Water Bottom Channels’ Impact on Pre-stack Depth Migration on Elgin Field, North Sea

This paper shows a case study where sea bed glacial channels have a strong influence on the imaging of the tilted blocks constituting the gas field located below 5000m. 2 models were built with the CGGVeritas tomographic software: the first without the channels, the second with the channels in the first 500 meters. The channels were input using a 1D method and then refined by tomography using the residual move-out of depth gathers down to 2000m. As velocity and anisotropy had to be found in those layers, additional iterations were necessary. The final result was a better structural aspect and a better imaging of the faults separating the panels of the field.