Subsalt Velocity Update and Composite Imaging Using RTM-based DIT Scan

摘要

Subsalt wave-equation based migration (WEM) scan is an effective way for subsalt velocity updating, and has become an industry standard practice, however, the cost of generating migration scan is still comparatively high. With the more expensive Reverse Time Migration (RTM) gradually becoming a outine migration tool, this standard subsalt scan approach, becomes impractical. In this paper, we propose a new methodology for updating subsalt velocity using RTM-based scan with a range of variable time maging conditions (Delayed Imaging Time or DIT scan). The generation of the RTM-based DIT scan equires only a single pass of RTM. We generate a set of RTM scan images by applying zero-time as well as non-zero time imaging condition. Synthetic and real data testing confirm the effectiveness of this new approach and suggest this DIT scan approach could serve as an efficient alternative or even a replacement o the standard subsalt migration scan approach for RTM.