Download or read book Laboratory studies of partially saturated infiltration dynamics in analog fractured porous rock systems under consideration of fracture matrix interaction and network geometry written by Florian Rüdiger and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fractured porous rocks are abundant groundwater reservoir formations often covered by a thick, unsaturated zone. The interplay between fractures and rock matrix can significantly impede infiltration, particularly when the matrix has high diffusivity. Despite extensive research on preferential fracture flow and retarding matrix imbibition, a unified theory remains elusive. This Ph.D. thesis employs laboratory infiltration experiments to assess (1) the controls of fracture-matrix interaction, which governs unsaturated infiltration, and (2) the role of fracture intersection dynamics in control...

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 2012-12-02 with total page 575 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past two or three decades, fractured rock domains have received increasing attention not only in reservoir engineering and hydrology, but also in connection with geological isolation of radioactive waste. Locations in both the saturated and unsaturated zones have been under consideration because such repositories are sources of heat and potential sources of groundwater contamination. Thus, in addition to the transport of mass of fluid phases in single and multiphase flow, the issues of heat transport and mass transport of components have to be addressed.

Download or read book On the Physics of Unstable Infiltration Seepage and Gravity Drainage in Partially Saturated Tuffs written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To improve understanding of the physics of dynamic instabilities in unsaturated flow processes within the Paintbrush nonwelded unit (PTn) and the middle nonlithophysal portion of the Tonopah Spring welded tuff unit (TSw) of Yucca Mountain, we analyzed data from a series of infiltration tests carried out at two sites (Alcove 4 and Alcove 6) in the Exploratory Studies Facility, using analytical and empirical functions. The analysis of infiltration rates measured at both sites showed three temporal scales of infiltration rate: (1) a macro-scale trend of overall decreasing flow, (2) a meso-scale trend of fast and slow motion exhibiting three-stage variations of the flow rate (decreasing, increasing, and [again] decreasing flow rate, as observed in soils in the presence of entrapped air), and (3) micro-scale (high frequency) fluctuations. Infiltration tests in the nonwelded unit at Alcove 4 indicate that this unit may effectively dampen episodic fast infiltration events; however, well-known Kostyakov, Horton, and Philip equations do not satisfactorily describe the observed trends of the infiltration rate. Instead, a Weibull distribution model can most accurately describe experimentally determined time trends of the infiltration rate. Infiltration tests in highly permeable, fractured, welded tuff at Alcove 6 indicate that the infiltration rate exhibits pulsation, which may have been caused by multiple threshold effects and water-air redistribution between fractures and matrix. The empirical relationships between the extrinsic seepage from fractures, matrix imbibition, and gravity drainage versus the infiltration rate, as well as scaling and self-similarity for the leading edge of the water front are the hallmark of the nonlinear dynamic processes in water flow under episodic infiltration through fractured tuff. Based on the analysis of experimental data, we propose a conceptual model of a dynamic fracture flow and fracture-matrix interaction in fractured tuff, incorporating the time dependent processes of water redistribution in the fracture-matrix system.

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.

