Simulation of the Spatial Heterogeneity of Geologic Properties

Webb, Erik K.; Davis, J. Matthew

doi:10.2110/sepmcheg.01.01

Cited by 21 publications

(13 citation statements)

References 145 publications

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“…Webb and Davis 1998). These elements determine the local distribution of permeabilities, the hydraulic correlation lengths and thus the connectivity of permeable units.…”

Section: Hydrostratigraphymentioning

confidence: 99%

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy

Heinz

Aigner

2003

International Journal of Earth Sciences

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The approach of 'dynamic stratigraphy' aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales. This approach was used to investigate Quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties. Facies analysis within 62 gravel pits, laboratory permeability measurements of field samples and geophysical surveys (3-D georadar, 2-D seismic reflection) led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units. (1) Particles and pores (micro scale) that reflect depositional and diagenetic fluid dynamics as well as source material behaviour (e.g. grainsize, roundness, lithological composition). This was found to be important for the hydrogeochemistry of groundwater in gravel aquifers (e.g. higher sorption capacity of carbonrich limestone particles for organic pollutants). (2) Strata (meso scale) contain the recognition of sorting, fabric, texture and stratinomic features, which can give an indication of transport and depositional dynamics. Five major lithofacies groups, for example, were distinguished within fluvial gravel-bed deposits. Their variable hydraulic properties led to their subdivision into 12 hydrofacies types. They form the smallest mappable hydrostratigraphic units, which may result in either preferred pathways for fluid flow or flow barriers. (3) Depositional elements (macro scale) enable reconstruction of sedimentary/geomorphic elements and their dynamics within a depositional system (e.g. gravel-bed braided river systems are dominated by gravel sheet, gravel dunes and scour pool depositional elements). Hydrostratigraphically, the architecture of depositional elements influences the hydraulic connectivity and local permeability structure/distribution within an aquifer body.Five types of depositional elements in fluvial gravel-bed deposits were distinguished and their geometries/dimensions quantified. (4) Facies bodies (mega scale) composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics (e.g. a coarse-grained prograding delta system). Hydrostratigraphically, facies bodies represent major compartments of an aquifer. Six major types of meltwater-controlled facies bodies were identified in the study area. (5) Genetic sequences (mega scale) reflect the shifts of depositional environments caused by allocyclic changes (e.g. glacial advance recorded by a coarsening upward sequence) or autocyclic changes of landscape shaping events. These sequences may form separate hydrostratigraphic units or aquifer storeys. (6) Basin fill (giga scale) comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long-term glacier dynamics or short term flood events. The regional distribution of permeable gravel units and, for example, less permea...

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“…Webb and Davis 1998). These elements determine the local distribution of permeabilities, the hydraulic correlation lengths and thus the connectivity of permeable units.…”

Section: Hydrostratigraphymentioning

confidence: 99%

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy

Heinz

Aigner

2003

International Journal of Earth Sciences

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“…Nevertheless, realistic models reproducing the spatial variability of facies are necessary to provide control over the uncertainty in facies correlations, and stochastic simulation is applied with either objectbased or geostatistical methods (i.e. Haldorsen and Damsleth 1990;Deutsch and Hewett 1996;Koltermann and Gorelick 1996;Webb and Davis 1998;de Marsily et al 1998;Kupfersberger and Deutsch 1999;de Marsily et al 2005;Falivene et al 2006a and2006b). In siliciclastic aquifers, the use of realistic facies models to guide the modeling of porosity and permeability improves predictions, because these parameters are commonly correlated with facies (Anderson 1989;Jussel et al 1994;Ritzi et al 1995;Fogg et al 1998;Gómez-Hernández and Deutsch 1999).…”

Section: Sedimentary Analoguesmentioning

confidence: 99%

Large to intermediate-scale aquifer heterogeneity in fine-grain dominated alluvial fans (Cenozoic As Pontes Basin, northwestern Spain): insight based on three-dimensional geostatistical reconstruction

2007

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Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability.. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A 3D reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from a large number of continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings.

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“…The character of the alluvial architecture plays an important role in determining the geotechnical properties within the floodplain, such as areas of high and low fluid seepage potential (Webb and Davis 1998;Willis and Tang 2010;Li and Caers 2011). Relatively coarsegrained architectural elements such as sand or gravel sedimentary deposits are porous and can be effective reservoirs of underground fluid such as water and hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

A Computational Model to Simulate Groundwater Seepage Risk in Support of Geotechnical Investigations of Levee and Dam Projects

Yuill¹,

Roig-Silva²

2013

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The amount and distribution of coarse-grained sediment relative to finegrained sediment within a floodplain influences the floodplain's geotechnical properties, including the potential for groundwater seepage. Seepage is a primary driver of levee and dam failure, and understanding it is of paramount concern to water resource engineers and managers. This report documents the results of a computational modeling study that simulated alluvial floodplain construction by using simple geomorphic process-imitating rules. The model aggrades an alluvial floodplain, creating floodplain architecture by differentiating between sediment deposited by channel processes (coarse sediment) and sediment deposited by overbank flood processes (fine sediment). The evolution of two floodplain cross sections of the Trinity River near Dallas, Texas, is simulated under five scenarios. The study area is the site of large levee rehabilitation projects in which accurate characterization of the geologic environment has significant engineering importance. Results of the simulations predict that the average channel deposit dimensions are sensitive to the sedimentation scenario employed and are generally similar to those typically observed in fully meandering rivers. The results suggest that the channel aggradation rate influenced heavily the relative channel avulsion frequency during floodplain construction. Increased avulsion frequency equated to more numerous, yet smaller, channel deposits. Avulsion frequency and floodplain width affected the predicted fraction of the floodplain's cross-sectional width with subsurface channel deposits. The model for this study is simple and can be run in multiple iterations to produce probabilistic outputs. Such information can be used to predict the data collection density necessary to characterize the geotechnical properties of a project site.

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Simulation of the Spatial Heterogeneity of Geologic Properties

Cited by 21 publications

References 145 publications

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy

Large to intermediate-scale aquifer heterogeneity in fine-grain dominated alluvial fans (Cenozoic As Pontes Basin, northwestern Spain): insight based on three-dimensional geostatistical reconstruction

A Computational Model to Simulate Groundwater Seepage Risk in Support of Geotechnical Investigations of Levee and Dam Projects

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