Improved Imaging of Deepwater Reservoir by TTI Model Building and Optimized Use of OBN Data

Abstract

Over the last decade, ocean bottom nodes (OBN) acquisition became the preferred solution for acquiring seismic data over deepwater mature reservoirs in highly congested by production related infrastructure areas. Today, it is widely accepted that OBN data will play important role in the life cycle of many mature reservoirs around the globe. We present an imaging case study from OBN data set shot over a deepwater mature reservoir offshore Nigeria. We describe the initial anisotropic model building strategy, based on narrow-azimuth towed-streamer data and aimed to ensure on-time delivery of fast-track depth image of the downgoing wavefield shortly after the completion of the OBN acquisition. We show the improvements in model resolution arising from the transition to tilted transverse isotropy (TTI) and the use of the downgoing wavefield mirror-migrated data for wide-azimuth, high-resolution, multiscale tomographic updates. We demonstrate that the enhancements achieved in the data reprocessing, together with the optimum use of the advantages OBN data offer in model building, enable producing of high-resolution TTI model and yield improved quality of the final images. The results of the TTI imaging exercise with reprocessed OBN data lead to better understanding of the reservoir and, therefore, to better interpretation.