Migration Velocity Analysis in TI Media

Isotropic migration velocity analysis is routinely applied to production data. However, the search for an anisotropic model could further improve depth imaging results. We propose a tomographic approach to anisotropic parameters estimation which is completely based on PSDM and on the CIG flattening principle. We show on a simple synthetic model how it is possible to use the non-hyperbolic moveout of CIG events to invert for anisotropic parameters. We compare the results of two processing techniques: the first method consists of isotropic analysis at short offsets and anisotropic analysis using longer offsets, the second method is a joint tomographic inversion of the anisotropic parameters using all available offsets. The inverted models are then rescaled using well misties, providing an estimation of vertical velocity. The results of the two techniques show similar imaging quality, but the joint inversion provides slightly improved focusing and a more accurate Thomsen parameters estimation after well mistie correction.