双相介质分界面上弹性波的反射与透射

本文基于Biot理论,推导出Zoeppritz形式的双相介质分界面上弹性波的反射与透射公式,对单相Zoeppritz公式与双相反射系数公式进行了比较,对双相介质含油、水、气不同流体时的反射规律以及孔隙度、渗透率、饱和度等储层参数对纵波反射的影响进行了研究.数值模拟分析表明,双相与单相反射公式的主要差异在于双相介质反射公式中考虑了液相、固液耦合相弹性模量的影响;油砂、水砂、气砂岩的慢P波反射差异明显;快P波反射对孔隙度的变化敏感,饱和度次之,对渗透率和频率的变化不敏感.

Reflection and transmission of elastic waves from a boundary of two-phase media

Based on Biot's theory,the Zoeppritz-style reflection and transmission coefficients of elastic waves from a boundary of porous media are deduced.The comparison between the one-phase Zoeppritz equation and the two-phase reflection equation is studied.The reflections in oil,gas or water bearing sandstones and the influence of porous medium parameters on P-wave reflection are also analyzed in this paper.The numerical examples indicate that the main difference between the one-phase and two-phase reflection equation lies in adding the fluid elastic modulus and the fluid-solid coupling modulus to the two-phase reflection equation.The reflected slow P-waves are distinct in three different fluid-saturated sandstones.The reflection of fast P-wave is most sensitive to the porosity variations,less sensitive to the saturation variations and least sensitive to the permeability and frequency variations.