致密储层应力敏感性及其对油田开发的影响

Stress sensitivity of tight reservoir and its influence on oilfield development

对致密储层的渗透率及应力敏感性进行了实验研究,建立了以原始储层有效应力(上覆岩层压力与原始储层孔隙压力之差)为有效应力起点的压敏评价方法。实验结果表明,该方法能够反映储层岩石的真实应力状态,其应力敏感伤害程度符合储层的真实情况,有效应力与渗透率之间符合二次多项式的关系。应力恢复实验表明,岩石的弹塑性变形使得压敏伤害成为一种永久的、不可逆的伤害。利用扫描电镜和恒速压汞实验,分析了应力敏感机理。孔隙受压敏影响较小,喉道的大小和形态决定了岩石的渗透率-应力敏感程度。从理论上计算了压敏对油田开发的影响,结果表明,在生产井井底附近的储层中存在渗透率漏斗,压敏伤害对油井产量有一定影响。

The relationship between permeability and net stress of tight reservoir was experimentally studied,and a method to evaluate permeability-stress sensitivity was established on the basis of the original net stress of reservoir rather than the low net stress. This method can correctly reflect the change of pore structure, and the quadratic polynomial curve can capture the nuances of the stress sensitivity. The permeability damage caused by the elastic and plastic distortion is permanent and irreversible. The pore structure tested by scanning electron microscope and rate- controlled mercury penetration showed that porosity was weakly affected by permeability-stress sensitivity,while the size and shape of throat determined the degree of permeability-stress sensitivity. The theoretical calculation shows that there is a cone of permeability depression near the well bottom. The stress sensitivity has some influence on oil production.