Download or read book Statistical Analysis of Liquid Seepage in Partially Saturated Heterogeneous Fracture Systems written by and published by . This book was released on 1999 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Field evidence suggests that water flow in unsaturated fracture systems may occur along fast preferential flow paths. However, conventional macroscale continuum approaches generally predict the downward migration of water as a spatially uniform wetting front subjected to strong inhibition into the partially saturated rock matrix. One possible cause of this discrepancy may be the spatially random geometry of the fracture surfaces, and hence, the irregular fracture aperture. Therefore, a numerical model was developed in this study to investigate the effects of geometric features of natural rock fractures on liquid seepage and solute transport in 2-D planar fractures under isothermal, partially saturated conditions. The fractures were conceptualized as 2-D heterogeneous porous media that are characterized by their spatially correlated permeability fields. A statistical simulator, which uses a simulated annealing (SA) algorithm, was employed to generate synthetic permeability fields. Hypothesized geometric features that are expected to be relevant for seepage behavior, such as spatially correlated asperity contacts, were considered in the SA algorithm. Most importantly, a new perturbation mechanism for SA was developed in order to consider specifically the spatial correlation near conditioning asperity contacts. Numerical simulations of fluid flow and solute transport were then performed in these synthetic fractures by the flow simulator TOUGH2, assuming that the effects of matrix permeability, gas phase pressure, capillary/permeability hysteresis, and molecular diffusion can be neglected. Results of flow simulation showed that liquid seepage in partially saturated fractures is characterized by localized preferential flow, along with bypassing, funneling, and localized ponding. Seepage pattern is dominated by the fraction of asperity contracts, and their shape, size, and spatial correlation. However, the correlation structure of permeability field is less important than the spatial correlation of asperity contacts. A faster breakthrough was observed in fractures subjected to higher normal stress, accompanied with a nonlinearly decreasing trend of the effective permeability. Interestingly, seepage dispersion is generally higher in fractures with intermediate fraction of asperity contacts; but it is lower for small or large fractions of asperity contacts. However, it may become higher if the ponding becomes significant. Transport simulations indicate that tracers bypass dead-end pores and travel along flow paths that have less flow resistance. Accordingly, tracer breakthrough curves generally show more spreading than breakthrough curves for water. Further analyses suggest that the log-normal time model generally fails to fit the breakthrough curves for water, but it is a good approximation for breakthrough curves for the tracer.

Download or read book Flow and Transport in Porous Media and Fractured Rock written by Muhammad Sahimi and published by John Wiley & Sons. This book was released on 2011-05-09 with total page 635 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this standard reference of the field, theoretical and experimental approaches to flow, hydrodynamic dispersion, and miscible displacements in porous media and fractured rock are considered. Two different approaches are discussed and contrasted with each other. The first approach is based on the classical equations of flow and transport, called 'continuum models'. The second approach is based on modern methods of statistical physics of disordered media; that is, on 'discrete models', which have become increasingly popular over the past 15 years. The book is unique in its scope, since (1) there is currently no book that compares the two approaches, and covers all important aspects of porous media problems; and (2) includes discussion of fractured rocks, which so far has been treated as a separate subject. Portions of the book would be suitable for an advanced undergraduate course. The book will be ideal for graduate courses on the subject, and can be used by chemical, petroleum, civil, environmental engineers, and geologists, as well as physicists, applied physicist and allied scientists that deal with various porous media problems.

Download or read book Fractured Porous Media written by Pierre M. Adler and published by Oxford University Press, USA. This book was released on 2013 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a systematic treatment of the geometrical and transport properties of fractures, fracture networks, and fractured porous media. It is divided into two major parts. The first part deals with geometry of individual fractures and of fracture networks. The use of the dimensionless density rationalizes the results for the percolation threshold of the networks. It presents the crucial advantage of grouping the numerical data for various fracture shapes. The second part deals mainly with permeability under steady conditions of fractures, fracture networks, and fractured porous media. Again the results for various types of networks can be rationalized by means of the dimensionless density. A chapter is dedicated to two phase flow in fractured porous media.

Download or read book Characterization Modeling Monitoring and Remediation of Fractured Rock written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2021-01-29 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fractured rock is the host or foundation for innumerable engineered structures related to energy, water, waste, and transportation. Characterizing, modeling, and monitoring fractured rock sites is critical to the functioning of those infrastructure, as well as to optimizing resource recovery and contaminant management. Characterization, Modeling, Monitoring, and Remediation of Fractured Rock examines the state of practice and state of art in the characterization of fractured rock and the chemical and biological processes related to subsurface contaminant fate and transport. This report examines new developments, knowledge, and approaches to engineering at fractured rock sites since the publication of the 1996 National Research Council report Rock Fractures and Fluid Flow: Contemporary Understanding and Fluid Flow. Fundamental understanding of the physical nature of fractured rock has changed little since 1996, but many new characterization tools have been developed, and there is now greater appreciation for the importance of chemical and biological processes that can occur in the fractured rock environment. The findings of Characterization, Modeling, Monitoring, and Remediation of Fractured Rock can be applied to all types of engineered infrastructure, but especially to engineered repositories for buried or stored waste and to fractured rock sites that have been contaminated as a result of past disposal or other practices. The recommendations of this report are intended to help the practitioner, researcher, and decision maker take a more interdisciplinary approach to engineering in the fractured rock environment. This report describes how existing tools-some only recently developed-can be used to increase the accuracy and reliability of engineering design and management given the interacting forces of nature. With an interdisciplinary approach, it is possible to conceptualize and model the fractured rock environment with acceptable levels of uncertainty and reliability, and to design systems that maximize remediation and long-term performance. Better scientific understanding could inform regulations, policies, and implementation guidelines related to infrastructure development and operations. The recommendations for research and applications to enhance practice of this book make it a valuable resource for students and practitioners in this field.

