基于角度域转换波的叠前深度偏移

Converted-wave Pre-depth migration based on angle domain

在偏移速度分析领域,共成像点道集对偏移速度分析(MVA)而言是非常重要的.目前,用于偏移速度分析的共成像点道集主要有偏移距域共成像点道集(ODCIG)和角度域共成像点道集(ADCIG).由于ODCIG是一种能量聚焦型道集,且在复杂介质条件下存在运动学假象,使其在MVA中的应用受到限制.ADCIG的出现解决了这些问题,它能够适应射线传播的多路径现象,避免假象的产生,波动方程偏移得到的ADCIG被证明是没有假象的道集,也被认为是当前最为合理的道集.论文在CMP域,利用双平方根算子对记录波场进行反向延拓,因为双平方根算子偏移具有倾角假频少、边界处理简单、无需求取震源子波、无需考虑偏移孔径问题以及计算效率高等特点;在频率-波数域将偏移距信息映射到角度域得到ADCIG.ADCIG的提取过程实际是转化了地震数据中的多偏移距信息,本质上,它仍旧是对地震数据中多偏移距信息的体现.最后论文将ADCIG道集应用在SEG/EAGE岩丘模型中,结果表明,不同反射角下的ADCIG可以对地下不同的区域进行成像,且角度域成像具有地震波成像剖面分辨率高,边界干扰较小等特点.

In the field of migration velocity analysis,common imaging point gathers is very important for migration velocity analysis（MVA）.At present,the common imaging point gathers used for migration velocity analysis mainly contains offset domain common image gathers（ODCIG）and angle domain common image gathers（ADCIG）.Since ODCIG is an energy-focusing gather,and there is the kinematics illusion in a complex medium, which leads to its application in MVA restricted. The appearance of ADCIG can solve these problems,it can adapt to multipath propagation of radiation,avoid artifacts produced.The ADCIG obtained from the wave equation migration method was proved to be a gathers which is no illusion,it is also considered the most reasonable gathers currently.In the CMP domain,the author make use of the double square root operator to reverse extension wave field records in this paper,because the migration using double square root operator has an superiority of less aliasing,a simple boundary treatment, without obtaining source wavelet,without consideration migration aperture and a high computing efficiency;In the frequency-wave number domain,the offset information is mapped to the angle domain,then I can get ADCIG. The actual extraction process of ADCIG is transforming the seismic data multi-offset information;in essence,it still is a reflection for multi-offset information of seismic data.Finally,this paper applied the ADCIG gathers to SEG/EAGE rock dome model,the results show,the result of imaging from different reflection angle in ADCIG can be imaging for different areas of underground,and imaging in ADCIG has a feature of high-resolution cross-sectional imaging of seismic waves,less boundary interference.