Material invariant properties of shales : nanoindentation and microporoelastic analysis

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2005.Includes bibliographical references (p. 228-236).Shales compose the major part of sedimentary rocks and cover most of hydrocarbon bearing reservoirs. Shale materials are probably one of the most complex natural composites, and their mechanical properties are still an enigma that has deceived many decoding attempts from experimental and theoretical sides. Advanced experimental techniques, such as nanoindentation, and theoretical microporomechanics make it possible today to break such a heterogeneous material down to a scale where physical chemistry meets mechanics, to extract intrinsic material properties that do not change from one material to another, and to upscale the intrinsic material behavior from the submicroscale to the macroscale of engineering application. This thesis identifies material invariant properties of shales by investigating the elastic properties of shales at multiple scales. We combine new experimental data of shale microstructure and mechanical properties, with nanoindentation analysis and microporomechanics. This leads to the development of a novel multiscale upscaling model for shale poroelasticity. The proposed model relies on a few quantities that can be easily obtained from mineralogy and porosity data. This model is calibrated and validated, and its domain of application and limitations are discussed. The strong predictive capabilities of the model are particularly important for the Oil and Gas Industry, which can apply our predictive model of shale elasticity for geophysics and exploitation engineering applications.by A. Delafargue.S.M

Experimental Microporomechanics

© 2005, CISM, Udine. Is it possible to break down natural porous material systems down to a scale where materials no longer change from one material to another, and upscale (‘nanoengineer’) the behavior from the nanoscale to the macroscale of engineering applications? — This is the challenging question we address in these lecture notes through a review of tools and methods of experimental microporomechanics. The combination of advanced experimental indentation techniques and microporomechanics theory provides a unique opportunity to understand and assess nanoproperties and microstructure, as a new basis for the engineering prediction of macroscopic poromechanical properties of natural composites. This is illustrated for cement-based materials and shales

Broad individual immersion-scattering of respiratory compliance likely substantiates dissimilar breathing mechanics

International audienceHead-out water immersion alters respiratory compliance which underpins defining pressure at a "Lung centroid" and the breathing "Static Lung Load". In diving medicine as in designing dive-breathing devices a single value of lung centroid pressure is presumed as everyone's standard. On the contrary, we considered that immersed respiratory compliance is disparate among a homogenous adult group (young, healthy, sporty). We wanted to substantiate this ample scattering for two reasons: (i) it may question the European standard used in designing dive-breathing devices; (ii) it may contribute to understand the diverse individual figures of immersed work of breathing. Resting spirometric measurements of lung volumes and the pressure-volume curve of the respiratory system were assessed for 18 subjects in two body positions (upright Up, and supine Sup). Measurements were taken in air (Air) and with subjects immersed up to the sternal notch (Imm). Compliance of the respiratory system (Crs) was calculated from pressure-volume curves for each condition. A median 60.45% reduction in Crs was recorded between Up-Air and Up-Imm (1.68 vs 0.66 L/kPa), with individual reductions ranging from 16.8 to 82.7%. We hypothesize that the previously disregarded scattering of immersion-reduced respiratory compliance might participate to substantial differences in immersed work of breathing