Abstract

During a geohazards evaluation of an area in deep-water Green Canyon, using standard exploration three-dimensional (3-D) seismic data, different features of significance to drilling operations and the planning of seabed installations were observed. These features were indications of seabed slope instability, shallow gas accumulations in a channel deposit, gas chimneys, faults, and a seabed mound above a gas chimney. Edge-detection maps were used to highlight slope-failure scars, faults, the channel, and the seabed mound. Average absolute-amplitude maps were used to highlight slope-failure scars, faults, and possible shallow gas accumulations. Possible gas chimneys were mapped to identify fluid-migration pathways. The mapping of chimneys was done by the use of a recently developed method for detection of gas chimneys in 3-D seismic data. The method was developed to facilitate and increase the consistency in the mapping, as well as make gas chimneys visible in the map view. The results of the geohazards assessment were identification of a seabed slope-failure risk and a risk of overpressured gas in channel deposits.

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