Experiments on the Stress Sensitivity of Ultra-low Permeability Sandstone Reservoirs

By means of experimental physical simulation,the influence of stress variation on the permeability of fractured and non-fractured ultra-low permeability sandstone cores were researched,the permeability variation of the two types of cores were compared with each other,and the stress sensitivity characteristics of the fractured and non-fractured reservoirs were summarized.The results show that for both fractured and non-fractured reservoirs,the lower permeability is,the stronger sensitivity of permeability stress is.For non-fractured reservoirs,when the reservoir permeability is lower than 2×10-3μm2,the sensitivity of permeability stress is strong and the strength increases rapidly as the permeability decreases,and when the reservoir permeability is higher than 5×10-3μm2,the sensitivity of permeability stress is weak;the fractured reservoirs stress sensitivity is much stronger than that for non-fractured ones;and the permeability loss of fractured reservoirs caused by the effective stress increase is 2—3 times of that for non-fractured reservoirs;and the permeability is unable to recover completely after the effective stress decreases,and the permeability loss of fractured reservoirs is 5 times of that for non-fractured reservoirs.The research findings are useful for engineers to determine the development strategy for ultra-low permeability sandstone reservoirs.