TOUGH2 User's Guide Version 2

Pruess, Karsten; Oldenburg, C. M.; Moridis, G.J.

doi:10.2172/751729

Cited by 1,413 publications

(1,362 citation statements)

References 34 publications

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“…The experiment was simulated with the TOUGH2 and iTOUGH2 codes (see [26] and [27], respectively). We discretized the tube with a grid cell spacing of 0.5 mm and we neglected gravitational effects.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Electrokinetic coupling in unsaturated porous media

Revil

Linde

Cérepi

et al. 2007

Journal of Colloid and Interface Science

216

337

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Abstract. We consider a charged porous material that is saturated by two fluid phases that are immiscible and continuous at the scale of a representative elementary volume. The wetting phase for the grains is water and the non-wetting phase is assumed to be an electrically insulating viscous fluid. We use a volume averaging approach to derive the linear constitutive equations for the electrical current density as well as and the seepage velocities of the wetting and non-wetting phases at the scale of a representative elementary volume. These macroscopic constitutive equations are obtained by volume-averaging Ampère's law together with the Nernst-Planck equation and the Stokes equations. The material properties entering the macroscopic constitutive equations are explicitly described as a function of the saturation of the water phase, the electrical formation factor, and parameters that describe the capillary pressure function, the relative permeability function, and the variation of electrical conductivity with saturation. New equations are derived for the streaming potential and electro-osmosis coupling coefficients. A primary drainage and imbibition experiment is simulated numerically to demonstrate that the relative streaming potential coupling coefficient depends not only on the water saturation, but also on the material properties of the sample as well as the saturation history. We also compare the predicted streaming potential coupling coefficients with experimental data from four dolomite core samples. Measurements on these samples include electrical conductivity, capillary pressure, the streaming potential coupling coefficient at various level of saturation, and the permeability at saturation of the rock samples. We found a very good agreement between these experimental data and the model predictions.

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Section: Numerical Simulationsmentioning

confidence: 99%

Electrokinetic coupling in unsaturated porous media

Revil

Linde

Cérepi

et al. 2007

Journal of Colloid and Interface Science

216

337

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“…The physical processes associated with fluid and heat flow in fractured porous media are simulated using TOUGH2 software [22]. Fluid flow and heat-transfer processes in an airwater, two-phase system of fractured rock are described separately using a doublet of governing equations, respectively, for the two fracture and matrix continua.…”

Section: Mathematical Formulation and Numerical Codesmentioning

confidence: 99%

A mountain-scale thermal–hydrologic model for simulating fluid flow and heat transfer in unsaturated fractured rock

Mukhopadhyay

Zhang

et al. 2006

Journal of Contaminant Hydrology

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A multidimensional, mountain-scale, thermal-hydrologic (TH) numerical model is presented for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository in the Yucca Mountain unsaturated zone (UZ), Nevada. The model, consisting of both two-dimensional (2-D) and three-dimensional (3-D) representations of the UZ repository system, is based on the current repository design, drift layout, thermal loading scenario, and estimated current and future climate conditions. This mountain-scale TH model evaluates the coupled TH processes related to mountain-scale UZ flow. It also simulates the impact of radioactive waste heat release on the natural hydrogeological system, including heat-driven processes occurring near and far away from the emplacement tunnels or drifts. The model simulations predict thermally perturbed liquid saturation, gas-and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. These simulations provide mountain-scale thermally perturbed flow fields for assessing the repository performance under thermal loading conditions. Key Words: thermal-hydrologic processes in subsurface, thermal load, Yucca Mountain, fluid and heat flow in porous media, heat pipe, reservoir simulation, fractured unsaturated rock * Corresponding author. Tel.: +1-510-486-7291; fax: +1-510-486-5686, E-Mail address: YSWu@lbl.gov. 2 IntroductionIn the past decade, the 500-700 m thick Yucca Mountain unsaturated zone (UZ) has been extensively investigated as a potential subsurface repository for storing high-level radioactive wastes. While the site characterization has been mostly carried out for analyzing unsaturated flow and radionuclide transport in ambient, isothermal conditions [30,31], the inherent nature of nonisothermal flow and transport processes, created by repository heating from radioactive decay, has also motivated many research efforts to understand thermal-hydrologic (TH) behavior and its impact on the repository performance within the UZ. In particular, significant progress has been made in quantitative TH modeling studies at Yucca Mountain [9,10,6].Emplacement of heat-generating high-level radioactive waste in the UZ system of unsaturated welded and unwelded fractured tuff at Yucca Mountain will perturb the ambient condition and create complex multiphase fluid flow and heat-transfer processes.The physical phenomena associated with repository heating include conduction and convection heat transfer, phase change (boiling and condensation), two-phase flow of liquid and gas phases under variably saturated conditions, enhanced fracture-matrix interaction caused by rapid matrix drying and subsequent imbibition, diffusion and dispersion of vapor and gas, and vapor-pressure-lowering effects. These TH processes will last hundreds to thousands of years after waste emplacement, and will significantly redistribute the in-situ moisture content and alter the per...

