Revisiting Multi-Azimuth data using Reverse Time Migration and Vector Offset Output
Mark McCluskey, Olivier Hermant, Alessandro Tansini, and Alaa Khodeir
Multi azimuthal acquisition (MAZ) and processing has been popular in the Nile delta and Mediterranean basin as a solution to sub Messinian imaging problems. It is this Messinian layer that causes frequency loss, multiple contamination and migration artifacts which can lead to a confusing and inadequate image that MAZ processing addresses. In an attempt to decrease these negative sub-salt influences Vector Offset Output (VOO) technology was implemented on a legacy MAZ data set. The principle of VOO relies on wide azimuth data (WAZ) and shot based reverse time migration (RTM). To achieve a WAZ input we regularize each single or narrow azimuth survey (NAZ) to obtain super shot records whilst preserving the MAZ/NAZ nature of the data. This mapping is achieved by utilizing 5D regularization techniques which are commonly used in land processing. The generated target geometry retains the survey’s intrinsic ray path information whilst proving a rich azimuth range for the near offsets and allowing shot based RTM algorithms to be used. The vector offset output reverse time migration divides the aperture area for one shot into nine vector offset tiles. By careful selection and individually weighting, based on coherency algorithms the individual sub-stacks can be combined to form a single image that minimizes the unwanted migration noise and thus maximizes the sub-salt image.
AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013