岩石非线性细观响应中孔隙液体的影响

INFLUENCES OF PORE FLUID ON NONLINEAR MESOSCOPIC RESPONSES OF ROCKS

在细观尺度上对孔隙流体对岩石力学性质的影响进行定量化研究。将孔隙流体带来的非线性应变的影响分为经典应变的影响和非经典弹性单元(NCU)对非经典应变的影响。分析低饱和度和高饱和度时微细观机制的作用,以此分别讨论流体对岩石非线性力学行为和岩石介质宏观刚度的影响。为适应不同饱和度下岩石力学行为,提出一种新的固液相互作用函数关系,对试验数据进行非线性反演,获得不同饱和度时的PM空间图像,分析孔隙流体对PM空间密度(NCU数目)的影响。首次反演杨氏模量、压缩波速度随饱和度变化完整过程。饱和度为0%～20%时,由于液体的激活作用,对于经典部分,动态杨氏模量随饱和度增加而减小;对于非经典部分,随饱和度增大PM空间NCU密度增大,NCU数目增多,非线性增强,杨氏模量下降。当饱和度为20%～80%时,动态杨氏模量不随饱和度变化,PM空间NCU密度也基本保持不变。当饱和度由80%以上增大到全饱和时,杨氏模量、弹性波速度反而随饱和度增加而增大,PM空间NCU数目有所减小,非线性程度下降。饱和岩石的经典和非经典非线性应变比干燥岩石有显著的增长,与模拟的PM空间NCU密度分布结果是一致的。这些数值分析结果与试验结果的规律性基本吻合。该项研究对于储层预测、油藏描述、斜坡附近建筑的安全性、核仓库性能及地球物理反演、资料解释都具有潜在的应用前景。

Quantitative studies of pore fluid influence on the mechanical properties of rocks are carried out on mesoscopic scale. The nonlinear strain is decomposed into a classical part and a nonclassical contribution which is described by nonclassical elastic units（NCU）. Based on the analysis of the mechanism on mesoscopic scale, fluid influences on rock mechanical behavior and stiffness under various saturations are discussed. Introducing new forms of macroscopic solid-fluid interaction functions, are obtained from the inversion of experimental data; are investigated. The entire variation between Young＇s Preisach-Mayergoyz（PM） space under different saturations and the influences of fluid saturation on PM space density modulus and compressional wave velocity with saturation is studied. When saturation increases from 0% to 20%, the dynamic modulus decreases for classical part, and the PM space density increases for nonclassical part, respectively. Whereas saturation is between 20% and 80%, the dynamic modulus and PM space density barely changes. As saturation increases from 80% to 100%, the dynamic modulus increases and the PM space density decreases, contrary to the low saturation condition. The classical and nonclassical nonlinear strains of saturated rocks are obviously larger than those of dry rocks in accord with the PM space density distribution. These numerical results are generally consistent with the experimental results. This simulation research has potential prospects for the problems such as reservoir prediction and description, safety of constructions near slope area, nuclear storehouse properties, geophysical inversion, and data interpretations.