Poroelastic behaviour of physical properties in Rotliegend sandstones under uniaxial strain

Laboratory experiments simulating reservoir depletion and reinjection of fluids have been conducted on Rotliegend reservoir sandstones. Pore pressure dependence of petrophysical properties have been measured under uniaxial strain boundary conditions, i.e., zero lateral strain at constant overburden pressure. Permeability, formation resistivity factor, and compressional as well as shear wave velocities were recorded simultaneously and continuously during deformation in direction of maximum principal stress. The results show that the stress development is specific for different sandstones depending on the efficiency of pore pressure. The stress anisotropy increases with decreasing pore pressure, leading to stress-induced anisotropy of pore structure with preferred closure of horizontally oriented pore space. Permeability decline of initially lower permeability sandstones indicate the opening of axially oriented pores at lower pore pressure.