共散射点道集与角道集串级优化叠前偏移速度分析

摘要

推导了基于角度域共成像点道集的叠前深度偏移层析速度分析公式,提出一种共散射点(CSP)道集与角道集串级优化叠前偏移的速度分析方法.该方法通过基于CSP道集的叠前时间偏移速度分析获取初始速度,利用基于角度域共成像点道集(ADCIGs)的叠前深度偏移速度分析进行速度更新.实现步骤概括为:将叠前地震数据映射为CSP道集,利用CSP道集叠加速度谱拾取能量团获取均方根(RMS)速度场；通过Dix公式将RMS速度转换为层速度作为层析的初始输入速度,基于ADCIGs实现叠前深度偏移层析速度反演,最终得到高精度的叠前偏移速度场.断层模型和实际资料试算结果验证了该方法的正确性和有效性.%This paper derived a formula to analyze tomographic velocity in pre-stack depth migration based on angle domain common imaging gathers (ADCIGs) and proposed a pre-stack migration velocity analysis method using sequent optimization which gets the initial velocity through the pre-stack time migration velocity analysis on the basis of common scattering point (CSP) gathers and obtains velocity update through pre-stack depth migration velocity analysis on the basis of ADCIGs. The implement steps can be summarized as follows: (l)mapping pre-stack seismic data to CSP gathers and getting root-mean-square velocity by stack velocity spectrum of CSP gathers; (2) transforming root-mean-square velocity to interval velocity in order to model the initial tomography velocity field; (3) obtaining pre-stack migration velocity field by pre-stack depth migration tomographic velocity inversion based on ADCIGs. Examples of fault model and field dataset proved the correctness and validity of this method.