3D Boulder Detection
Diffractions in marine seismic data sets provide valuable information about the structure and the physical properties of the sub-sea floor. As boulders buried in sediments cause point diffractions and are a significant threat to the installation of offshore wind energy facilities, the imaging of point diffractions in particular is an important task. Currently, diffractions are treated as noise in standard seismic processing techniques and even more specialized methods fail to image diffractions unambiguously or effectively.
In a novel beamforming technique, which is based on an apex-centered Radon transform, an optimized acquisition geometry was developed to image three dimensionally point diffractions. A fixed frame of 3 m by 8 m with 48 hydrophones attached, was deployed in a marine environment to detect boulders in areas, where they represent a high risk for offshore wind mill foundations.
Besides the development of the algorithms, a set of experiments – including beam pattern analysis, synthetic seismic data generation, validation of the techniques with synthetic and real data sets was carried out. Based on those experiments, it is possible to specify an optimized acquisition geometry and to demonstrate that point diffractions can be effectively and unambiguously imaged.
The analyzed diffractions of a real data set fit to the general geological interpretation and additional velocity information is obtained in a reflection free unit.