致密储层应力敏感性研究

在油田开采过程中，地层压力逐渐下降，作用在岩石颗粒上的有效应力增加，这种效应使岩石发生形变，产生应力敏感，使得岩石的渗透率减小，从而影响到流体的流动及产能，给高效、合理地开发带来许多困难和问题。为此，对大庆油田低渗透致密岩心进行了应力敏感性试验，考虑其微观孔隙结构特征及黏土矿物的赋存状态，提出了新的毛管模型，并研究了单毛管在应力作用下的变形规律。研究表明：应力敏感程度与岩心的渗透率初值具有较好关系，随着渗透率降低，应力敏感性变强，渗透率损失率与渗透率初值具有乘幂递减关系。基于弹性力学理论，应用新的毛管模型，通过对单毛管在应力作用下的变形规律研究，从应力敏感性微观作用机制角度解释低渗透储层与中高渗透率储层在应力敏感性上的差异。这些研究对该低渗透致密储层的合理开发及合理生产工作制度的确定具有重要意义。

Study of stress sensitivity of tight reservoir

During the exploitation of oilfield, the formation pressure depletes gradually, but the effective stress to the rock grain increases. The effective stress may cause rock to deform, resulting in the elastic or plastic deformation; and the rock permeability is quite sensitive to effective stress due to the deformation. Therefore, it is necessary to know the property of stress sensitivity for the low permeability tight reservoir. The permeability of sand rock core samples of Daqing oilfield under different effective stresses is tested, and the reduction property of permeability is obtained. Considering the microscopic characteristics of pore structure and occurrence states of clay, new capillary-tube model is proposed; and the deformation law of single capillary is studied. The research shows that the stress sensitivity of rock increases with the decrease of rock permeability; and there is exponent relation between initial permeability and the loss rate of permeability. The new capillary-tube model can explain the difference of stress sensitivity between low-permeability and medium-high permeability reservoirs based on the microscopic mechanism.