特低渗透砂岩储层应力敏感性实验

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

应用室内低渗透物理模拟实验手段,研究了微裂缝发育和微裂缝不发育的特低渗透砂岩岩样的应力敏感性特征,并对比分析了两类样品的应力敏感性差异。研究结果表明,无论储层是否发育微裂缝,储层渗透率越小,其应力敏感性越强;微裂缝不发育时,渗透率小于2×10-3μm2的储层应力敏感性较强且其强度随渗透率的降低而急剧增大,而渗透率大于5×10-3μm2的储层应力敏感程度较弱;微裂缝发育的储层的应力敏感性明显强于微裂缝不发育的储层,有效应力增大时,微裂缝发育的储层的渗透率损失为微裂缝不发育的储层的2—3倍,而有效应力降低后,渗透率不能完全恢复,微裂缝发育的储层的渗透率损失约为微裂缝不发育的储层的5倍。研究结果对制定合理的特低渗透油田开发方案具有实际指导意义。

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.