Download or read book Flow and Transport in Fractured Porous Media written by Peter Dietrich and published by Springer Science & Business Media. This book was released on 2005-03-02 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the characterization of flow and transport in porous fractured media from experimental and modeling perspectives. The volume explores porous media problems, from the origin of the present natural porous structures, to their characterization, and various flow and transport phenomena that exist within the porous media. Examples are miscible displacements in porous media and fractured rock and the physical and chemical interactions within porous fractured aquifers. The book is a comprehensive presentation of investigations performed and analysed on different scales, supporting the understanding and application of experimental studies and numerical simulations.

Download or read book Flows in Porous Media and Fractured Rock written by Muhammad Sahimi and published by Wiley-VCH. This book was released on 1995-02-22 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive discussion of porous media problems, experimental methods for characterizing porous structures, classical approaches and modern methods and a comparison of both, and fractured rock and porous media.

Download or read book Simulating Infiltration Tests in Fractured Basalt at the Box Canyon Site Idaho written by and published by . This book was released on 2003 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of a series of ponded infiltration tests in variably saturated fractured basalt at Box Canyon, Idaho, were used to build confidence in conceptual and numerical modeling approaches used to simulate infiltration in fractured rock. Specifically, we constructed a dual-permeability model using TOUGH2 to represent both the matrix and fracture continua of the upper basalt flow at the Box Canyon site. A consistent set of hydrogeological parameters was obtained by calibrating the model to infiltration front arrival times in the fracture continuum as inferred from bromide samples collected from fracture/borehole intersections observed during the infiltrating tests. These parameters included the permeability of the fracture and matrix continua, the interfacial area between the fracture and matrix continua, and the porosity of the fracture continuum. To calibrate the model, we multiplied the fracture-matrix interfacial area by a factor between 0.1 and 0.01 to reduce imbibition of water from the fracture continuum into the matrix continuum during the infiltration tests. Furthermore, the porosity of the fracture continuum, as calculated using the fracture aperture inferred from pneumatic-test permeabilities, was increased by a factor of 50 yielding porosity values for the upper basalt flow in the range of 0.01 to 0.02. The fracture-continuum porosity was a highly sensitive parameter controlling the arrival times of the simulated infiltration fronts. Porosity values are consistent with those determined during the Large-Scale Aquifer Pumping and Infiltration Test at the Idaho National Engineering and Environmental Laboratory.

