Interfacial effects on the electrical properties of humid limestone

The simple Archie's equations relate the average conductivity to average porosity and average saturation and seem to work when the fluctuations of local porosity and local saturation are small. The presence of conducting minerals and grains or pore-surface conduction produces, in addition to Archie's suggested mechanism conduction, a second conducting component. Modification of the classical Archie's relation is carried out. Since carbonate rocks are of special importance in the petroleum as well as underground water explorations, samples of limestone rock are studied under varying conditions of atmospheric relative humidity to identify their interfacial effects. Power law is discussed as an empirical relationship for describing the experimental results. Debye behavior is also noticed under particular conditions

Electrical properties of moist limestone samples in the frequency range 1Hz-10[7] from Abu Rawash area

The dielectric constant and electrical resistivity of Abu Rawash limestone samples are measured at some varying atmospheric relative humidity and room temperature [almost equal to] 22C [degree sign]] in the frequency range [1 Hz- 10[7] Hz]. Little increase in the atmospheric humidity varies resistivities by 4 orders or more of magnitude. Variations in the dielectric constant of the same order can also be obtained. Frequency dependent impedance measurements indicate that, the overall electrical response of a rock sample is controlled by one or more of three conduction mechanisms, which can be identified as: [i] conduction through adsorbing water layer on solid surfaces, [ii] conduction through mass transportation or diffusion through pore spaces filled with water and [iii] high frequency [radio frequency and higher] conduction. Cation exchange capacity [CEC] plays the essential role in defining the electrical properties of solid-solution interfaces. Mass transport or diffusion impedance, as affected by measuring electrode properties, may also be called diffusion controlled impedance. It takes place at frequencies lower than the chemical reaction. The high frequency conduction mechanism is controlled by the intrinsic properties of the sample constituents

Induced polarization in humid limestone in the radio frequency range and lower

Experimental investigations in the laboratory led to a better understanding of the fundamental relationship between rock properties and electrical characteristics. Some fundamental relationships and mechanisms are represented for a quantitative interpretation of the induced polarization data of limestone rock samples, when subjected to humid atmosphere. An equivalent circuit is assumed to identify the diffusion ZD, reaction and adsorption impedances. Limestone rock samples are studied at a frequency range of 102 - 107 Hz and at atmospheric relative humidities between 18%-50%. Abnormal high dielectric Constant and abnormal behavior of the conductivities for the studied samples are observed which are ascribed to electrochemical kinetics

effect of water content in the electrical properties of limestone rocks in the frequency domain

The effect of water content on the electrical properties of limestone rocks in the frequency domain was studied. Results of studying limestone rock samples with electrical impedance method was considered. Such a study was carried out in the frequency range from 20 Hz to 10 MHz, under some varying relative humidities. The chemical reaction impedance expresses polarization process of the measured sample under controlled environmental conditions. The chemical reaction impedance [Zr] shows a Debye behavior at maximum frequency [105 Hz]. When the sample is nearly dry, it gives a linear behavior in the Z plane. The chemical reaction mechanism based on the obtained data is discussed theoretically and experimentally