WIDE-OFFSET-RANGE PRE-STACK DEPTH MIGRATION METHOD FOR SEISMIC EXPLORATION

摘要

A method for using long-offset seismic reflected phases with offset to depth ratio > 1:1 (up to 3:1/1:1) for depth imaging through tomographic velocity analysis and pre-stack depth migration is disclosed, which involved the development of techniques: - to properly handle a number of seismic phases at a wide range of offsets, including long-offset arrivals (i.e. continuously refracted diving waves, head waves and reflected waves); - for tomographic velocity model update within the framework of migration velocity analysis for near vertical and wide-angle reflected phases including treatment of non-hyperbolic move-out; - to identify and distinguish the wide-angle reflected phases from the conjugated refractions at long-offset; - to reduce the effects of spatial aliasing during pre-stack depth migration and allowing the use of limited migration angles even in the presence of dipping reflectors.