低渗透储层应力敏感性研究

虽然目前国内外对于低渗透储层应力敏感性的研究很多，但争论较大，未形成一致的看法。本文从室内实验和理论研究两方面出发，深入研究了低渗透储层的应力敏感性及其变化规律。在此基础上，利用渗透率应力敏感系数，结合分形理论，建立了考虑岩石内部结构、外部有效应力变化等多种因素影响下的渗透率变化规律的公式。研究表明，由于孔隙结构的特殊性，有效应力变化对储层渗透率影响较大，而对孔隙度影响很小。渗透率随有效应力的增加而不断减小，但其程度不断减弱，且存在永久伤害；渗透率越小，应力敏感性越强；同时快速的加压方式比慢速的加压方式对岩石的伤害更大。应力敏感系数可以定量表征岩石应力敏感性的强弱；考虑多种因素影响的预测公式，可以准确反映岩石的应力敏感情况，具有广泛的适用性。

The study on stress sensitivity in low permeability reservoir

There are many studies on stress sensitivity in low permeability reservoir at home and abroad,but to this day,the differences among each opinion are very large and there is no unified understanding about it.The stress sensitivity and the change laws in detail with laboratory experiments and theory method are studied.Based on the results,combining with the stress sensitivity coefficient of permeability and fractal theory,a formula of permeability change laws is built taking account of the effects of pore structure,effective stress changes.The results show that,the effect of stress changes on permeability is very large,while its influence on porosity is very small because of the specialization of pore structure.The permeability decreases with the increase of effective stress,but the extent is weaker and weaker,and there exists permanent damage on permeability: the permeability can’t recover to the initial value while the effective stress reduces.The smaller the permeability is,the larger the stress sensitivity is;and the faster the stress loads,the larger the stress sensitivity is.The stress sensitive coefficient can characterize the rock sensitivity quantitatively.The forecast formula,taking into account many effect factors,can reflect the rock sensitivity accurately,so it has a wide adaptability.