We show here a novel velocity model building approach using the Beam-derived wavelet attributes through a 3D PSDM case study in the UK northern North Sea. There are several advantages by using the Beam-derived wavelet attributes to update the velocity model compared with the conventional method. The most important experience acquired from this project is the velocity model building lifecycle is significantly shortened without compromising the quality. Additionally, this Beam approach has its unique flexibility in pre-conditioning and post-processing seismic data, e.g. demultiples, as well as resolving local velocity anomalies. It is also demonstrated how the pre-BCU challenge was tackled in this project.

Historically, velocity model building (VMB) in salt terrains has followed a layer stripping progression, where interpretation is confined to defining salt boundaries with the primary focus on defining the macro attributes for the post-salt, salt & pre-salt volumes. The imposition these horizons have on local and deeper imaging has generally been of lesser importance to the construction of the macro model, whilst the bulk of the interpretation effort has followed final imaging. This may result in subsequent ambiguity over the influence of the overburden model on the final interpretation. We propose an alternative flow where significant interpretation effort is involved at an early stage during the VMB process in order to assess the effect of the overburden model on the final image. This leads to the dual advantage of a progressive interpretation phase combined with increased confidence in the reliability of the final interpretation.

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As exploration moves into areas of increasing geological complexity and limited legacy data, reservoir evaluation is often based on the interpretation of one seismic image. Building a suitable velocity model followed by pre-stack depth migration plays an important role in the creation of this image on which economic evaluations are often based. In many cases drilling commitments are planned long in advance. Geologists have a good idea about the geometry and size of a potential reservoir but require accurate interpretation and positioning in the depth domain.Here we present data from Taranaki Basin, Offshore New Zealand, and show how a model uncertainty workflow could de-risk exploration and development decisions.