Forward Simulation Of Elastic Wave And Analysis Of Wave Field Characteristics In Anisotropic & Two-phase Medium

The worldwide experts in seismology attaches great importance to the research ofseismic wave propagation ,which is the basis for seismology, seismological, seismicprospecting and exploration and earthquake engineering .On the one hand,the scholarsof the geophysics have recognized that the sedimentary rock from the mantle to theupper crust have varying degrees of anisotropy;on the other hand, the traditionaltheory of seismic wave treat the subsurface medium as the single-phase mediumapproximatively,and actually the reservoir is the two-phase or multi-phasemedium.When the porosity of the rock and the elastic modulus and density of thefluids in the pore are large,the seismic wave theory based on single-phase media willhave large error.Thus the theoretical studies of seismic wave based on anisotropicmedia and multi-phase media has important theoretical and practical significance forthe complex exploration of oil and gas reserves.This thesis discusses the seismic wave theory of anisotropic and two-phasemedium in detail.Specifically, this thesis discuss and analysis wave fieldcharacteristics and mechanism of seismic wave propagation in the anisotropic andtwo-phase medium by establishing,solving in the way of numerical method andextending the wave equation.First,this thesis overview the research status quo of anisotropic medium theory,two-phase medium theory and numerical simulation technology. Unifyingpredecessor's researches, we derived the anisotropic media,viscoelastic anisotropicmedia,two-phase isotropic media and two-phase anisotropic medium's the secondorder partical differential wave equation with a displacement variable by using theCauchy equations,Hooke's Law and differential equations of motion. Second thispaper introduces and discuses the staggered grid high-order finite-difference method,including the boundary conditions,dispersion,differential format of the finitedifference method and the way of loading souce.Unifying predecessor's researches, weuse PML to deal with the artificial boundaries,use FCT to eliminate numericaldispersion and add the source on the velocity item. By solving the first-order velocitystressequations which is equal with the second order partial differential equations using staggered grid finite difference method,simulating the propagation of seismicwave of various mediums and analysising the multi-wave field of different geologicalmodels, we have understood better the law of the wave propagation in anisotropicmedia and two-phase media, which has some signigicances for distinguishing themulti-wave information.This thesis has extended the phase velocity,group velocity and energydistribution equation in the free and flexibility interface from elastic wave equation,because seismic wave dispersion,attenuation and the energy distribution law ofseismic wave propagation are very important issues of the theory of seismic wave.This part of the work include: we have derived Chrisotoffel equations of theanisotropic media and analyzed the phase velocity and group velocity with the changeof the phase and group angle when the Thomson parameter had different values; wehave derived the Chrisotoffel equation of the two-phase medium based on BISQtheory and studied the relationship between the phase velocity of elastic waves,Qfactor and frequency,porosity,permeability,saturation and the direction of wavepropagation; Jointing the wave equation of two-phase isotropic medium based on theBiot thory and four boundary conditions, we have proved the Mou's equation anddiscussed the AVA characteristic curves of the top reservoir interface,the interfacewithin the reservoir and the bottom reservoir interface, which is compared with theresult calculated using the single-phase medium's Zoeppritz equation, at the same timewe have analysed the AVA curves changes with the reservoir porosity.Through theanalysis,we further understand the elastic wave attenuation characteristics and thedegree of influence about elastic wave caused by reservoir parameters,which isfoundation for inversing lithology parameters using multi-wave joint prestack AVAand identifying the reservoir parameters and fluid parameters.Finally,this thesis has established layer model without dissipation based on Biotthory using reservoir parameters of a certain well in the region of Miyan of Henanoilfield,have simulated the wave field records using high-order staggered-grid finitedifference technique and have analysed the impact of common shot records caused bythe change of porosity and AVA characteristic curves of each interface.Overall, this paper analysis the wave field characteristics and seismic wavepropagation characteristics of the anisotropic medium and two-phase medium usingforward simulation, the research results have a reference value for studying the seismicwave propagation and understanding the seismic wave propagation,and have practicalapplication value for the seismic exploration and development in the complex media,forecasting the oil and gas,etc.