Effects of Ghost Cavitation Cloud on Near-field Hydrophones Measurements in the Seismic Air Gun Arrays

Abstract

Summary Air gun arrays are the most common marine seismic sources and knowledge of their directional source signature is essential in several reflection seismology areas. Having the far-field signatures for different angles, it is possible to get higher quality seismic images by removing the source signature variation effects. It is challenging to measure far-field source signatures directly and therefore other methods are developed to estimate directional far-field signatures. Using near-field measurements for calculation of far-field signatures is a common technique. This method requires pressure measurements near each air gun in the array. On the other hand acoustic pressures of individual air guns reflected from sea surface can drop the hydrostatic pressure around the array and generate underwater vapor cavities. In this paper numerical simulation which is validated by field data is used to show the effects of several cavity collapses on the hydrophones used for near field measurements. Including other source of pressure fluctuations than the air guns and ghost signals, it is possible to better estimate the notional source signatures and eventually having better far-field array source signature computation.