Publications

Widespread seismic anomalies are identified on modern 3D data over a large structure, causing severe seismic quality distortion, anomalous ray paths and generating intriguing features.A 2D/4C sea bed survey was acquired to improve imaging through gas clouds, characterize these brightspots in terms of fluid content and provide clues as to the origin of these anomalous features.Advances in seismic acquisition technology have enabled the routine recording of shear waves in a marine environment. Processing of PS converted waves is still interpretative and requires permanent input to validate in particular the Vp/Vs ratio based on the correlation of compressional and shear wavefields.The quality of the shear waves is excellent matching favorably the best compressional wave data. Interpretation of these 2D/4C data has enabled seismic amplitude anomaly characterization, and imagery has been improved in poor quality areas on the 3D providing a clue as to the origin of a prominent, quite unique, anomalous feature on the conventional data. It is interpreted as a gas migration front through an alternating series of sands and shales. Visualization tools are a useful inunderstanding the 3D geometry of these unusual seismic events.