基于双曲线校正的偏移距VSP速度分析

Non-zero offset VSP velocity analysis based on hyperbolic correction method

本文引入了一种VSP速度估算方法——基于双曲线校正的VSP速度分析方法,它将VSP记录沿反射波射线路径按时间外推成地面地震记录,然后利用上行波,按地面双曲线公式,给定一系列叠加速度,在共炮点道集内进行速度扫描,制作叠加速度谱,然后根据动校正结果的好坏,来估算地层的均方根速度.这种方法与常规的利用下行直达波计算速度相比,可以获取视观测井段以下的地层速度,并且获取的速度与地面地震的叠加速度一致,有机地将VSP与地面地震结合起来.

In this paper,a method called hyperbolic curve based VSP velocity estimation for estimating VSP velocity is introduced. It extrapolate the VSP record along the reflection ray path according to time to get surface seismic record. Then set a series of stack velocities to apply velocity stack on up-going wave using hyperbolic curve formula to get velocity stack spectrum in common shot gathers,and estimate the square root velocity by the NMO correction effect. Comparing with conventional velocity computing method that use down-going wave,this method can compute velocities of strata that deeper than the VSP sensor can reach, and the velocities computed using this method are the same with surface stacking velocities,so that to combine VSP with surface seismic survey.