Comparisons between Buried and Laid Seabed Cable on the Valhall Field and Challenges Processing PZ and PS Data

Using buried cables can create significant issues with statics and spectra in processing Ocean Bottom Cable (OBC) data. These should be taken into account where possible in the processing, especially where there are variations in the depth of the receivers and when processed alongside receivers laid on the seabed. Differences observed can be explained by the differences in arrival times due to variations in depth and considering that for a buried receiver an upgoing event from below the receiver will have a ghost off the seabed. The recorded S-wave as used for PS converted-wave processing could also suffer from a receiver ghost with a large highly variable ghost delay time due to burial depth variations or variations in the velocity of the overlying sediment. These are difficult to correct, and, therefore, they have an undesirable impact on the final PS image. Using the up and downgoing wavefields, it is thought possible to get an approximate one-way time from the receiver to the surface, and, therefore, if the velocity is known, the depth of burial of the receivers, which could be utilized for static correction and perhaps to correct for ghost differences in future processing.