Reflection And Transmission Of The Elastic Waves At A Fluid/Patchy Saturated Rock Interface

The propagation of the elastic waves at a fluid/fluid-saturated poroelastic solidinterface has been the concern of many researchers in many fields. Such as seismicexploration, rock physics, soil engineering, underwater acoustics, etc. Such problemsnot only have important academic theoretical values, but also have major guidingsignificance in engineering applications. Reflection and transmission of the elasticwaves at a interface of a poroelastic solid has always been an important branch ofacoustic research.In recent years, results of series of researches have been made about seismicwave propagation in porous fluid-saturated medium. From the overall point of view,the developmental trend of the basic theory has experienced through:(1) the simplestmodel of the single-phase fluid,(2) the two-phase solid and liquid fluid model,(3) thecontaining crack model in porous media. On the basis of heterogeneity scale, theexisting wave theory of porous medium can be divided into three broad categories：(1)macroscopic scale(2)mecroscopic scale(3)microscopic scale.Recent years, compared macroscopic with microcosmic scale, most researchersagreed that the mesoscopic scale of porous media model can better explain thefrequency dispersion and attenuation problem of seismic wave and generally believedthat the mechanism has magificant applicational value for engineering problems inseismic exploration in geophysical field. At present,The characteristics and disciplineof the reflection and transmission of elastic wave at heterogeneous saturated porousmedia interface were very few. In this article,we adopt Patchy saturated rock acousticmodel(Pride2004) and research into the attenuation and frequency ofdispersion,reflection and transmission characteristics of elastic wave at the interfaceof a fluid/Patchy saturated rock in mesoscopic scale.Firstly, the basis of the research in this paper is Biot theory. We make athorough comprehension of the Biot model and its related model----Biot-Stoll modeland Patchy saturated model, and all kinds of wave phenomenon in porous media.Secondly, based on Pride-Patchy saturated rock acoustic model, the Helmholtz potential functions are used,for deduction of reflection and transmission theoreticalformula of elastic waves at a fluid/fluid-saturated poroelastic solid interface, and thefomula of refraction and reflection coefficient of fast compressional wave and slowcompressional wave and transverse wave displacement and energy,etc. Then,calculate the frequency dispersion and attenuation of elastic wave on Patchysaturation model. The last procedure is the calculation of refraction and reflectioncoefficients of the elastic waves at a fluid/Patchy saturated rock interface.The results show that in the heterogeneous fluid in saturated rocks,displacemental reflection coefficient, energy reflection coefficients, the verticalincident displacement refraction coefficient of seepage, the energy interferencecoefficient of fast and slow compressional wave and shear wave change as thevariation of saturation of water. Among them, the heterogeneity of gas-water saturatedcondition, the value of the refraction and reflection coefficient are greatly influencedby water saturation. However, the water saturation has relatively small impact inheterogeneous oil-water refraction and reflection coefficients effect.This article research is helpful to comprehend the characteristics of attenuationand dispersion,reflection and transmission of elastic wave at a fluid/Patchy saturatedrock interface. In further, it has practical engineering significance on seismicexploration and acoustic logging application and interpretation.