Showing papers on "Effective porosity published in 1976"

Hydrogeophysical properties of parts of the British Trias

Abstract: Laboratory studies of Bunter Sandstone specimens from Northwest Lancashire, Shropshire, West Cumberland, and the Vale of Clwyd have indicated that the parameters effective porosity, intergranular permeability, compressional wave velocity, formation resistivity factor, and effective matrix resistivity have significantly different distributions in each of these four regions. Regression analyses have shown that bivariate and trivariate expressions for the prediction of the two hydrological parameters from petrophysical data vary from region to region. It is concluded that, in quantitative geophysical investigations of these formations, each area must be investigated independently. For all four aquifers, and for both horizontally and vertically oriented specimens, effective porosity can be most reliably and readily estimated through a bivariate relationship involving formation resistivity factor. On the other hand, the best estimate of intergranular permeability from geophysical data is obtained through a trivariate expression involving both formation resistivity factor and effective matrix resistivity. The use of hydrogeophysical relationships to estimate hydrological parameters in situ is illustrated by reference to field examples.

Groundwater Fluctuations and Calculation of Effective Porosity of Laterite and Effective Fissure Porosity of Basalt of the Karanja Basin, Karnataka, India

Abstract: The estimated evaporation and surface run-off have been used to calculate the effective porosity of laterite and effective fissure porosity of weathered basalt which ranges between 0.50 to 6.04 per cent and from 0.94 to 1.67 per cent respectively.

Influences of Diagenetic Environment on Porosity and Permeability of Holocene and Pleistocene Corals: GEOLOGIC NOTES

Abstract: Changes in effective porosity and permeability during diagenesis in Holocene and Pleistocene corals from the Bahamas and Florida Keys are influenced by environmental and, to some extent, by taxonomic variations. Submarine and vadose samples show a decrease in permeability during porosity reduction by cementation, whereas phreatic samples increase in permeability with decreasing porosity because of larger and better sorted pore apertures. As a result, reef rock built mainly of corals may be a better reservoir rock if it has undergone diagenesis in the phreatic zone rather than in the submarine or vadose environments.

Dipole-dipole resistivity surveys, Roosevelt Hot Springs KGRA. Final report, Volume 2

Abstract: Dipole-dipole resistivity surveys were conducted at Roosevelt Hot Springs KGRA. Three different dipole spacings were used; 99km of traverse line were surveyed with 100m dipoles, 50km with 300m dipoles, and 44km with 1km dipoles. The objectives of the resistivity surveying were to detect and delineate regions of low resistivity associated with fracturing, brines, high temperatures, and clay alteration. The resistivity of rocks that are typical of hydrothermal environments is due to two main conduction mechanisms: (1) electrolytic conduction through pores and fractures; and (2) surface conduction due to a thin zone of cations attracted to those mineral surfaces with net negative charges (especially clay minerals). For saturated rocks, the resistivity due to electrolytic conduction is a function of the effective porosity of the fractured rock, of the temperature, and of the salinity of the fluid filling the pores and fractures. The resistivity decreases as the effective porosity, water saturation, salinity, and temperature increase. The presence of clay minerals and pyrite will also decrease the resistivity.