Using 3D4C Data to Image and Interpret theSeismically Obscured Area over the TommelitenAlpha Discovery

摘要

Ahigh density 3D4C seismic survey was acquired over the TommelitenAlpha gas condensate discovery in2005 to image a seismically obscured area caused by complex velocity and density variations in theoverburden. Both full azimuth PP and PS data were used and pre-stack co-depth migrated. The result wasan improved image of the previously obscured area, especially in the PS dataset. The size of theSeismically ObscuredArea (SOA) was reduced also in the pre-stack depth migrated PP data, but in thisouter part of the SOAthe PP data gave a different image compared to the PS dataset - making theinterpretation challenging.Although the resolution of the PS data is lower at the target level, and the mainEkofisk Fm reservoir target (21-24m thick) is below PS seismic resolution, the PS dataset proved veryuseful in mapping the structural shape and faults inside the SOA, leaving only a small central areaobscured.