Automatic NMO correction and Full Common Depth Point NMO Velocity Field Estimation In Anisotropic and lateral heterogeneous Media

摘要

#$%^&*AU2016202792A120171116.pdf#####ABSTRACT Although several anisotropic traveltime equations have been written by different researchers to perform normal moveout (NMO) correction of common depth point (CDP) seismic gathers, none has been able to address the problems associated with the far offset data. In this paper, we present a computational process that, not only accurately flattens and NMO-correct the far offsets data to zero-offset times no matter how far, but simultaneously provide full NMO velocity (Vnmo) fields and corresponding anisotropy field. The method is based on doing a predefined number of NMO velocity iterations using linear vertical interpolation of different NMO velocities at each seismic trace individually. At each iteration, we measure the semblance between the zero offset trace and the next seismic trace, then after all the iterations are done, the one with the maximum semblance value is chosen, which is assumed to be the most suitable NMO velocity trace that accurately flattens seismic reflection events. The other traces follow the same process, and a final velocity field is then extracted. Isotropic, anisotropic and lateral heterogenous synthetic geological models were built based on a ray tracing algorithm to test the method. A range of synthetic background noise, ranging from 10 to 30 %, was applied to the models. In addition, the method was tested on Hess's VTI (vertical transverse isotropy) model and Alaska (gas field) pre-stack seismic CDP field example. The results from the presented examples show an excellent NMO correction and extracted a reasonably accurate NMO velocity field.