GIS Analysis Of Pockmarks From 3D Seismic Exploration Surveys

Abstract Today Geographical Information Systems (GIS) are present at all stages of Exploration and Production process. Its strength is the ability to combine datasets from each specialty of Geosciences: geology, geophysical, geochemistry, geotechnic, metocean. GIS are widely known for being a powerful tool to gather and archive all geographical data but one of the major strength of a GIS is its capacity to be used for analyzing the data. The proposed GIS approach is a real added value for seabed geohazards assessment for subsea layout validation. The semi-automatic method of seabed pockmarks characterization using GIS and multibeam datasets established by the British Geological Survey in 2012 (Gafeira et al. 2012) has been re-used and improved on exploration 3D seismic data. 1688 seabed pockmarks are mapped over a particular area of interest offshore West Africa. Geomorphologic characteristics are extracted and cross-correlated with 3D seismic amplitude for each pockmark. Correlation coefficients are calculated to highlight the link between pockmark shape and amplitude (indirectly pockmark activity). A second horizon extracted from 3D seismic data has been used to map buried pockmarks, allowing a comparison with seabed pockmarks. The migration path of each pockmark is automatically generated. Orientation of the migration line is found to be consistent with seabed currents, confirming the influence of seabed currents on pockmark migration. Density maps set up for the seabed and buried pockmarks show particular areas with a strong increase of pockmark density, other areas more stable and some areas with a decline of activity.