Seismic Monitoring Combining Nodes and Streamer Data on Dalia field

Dalia (Block17, Angola) is a deep offshore turbidites field composed of confined (channels) and unconfined deposits (lobes), which are imaged by a high quality 3D seismic data set dated from 1999. During this first seismic monitor acquisition over the Dalia field in 2008, three types of acquisition were performed: a conventional 3D towed streamer acquisition in the non obstructed areas, a dual-vessel towed streamer acquisition and an OBN (nodes) acquisition to undershoot the field obstructions (FPSO, loading buoys, drilling rigs). Different types of processing were performed on nodes data using the up-going and the down-going wave fields. Warping and 4D interpretation were made with these cubes in order to see the best 4D workflow. Among the tested processing products, the nodes down-going wave field data set with the Common Offset Vector migration deemed to offer the following advantages: 1- A broadband frequency content, which allows a better 4D resolution. 2-Less noise and a better 3D image. 3- Lower 4D Noise and residual time shifts. On Nodes data, larger extensions of depletions anomalies are observed in consistency with the main sandy deposits (negative DV/V) due to incremental production between streamer undershoot and nodes acquisitions (2-6 months).