Resolving the Challenges of Imaging Steeply-Dipping Reservoirs Against a Complex Salt Diapir

The Mungo field in the North Sea is both structurally and stratigraphically complex - salt diapirism has resulted in large dips on the Palaeocene and Cretaceous reservoirs that drape the flanks of the salt intrusion. To improve the imaging, two adjacent ocean bottom surveys were conducted between 2010 and 2011. Despite improvements over the legacy towed streamer data, interpretational challenges, particularly with respect to the salt geometry, remained. Overcoming these challenges was crucial for field development. To achieve the required improvement in imaging within the project's short timeframe, a high degree of technical content had to be adopted to provide early access to a consistent, demultipled dataset that would be used to update the velocity model. Key challenges were the highly channelized nature of the near-surface, the poor ties of the highly deviated wells to the existing seismic data, contamination of the target interval by interbed multiples and poor salt flank imaging. These objectives were achieved by employing a robust pre-processing sequence, including up-down deconvolution, along with an iterative approach to the velocity model build, utilising GWI, FWI, high-density tomography and anisotropic information derived from the PS data.