泵油饱和砂岩黏弹行为的实验研究

通过Metravib热机械分析仪, 用固定静载为100 N、 正弦波动载荷为60 N的应力-应变实验方法, 在温度为-50---175 ℃, 升温速率为1 ℃/min, 频率为1---1000 Hz的条件下, 对泵油饱和长石砂岩、 彭山砂岩样品进行单轴循环加载实验, 研究了饱和多孔岩石在弹性范围内的衰减、 耗散角、 杨氏模量和弹性波波速随温度和频率的变化规律. 取得了随频率增高饱和多孔岩石的衰减峰和耗散角峰的峰位向高温方向移动的热激活弛豫规律, 并求得弛豫峰的激活能和跃迁频率, 以饱和砂岩的特点对此作出了解释. 发现岩石中矿物离子置换时的相变内耗峰, 并用动态观点解释了该相变峰. 还获得杨氏模量和弹性波波速随温度升高而下降、 随频率增高而增大的频散效应, 随温度升高频散效应有减弱的趋势. 该研究结果对理论模型研究具有指导意义, 对地震资料的解释具有实用价值.

Experimental research on viscoelastic behavior for pump-oil saturated sandstones

Experiments are performed by Metravib dynamic mechanical analyzer(DMA+450) using the stress-strain method.The static load is fixed at 100 N,and the dynamic load amplitude of the sine wave is 60 N,so that the total loading force is controlled under yield stress. Temperature is controlled between—50℃and 175℃,and the heating rate is 1℃per min.The frequency ranges from 1 Hz to 1000 Hz.Pump-oil saturated arkoses and Pengshan sandstones are tested under uniaxial cyclic loading.The variations of attenuation,phase angle,Young’s modulus,and velocity with temperature or frequency are obtained.The attenuation peak and the phase angle peak shift toward higher temperatures with frequency increasing,which can be considered as thermal relaxation regularity.The activation energy and the transition frequency corresponding to the thermal relaxation peak are determined by experimental results and explained by the sandstone characteristics.A new phase transition attenuation peak,which is corresponding to mineral ion exchange in rock,is observed in the present experiments.Some dynamic characteristics of rock minerals under thermal and vibration loading are used to explain the peak.The Young’s modulus and the velocity increase with frequency increasing and decrease with temperature increasing.There is obvious frequency dispersion,and the dispersion weakens when temperature increases.This investigation is helpful for studying theoretical model and interpreting seismic data.