| Seismic Numerical simulation is an important basis of Seismic exploration and seismology, which refers to a numerical simulation method of stimulatory investigating the prorogation rule of seismic wave through various underground medium and calculating the numerical seismic record observed at points on or under the ground, under the assumption that the structure model and the corresponding physical parameter are known.This paper mainly includes two aspercts of research..One is the wave equation numerical simulation and the other is the migration.Both of them are important technical means of oil and gas exploration.First of all, this thesis studies the basic theory of wave equation and induces the wave equation of acoustic wave and elastic waves in various formation from the constitutive equations,geometric equations and differential equation of motion. Secondly, based on preceding study, forward modeling and analysis of wave field characteristics to acoustic and elastic wave equation are conducted through finite difference method. Systematic study of important issues in the process of forward modeling like finite difference scheme, boundary conditions, steady condition and frequency dispersion is carried out.Secondly, starting with the second order scalar acoustic wave equation, Numerical simulation of acoustic wave equation is realized and a preliminary understanding of seismic wave field characteristics is acquired through finite difference method. Based on it, forward modeling of elastic wave equation is achieved and a comparative analysis to acoustic wave field characteristics is conducted. Meanwhile, a study on boundary problem in Wave equation numerical simulation is carried out.Lastly, a study on migration is conducted. The current development situation of migration is introduced above all, then the important theory in acoustic wave equation migration, that is continuation and imaging, is presented and two continuation operator of migration are induced. Thereafter, poststack depth migration and prestack depth migration are proceed toContinuation and imaging introduced by the application of founded P-wave velocity model,the result is evaluated, and the adaptability of migration operator and homing effect of geologic body is estimated. Finally, P-wave velocity model and Shear wave velocity model is established.Forward modeling is conducted by making use of elastic wave equations。At the same time, x、z component in migrated section is analyzed to acquire some characteristics of converted wave migration section. Some remained questions and the research direction in the future are also mentioned. |
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