PS Converted-Wave NMO Correction and Its Application to Improve PS Reflection Imaging Quality of VSP Data

Summary We have developed a new three-term formulation of normal moveout (NMO) correction for PS converted reflection waves in VSP data. The formulation is accurate for multi-layered media with a large source offset (up to a ratio of ∼2.5 of offset to reflector depth) in VSP survey. Based on the new NMO correction formulation, we also developed a new methodology to improve signal to noise (S/N) ratio and the final imaging quality of PS converted reflection waves in VSP data. The methodology consists of three major processing steps in the common receiver gather domain: NMO correction for flattening/aligning PS converted wave reflection events, median filtering for attenuating coherent and incoherent noise, and reverse PS NMO correction for migrating PS converted reflection waves. The processing of a field walkaway VSP dataset with our methodology demonstrates the effectiveness of the methodology in improving the imaging quality of PS converted reflection waves.