STUDIES ON DEFORMATION OF MATERIALS VIA RATE TREATMENT OF COMPRESSION TEST

Abstract

Fractures in sandstone formations are responsible for well instabilities. The micro properties of sandstone grains are crucial to their deformation. However, little attention has been given to the study of these properties because it is challenging to determine the said properties. Advances in the data acquisition systems attached to the compression test on rock materials have been employed. Here we obtain a procedure which has made it possible to explore the role played by micro-parameters of sandstone in understanding mechanisms of well fractures experimentally. The macroscopic deformation of rock model samples used in experiment coupled with data acquisition confirmed the deformation of bonded grains structure starts with a single grain distortion, which is where microparameters are obtained as calibrations. It was observed that the grain and bond stiffness can be related to the elastic modulus while the bond strength can be related to the tensile strength of the bonds within the grains. The synergetic effect of the grain distortion due to bond softening, grain stiffness and bond strength controlled the mode of deformation along the crack path, which occurred along the highly stressed points. Core sample examination was observed to re-define mechanical stress or loading magnitude to enhance operational safety. Obtaining micro-properties of core samples prior to drilling program will provide reliability of macroscopic elastic properties of handling rock structures under engineering project. The initial data of the micro-properties representing the physical rock under mechanical stress can be enhanced if a simulation is required to plan drilling operations. Keywords: Micro-measurements, fracture, micro-properties, stiffness, sandstone.