虚拟偏移距方法在转换波叠前时间偏移中的分析与应用

摘要

虚拟偏移距偏移(POM)是一种新的转换波叠前时间偏移方法,是对等效偏移距偏移(EOM)的一种改进,它与EOM方法映射方式上虽然不同,但本质都是相同的,都是将原始输入道集映射成为共转换散射点道集.本文主要介绍了两种偏移方法的原理,通过理论模型来验证两种方法对模型参数的敏感性.在远偏移距情况下,为了能在速度分析中得到更精确的偏移速度,分别用小排列拟合的双曲线公式、三阶近似式、双平方根旅行时公式对映射后的POM道集做动校正,从而验证了三个公式的精度.最后用POM方法对复杂构造进行了叠前时间偏移.%Pseudo-offset migration (POM) is a new method for prestack time migration of converted waves that improves on equivalent-offset migration (EOM). The mapping of POM is different than EOM but the purpose of the two methods is to map the input samples to the common conversion scatter point (CCSP) gathers. This paper introduces the principles of the two migration methods and model parameter sensitivity tests for both POM and EOM. At large offset-to-depth ratios the hyperbolic approximation, the three-term approximation and the double square root (DSR) equation are used to NMO-correct the mapped POM gathers to obtain more accurate migration velocities. These equations were derived and calculated by small pseudo offset. POM is then used to image complex structure and prestack time migration.