Wave Field Modeling In Viscoelastic Anisotropic Media And Reservoir Information Study

With the improvement in data quality and the use of new exploration technique, the correct description of the real media and the seismic wave field have become more important. Different media model, including acoustic rheology, elastic isotropic rheology, viscoacoustic rheology, viscoelastic rheology, elastic anisotropic rheology, fluid-saturated porous rheology, etc, have been introduced in seismic modeling study. Each of rheologie can descript real media to some extent. The introduction of more suitable rheology can benefit the acute description of real media and study of wave phenomena. Viscoelastic anisotropic rheology can descript anisotropy induced by thin bedded sediments, oriented-array fractures, etc, as well as anelasticity induced by fluid filled in porosity and fractures. New wave phenomena associated with these factors can also be studied through viscoelastic anisotropic theory.1.Wave equations are developed through basic equations for qP,qS and SH waves in viscoelastic anisotropic media. Then the reasons for attenuation of wave field are discussed. The effect of viscoelasticicy and anisotropy on the propagation of wave in viscoelastic anisotropic media are studied through snapshots, seismograms, and vector maps of qP,qS and SH waves achieved by wave field simulation using pseudospectral method in viscoelastic anisotropic media. Elastic and isotropic wave fields can also be modeled, according to limiting input parameters of media to elastic or isotropic characters. Therefore, difference characters across reflection interface are available when modeling waves associated with reflection and transmission.2. Phenomenon of reflection and transmission of waves are one of the most basic problems in seismic exploration. This phenomenon is fully studied though wave field simulation and calculations of reflection and transmission coefficients for the reflection interfaces models, including viscoelastic anisotropic interface, viscoelastic anisotropic thin layer, and the interface between viscoacoustic fluid and viscoelastic anisotropic solid. Changes of amplitude and phase of reflection and transmission waves compared with incidence wave, as well as the phenomenon of critical angle are studied through complex reflection and transmission coefficients. The result can benefit the studies of wide-angle reflection, studies of features of reflections from the interface between overburden and reservoir and from thin bedded layer, and studies associated with viscoelastic anisotropic sea floor reflection.3. Petrophysics is the bridge between seismic data and reservoir characters and is playing a crucial role in direct detecting technologies of hydrocarbon. The effects of reservoir parameters such as oil- gas- or water-saturation, porosity, content of kerogen, and pressure of underground layers, etc, on seismic features such as P-, S- wave velocities have been investigated through petrophysics models viscoelastic anisotropic reflection and transmission theory. Then AVO response of thin bedded reservoir according to various seismic features has been studied on the basis of thin layer reflection dynamics and AVO theory for viscoelastic anisotropic media. Petrophysics models include Gassmann equations, Backus averaging, and pressure gradient zones.4. The topic of anisotropic attenuation in viscoelastic anisotropic media has been investigated. AVO technology detects lithologic characters across reflectors by analyzing reflection coefficients, however, data received on the ground surface may include both reflection information and anisotropic attenuation information for deep reflector because of the viscoelastic anisotropic rheology of overburden. Thus, the effect of anisotropic attenuation of overburden on AVO analysis has been detected through the designed overburden/reservoir model.