Compaction of quartz-kaolinite mixtures: The influence of the pore fluid composition on the development of their microstructure and elastic anisotropy

Theoretical Modeling of Dielectric Properties of Artificial Shales

“…By using the silt aspect ratios of 0.1 and 0.06 the modeled dielectric responses give satisfactory fit to the dielectric measurements at the vertical and horizontal directions, respectively, with correlation coefficients of R = 0.9833 and R = 0.9775 for the relative permittivity and conductivity in the vertical direction and R = 0.9979 and R = 0.9940 for the relative permittivity and conductivity in the horizontal direction, respectively. The obtained silt aspect ratios of 0.1 and 0.06 are within the aspect ratio range of the silt from the micro-CT image of the compacted sample [35] and can also be explained by the nonhomogeneous microstructure at the sample scale [40]. It is interesting that different values of the silt aspect ratio are inverted in the orthogonal directions and this can be explained by the fact that although randomly dispersed silts are assumed in the model, they are in fact aligned to some extent, and therefore their contributions to the dielectric responses at different directions are varying; as a result, different values for the silt grain aspect ratio should be used.…”

“…The inversion is done on sample A0100 75 by minimizing the difference between the laboratory measurements and the model prediction for relative permittivity and conductivity in the directions parallel and perpendicular to the bedding, respectively, at each frequency between 0.1 MHz and 100 MHz where the laboratory data are collected. In the modeling, an aspect ratio of 0.1 is employed for the kaolinite grains based on analysis of the SEM images of the compacted sample [35].…”

Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

“…Figure 7 shows that across the wide range of frequencies horizontal conductivity in different samples is almost always higher than the vertical one. Previously we showed that the particles of clay and silt tend to orient with compaction normal to the direction of an applied compaction stress [16,22]. Therefore, the interconnected pore network in artificial shale samples is also more oriented in the bedding direction and provides an effective pathway for charge carriers, whereas in the direction normal to bedding the conductive pathways exhibit greater tortuosity and obstruct the movement of charges.…”

“…Compacted shales were gently ejected from the oedometer, covered with thick layer of wax, and preserved in a low-temperature humid atmosphere to prevent desiccation. Further details on the mechanical compaction methodology can be found in Beloborodov et al [16].…”

“…The least known parameter in terms of its effect on dielectric response is the microstructure of the clay fraction in shales. Different geological settings may significantly affect the microstructure of sediment and consequently its properties [16]. For example, Dong and Wang [17] showed that the kaolinite sediments saturated with water solutions of different pH exhibit significantly different dielectric spectra due to the different mechanisms of microstructure formation.…”