Effects of Microstructure on the Elastic Properties of Sandstones and Its Seismic Implication
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The primary focus of this dissertation is to link the geological diagenesis mechanism of sandstones to theoretical rock-physics models and experimental measurements to quantitatively characterize the elastic modulus of sandstone from high-porosity (early geological stage) sediments to low-porosity consolidated (aged geological stage) rocks. In order to quantitatively investigate the velocity dispersion and attenuation mechanism of sandstones, the seismic-frequency measurements are conducted under both room-dry and partial gas or water-saturation conditions. I address two main aspects of this research topic, from the theoretical point of view: (1) to modify the grain-contact models and understand the effect of micro-scale physical parameters on the elastic properties of porous-granular packs; and (2) to characterize the cementation thickness and cement material as feature-effects on the elastic modulus of cemented grain packs, with consideration of geological diagenesis. Meanwhile, from the experimental point of view: (1) to integrate the seismic-frequency measurements with ultrasonic measurements, and to quantitatively characterize velocity dispersion and attenuation mechanism of weakly consolidated sandstone under room-dry and partial water-saturation conditions; and (2) to conduct specialized ultrasonic measurements on the mixture of heavy oil-glass bead to investigate the uniquely elastic property of heavy oil-sand, which is predominant temperature-dependent.