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Analyzing Flow Patterns In Unsaturated Fractured Rock Of Yuccamountain Using An Integrated Modeling Approach
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Book Synopsis Analyzing Flow Patterns in Unsaturated Fractured Rock of YuccaMountain Using an Integrated Modeling Approach by :
Download or read book Analyzing Flow Patterns in Unsaturated Fractured Rock of YuccaMountain Using an Integrated Modeling Approach written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a series of modeling investigations to characterize percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The investigations are conducted using a modeling approach that integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model through model calibration. This integrated modeling approach, based on a dual-continuum formulation, takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. In particular, the model results are examined against different types of field-measured data and used to evaluate different hydrogeological conceptual models and their effects on flow patterns in the unsaturated zone. The objective of this work to provide understanding of percolation patterns and flow behavior through the unsaturated zone, which is a crucial issue in assessing repository performance.
Book Synopsis Analyzing Unsatirated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach by :
Download or read book Analyzing Unsatirated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies, because of the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. This paper presents an integrated modeling methodology for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The modeling approach integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for modeling analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations and their results of flow patterns in the unsaturated zone. In particular, this model provides a much clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain's flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.
Book Synopsis Rock Fractures and Fluid Flow by : National Research Council
Download or read book Rock Fractures and Fluid Flow written by National Research Council and published by National Academies Press. This book was released on 1996-08-27 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scientific understanding of fluid flow in rock fracturesâ€"a process underlying contemporary earth science problems from the search for petroleum to the controversy over nuclear waste storageâ€"has grown significantly in the past 20 years. This volume presents a comprehensive report on the state of the field, with an interdisciplinary viewpoint, case studies of fracture sites, illustrations, conclusions, and research recommendations. The book addresses these questions: How can fractures that are significant hydraulic conductors be identified, located, and characterized? How do flow and transport occur in fracture systems? How can changes in fracture systems be predicted and controlled? Among other topics, the committee provides a geomechanical understanding of fracture formation, reviews methods for detecting subsurface fractures, and looks at the use of hydraulic and tracer tests to investigate fluid flow. The volume examines the state of conceptual and mathematical modeling, and it provides a useful framework for understanding the complexity of fracture changes that occur during fluid pumping and other engineering practices. With a practical and multidisciplinary outlook, this volume will be welcomed by geologists, petroleum geologists, geoengineers, geophysicists, hydrologists, researchers, educators and students in these fields, and public officials involved in geological projects.
Book Synopsis Modeling Unsaturated Flow and Transport Processes in Fractured Tuffs of Yucca Mountain by : G. S. Bodvarsson
Download or read book Modeling Unsaturated Flow and Transport Processes in Fractured Tuffs of Yucca Mountain written by G. S. Bodvarsson and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a field modeling study characterizing fluid flow and tracer transport in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository for storing high-level radioactive waste. The 500 to 700 meter thick unsaturated zone of Yucca Mountain consists of highly heterogeneous layers of anisotropic, fractured ash flow and air fall tuffs. Characterization of fluid flow and heat transfer through such a system has been a challenge due to the heterogeneities prevalent on various scales. Quantitative evaluation of water, gas, and heat flow by means of numerical simulation is essential for design and performance assessment of the repository. A three-dimensional numerical flow and transport model will be discussed. The model has been calibrated against field-measured data and takes into account the coupled processes of unsaturated flow and tracer transport in the highly heterogeneous, unsaturated fractured porous rock. The modeling approach of the model is based on a dual-continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. As application examples, effects of current and future climates on the unsaturated zone processes are evaluated to aid in the assessment of the proposed repository's system performance.
Book Synopsis Modeling Flow and Transport in Unsaturated Fractured Rock by :
Download or read book Modeling Flow and Transport in Unsaturated Fractured Rock written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock.
