Micromechanical evaluation of rock and fluid interactions

Abstract

The deformation of the solid system in the process of fluid flow in deformable porous media, such as underground fluid flow, carbon-dioxide (CO2) sequestration, is the result of external stress, particle-particle, and fluid-particle interactions. Such behavior is very crucial in CO2 sequestration as it causes a significant instability and onset of displacements. The small-scale deformations of pore-pressure may trigger waking up of the pre-existing and unrevealed fractures and faults, which in turn cause seismicity. Thus, studying the effect of fluid flow on rock deformation is very important. In this paper, the effect of external stress and fluid-particle interactions on the deformation of porous media is elucidated through evaluating of micromechanical behaviors of rock and fluid under an external stress. To this end, packing of multi-size spherical particles in dry and wet conditions are used to represent the medium. Then, the deformation under different external stress is quantified using various morphological and flow properties, such as strain, pore-size distribution, porosity, and velocity field. The results indicate that as the external stress increases, the deformation of both dry and wet states increase. By increasing the external stress, the discrepancy between the deformation of the dry and wet cases declines, whereas the deformation of the dry cases is always bigger than that of the wet samples as the fluid-particle drag force inhibits the solid deformation.