Subsalt velocity update using RTM‐based DT scan

Abstract

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 routine 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 imaging conditions (Delta‐T or DT scan). The generation of the RTM‐based DT scan requires 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 DT scan approach could serve as an efficient alternative or even a replacement to the standard subsalt migration scan approach for RTM.