Fractured rock aquifers

Fractured rock aquifers may be analyzed in a manner similar to unconfined aquifers, providing the responses exhibit the same general characteristics. During the initial testing, the fracture contributes water to the well, followed by primarily... 

For application in fractured rock aquifers, it is assumed the aquifer behavior approximates that of a porous medium. Standard methodologies and their applicable assumptions are used to obtain values of transmissivity and storage, from which anisotropy is calculated. 

Jenkins, J. D. and Prentice, J. K., 1982, Theory for Aquifer Test Analysis in Fractured Rock under Linear (Non-Radial) Flow Conditions Ground Water, Vol. 20, pp. 12-21. 

Papadopoulos, I. S., 1965, Nonsteady Flow to a Well in an Infinite Anisotropic Aquifer In Proceedings of the Symposium on Hydrology of Fractured Rocks, IAHS, Dubrovnik, pp. 21-31. 

In fractured rock aquifers in which the porosity of the solid mass between fractures is insignificant. Freeze and Cherry (1974) report the retardation equation as ... 

Metamorphic rocks are rich in open foliation fractures and fissures, but these are isolated or poorly interconnected. Such rocks make poor recharge terrains and poor aquifers. These rocks are occasionally fractured by tectonic processes, improving their infiltration and storage properties. 

The present hydrogeological framework of the sedimentary basin, which is characterized by the distribution, thickness and dip of porous and permeable hydrogeological units (aquifers/potential carrier-reservoir rocks, e.g. sands, sandstones, carbonates, fractured rocks) and poorly permeable hydrogeological units (aquitards/potential barrier rocks, e.g. shales, evaporites), and the location of geological structures and tectonic elements of importance for subsurface fluid flow, e.g. permeable or impermeable faults, unconformities... 

Bear, J. and Beikowitz, B. 1987. Groundwater flow and pollution in fractured rock aquifers. In Developments in Hydraulic Engineering. Elsevier, New York, pp. 175-238. 

Spayd SE. 1985. Movement of volatile organics through a fractured rock aquifer. Ground Water 23 496-502. 

For various aquifer minerals, porosity varies over a fairly narrow range (ca. 0.3 to 0.5) but hydraulic conductivity varies over many orders of magnitude.2 Even for a specific type of aquifer material, ranges of 1-4 orders of magnitude are common (e.g., 10 8 5 to 10 4 m/s for fractured rock, 10-5 to 10 3 m/s for well-sorted sand). The lowest hydraulic conductivities are found for crystalline rock (10 14 to 10 10 m/s) and the highest for well-sorted gravel (10-2 to 1 m/s) and clean sand or cavernous limestone (10 6 to 10 2 m/s). 

H- He dating has also been applied in fractured rock aquifers (Cook et al. 1996 Aeschbach-Hertig et al. 1998). Typical problems encountered in fractured systems are their extreme heterogeneity, double porosity causing differences between hydrodynamic and H- He age, and geochemical complications due to the presence of other He sources. 

Cook PG, Solomon DK, Plummer LN, Busenberg E, Schiff SL (1995) Chlorofluorocarbons as tracers of ground water transport processes in a shallow, silty sand aquifer. Water Resour Res 31 425-434 Cook PG, Solomon DK, Sanford WE, Busenberg E, Plummer LN, Poreda RJ (1996) Inferring shallow ground water flow in saprohte and fractured rock using environmental tracers. Water Resour Res 32 1501-1509... 

Allen, M. Shapiro. Interpretation of oscillatory water levels in observation wells during aquifer tests in fracture rock. Water Resources Research, 1989, 25(10) 2129-2137. 

Understanding of RN migration mechanism at large scale either for porous-aquifer or fracture-rock flow system has to consider inhomogeneities for a better concepmalisation of the hydrogeological model ... 

Aquifers are regions of saturated material that are at least moderately conductive to water and may be tapped via wells for potable, industrial, or agricultural purposes. Although many aquifers are made of coarse, unconsolidated material such as gravel, the water-bearing material also can be a porous rock such as sandstone, or even a relatively nonporous but fractured rock such as granite. Beneath an aquifer maybe a nearly impermeable layer aquiclude) or low-permeability layer (aquitard). Sometimes the aquiclude or aquitard is thin and has unsaturated material beneath it. 

Aquifers with high hydraulic conductivity can transport contaminants at high velocity over great distances, e.g., solution limestones, highly fractured rocks or gravel deposits. 

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... 

The selection and preparation of sites for any of these gas stores is a fairly delicate process, because tightness can rarely be guaranteed on the basis of geological test drillings and modelling. The detailed properties of the cavity will not become fully disclosed until the installation is complete. The ability of the salt cavern to keep an elevated pressure may turn out not to live up to expectations. The stability of a natural rock cave, or of a fractured zone created by explosion or hydraulic methods, is also imcertain until actual full-scale pressure tests have been conducted. For the aquifers, the decisive measurements of permeability can only be made at a finite number of places, so surprises are possible due to rapid permeability change over small distances of displacement (Sorensen, 2004a). 

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