WAZ Mirror Imaging with Nodes for Reservoir Monitoring – Dalia Pilot Test

Repeated marine seismic recorded with towed streamer have been proved successful for imaging reservoir productions. Unfortunately major infrastructures (FPSO) constitute a “blind zone” for the reservoir illumination from the sea surface. Because undershooting surveys come with repeatability and HSE issues, nodes imaging appears to be a valuable solution. In 2009 a deep water nodes surveys was acquired by Total Angola. Since “Base” surveys are acquired usually with marine streamers, the first objective of this paper is to find out how to reconcile nodes and streamer data in order to provide comparable images. The second objective is to propose an azimuth compliant processing approach valid for an optimum node WAZ mirror imaging. Two original processing approaches are described: firstly, data cross-matching is done in angle domain in order to provide similar ray path and equivalent sea surface offset. Secondly, we show that the concept of offset vector binning using hexagonal tiles is applicable to the nodes acquisition geometry. Mirrored data migration in common offset vector domain provides CIGs with preserved offset and azimuth information. Post-migration processing like full azimuthal residual move-out and azimuthal illumination selection can then be applied for an optimal reconciliation between nodes and streamer data.