FWI imaging of complex subsalt Mesozoic targets from land to shallow waters

Significant exploration and development interest exists in the subsalt Mesozoic sections in the transition zone (from land to shallow water) of the southern Gulf of Mexico, where seismic imaging is particularly challenging due to the complexity in geology and available data. Many data sets cover this region, including coarse Ocean Bottom Cable (OBC), narrow-azimuth OBC, transitional, and sparse onshore surveys. The topography and acquisition variations pose challenges in building accurate velocity models and make it difficult to achieve the correct phase and amplitude for conventional imaging methods like Reverse-time Migration (RTM). We used Time-Lag FWI (TLFWI) to build a seamless velocity model from one land, two transitional, and three shallow water data sets, which resulted in substantially more coherent RTM images. FWI Imaging further naturally harmonized the various data types by inverting for a common subsurface reflectivity, resulting in a more geophysically accurate merge of the different surveys. The results demonstrate how TLFWI can generate a much improved and seamless model and an FWI Image of the subsurface that is, for the most part, agnostic to the input data set and surface topography (land or marine).