微观与介观波致流下的速度频散与衰减

发布时间：2019-04-19 08:36

【摘要】：地震波在含软、硬孔隙斑块饱和介质传播过程中会诱发多个尺度孔隙流体流动而产生衰减和速度频散,并且多个尺度间的流体流动相互影响。综合考虑微观喷射流与介观尺度流体流动的相互作用,从Biot理论出发,推导出一个新的衰减模型——双尺度模型,以及该模型下流体流动引起的固体相位移、弹性模量、相速度及衰减系数的表达式,并与层状斑块饱和模型进行了对比。同时基于双尺度模型,分析了改进湿岩石骨架参数以及不同的储层物性参数对纵波传播特征的影响。结果表明:改进湿岩石骨架会增加岩石骨架刚度,减小介观尺度下界面处流体流动引起的固体相位移,增加速度频散与衰减,进而解释了微观喷射流与介观波致流相互作用的机理;当上、下层介质饱含不同的流体类型时,双尺度模型在整个频段上会出现两到三个"频散台阶",喷射流与介观流有可能作用于同一频段;随着含水饱和度的增大,纵波衰减峰值增大,且向低频移动,当含水饱和度达到较大值时,衰减峰值移向高频、衰减减小,速度随着含水饱和度的增大而增大。
[Abstract]:Seismic wave propagation in saturated medium with soft and hard pores will induce attenuation and velocity dispersion of multi-scale pore fluid flow, and the fluid flow among multiple scales will influence each other. Considering the interaction between microscopic jet flow and mesoscopic fluid flow, a new attenuation model, two-scale model, is derived from Biot theory, and the solid phase shift and elastic modulus caused by fluid flow in this model are derived. The expressions of phase velocity and attenuation coefficient are compared with those of layered patch saturation model. At the same time, based on the two-scale model, the effects of improved wet rock skeleton parameters and different reservoir physical parameters on P-wave propagation characteristics are analyzed. The results show that the improvement of wet rock skeleton will increase the stiffness of rock skeleton, decrease the solid phase shift caused by fluid flow at the interface at mesoscopic scale, and increase the dispersion and attenuation of velocity. Furthermore, the mechanism of interaction between micro-jet flow and mesoscopic wave-induced flow is explained. When the lower layer is full of different fluid types, two or three "dispersion steps" appear in the whole frequency band, and the jet and mesoscopic flow may act in the same frequency band. With the increase of water saturation, the attenuation peak of P wave increases and moves to low frequency. When the water saturation reaches a higher value, the attenuation peak shifts to high frequency, the attenuation decreases, and the velocity increases with the increase of water saturation.
【作者单位】：中国石油大学(华东)地球科学与技术学院;
【基金】：国家“973”计划项目(2014CB239201-7Hz) 国家科技重大专项(2016ZX05027004-001,2016ZX05002006-004) 国家自然科学基金项目(41404088) 中央高校基本科研业务费专项资金项目(14CX02113A)联合资助
【分类号】：P631.4

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