A new 3D seismic acquisition system for very high and ultra high resolution shallow water studies

The adaptation of 3D techniques to very high and ultra high (multi-kHz) frequency marine seismic investigations is progressing steadily. In recent years, the Renard Centre of Marine Geology (University of Gent) has scaled down the shallow marine 3D method to very high resolutions, thereby entering the world of small-scale geological structures (Henriet et al. 1992). VHR 3D seismic data were acquired in a modest and cost-effective way, using a compact field system with close streamer and channel spacing. Despite good results, the data were not of optimum quality due to a number of technical shortcomings (low sampling rate, positioning restrictions, coverage difficulties). In order to further increase the resolution, adaptation and optimization of the 3D acquisition method were required, taking into account recent developments in positioning and data sampling techniques. In doing so, the seismic strategy must be chosen as a function of the geological target, sampling laws, the desired resolution and the acquisition and processing costs. Based on past 3D experience, a new compact 3D acquisition system was developed in the framework of the EC MAST3 Project ‘Very high resolution marine 3D seismic method for detailed site investigation – VHR3D’. The acquisition array is flexible, which allows it to be tailored to specific site characteristics. The system is designed for studies in shallow water (< 30 m), providing limited penetration (< 50 m bsf) and is aimed at target sites of limited areal extent (approximately 100-100 m2). The desired resolution (both horizontal and vertical) is in the decimetre range.