Multi-Wave (Including VSP) Velocity Analysis And Nmo Correction Imaging

Because of the ray asymmetry of the downgoing and upgoing waves, the velocity analysis ,NMO correction and CMP stacking based on the CMP gather cannot be adapted to that of the converted wave(CCP). Converted wave data processing is more complicated than a single P-P wave reflection data processing. Main difficulties come from the accurate sorting and high-precision velocity analysis of CCP bins.Conventional NMO correction will generate serious stretch at long spread event. In this paper, we describe a new implementation of the NMO correction that is applied to P wave reflection data ,which called nonstretch NMO. We illustrate the use of nonstretch NMO by applied it to synthetic data and get good resistent stretch effect.Based on the previous work, this paper introduces two velocity estimation factors on the resolution of velocity analysis and has realized two high resolution velocity analysis methods—the convariance measure and selective correlation. Furthermore, both of them were used in converted wave velocity analysis and VSP velocity estimation. Meanwhile, it aims at the conversion point formula and chooses the best conversion point solution formula, which is applied to CCP gather sort based on the time window. This process is going along with the two high resolution velocity analysis methods in order to achieve the converted wave velocity analysis.To solve the problem of VSP velocity analysis, we sort the VSP data based on common geophone gather, and conduct the velocity analysis procedure on this kind of gather. The result on synthetic data show that the two velocity analysis methods introduced in this paper obtain a higher resolution in time and velocity compared with conventional velocity estimation factors.