Fractures transport

Changes in fracture transport characteristics that result from the removal or redistribution of mineral mass within a fracture may be constrained by calculating the evolution of permeability with the concurrent loss or redistribution of mineral mass. Mass loss is unambiguously recorded by the effluent flux, but redistribution may only be discerned by imaging. Independent measurements of fluid and mineral flux, concurrent with non-invasive imaging, are used to constrain the processes controlling mass redistribution within the fracture. 

Models for transport distinguish between the unsaturated zone and the saturated zone, that below the water table. There the underground water moves slowly through the sod or rock according to porosity and gradient, or the extent of fractures. A retardation effect slows the motion of contaminant by large factors in the case of heavy metals. For low level waste, a variety of dose calculations are made for direct and indirect human body uptake of water. Performance assessment methodology is described in Reference 22. 

Plutonium is transported by the groundwater in fractures in the rock (usually <1 mm wide). A typical groundwater velocity (vw) at >100 m depth in Swedish bedrock is 0.1 tn/y. The fractures are filled with crushed, weathered, clayish minerals, which have a high capacity to sorb the plutonium. Assuming instantaneous and reversible reactions, the sorption will cause the plutonium to move considerably slower (with velocity vn) than the groundwater. The ratio between these two velocities is referred to as the retention factor (RF), defined by... 

Sahimi, M, Flow and Transport in Porous Media and Fractured Rock VCH Weinheim, Germany, 1995. 

These properties were used to synthesize an organic cation (Table 17-10) with a higher efficiency as a clay stabilizer than the typical salts used in the oil industry to this point. These additives provide additional benefits when used in conjunction with acidizing and fracturing treatments. A much lower salt concentration can be used to obtain the same clay-stabilizing effectiveness [830, 833]. The liquid product has been proven to be much easier to handle and transport. It is environmentally compatible and biodegradable in its diluted form. 

The fracture must be wide enough to permit entry of proppant to a distance sufficient to stimulate production. Tons of proppant are normally required to fill this void. Therefore the fracturing fluid must suspend the proppant long enough for it to be transported and placed, by flow, throughout the fracture. To preserve the maximum accessible flow area, the proppant should be uniformly suspended inside the entire propped fracture area while the fracture closes. Kaspereit(15), as well as Smith(16), has made the point that fracture conductivity can be a limiting factor. If the... 

Clark, P.E. and Quadir, J.A. "Prop Transport in Hydraulic Fractures A Critical Review of Particle Settling Velocity Equations," SPE/DOE paper 9866, 1981 SPE/DOE Low Permeability Symposium, Denver, May 27-29. 

Clark, P.E. and Guler, N. "Prop Transport in Vertical Fractures Settling Velocity Correlations," 1983 SPE/DOE paper 11636, SPE/DOE Symposium on Low Permeability, Denver, March 14 16. 

Lee, W.S. and Daneshy, A.A. "Fracture Geometry and Proppant-Transport Computation for Multiple-Fluid Treatment," SPE Prod. Eng. J.. (November 1987) 257 266. 

Daneshy, A.A. "Numerical Solution of Sand Transport in Hydraulic Fracturing," J. Pet. Technol.. January, 1978, 132 140. 

Acharya, A. "Particle Transport in Viscous and Viscoelastic Fracturing Fluids," SPE Prod. Eng.. March 1986, 104 110. 

Xu T. and Pruess K. Coupled modeling of non-isothermal multiphase flow, solute transport and reactive chemistry in porous and fractured media 1. Model develop-... 

Wu Y.S., Zhang K., et al. An efficient parallel-computing scheme for modeling noni-sothermal multiphase flow and multicomponent transport in porous and fractured media. 2002 Advances in Water Resources 25 243-261. 

However, ultrasonic rate enhancements of heterogeneous catalysis have usually been relatively modest (less than tenfold). The effect of irradiating operating catalysts is often simply due to improved mass transport (58). In addition, increased dispersion during the formation of catalysts under ultrasound (59) will enhance reactivity, as will the fracture of friable solids (e.g., noble metals on C or silica (60),(62),(62) or malleable metals (63)). 

The geology not only provides the chemical source for trace-element mobility but it also provides the physical framework for water-flow paths. The structural properties of the rocks, the porosity, permeable fractures, provide for water-mineral reaction and element mobility. The geomorphology contributes to water-table levels, aquifer permeability, surface-water travel times, and time periods for erosion and sediment transport. Examples of... 

Prior to its cloning, GLT-1 was reconstituted and purihed and shown to have a relative molecular mass of 64 kDa, which agrees well both with the value of 65 kDa of the purihed and deglycosylated transporter (28,37) and its 573 amino acids determined from its nucleotide sequence (25). Reconstituted GLT-1 has been shown to form dimers, trimers, and higher molecular-weight homomers in the absence of reducing agents (38). The possibility of homomeric assemblies is corroborated by a recent freeze fracture, which shows pentameric assemblies (39). 

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