Method Study Of Elastic Wave Numerical Modeling Under Complex Surface Conditions

At present, Oil and gas exploration is turning to the areas with irregular topography and complex geologic structures, and the conditions of complex surface seismic exploration is a global problem in China's western region. Complex surface fluctuation and weathering belt have great impact on the results of the seismic data processing, the impact of simple topography can be very good eliminate by static correction, but complex surface topography of the scattering and the rolling waves of seismic records of serious pollution and distortion can not be eliminated by simply static correction. So the study of surface seismic numerical simulation method for understanding seismic wave propagation regularity on complex near-surface condition, the elimination of surface topography on the impact of seismic data, and the study of the pre-stack depth migration seismic imaging method basing on the rolling topography have very important significance. In this paper, basing on the previous work, using FDE method to numerical simulate and characteristics analysis for the seismic wave equation under the conditions of complex surface.First, this paper outlines a variety of seismic wave numerical simulation method in the complex surface conditions. In order to analyze the rolling topography of the impact of direct wave and reflection wave, using coordinate transformation of the principle of relations between the coordinate mapping, deriving the second scalar acoustic wave equation under the mapping coordinates, analyzing of the rolling topography of the impact of the energy and wave amplitude, frequency spectrum of the direct wave and reflection wave. This paper also derived the no reflection wave equation under the conditions of complex surface, and achieved a post-stack numerical simulation and reverse migration.For the numerical simulation of elastic wave under the conditions of complex surface, this paper has a band of elastic wave equation numerical solution using the variable grid and the staggered grid with high-order finite difference method, then using the irregular undulating surface of the medium staggered grid finite-difference algorithm deals with the fluctuation free boundary. Through the elastic wave equation numerical simulation results of the typical fluctuation surface and near-surface velocity mode, understanding and analyzing the characteristics of seismic wave field, main types of seismic waves and seismic wave propagation, thus the near-surface analysis of the impact of reflected wave field.