Book Synopsis Modeling Coupled Thermal-Hydrological-Chemical Processes in the Unsaturated Fractured Rock of Yucca Mountain, Nevada by :
Download or read book Modeling Coupled Thermal-Hydrological-Chemical Processes in the Unsaturated Fractured Rock of Yucca Mountain, Nevada written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of processes affecting seepage into emplacement tunnels is needed for correctly predicting the performance of underground radioactive waste repositories. It has been previously estimated that the capillary and vaporization barriers in the unsaturated fractured rock of Yucca Mountain are enough to prevent seepage under present day infiltration conditions. It has also been thought that a substantially elevated infiltration flux will be required to cause seepage after the thermal period is over. While coupled thermal-hydrological-chemical (THC) changes in Yucca Mountain host rock due to repository heating has been previously investigated, those THC models did not incorporate elements of the seepage model. In this paper, we combine the THC processes in unsaturated fractured rock with the processes affecting seepage. We observe that the THC processes alter the hydrological properties of the fractured rock through mineral precipitation and dissolution. We show that such alteration in the hydrological properties of the rock often leads to local flow channeling. We conclude that such local flow channeling may result in seepage under certain conditions, even with nonelevated infiltration fluxes.
Book Synopsis Conceptual Models of Flow and Transport in the Fractured Vadose Zone by : National Research Council
Download or read book Conceptual Models of Flow and Transport in the Fractured Vadose Zone written by National Research Council and published by National Academies Press. This book was released on 2001-05-21 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid flow and solute transport within the vadose zone, the unsaturated zone between the land surface and the water table, can be the cause of expanded plumes arising from localized contaminant sources. An understanding of vadose zone processes is, therefore, an essential prerequisite for cost-effective contaminant remediation efforts. In addition, because such features are potential avenues for rapid transport of chemicals from contamination sources to the water table, the presence of fractures and other channel-like openings in the vadose zone poses a particularly significant problem, Conceptual Models of Flow and Transport in the Fractured Vadose Zone is based on the work of a panel established under the auspices of the U.S. National Committee for Rock Mechanics. It emphasizes the importance of conceptual models and goes on to review the conceptual model development, testing, and refinement processes. The book examines fluid flow and transport mechanisms, noting the difficulty of modeling solute transport, and identifies geochemical and environmental tracer data as important components of the modeling process. Finally, the book recommends several areas for continued research.
Book Synopsis Characterizing Fractured Rock for Fluid-flow, Geomechanical, and Paleostress Modeling by :
Download or read book Characterizing Fractured Rock for Fluid-flow, Geomechanical, and Paleostress Modeling written by and published by . This book was released on 1993 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Yucca Mountain Site Characterization Project Bibliography, 1994-1995 by :
Download or read book Yucca Mountain Site Characterization Project Bibliography, 1994-1995 written by and published by . This book was released on 1996 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flow and Transport Through Unsaturated Fractured Rock by : Daniel D. Evans
Download or read book Flow and Transport Through Unsaturated Fractured Rock written by Daniel D. Evans and published by American Geophysical Union. This book was released on 1987 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Small-scale Fractures on Flow and Transport Processes at Yucca Mountain, Nevada by :
Download or read book Effect of Small-scale Fractures on Flow and Transport Processes at Yucca Mountain, Nevada written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although many conceptual models for fracture-matrix interaction have been evaluated for Yucca Mountain site-characterization studies, the most widely used model is currently based on the dual-permeability concept. It was chosen for use in site-characterization partially because it has proved to be capable of matching many types of field observed data. Another consideration is that net infiltration rates at the site are estimated to be very low (on the order of millimeters/year), or close to saturated matrix hydraulic conductivity. Recent field studies and tests, in particular, fracture mapping data, collected along the walls of the underground tunnels reveal that there exists a significantly large variety in fracture sizes from centimeters to tens of meters. There is a considerable amount of small-scale fractures that have not been considered in the previous modeling studies. Although the majority of these small fractures may not contribute much to global flow and transport through the fracture-matrix system, they may provide large amounts of storage pore space and allow for additional connection areas for well-connected, large-scale fractures and surrounding matrix blocks, which ultimately affect fracture-matrix interactions. However, the currently used dual-permeability model is unable to include the potentially important effect of small fractures. To overcome the limitations of the dual-permeability approach, we have developed a triple-continuum conceptual model to investigate the impact of small-scale fractures on flow and transport processes in fractured rocks. This new conceptual model subdivides fractures into two types: large-scale and small-scale. Large-scale fractures are those responsible for global connections; small-scale fractures are those that provide large-fracture storage space and enhance the local connections to the matrix system without contributing to global flow or transport. Because the triple-continuum model is composed of the rock matrix and two types of fractures, it can be regarded as an extension of the traditional dual-permeability model. Using a generalized triple-continuum approach, the model formulation uses three parallel sets of conservation equations to describe flow and transport processes at each location of the system, for the two-fracture and one-matrix systems, respectively. The proposed triple-continuum model has been implemented using both analytical and numerical approaches and applied to field problems at Yucca Mountain. First we apply the new conceptual model to estimate model-related fracture-matrix parameters using field observation data and inverse modeling approach. Then we incorporate the estimated parameters to perform 3-D site-scale flow and transport simulations with the current hydrogeological model of Yucca Mountain. The 3-D modeling results with the triple-continuum model indicate that small fractures have significant impact on radionuclide transport in the UZ system, while their effects on flow and heat transfer are insignificant.
