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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。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。
Although there are many researches on the stress sensitivity of low-permeability reservoirs at home and abroad, there is still much controversy and no consensus has been reached. Based on laboratory experiments and theoretical studies, the stress sensitivity of low-permeability reservoirs and its variation are studied in depth. On this basis, the formula of permeability change under the influence of many factors including the internal structure of rock and the change of external effective stress is established by using permeability stress sensitivity coefficient and fractal theory. The results show that due to the particularity of the pore structure, the effective stress has a great influence on the permeability of the reservoir, but has little influence on the porosity. Permeability decreases with the increase of effective stress, but its degree decreases continuously, and permanent damage exists. The smaller the permeability is, the stronger the stress sensitivity is. Meanwhile, the rapid pressurization method is more effective than the slow pressurization method on rock Hurt more. The stress sensitivity coefficient can quantitatively characterize the strength of rock stress sensitivity. Considering the prediction formula of various factors, it can accurately reflect the stress sensitivity of rock and has a wide range of applicability.