Vicky L. Freedman

Bio: Vicky L. Freedman is an academic researcher from Pacific Northwest National Laboratory. The author has contributed to research in topics: Vadose zone & Hanford Site. The author has an hindex of 13, co-authored 61 publications receiving 589 citations. Previous affiliations of Vicky L. Freedman include Battelle Memorial Institute & Ohio State University.

Changes in hydrologic properties of aquifer media due to chemical reactions: A review

Abstract: Hydrologic properties that govern fluid flow through the sub-surface are porosity, permeability, relative permeability, fluid-fluid and fluid-solid interfacial areas, pore and particle size distributions, which may change due to dissolution/precipitation of minerals, fine particle release and capture, ion exchange and clay swelling. Provided here is a review on the change of hydrologic properties in sub-surface media due to chemical processes, and modeling of such changes. Precipitation and dissolution processes affecting the hydrologic properties, their kinetics and the effect of hydrodynamic factors on such processes were discussed. Precipitation in carbonaceous, siliceous, alkaline and acidic environments, and the role of dissolution and clay swelling in formation damage were reviewed. Changes in properties of unsaturated and fractured media were also discussed. Traditionally, different approaches were used to model various physico-chemical processes and their effect on the hydrologic properties. A detailed review of these methods, including the geochemical equilibrium and kinetic models, chemical divide pathway models, flow and transport models, precipitation/dissolution wave theory, network models, porosity and permeability reduction models, is presented. Recommendations are provided for the assessment of changes in the hydrologic properties of sub-surface media attributable to chemical reactions, and modeling flow and transport in their presence. Further, research needs on themore » changes in hydrologic properties and constitutive relationships among such properties in unsaturated media were identified.« less

Simulating the heterogeneity in braided channel belt deposits: 1. A geometric‐based methodology and code

Abstract: [1] A geometric-based simulation methodology was developed and incorporated into a computer code to model the hierarchical stratal architecture, and the corresponding spatial distribution of permeability, in braided channel belt deposits. The code creates digital models of these deposits as a three-dimensional cubic lattice, which can be used directly in numerical aquifer or reservoir models for fluid flow. The digital models have stratal units defined from the kilometer scale to the centimeter scale. These synthetic deposits are intended to be used as high-resolution base cases in various areas of computational research on multiscale flow and transport processes, including the testing of upscaling theories. The input parameters are primarily univariate statistics. These include the mean and variance for characteristic lengths of sedimentary unit types at each hierarchical level, and the mean and variance of log-permeability for unit types defined at only the lowest level (smallest scale) of the hierarchy. The code has been written for both serial and parallel execution. The methodology is described in part 1 of this paper. In part 2 (Guin et al., 2010), models generated by the code are presented and evaluated.

Groundwater Data Package for Hanford Assessments

Abstract: This report presents data and interpreted information that supports the groundwater module of the System Assessment Capability (SAC) used in Hanford Assessments The objective of the groundwater module is to predict movement of radioactive and chemical contaminants through the aquifer to the Columbia River or other potential discharge locations This data package is being revised as part of the deliverables under the Characterization of Systems Project (#49139) aimed at providing documentation for assessments being conducted under the Hanford Assessments Project (#47042) Both of these projects are components of the Groundwater Remediation and Closure Assessments Projects, managed by the Management and Integration Project (#47043)

Simulating the heterogeneity in braided channel belt deposits: 2. Examples of results and comparison to natural deposits

