Resolving Shallow Reef Effect with New Water Layer Demultiple Method and Diving Wave Tomography: A Case Study from South China Sea

The survey with shallow reef is located at the Pearl River Mouth Basin of South China sea. Water depth is around 100 meters but variable across the survey. The shallow reef is in the middle of survey. It is about 14km width and 10km length spatial size. With such huge spatial size, it had posed big challenges to subsurface reservoir imaging. Firstly, the variable water bottom generates complicated water layer related multiples, especially at the shallow reef area. Meanwhile, with limited near offset information in the legacy NAZ data, accurate water layer multiple model is very difficult to predict with conventional methods. Secondly, the shallow reef mainly composed of carbonates, which have higher velocity compared to surrounding sediments. This high velocity carbonates thus cause severe distortion to the wave field propagated through and severely distorted the underlying reflections. Without correct imaging of reef at shallow, little confidence can be brought to deeper structures imaging, and interpretation.