低渗透储层应力敏感性定量解释研究

对致密及发育微裂缝、裂缝的低渗透岩心应力敏感性进行了实验;采用不等径迂曲毛管束模型,通过弹性力学原理对粗、细毛细管变形量的计算,研究了单毛细管和多孔介质应力敏感性定量表征关系,并通过有效毛细管半径分数探讨了低渗透储层应力敏感性的作用机制。研究表明,低渗透储层的应力敏感性主要表现为渗透率的应力敏感性,低、中高渗透率储层在应力敏感性上的差异与微观孔隙结构、固液界面作用力和启动压力梯度效应等密切相关,且这种差异性集中体现为有效毛细管半径分数的不同。考虑有效毛细管半径分数的多孔介质应力敏感性量化模型可以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。

Quantitative research on stress sensitivity of low-permeability reservoir

The stress sensitivity of micro-fractured, fractured and dense cores from low-permeability reservoir was experimentally analyzed. The non-equivalent diameter and circuitous capillary module was used to express the stress sensitivity of single capillary and porous media by calculating elastic deformation amounts of big capillary and small one. The function mechanism on stress sensitivity of low-permeability reservoir was discussed by using the effective percentage of capillary diameter. The research results show that the stress sensitivity for permeability is more important than that for porosity in the low-permeability reservoir. The difference of stress sensitivity between low-permeability reservoir and medium-high permeability reservoir depends on some distinct factors such as microscopic pore structure, solid-fluid interfacial force and start-up pressure gradient, which can reflect the effective percentage of capillary diameter. The quantitative module of stress-sensitivity considering the effective percentage of capillary diameter can explain the difference of stress sensitivity between low-permeability and mediumhigh permeability reservoirs based on the microscopic mechanism.