Collaborative Research: Solute Transport in Multimodal, Heterogeneous Geological Formations, Combining Sedimentologic and Engineering Approaches

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

0001165 Rubin We will develop a hierarchical spatial random function (HSRF) model that represents permeability, sedimentary structures, and sedimentary units defined by bounding surfaces in granular aquifer systems. At the smallest scale, facies are defined as regions of unimodal permeability and, if present, of cross-strata sets with common orientation to the laminae. Facies will be represented by a continuous random variable having anisotropic correlation controlled by bedding and/or the orientation of cross-strata sets. Assemblages of facies, such as the combination of facies filling a single channel, will be represented by an indicator random variable and associated transition probabilities which represent the proportions, geometries, and juxtapositioning of each facies. A complex of facies assemblages, such as juxtaposed channel fill, bar accretion, and overbank assemblages within channel belt deposits, is represented by a higher-tier indicator random variable with transition probabilities representing the proportions, geometries, and juxtapositioning of the assemblages. The continuous and indicator variables of all three levels will be mathematically expressed in a single HSRF model suitable for integration with analytical expressions for solute spreading. The HSRF model departs from current models and approaches in that it can capture complex, non-Gaussian spatial distributions and can incorporate interpretive sedimentology to constrain the geostatistical models. In combined field studies and model temperament, we seek to address the following questions relating to (1) the distribution of permeability in granular media and (2) solute spreading. (1) Questions relating to distribution of permeability: o Does the HSRF model, with its three hierarchical levels, capture the aspects of permeability and sedimentary structure important for understanding solute spreading at the scale of typical plumes? o Are the attributes of any one hierarchical level correlated with those of another level? o Can the HSRF model be used to improve the conditional estimation of permeability at unknown locations? o Can the HSRF model be used as a framework for incorporating geological/sedimentological soft data as geostatisticl models are developed? (2) Questions related to solute spreading: o What are the relative contributions of the three hierarchical levels to both longitudinal and lateral solute spreading? o As the univariate statististics and the spatial correlation of permeability become increasingly different across facies boundaries, at what point are the moments of solute spreading significantly affected? o Under what conditions can representation of any of the hierarchical levels be ignored? o Under what conditions can transport in a multimodal heterogeneity be modeled with effective, plume-scale-dependent parameters? To answer these questions, we are conducting a collaborative, interdisciplinary project involving investigators at both the University of California, Berkeley, and Wright State University. As in past URI-funded projects at Wright State University, the project will provide research experiences for undergraduates.