Pre-Migration Receiver Deghosting and Amplitude Fidelity: A Case Study From NWS Australia

Abstract

Pre-migration receiver deghosting has gained significant momentum and wider acceptance in the seismic industry in the past two to three years. With increasing experience, interpreters are beginning to enjoy the benefits broadband data brings: richer texture, higher resolution, smaller frequency gap between migration velocity and migration volumes, and so on. So far the bandwidth benefits have been the key focus and has been studied thoroughly by many people in the industry. The impact on amplitude fidelity has also been studied but to a lesser extent. In this work we demonstrate the impact of pre-migration receiver deghosting on amplitude fidelity by mitigating the amplitude distortions caused by receiver depth variations during acquisition. An analysis was performed on several saillines extracted from a shallow water, North West Shelf Australia 3D survey acquired using streamers apparently deployed at a constant 6 m depth. The input to the analysis was after full preprocessing including demultiple. In actual fact, recovered field navigation data showed that the receiver depths actually varied widely, between 1.1 m and 13 m. A QC of these data also revealed significant and odd amplitude variations and these correlated with the recorded receiver depth variations. Synthetic tests confirmed the amplitude variations were due to the receiver ghost effect. Pre-migration receiver deghosting was shown to greatly improve the amplitude fidelity of this dataset when using the recorded receiver depths. This potentially adds value to all existing acquired data, especially older acquisitions where cable depthing isn't as good as recent acquisitions. We also showed that the amplitude variation itself can act as a good indicator for receiver depth. Checking the amplitude pattern before and after deghosting can be a good QC for receiver depth especially when the non-zero notch frequency is difficult to see.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015