Download or read book Physical Processes that Control Droplet Transport in Rock Fracture Systems written by Katrina Moran Hay and published by . This book was released on 2008 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aquifer recharge is generally driven by fluids that move from the Earth's surface to groundwater through the unsaturated zone, also known as the vadose zone. When the vadose zone is fractured, fluids, which may include contaminants, can move through the fracture network as well as the porous matrix. Such a network of fractures can provide a more rapid path, thereby reducing contact time between the fluid and the matrix. Contact time allows for exchange of solutes between the fluid and the porous matrix, thus being able to quantify contact time is important. In addition, the behavior of fluids within a fracture network has been found to be very complex; large-scale models are yet not able to predict transport paths or flux rates. Because, small-scale flow phenomena can strongly influence the large-scale behavior of fluid movement through systems of fractures, it is important that small-scale dynamics be properly understood in order to improve our predictive capabilities in these complex systems. Relevant flow dynamics includes the impact of boundary conditions, fluid modes that evolve in time and space and transitions between modes. This thesis presents three investigations aimed at understanding the physical processes governing fluid movement in unsaturated fractures, with the ultimate goal of improving predictive relationships for fluid transport in rock fracture systems. These investigations include a theoretical analysis of the wetting of a rough surface, an experimental study of the dynamics of fluid droplets (or liquid bridges) moving in a single fracture and a theoretical analysis of the movement of a fluid droplet encountering a fracture intersection. Each investigation is motivated by environmental applications. Development of an analytical equation for the wetting of a rough surface is based on a balance between capillary forces and frictional resistive forces. The resulting equation predicts movement of the liquid invasion front driven solely by the surface roughness; the relationship was found to exhibit a square root of time dependence. Rough surfaces also affect the movement of bulk fluid through the fractures. The speed of droplets moving downward between smooth and rough surfaces is seen to be significantly different. Experiments were used to develop predictive algorithms to calculate the speed of droplets in unsaturated rock fractures, which incorporate an adjusted contact angle for wet rough surfaces, and also incorporate the effect of dynamics on the evolution of the advancing contact angle. The third paper investigates the effect of intersection geometry on the larger scale distribution of fluid in a system of fractures. Fluid movement through fracture intersections depends on input flow parameters, geometry of the system, and capillary and gravitational forces. The physical mechanisms governing the process are analyzed to predict distribution of liquid into fracture branches and velocity of the output flow. This study will improve the ability to incorporate pore-scale fluid physics phenomena into large-scale models for predicting flow transport in rock fracture systems.

Download or read book Secondary Interaction of Fracturing Fluid and Shale Plays written by Reza Keshavarzi and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: During hydraulic fracturing in unconventional tight formations a high percentage of the injected fluid may remain in the formation and only a small portion of the fracturing fluid is typically recovered. Although spontaneous imbibition is mainly introduced as the main dominating mechanism, a clear understanding of the fundamental mechanisms through which the fracturing fluid would interact with the formation remains a challenge. The impact of these mechanisms on rock property changes is even more challenging but is important to account for post-fracturing reservoir characterization. In this study, an integrated analytical-experimental-numerical approach was adopted to study these issues using a case study within the Montney Formation in Farrell Creek field in northeast British Columbia. The results of experiments on Montney samples from different depths revealed that because of spontaneous water imbibition, the geomechanical properties of the samples were altered. Also, small scale heterogeneity in tight gas formations and shale results in these property changes occurring at various scales, such as beds. Property changes occurring along the beds and bedding planes, as a result of interaction with hydraulic fracturing fluid, can contribute to increased potential for shear failure along these planes. Therefore, a systematic micro-scale analysis (including micro-indentation and micro-scratch along the beds to capture micro-geomechanical responses) and macro-scale analysis (including ultrasonic measurements, uniaxial compressive loading in high and low capillary suctions and unloading-reloading cycles at varying capillary suction) have been developed and applied to capture the changes in rock behavior in different scales as a result of spontaneous water imbibition and how different behaviors in micro-scale would affect the responses in macro-scale. QEMSCAN analysis, nitrogen adsorption-desorption tests, thermogravimetric analysis (TGA), capillary condensation experiments, pressure-decay and pulse-decay permeability measurements and direct shear tests were also completed for quantitative analysis of minerals, pore shapes and porosity, initial water saturation, capillary suction as a function of water saturation, permeability and strength parameters in both macro-scale and micro-scale (bed-scale). QEMSCAN analysis indicated that mineral components were not the same in different beds and they could be categorized into quartz-rich and clay-rich. The results of the experimental phase indicated that the geomechanical and flow properties of Montney specimens were altered due to fluid imbibition. As the water saturation and capillary suction were changing in quartz-rich and clay-rich beds, they responded differently which would trigger some geomechanical behaviors in macro scale. In addition, it was observed that capillary suction would add extra stiffness and strength to the media and as it was diminishing, the media became weaker. A nonlinear response with hysteresis during unloading-reloading cycles at varying capillary suction implied that as a result of the water softening effect, the reduction in capillary suction and changing the local effective stress there is a high possibility of activation and propagation of pre-existing micro fractures. In the numerical modeling phase of this research, fully coupled poro-elastoplastic partially saturated models were developed that included transversely isotropic matrix properties and bed-scale geometry. Inclusion of bed-scale features in the numerical approach provided better analysis options since different properties of the adjacent beds (including different capillary suction change) that can trigger the failure in the planes of weakness (such as the interface between the beds) can be directly included in the model while it is not possible to have that in transversely isotropic numerical modeling. This implies that conventional numerical analysis of geomechanical responses originated from spontaneous imbibition needs to be revisited. Beds-included numerical analyses indicated that since the changes in local effective stress and rock mechanical properties were not the same in adjacent quartz-rich and clay-rich beds, differential volumetric strain along the interfaces between quartz-rich and clay-rich beds would take place which in turn generated induced shear stress components on the interface planes. For the interfaces where total shear stress along them exceeded the shear strength, failure occurred. Comparing the result of micro-geomechanical (bed scale) and macro-geomechanical analysis with the results of numerical modeling at reservoir in-situ conditions would suggest that as a result of post-fracturing spontaneous water imbibition in the studied Montney Formation, the failures/micro fractures would be generated along the interfaces. Then because of the propagation of activated pre-existing micro fractures in the adjacent beds followed by coalescence with the failed interfaces, a complex micro fracture network can be formed. Accordingly, rock mass geomechanical responses and flow properties would be affected which means that any numerical modeling or analytical approach to account for the production, refracturing and any other reservoir-related analysis without considering this fact is under question mark.

