基于走时的保幅偏移方法

振幅随偏移距变化是描述储层特征的重要方法之一，保幅偏移方法就是使偏移剖面能够反映出振幅随偏移距的变化.本论文中的保幅偏移是以走时为基础，主要的方法是采用走时的双曲线展开法，通过走时的二阶空间导数来确定波前曲率.该方法通过建立在大网格上的走时表来确定插值系数，将大网格插值成为较为精细的网格，这样就节省了数据的存储空间.对于相同的网格密度，通过插值来计算走时表比采用程函方程有限差分法直接计算走时要节省5至6倍的时间.走时的插值系数还可以用来计算几何扩散因子、权函数，不仅提高了成像质量，还大大节省了计算时间.

The study on amplitude-preserving migration

Amplitude versus offset information is a key feature to seismic reservoir characterization.Therefore amplitude preserving migration was developed to obtain this information from seismic reflection data.In this paper we present an efficient traveltime based strategy for amplitude preserving migration of the Kirchhoff type and mainly use hyperbolic traveltime expansion method.High accuracy is achieved because second-order spatial derivatives are included in order to acknowledge the curvature of the wavefront.The migration includes the interpolation from the coarse gridded input traveltime table onto the fine migration grid,thus reducing the requirements in data storage.The interpolation is 5-6 times faster than the calculation of traveltime tables using a fast finite differences eikonal solver.On the other hand,the weight functions and geometrical spreading can be directly computed from the interpolation coefficients.It not only increase the image quality,but also reduces the need in computational time.