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远年来,波动方程偏移技术已经有了很大的发展。随着勘探工作的复杂化,要求有更完善的偏移技术。针对横向变速层的地质模型,有限差分法较其它方法有独到的优点,差分网格可以灵活地区划变速空间,而在每个网格之内只要求速度恒定。但是,传统的有限差分方法也有它的局限性,15°有限差分在降阶时忽略了波场对深度的二次导数,45°有限差分在降阶时忽略了波场对深度的三次导数,它们均没有实现全波动方程偏移。鉴于这种情况,本文提出一种新的方法——共轭偏移法,通过把一个全波动方程差解成两个低阶微分方程,一次共轭迭代,基本实现了全波动方程偏移。通过理论模型的试算和实际资料的处理,证明了共轭思想是成功的。
In recent years, the wave equation migration technology has been greatly developed. With the complexity of exploration work, more sophisticated offset techniques are required. The finite difference method has unique advantages over other methods for the geomechanical model of the transverse speed change layer. The differential grid can be used to divide the speed change space flexibly, but only the speed is required to be constant within each grid. However, the traditional finite difference method has its limitations. The 15 ° finite difference ignores the second derivative of the wave field when it is reduced, while the 45 ° finite difference ignores the third derivative of the wave field when it is reduced. None of them achieved full wave equation migration. In view of this situation, this paper presents a new method, the conjugate offset method, which basically achieves the full wave equation migration by decomposing a full wave equation into two lower order differential equations and a conjugate iteration. Through the trial calculation of the theoretical model and the processing of the actual data, it is proved that the conjugate idea is successful.