| Abstract: | The far-field signatures from a comprehensive and systematic airgun pulse test have been analyzed. Empirical relations between the characteristic signature parameters and depth (5–12 m), pressure (100–137 bar = 10–13.7 MPa) and total chamber volume (0.65–9.5 l) have been derived. Also, the influence of using waveshape kits in different positions within the chamber has been tested. The results indicate that: - 1 The amplitude is proportional to chamber pressure to the power 3/4.
- 2 The bubble period is nearly independent of the position of the waveshape plate.
- 3 The increase in primary/bubble amplitude ratio is inversely proportional to the chamber volume above the waveshape plate.
- 4 The amplitude is independent of airgun depth.
Suggestions and comments regarding this work from Dr B. Ursin and Dr A. Ziolkowski are appreciated. The field work was supported by the Norwegian Petroleum Directorate through the Continental Shelf Project at the Seismological Observatory, University of Bergen. An airgun allowing for continuous variation of the chamber volumes was supplied by GECO (Geophysical Company of Norway). The purchase of two airguns was financed by Norske Getty Exploration A/S. |
