow and transport in fractured media from detailed-scale data and (ii) accounting for THM-induced effects on regional-scale transport. An example field data set was used for demonstration.A systematic framework was developed where equivalent properties of flow, transport, and stress-effects were estimated with discrete fracture network (DFN) modelling, at some block scale, and then transferred to a regional-scale stochastic continuum (SC) model. The selected block scale allowed a continuum approximation of flow, but not of transport…


1. Introduction
1.1 Objectives and aims
2. Background
2.1 Characterization of fractured media
2.2 Stochastic parameterization of data
2.3 Modelling representation of fractured media
2.3.1 Discrete fracture network modelling
2.3.2 Stochastic continuum modelling
2.4 Hydraulic data parameterization
2.4.1 Input for fracture network models
2.4.2 Input for stochastic continuum models
2.5 Upscaling fractured media properties to a continuum approximation
2.5.1 Scale dependency in conductivity
2.5.2 Methods based on equivalent porous media
2.5.3 Fracture-network based upscaling methods
2.6 Transport in fractured media
2.7 Progress in modelling of fractured media
3. Approach
4. Upscaling of hydraulic data (Paper I)
4.1 Methodology
4.1.1 DFN-based upscaling
4.1.2 SC-based upscaling
4.1.3 Hydraulic correlation structure beyond block scale
4.2 Results
4.2.1 DFN-based upscaling
4.2.2 SC-based upscaling
4.2.3 Upscaled variogram for block scale conductivity
5. Upscaling of solute transport (Paper II)
5.1 Methodology
5.1.1 Dispersion tensor at block scale
5.1.2 Transit time distributions at block scale
5.2 Results
5.2.1 Dispersion tensor at block scale
5.2.2 Transit time distributions at block scale
6. Regional-scale transport (Paper II)
6.1 Methodology
6.1.1 Regional SC flow model
6.1.2 Particle random walk
6.1.3 Consideration of channelling
6.2 Results
6.2.1 Regional-scale flow fields for particle random walk
6.2.2 Channelized transport and macro-scale dispersion
7. Accounting for THM effects (Papers III and IV)
7.1 Methodology
7.1.1 Combining rock-mechanical and well-test data in the hydraulic parameterization of fractures (Paper III)
7.1.2 Effect of thermal stress in a repository near-field (Paper IV)
7.2 Results
7.2.1 Including stress regime in hydraulic parameterization
7.2.2 Thermal stresses in the repository near-field
8. Discussion
8.1 Hydraulic upscaling
8.1.1 Validity of stochastic continuum approximation
8.1.2 The oriented correlated stochastic continuum approach
8.2 Transport upscaling
8.3 Regional-scale transport
8.4 THM effects
9. Conclusions
10. Acknowledgements
11. Summary in Swedish

Author: Ohman, Johan

Source: Uppsala University Library

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