饱和砂岩的滞弹性弛豫衰减特征及微观机理的探索

应用Metravib热机械分析仪,以饱和岩石进行正弦波加载的方式, 分别对三种不同孔隙度的泵油饱和彭山砂岩、泵油和甘油饱和自贡长石砂岩进行了衰减实验研究,得到衰减的热弛豫规律.据此规律求得它们的激活能和原子振动频率, 其激活能和原子的振动频率比间隙原子的激活能和振动的频率低, 此现象用饱和砂岩中产生的缺陷原子簇的整体振动比单个或孤立的原子的振动频率低做出了解释. 在饱和岩石的晶粒间界缺陷处参与扩散的是固体原子、液体及气体原子. 并得出随孔隙度和黏滞系数增大,衰减强度和激活能增大,原子的振动频率增高,弛豫时间减小的结论. 在正弦波应力作用下,由多种矿物晶体胶结而成的饱和砂岩是一种多晶、多相的固体, 由于内部结构复杂、缺陷广布,产生弛豫衰减是普遍现象.砂岩中存在点缺陷、位错、 晶界及孪晶界面等许多缺陷及缺陷间的相互作用都可以产生弛豫型衰减峰. 用饱和砂岩中特有的饱和液体及砂岩内部结构的复杂性解释了饱和砂岩的衰减机理, 很自然地将其宏观衰减特征与微观结构紧密连在一起.饱和砂岩中的各种缺陷、 相界等会导致多重弛豫,使它们的弛豫衰减峰变宽,分布参数增大.这项研究既具有理论意义,也具有实用价值.

Viscoelastic relaxation attenuation property for saturated sandstones and corresponding investigation of micro-scale mechanism

Attenuation experiments are performed by Metravib dynamic mechanical analyzer with sine wave loading style to study the viscoelastic relaxation property of pump-oil saturated and glycerol saturated Pengshan sandstone and Zigong arkoses with three kinds of porosities. Based on the thermal relaxation regularities, the activation energies and the atomic vibration frequencies of relaxation attenuation peaks for three kinds of saturated sandstones are evaluated. The results show that activation energies and atomic vibrations frequencies of sandstone samples are lower than those of interstitial atoms. The overall vibration behavior of atomic cluster with defects can be used to explain why vibration frequencies are low in samples. Besides the solid atoms, the gas and liquid atoms filled in defects contribute greatly to overall vibration of sample. Saturated sandstone, cemented by a combination of mineral crystals, is a polycrystalline, multiphase solid with internal complex structure and widespread defects, and it easily takes on thermal relaxation property under sine wave loading. Such flaws and defects as point defects, dislocation and grain boundary in samples and their interaction interaction can produce relaxation attenuation peak. To explain the relaxation mechanism by saturated liquid and internal structure of the sandstone, it is natural to relate the attenuation characteristics to its macro-meso-structure. It is notable that when taking the defects, multiple phase boundary into consideration, a new interesting phenomenon appears, there produces multi relaxation with broader peak and more widely distributed parameter. This investigation is helpful to study theoretical model and seismic data interpretation.