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“…On the scale of an individual gridblock, we assume that unsaturated flow can be described using Richards' equation (Richards, 1931), which is implemented in the integral finite-difference simulator TOUGH2 (Pruess et al, 1999): …”

Section: Model Developmentmentioning

confidence: 99%

“…The fields are conditioned on the measured air-permeability data and mapped onto the numerical grid (see Figure 2). Only one permeability field realization is produced for each niche.On the scale of an individual gridblock, we assume that unsaturated flow can be described using Richards' equation (Richards, 1931), which is implemented in the integral finite-difference simulator TOUGH2 (Pruess et al, 1999): where the effective saturation e S is defined asIn the van Genuchten model, lr S is residual liquid saturation, and a [Pa -1 ] and m are fitting parameters. The use of continuous relative-permeability and capillary-pressure functions, which apply to porous media, is considered appropriate also for small fracture segments that are roughwalled and/or partially filled with porous material.…”

mentioning

confidence: 99%

Inverse and predictive modeling of seepage into underground openings

Finsterle

Ahlers

Trautz

et al. 2003

Journal of Contaminant Hydrology

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Abstract. We discuss the development and calibration of a model for predicting seepage into underground openings. Seepage is a key factor affecting the performance of the potential nuclear-waste repository at Yucca Mountain, Nevada. Three-dimensional numerical models were developed to simulate field tests in which water was released from boreholes above excavated niches. Data from air-injection tests were geostatistically analyzed to infer the heterogeneous structure of the fracture permeability field. The heterogeneous continuum model was then calibrated against the measured amount of water that seeped into the opening. This approach resulted in the estimation of model-related, seepage-specific parameters on the scale of interest.The ability of the calibrated model to predict seepage was examined by comparing calculated with measured seepage rates from additional experiments conducted in different portions of the fracture network. We conclude that an effective capillary-strength parameter is suitable to characterize seepage-related features and processes for use in a prediction model of average seepage into potential waste emplacement drifts.Keywords: capillary barrier, unsaturated zone, parameter estimation * Corresponding author: Fax: +1-510-486-5686; e-mail: SAFinsterle@lbl.gov 2 IntroductionSeepage of water into emplacement drifts for nuclear waste is considered a key factor affecting the long-term safety of a potential repository at Yucca Mountain, Nevada. The number of waste packages contacted by water, the corrosion rate of engineered barriers and waste containers, the dissolution and mobilization of radioactive contaminants, and their release and migration towards the accessible environment all depend on the rate, the chemical composition, and the spatial and temporal distribution of water seeping into the waste-emplacement drifts.Accurately estimating seepage into underground openings excavated from an unsaturated fractured formation requires process understanding on a wide range of scales. Processes to be studied include (1) the mountain-scale distribution of percolation flux, (2) the intermediate-scalechanneling, bifurcation, and dispersion of flow in the fracture network, (3) the small-scale capillary-barrier effect in the boundary layer around the opening, and (4) the micro-scale phenomena of film flow, drop formation, and drop detachment at the drift surface. In addition, the thermodynamic environment in the drift (temperature, relative humidity, ventilation regime, etc.) must be known as it impacts the boundary condition at the drift wall.Developing a comprehensive, physically based seepage model that covers all scales discussed above would require a large amount of characterization data that are difficult or practically impossible to measure in the field. Moreover, a suite of model assumptions would have to be made to relate fracture and surface properties to hydrogeologic model parameters.Finally, the spatial and temporal resolution of a numerical model necessary to accurately and explicitly ca...

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TOUGH2 User's Guide Version 2

Cited by 1,413 publications

References 34 publications

Electrokinetic coupling in unsaturated porous media

Electrokinetic coupling in unsaturated porous media

A mountain-scale thermal–hydrologic model for simulating fluid flow and heat transfer in unsaturated fractured rock

Inverse and predictive modeling of seepage into underground openings

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