应力诱导饱和流体岩石弹性波各向异性  

Elastic wave anisotropy in a fluid-saturated rock under stress

作　　者：孟贺 唐晓明 陈雪莲[1] 徐志彦 韩海力 程翠鹏 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]连云港杰瑞自动化有限公司,江苏连云港222000

出　　处：《地球物理学进展》2017年第3期1217-1222,共6页Progress in Geophysics

基　　金：国家重点基础研究发展计划(2014CB239006);国家自然基金(41174088);国家国际科技合作专项资助(2015DFA61030);中央高校基本科研业务费专项资金(14CX05010A)联合资助

摘　　要：各向同性岩石中裂隙随机分布,施加单轴方向的压应力后,与压应力方向垂直的缝隙会优先闭合.应力作用下裂隙的闭合导致岩石呈现出横向各向异性的特征,进而影响弹性波的传播特征.前人对干燥岩石中应力引起的弹性波速度各向异性开展了大量研究,但未考虑充填流体对于应力诱导各向异性和弹性波传播的影响.弹性波通过应力作用的岩石时会诱导微孔隙结构上的"挤喷流"效应,从而造成弹性波显著的频散和衰减.在本文中,我们分析应力诱导各向异性岩石中挤喷流对弹性波传播的影响.利用硬币型裂隙模型,同时考虑挤喷流和应力诱导各向异性的影响,我们建立了应力作用下含流体岩石各向异性模型.基于本文的模型,我们研究了裂隙介质中单轴应力和充填流体对弹性波传播的影响.我们的模型成功预测了弹性波速度随应力的增加,同时表明了挤喷流造成纵波的各向异性频散更显著.In the isotropic rock with randomly distributed cracks,due to the uniaxial stress,cracks perpendicular to the uniaxial stress are preferentially closed. The crack closure under stress results in transversely anisotropic behavior of the rock＇s elasticity,influencing the elastic wave propagation characteristics. Many researchers have studied the stress-induced elastic wave velocity anisotropy of dry rock. However,the effects of fluid on the stressinduced anisotropy and elastic wave propagation have not been studied in detail. The elastic wave propagation through the stressedrock induces the squirt flow in the micro pore structure,resulting in significant wave attenuation and dispersion. The effects of the squirt flow in the stress-induced anisotropic rock on elastic wave propagation are analyzed in this paper. Using a penny-shaped crack model and considering both the squirt flow and the stress-induced anisotropy,we establish the anisotropy model for the fluid-filled rock under stress. Based on the model,we study the effect of the uniaxial stress and fluid on the elastic wave propagation in the cracked medium. Our model result successfully predicts the increase of elastic-wave velocities with stress and the stress-induced anisotropy. The result also shows the anisotropic dispersion effect caused by squirt flow,which is more significant on P waves than on S waves.

关 键 词：应力诱导各向异性 挤喷流 频散 衰减 

分 类 号：P631[天文地球—地质矿产勘探]