Three Dimensional Pore Geometry change under different axial differential stress and Fluid Flow of Berea sandstone by LBM

The Berea sandstone has a clear bedding plane and not clear cross lamina in cm size specimen, which is mainly caused by grain orientation and void space in microscopic scale. During the confined triaxial compression test, we measured permeability of Berea sandstone by constant head test for three mutually perpendicular directions under increasing differential axial stress. In general, the permeability of Berea sandstones decreased slightly with increasing the effective confining pressure and axial differential stress. Permeability anisotropy was also observed in the normal and two parallel directions to the bedding planes. We introduced the three-dimensional medial axis (3DMA) method of Lindquist et al. (2000) to quantify the flow-relevant geometric properties of the voids structure in Berea sandstone. Using these data, we also evaluated the number of connecting path between two faces, tortuosity and the shortest path distribution within an arbitrary region of Berea sandstone specimen. Geometrical information on the number of connecting path in an arbitrary volume CT data shows reasonable correlation between permeability anisotropy and mutually perpendicular directions normal and parallel to bedding planes. In addition, we introduced numerical simulation of fluid flow of pressurized Berea sandstone by LBM, to discuss the permeability change caused by pressurization on effective confining pressure and differential axial stress. We obtained the detail distributions of fluid pressure, fluid velocity and its vector distribution in rather narrow voids space more than 10 μm. It is confirmed that pressurization effect on permeability caused by the decrease of the connecting path and the shortest path between arbitrary faces, and then caused a complex condition of on fluid pressure and fluid velocity.