Abstract: In Part 1 of this series we presented a methodology and a code for modeling the hierarchical sedimentary architecture in braided channel belt deposits. Here, in Part 2, the code was used to create a digital model of this architecture, and the corresponding spatial distribution of permeability. The simulated architecture was compared to the real stratal architecture observed in an abandoned channel belt of the Sagavanirktok River, Alaska by Lunt et al. (2004). The comparisons included assessments of similarity which were both qualitative and quantitative. From the qualitative comparisons we conclude that a synthetic deposit created by the code has unit types, at each level, with a geometry which is generally consistent with the geometry of unit types observed in the field. The digital unit types would generally be recognized as representing their counterparts in nature, including cross stratasets, lobate and scroll bar deposits, channel fills, etc. Furthermore, the synthetic deposit has a hierarchical spatial relationship among these units which represents how the unit types are observed in field exposures and in geophysical images. In quantitative comparisons the proportions and the length, width, and height of unit types at different scales, across all levels of the stratal hierarchy compare wellmore » between the digital and the natural deposits. A number of important attributes of the channel belt model were shown to be influenced by more than one level within the hierarchy of stratal architecture. First, the high-permeability open-framework gravels percolated at all levels and thus formed preferential flow pathways. Open framework gravels are indeed known to form preferential flow pathways in natural channel belt deposits. The nature of a percolating cluster changed across different levels of the hierarchy of stratal architecture. As a result of this geologic structure, the percolation occurs at proportions of open-framework gravels below the theoretical percolation threshold for random infinite media. Second, when the channel belt model was populated with permeability distributions by lowest-level unit type, the composite permeability semivariogram contained structures that were identifiable at more than one scale, and each of these structures could be directly linked to unit types of different scales existing at different levels within the hierarchy of strata. These collective results are encouraging with respect to our goal that this model be relevant as a base case in future studies for testing ideas in research addressing the upscaling problem in aquifers and reservoirs with multi-scale heterogeneity.« less

Applications of soil physics.

Abstract: Keywords: Mecanique des sols ; Drainage ; Ecoulement souterrain Reference Record created on 2004-09-07, modified on 2016-08-08

Assessing the performance of recent density functionals for bulk solids

Abstract: We assess the performance of recent density functionals for the exchange-correlation energy of a nonmolecular solid, by applying accurate calculations with the GAUSSIAN, BAND, and VASP codes to a test set of 24 solid metals and nonmetals. The functionals tested are the modified Perdew-Burke-Ernzerhof generalized gradient approximation PBEsol GGA, the second-order GGA SOGGA, and the Armiento-Mattsson 2005 AM05 GGA. For completeness, we also test more standard functionals: the local density approximation, the original PBE GGA, and the Tao-Perdew-Staroverov-Scuseria meta-GGA. We find that the recent density functionals for solids reach a high accuracy for bulk properties lattice constant and bulk modulus. For the cohesive energy, PBE is better than PBEsol overall, as expected, but PBEsol is actually better for the alkali metals and alkali halides. For fair comparison of calculated and experimental results, we consider the zeropoint phonon and finite-temperature effects ignored by many workers. We show how GAUSSIAN basis sets and inaccurate experimental reference data may affect the rating of the quality of the functionals. The results show that PBEsol and AM05 perform somewhat differently from each other for alkali metal, alkaline-earth metal, and alkali halide crystals where the maximum value of the reduced density gradient is about 2, but perform very similarly for most of the other solids where it is often about 1. Our explanation for this is consistent with the importance of exchange-correlation nonlocality in regions of core-valence overlap.

Comprehensive review of caprock-sealing mechanisms for geologic carbon sequestration.

Abstract: CO(2) capture and geologic sequestration is one of the most promising options for reducing atmospheric emissions of CO(2). Its viability and long-term safety, which depends on the caprock's sealing capacity and integrity, is crucial for implementing CO(2) geologic storage on a commercial scale. In terms of risk, CO(2) leakage mechanisms are classified as follows: diffusive loss of dissolved gas through the caprock, leakage through the pore spaces after breakthrough pressure has been exceeded, leakage through faults or fractures, and well leakage. An overview is presented in which the problems relating to CO(2) leakage are defined, dominant factors are considered, and the main results are given for these mechanisms, with the exception of well leakage. The overview includes the properties of the CO(2)-water/brine system, and the hydromechanics, geophysics, and geochemistry of the caprock-fluid system. In regard to leakage processes, leakage through faults or fracture networks can be rapid and catastrophic, whereas diffusive loss is usually low. The review identifies major research gaps and areas in need of additional study in regard to the mechanisms for geologic carbon sequestration and the effects of complicated processes on sealing capacity of caprock under reservoir conditions.