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Cross-hole Seismic Wave Simulation By Compact Staggered Grid Finite Difference Method

Posted on:2013-08-17Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhangFull Text:PDF
GTID:2230330377951930Subject:Earth Exploration and Information Technology
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As the urgent needs for oil and gas exploration and production and the technicalimprovements of cross-hole source and receive, cross-hole seismic has beenbecoming one important technology to structure accurate imaging and reservoircharacterization and monitoring. The wave field of the multi-component cross-holeseismic data is terribly complicated, it is difficult to distinguish and separate the wavefield each other, and the feature of anisotropy is prominent and extensive, so theconventional imaging method based on isotropy theory can not meet the needs of highaccuracy and resolution imaging for cross-hole seismic reflection wave anymore. Inorder to solve this problem, this paper discusses the compact staggered-gridfinite-difference modeling of elastic equation for cross-hole seismic data. This paperderives completely the first-order coupled elastic equation of particle velocity andstress and the any order accurate time and space formulation of2D compactstaggered-grid finite-difference scheme based on the research of previous author.By simulating crosswell seismic wave field in different medium obtained thefollowing results:1.Compact staggered-grid can solution to boundary problem, numericaldispersion, stability problems of the finite difference numerical simulation,.Applingthe perfectly matched layer absorbing boundary conditions, the simulation resultsshow that: Perfectly matched layer absorbing boundary condition of compactstaggered grid finite difference method can well solve the problem of artificialboundary reflection; High order compact staggered grid can greatly improve thesimulation precision, reduce the numerical dispersion; Compact staggered grid finitedifference is a kind of implicit difference scheme with its unconditional stabilityproperties of effective solution of the finite difference numerical simulation stabilityproblem.2.When the random medium random perturbations is small, longitudinal wave front is the same as in a homogeneous isotropic medium, the wave front is smooth.ButWhen the random disturbance is large, the longitudinal wave front is rough in randommedium; The longitudinal wave front is smoother than shear wave wave front. Thecoordinate orientation of compressional and shear waves in random media aredistorted, shear wave front more seriously distorted than longitudinal wave front bythe scattering wave effect,so shear wave is more difficulity to identify thanlongitudinal wave in random medium.3.Compact staggered grid finite difference simulation cross-hole VTI mediumwave field shows that: Even with the longitudinal wave excitation, in VTI mediumwill generate shear waves, under certain conditions shear wave will appear wavefrontbifurcation phenomena, and the wave front is not a circular. All of these make thecrosswell seismic wave field complexly, so the subsequent data processing andinterpretation is difficult, but should certainly, VTI medium recording provides moreuseful information.4.Compact staggered grid simulation cross-well VTI medium quasi P wavepropagation process, obtained the accuracy of the simulation results, effective solutionto the elastic wave numerical simulation of wave field complex, the low ofcomputation efficiency, the elastic constants of physics significance is not clear andso on. Analysis of quasi P equation of kinematics and dynamics feather, the resultsshowed that: first order quasi P wave equation with sufficient precision to describeVTI medium quasi P dynamics features.5.Compact staggered grid simulation cross-well viscous elastic wave field theresults show that: with the propagation of seismic wave, viscous media on seismicwave energy attenuation, reflection wave amplitude was significantly attenuated, withthe axial energy become weak, dominant frequency moves to low frequency, and theeffective frequency band becomes narrow.
Keywords/Search Tags:compact staggered grid, random medium, VTI media, quasi Pwave equation, viscous elastic wave, PML
PDF Full Text Request
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