The Study Of Wave Equation Finite Differential Datum Correction Method For Irregular Topography

With the development of the oil-gas exploration technology and the change of theexploration area, the problem of irregular topography becomes a global problem. Theproblems of irregular topography mainly reflect in the following aspects: First, the surfaceelevation changes tremendously. Second, the near-surface velocity changes rapidly,high-speed layer expose to the surface, and the surface lithology is complicated. Theseproblems lead to the serious interference wave, even reflected wave changed seriously, and soon. Generally, the problem of irregular topography is solved by statics correction, but thehypothesis of statics correction is often surface consistency which dose not apply for theproblem of complex surface. The wave equation reverse-time extrapolation datum correctionmethod is of importance in removing the influence of irregular topography and low velocitylayer.Combined with the perfectly matched layer absorbing boundary condition, therectangular grid finite difference method and the irregular triangular grid finite differencemethod are used to solve the wave-equation, and achieve the numerical simulation ofseismic wave propagation in a model with irregular topography. The rectangular grid finitedifference method is poor to describe the condition of irregular topography. However, theirregular triangular grid finite difference method has the advantage of describing theirregular topography. It can describe the shape of irregular topography more accurately, andcalculate more quickly. In addition, it is compatible with the irregular triangular grid finitedifference method. Therefore, this method could be thought as an effective improvementover the conventional rectangular grid finite difference methods. These two methods supplythe basis for wave-equation datum correction. This paper uses the wave-equationreverse-time extrapolation datum correction method. The reverse-time extrapolation is animportant part of reverse-time migration. This method has advantages of guaranteeing thetruth of seismic amplitude and phase, and is fit for the lateral velocity variation, and so on.The result of reverse-time extrapolation datum correction of theoretical model and realitydata prove the validity of the method, it can work well in solving the problems of the deformation of seismic wave and the unbalanced energy which is resulted from complicatedsurface. It perfectly reserves the dynamic characteristics during the propagation of seismicwave which establishes good basis for migration.