Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

Cohen, Andrew J.

doi:10.2172/10115406

Cited by 16 publications

(13 citation statements)

References 18 publications

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“…Cohen (1993) summarizes the different works and hypotheses regarding the geologic history associated with these fractures. It has long been acknowledged that they formed in response to tectonic forces.…”

Section: Regional Fracture Sets and Geologic Historymentioning

confidence: 99%

“…Visual inspection of the resistivity logs and ATV logs revealed that zones of low apparent resistivity zones are associated with the occurrence of westwardly dipping and closely spaced fractures. The measurements of fractures obtained from ATV logs was used in combination with the 16-inch resistivity logs to confirm that zones with apparent resistivities less than 700 ohm-m are mainly associated with these fractures (Cohen, 1993). The 16-inch normal resistivity log was used rather than the @-inch log because the volume of investigation of the resistivity probe is considered to a sphere with a diameter approximately twice the spacing of the electrodes (Keys, 1989), and it is more appropriate to correlate measured fractures to properties close to the borehole.…”

Section: Heat-pulse Flowmeter and Standard Geophysical Logsmentioning

confidence: 99%

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Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

Cohen¹

1995

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A field site was developed in the foothills of the Sierra Nevada, California to develop and test a multi-disciplinary approach to the characterization of ground water flow and transport in fractured rocks. Nine boreholes were drilled into the granitic bedrock, and a wide variety of new and traditional subsurface characterization tools were implemented. The hydrogeologic structure and properties of the field site were deduced by integrating results from the various geologic, geophysical, hydrologic, and other investigative methods. The findings of this work are synthesized into this report, which is structured in a guidebook format. The applications of the new and traditional technologies, suggestions on how best to use, integrate, and analyze field data, and comparisons of the shortcoming and benefits of the different methods are presented.

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Section: Regional Fracture Sets and Geologic Historymentioning

confidence: 99%

Section: Heat-pulse Flowmeter and Standard Geophysical Logsmentioning

confidence: 99%

Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

Cohen¹

1995

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“…15a) and trial and error BORE II analysis (corresponding C(z) profiles are shown in Fig. 15b (Cohen, 1993).…”

Section: Discussionmentioning

confidence: 99%

Signatures in flowing fluid electric conductivity logs

Doughty¹,

Tsang²

2005

Journal of Hydrology

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“…The water level is normally between 2 and 3 meters below the casing head. Various geophysical logs, geophysical imaging techniques and hydraulic tests have been conducted to image the hydrologic connection of the fractured rock mass [Cohen, 1993;Karasalki e t al., 1995;Cook, 1995;Cohen, 1995;Vasco et al, 19961. Regional characterization and site specific fracture measurements show that there are two sets of subvertical tectonic fractures: one of the set strikes at N30W and the other strikes at N60E [Cohen, 19951.…”

Section: Site Descriptionmentioning

confidence: 99%

Sensitivity Study on Hydraulic Well Testing Inversion Using Simulated Annealing

Nakao¹,

Najita

Karasaki

1999

Groundwater

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Cluster variable aperture (CVA) simulated annealing has been used as an inversion technique to construct fluid flow models of fractured formations based on transient pressure data from hydraulic tests. A two-dimensional fracture network system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes an aperture of cluster of fracture elements, which are chosen randomly from a list of discrete apertures, to improve the match to observed pressure transients. The size of the clusters is held constant throughout the iterations. Sensitivity studies using simple fracture models with eight wells show that, in general, it is necessary to conduct interference tests using at least three different wells as pumping well in order to reconstruct the fracture network with a transmissivity contrast of one order of magnitude, particularly when the cluster size is not known a priori. Because hydraulic inversion is inherently non-unique, it is important to utilize additional information. We investigated the relationship between the scale of heterogeneity and the optimum cluster size (and its shape) to enhance the reliability and convergence of the inversion. It appears that the cluster size corresponding to about 20 -40 % of the practical range of the spatial correlation is optimal. Inversion results of the Raymond test site data are also presented and the practical range of spatial correlation is evaluated to be 5 -10 m from the optimal .cluster size in the inversion.

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Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

Cited by 16 publications

References 18 publications

Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

Signatures in flowing fluid electric conductivity logs

Sensitivity Study on Hydraulic Well Testing Inversion Using Simulated Annealing

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