Wide Azimuth Towed Streamer: Applications for Exploration as Well as Development

Abstract

Marine 3D wide-azimuth towed streamer acquisition methods have provided signifiant improvments in seismic imaging of deep water sub-salt reservoirs in the Gulf of Mexico. The initial surveys were designed to provide very dense trace sampling and illumination under the salt.

Subsequent to these successful field specific surveys, wide-azimuth acquisition designs have been developed to allow cost effective use of the technique over large areas for exploration objectives. This paper will describe a “sparse” acquisition configuration that has been derived from the source / receiver geometry used on the Mad Dog survey for BP. This design allows a full suite of data densities from the initial first pass for the exploration objectives to successively appended additional data acquired through the appraisal and management phases of field development.

In addition, initial results from wide azimuth and multi-azimuth surveys have shown significant improvements in attenuation of multiples and scattered noise, not just improvements in sub-salt imaging. The scale of this S/N improvement will be modelled for fast velocity geological environments such as carbonates to demonstrate that these benefits may also apply in a wider range of basins than first thought. In turn, this improvement, together with the wide range of azimuths recorded, allows azimuthal anisotropy to be estimated thus leading to possible identification of fracture patterns in fractured carbonate reservoirs.

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