Book Synopsis Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses by : Xing Zhang
Download or read book Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses written by Xing Zhang and published by Elsevier. This book was released on 2002-05-14 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our understanding of the subsurface system of the earth is becoming increasingly more sophisticated both at the level of the behaviour of its components (solid, liquid and gas) as well as their variations in space and time. The implementation of coupled models is essential for the understanding of an increasing number of natural phenomena and in predicting human impact on these.The growing interest in the relation between fluid flow and deformation in subsurface rock systems that characterise the upper crust has led to increasingly specialized knowledge in many branches of earth sciences and engineering. A multidisciplinary subject dealing with deformation and fluid flow in the subsurface system is emerging.While research in the subject area of faulting, fracturing and fluid flow has led to significant progress in many different areas, the approach has tended to be "reductionist", i.e. involving the isolation and simplification of phenomena so that they may be treated as single physical processes. The reality is that many processes operate together within subsurface systems, and this is particularly true for fluid flow and deformation of fractured rock masses. The aim of this book is to begin to explore how advances in numerical modelling can be applied to understanding the complex phenomena observed in such systems.Although mainly based on original research, the book also includes the fundamental principles and practical methods of numerical modelling, in particular distinct element methods. This volume explores the principles of numerical modelling and the methodologies for some of the most important problems, in addition to providing practical models with detailed discussions on various topics.
Book Synopsis A Triple-continuum Approach for Modeling Flow and Transportprocesses in Fractured Rock by :
Download or read book A Triple-continuum Approach for Modeling Flow and Transportprocesses in Fractured Rock written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents a triple-continuum conceptual model forsimulating flow and transport processes in fractured rock. Field datacollected from the unsaturated zone of Yucca Mountain, a repository siteof high-level nuclear waste, show a large number of small-scalefractures. The effect of these small fractures has not been considered inprevious modeling investigations within the context of a continuumapproach. A new triple-continuum model (consisting of matrix, small-fracture, and large-fracture continua) has been developed toinvestigate the effect of these small fractures. This paper derives themodel formulation and discusses the basic triple-continuum behavior offlow and transport processes under different conditions, using bothanalytical solutions and numerical approaches. The simulation resultsfrom the site-scale model of the unsaturated zone of Yucca Mountainindicate that these small fractures may have an important effect onradionuclide transport within the mountain.
Book Synopsis Estimating Large-scale Fracture Permeability of Unsaturatedrockusing Barometric Pressure Data by :
Download or read book Estimating Large-scale Fracture Permeability of Unsaturatedrockusing Barometric Pressure Data written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.
Book Synopsis Modeling Heterogeneous Unsaturated Porous Media Flow at Yucca Mountain by :
Download or read book Modeling Heterogeneous Unsaturated Porous Media Flow at Yucca Mountain written by and published by . This book was released on 1994 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geologic systems are inherently heterogeneous and this heterogeneity can have a significant impact on unsaturated flow through porous media. Most previous efforts to model groundwater flow through Yucca Mountain have used stratigraphic units with homogeneous properties. However, modeling heterogeneous porous and fractured tuff in a more realistic manner requires numerical methods for generating heterogeneous simulations of the media, scaling of material properties from core scale to computational scale, and flow modeling that allows channeling. The Yucca Mountain test case of the INTRAVAL project is used to test the numerical approaches. Geostatistics is used to generate more realistic representations of the stratigraphic units and heterogeneity within units is generated using sampling from property distributions. Scaling problems are reduced using an adaptive grid that minimizes heterogeneity within each flow element. A flow code based on the dual mixed-finite-element method that allows for heterogeneity and channeling is employed. In the Yucca Mountain test case, the simulated volumetric water contents matched the measured values at drill hole USW UZ-16 except in the nonwelded portion of Prow Pass.
