Reactive solute transport in physically and chemically heterogeneous porous media with multimodal reactive mineral facies: the Lagrangian approach.

Physical and chemical heterogeneities have a large impact on reactive transport in porous media. Examples of heterogeneous attributes affecting reactive mass transport are the hydraulic conductivity (K), and the equilibrium sorption distribution coefficient (Kd). This paper uses the Deng et al.

The influence of streambed heterogeneity on hyporheic flow in gravelly rivers.

Deposits of open-framework gravel occurring in gravelly streambeds can exert a significant influence on hyporheic flow. The influence was quantified using a numerical model of the hyporheic zone. The model included open-framework gravel stratasets represented with commonly observed characteristics including a volume fraction of about one-third of the streambed sediment, a hydraulic conductivity two orders of magnitude greater than other strata present, and a spatial connectivity forming preferential-flow pathways.

The Kozeny-Carman equation with a percolation threshold.

A procedure has been developed for calculating permeability (k) from the Kozeny-Carman equation, a procedure that links ideas from percolation theory with the ideas of Koltermann and Gorelick (1995) and Esselburn et al. (2011). The approach focuses on the proportion of coarser pores that are occupied by finer sediments relative to a percolation threshold proportion (ω(c)).

Conservative models: parametric entropy vs. temporal entropy in outcomes.

The geologic architecture in aquifer systems affects the behavior of fluid flow and the dispersion of mass. The spatial distribution and connectivity of higher-permeability facies play an important role. Models that represent this geologic structure have reduced entropy in the spatial distribution of permeability relative to models without structure.

Porosity and permeability in ternary sediment mixtures.

Permeability, k, and porosity, φ, were measured in mixtures of fine, medium, and coarse sand, where the volume fraction of each of the three components was systematically varied. The k was modeled well by the Kozeny-Carman equation for three-component mixtures by using a representative grain size parameter, d, computed by averaging the grain diameters of components recursively, with averaging methods based on whether finer components exist in sufficient volume to fill the pores within coarser components. The φ was modeled well by using linear interpolation with piecewise-planar models.

Measuring the permeability of open-framework gravel.

Open-framework gravel has permeability, k, above the measurement range of most laboratory constant-head permeameters because the head difference across the length of conventional permeameters is too small to be measured. Here we addressed the challenge of measuring the high k by using a 3 m long permeameter. The head difference over this length was of the order of 10(-2) to 10(-3) m, which we could measure to the nearest 10(-5) m.

Air-based measurements of permeability in pebbly sands.

We considered small-scale measurement of permeability in pebbly sands having coarser grains supported in a finer grained matrix (fine packing). Our central question was whether air-based measurements are representative if made with a permeameter tip seal pressed in the sand matrix. We created pebbly sands and variably sorted sands, with systematic variation in aspects of their fine packing.

Porosity and permeability in sediment mixtures.

Porosity in sediments that contain a mix of coarser- and finer-grained components varies as a function of the porosity and volume fraction of each component. We considered sediment mixtures representing poorly sorted sands and gravely sands. We expanded an existing fractional-packing model for porosity to represent mixtures in which finer grains approach the size of the pores that would exist among the coarser grains alone.

Modeling multiscale heterogeneity and aquifer interconnectivity.

A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer.