Shallow gas and gas seepage: expressions on seismic and otheracoustic data from the Netherlands North Sea

Abstract An inventory of indications for shallow gas and for seepage of gas to the seabed is given, as observed on seismic and acoustic data from the Netherlands offshore. Surface pockmarks (depth of about 2 m) have been observed on side-scan sonar and echo data. Acoustic blanking, acoustic turbidity and enhanced reflectors were frequently observed on 3.5 kHz sub-bottom profiles. Standard E&P seismic data sets (both 2D and 3D) show features such as bright spots (indicative for trapping of shallow gas), seismic chimneys, shallow enhanced reflectors and leaking fault systems (all indicative for leakage to the near-surface environment).