Experimental Study on Stress Sensitivity of Ultra-Low Permeability Sandstones

Ultra-low permeability rocks have plenty of microfractures. The stress-dependent permeability has a significant impact on the seepage. Previous studies are mainly on the permeability variation with stress in low permeability reservoir. But few are involved in ultralow permeability cores. In this paper, the experiment of stress sensitive ultralow permeability cores which are fabricated (both matrix cores and microfracture cores) is conducted. The experimental results shows that the permeability of microfracture low permeability cores which are fabricated increases greatly while the porosity of low permeability cores is little affected. This indicates that the fabricated microfracture cores are in line with that of the real situations of fracture media reservoir. By comparison, the permeability stress sensitive hysteresis degree of microfracture cores is not apparent and the permeability recovery degree is high in the unloading cycle. This study is of great benefit to reveals the stress sensitivity features of ultralow permeability reservoir