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].

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.

Download or read book A 3 Dimensional Discrete Fracture Network Generator to Examine Fracture matrix Interaction Using TOUGH2 written by and published by . This book was released on 2003 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water fluxes in unsaturated, fractured rock involve the physical processes occurring at fracture-matrix interfaces within fracture networks. Modeling these water fluxes using a discrete fracture network model is a complicated effort. Existing preprocessors for TOUGH2 are not suitable to generate grids for fracture networks with various orientations and inclinations. There are several 3-D discrete-fracture-network simulators for flow and transport, but most of them do not capture fracture-matrix interaction. We have developed a new 3-D discrete-fracture-network mesh generator, FRACMESH, to provide TOUGH2 with information about the fracture network configuration and fracture-matrix interactions. FRACMESH transforms a discrete fracture network into a 3 dimensional uniform mesh, in which fractures are considered as elements with unique rock material properties and connected to surrounding matrix elements. Using FRACMESH, individual fractures may have uniform or random aperture distributions to consider heterogeneity. Fracture element volumes and interfacial areas are calculated from fracture geometry within individual elements. By using FRACMESH and TOUGH2, fractures with various inclinations and orientations, and fracture-matrix interaction, can be incorporated. In this paper, results of flow and transport simulations in a fractured rock block utilizing FRACMESH are presented.

Download or read book Linking Reaction Transport and Hydrological Parameters Inunsaturated Fractured Rock written by Tianfu Xu and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling coupled water-gas-rock interactions in unsaturated fractured rock requires conceptual and numerical model considerations beyond those developed for saturated porous media. This paper focuses on the integration of the geological and hydrological parameters into the calculation of reactive-transport parameters and the feedback of mineral precipitation/dissolution to flow and transport. These basic relations have been implemented in the reactive transport code TOUGHREACT (Xu et al., 2003) that couples equilibrium and kinetic water-gas-rock inter-actions with multiphase flow and aqueous and gaseous species transport. Simulation results are presented illustrating the effects of water-rock interaction accompanying the heating of unsaturated heterogeneous fractured tuff. Unknowns associated with modeling water-rock interaction in fractured unsaturated systems are the area of the fracture surface that is wetted and which fractures are active components of the overall flow system. The wetted fracture area is important not only to water-rock interaction but to flow and transport between fluids flowing in fractures and the adjacent matrix. The other unknown relations are those describing permeability and capillary pressure modification during mineral precipitation and dissolution. Here we discuss solely the relations developed for fractures and the fracture-matrix interface.