Book Synopsis Advanced Conceptual Models for Unsaturated and Two-Phase Flow in Fractured Rock by :
Download or read book Advanced Conceptual Models for Unsaturated and Two-Phase Flow in Fractured Rock written by and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project was initiated in FY03. As of December 2003, we have accomplished the following: (1) We conducted a more detailed evaluation of the preliminary experiments used to develop our investigative approach. In those experiments, water was invaded at a variety of flow rates into an air-filled, two dimensional analog fracture network. Results demonstrated the critical control that fracture intersections place on two-phase flow in fracture networks. At low flows, capillary and gravitational forces combined to create a narrow pulsing flow structure that spanned the system vertically. At higher flows, viscous forces acted to remove the pulsation; however, the flow structure remained narrow. The intersections acted to impose a narrow ''slender ladder'' structure on the flowing phase that did not expand with depth, but instead remained focused. A manuscript documenting this effort has been published in Water Resources Research [Glass et al., 2003a]. (2) We initiated a collaborative relationship with a research group at Seoul National University. This group, which is led by Dr. Kang-Kun Lee is also using a combined experimental numerical approach to consider DNAPL migration in fracture networks. They are particularly interested in the influence of ambient groundwater flows, making their work complementary to ours. The first fruit of that collaboration is an article demonstrating that modification of an Invasion Percolation algorithm to include gravity and the first-order effects of viscous forces shows good agreement with physical experiments in a simplistic fracture network. Results were published in Geophysical Research Letters [Ji et al., 2003a]. (3) We carried out an extensive review of models for fracture networks. These include models developed from observations of networks on outcrops at several scales and stochastic models that are prevalent in the literature from the 1980s to very recent developments. The results of this review were included as par t of a review paper co-authored by Rajaram, which was submitted to Reviews in Geophysics [Molz et al., in press]. (4) We prepared a manuscript based on previous work that will be used to support the development of our new conceptual model(s) for transport in fractured rock. Eight experiments were conducted to evaluate the repeatability of flow under nearly identical conditions and to characterize general patterns in flow behavior. Collected data revealed that flow generally converged to a single fracture in the bottom row of blocks. Periods of pathway switching were observed to be more common than periods with steady, constant flow pathways. We noted the importance of fracture intersections for integrating uniform flow and discharging a ''fluid cascade'', where water advances rapidly to the next capillary barrier creating a stop and start advance of water through the network. The results of this simple experiment suggest that the interaction of multiple fracture intersections in a network creates flow behavior not generally recognized in popular conceptual and numerical models. A manuscript documenting this effort has been accepted for publication in Vadose Zone Journal [Wood et al., 2003]. (5) Slender transport pathways have been found in laboratory and field experiments within unsaturated fractured rock. We considered the simulation of such structures with a Modified form of Invasion Percolation (MIP). Results show that slender pathways form in fracture networks for a wide range of expected conditions, can be maintained when subsequent matrix imbibition is imposed, and may arise even in the context of primarily matrix flow due to the action of fractures as barriers to inter-matrix block transport. A manuscript documenting this effort has been submitted to Geophysical Research Letters [Glass et al., 2003b].
Book Synopsis Flow and Contaminant Transport in Fractured Rock by : Jacob Bear
Download or read book Flow and Contaminant Transport in Fractured Rock written by Jacob Bear and published by Academic Press. This book was released on 1993-04-20 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling flow and contaminant transport in fractured rocks / J. Bear -- Solute transport in fractured rock--applications to radionuclide waste repositories / I. Neretnieks -- Solute transport through fracture networks / L. Smith, F.W. Schwartz -- Stochastic models of fracture systems and their use in flow and transport modeling / J.-P. Chilès, G. de Marsily -- Tracer transport in fracture systems / C.-F. Tsang --Multiphase flow in fractured petroleum reservoirs / H. Kazemi, J.R. Gilman -- Unsaturated flow in fractured porous media / J.S.Y. Wang, T.N. Narasimhan -- Simulation of flow and transport in fractured porous media / G.F. Pinder, P.S. Huyakorn, E.A. Sudicky -- A summary of field test methods in fractured rocks / P. Jouanna -- Index.
