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虚拟偏移距(POM)偏移方法是基于Kirchhoff积分的叠前时间偏移方法,这种方法具有改善共反射点模糊成像的优势,较少依赖速度模型,具有良好的振幅保持能力,计算成本相对较低,且在横向速度变化不太剧烈的情况下能够取得较好的成像效果,是转换波叠前时间偏移的一种重要方法.因POM方法是通过将地震波旅行时的双平方根(DSR)方程转化为以虚拟偏移距为变量的单平方根双曲线方程,这种方法的虚拟震源与虚拟检波器并非并置在一起,其传播路径符合Snell定律,可抽取真正的共转换散射点(CCSP)道集,该道集不需要倾角时差校正(DMO),形成CCSP道集的过程就等于叠前时间偏移的过程.随着AVO技术的发展,振幅的保真性在偏移过程中越来越重要.本文详细分析了初始速度、虚拟偏移距和偏移孔径对共转换散射点(CCSP)道集的影响.通过转换波POM保幅成像模型试算,结果表明,利用虚拟偏移距进行叠前时间偏移时,选择合适的虚拟偏移距间隔和偏移孔径至关重要.
The POM offset method is based on Kirchhoff integral prestack time migration method. This method has the advantages of improving the common reflection point fuzzy imaging, less dependent on the velocity model, good amplitude holding ability, computational cost Which is relatively low and can obtain better imaging results under less severe lateral velocity changes.It is an important method to convert the prestack time migration waves.The POM method is based on the double square root DSR) equation into a single square root hyperbolic equation with a virtual offset as a variable. The virtual source and virtual detector of this method are not collocated and their propagation paths are in accordance with Snell’s law, so the real co-conversion scatter points (CCSP) gathers, which do not require dipole moment correction (DMO), the process of forming CCSP gathers is equal to the process of prestack time migration.With the development of AVO technology, the fidelity of amplitude The impact of initial velocity, virtual offset and offset aperture on the CCSP gathers is analyzed in detail.Through the POM amplitude-preserved imaging model of the converted wave, the experimental results show that using the virtual When the offset for prestack time migration, the virtual select the appropriate offset aperture critical interval and offset.