毛细管压力作用下的非饱和双重孔隙介质中弹性波传播  

Elastic wave propagation characteristics in unsaturated double-porosity medium under capillary pressure

作　　者：石志奇 何晓[1,2,3] 刘琳 陈德华 王秀明[1,2,3] Shi Zhi-Qi;He Xiao;Liu Lin;Chen De-Hua;Wang Xiu-Ming(State Key Laboratory of Acoustics,Institute of Acoustics,Chinese Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China;Beijing Engineering and Technology Research Center for Deep Drilling Exploration and Measurement,Institute of Acoustic,Chinese Academy of Sciences,Beijing 100190,China)

机构地区：[1]中国科学院声学研究所,声场声信息国家重点实验室,北京100190 [2]中国科学院大学,北京100049 [3]中国科学院声学研究所,北京市海洋深部钻探测量工程技术研究中心,北京100190

出　　处：《物理学报》2023年第6期376-386,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12174421,42074174)资助的课题.

摘　　要：岩石孔隙中常常含有两相或多相流体,了解弹性波作用下流体压力扩散对弹性波频散和衰减的影响对于地球资源探测至关重要.本文建立了由一种骨架和两种流体组成的非饱和双重孔隙介质模型,推导了考虑毛细管压力作用的,包含宏观全局流和中观局域流两种机制的弹性波传播方程.利用平面波分析的方法分析了三种纵波(P1,P2和P3波)和一种横波(S波)的频散和衰减特性,并重点讨论了嵌入体半径、饱和度、渗透率和孔隙度等孔隙介质参数对其中P1波传播特性的影响.经理论分析验证,该模型在特定参数条件下可退化为经典Biot饱和流体孔隙模型.根据数值模拟结果,低频P1波速度会出现低于Gassmann-Wood低频极限的现象,这是由于在考虑宏观尺度上流体间毛细管力作用的情况下,全局流和局域流的耦合作用加速了孔隙压力的平衡过程,使得岩石不排水的基本假设不再成立;孔隙介质参数与弹性波频散和衰减之间是复杂的非线性关系;与仅考虑宏观全局流机制的Santos模型相比,本模型预测的岩石弹性模量在低频段与实际岩心测量数据较吻合,证实了该模型在地震勘探速度场建模方面具有更好的可靠性.Rock pores often contain two-phase or multi-phase fluids,so it is important to understand how the wave-induced fluid pressure diffusion affects dispersion and attenuation of elastic waves for resource exploration.To describe the propagation of elastic wave in a double-porosity medium saturated by two-phase fluids,a wave propagation model,including both global and local flow mechanisms and considering the effect of capillary pressure,is derived.The dispersion and attenuation characteristics of three longitudinal waves(P1,P2,P3)and one transverse wave(S wave)are investigated by analyzing a plane wave,and the effects of physical parameters,such as inclusion radius,water saturation,permeability and porosity,on the propagation characteristics of P1 wave are investigated.Theoretical analysis shows that the model derived in this work can be degenerated into the Biot model under specific conditions.According to the numerical simulation results,due to the coupling of global flow and local flow,the P1 wave velocity may decrease below the Gassmann-Wood limit.The physical explanation of this phenomenon is as follows:when considering the effect of capillary pressure,the coupling effect of global flow and local flow will break the basic assumption that rock is undrained.The relationship between physical parameters of porous medium and the dispersion and attenuation characteristics of elastic wave is complicated and nonlinear.Compared with Santos model,elastic modulus predicted by Santos-Rayleigh model is in good agreement with the experimental data in the low frequency band,which proves that this model has good reliability in modeling the velocity field of seismic exploration.

关 键 词：孔隙介质 毛细管力 局域流 频散与衰减 

分 类 号：P631.4[天文地球—地质矿产勘探]