Pgs Geophysical As

National University of Singapore

Anders Goran Mattsson

Chan Ghee Koh

Jan Erik Stokkeland

Martin Austad

Jon Falkenberg

Bengt Boberg

Techniques are disclosed relating to wide towing of marine survey signal sources. In one embodiment, an apparatus includes a signal source and a wing coupled to the signal source. In this embodiment, the wing is configured to impart a force to the signal source when towed through a body of water by a survey vessel. In this embodiment, the force includes a lateral component and a vertical component. The wing may be configured to impart the force based on a shape of the wing and an orientation of the wing. The wing may extend over at least a third of a length of a keel of the apparatus. At least a majority of a top surface of the wing may be oriented within 20 degrees of parallel to a surface of the body of water. The wing may include a plurality of wing sections.

Wing for wide tow of geophysical survey sources

Techniques are disclosed relating to reducing drag on cables towed behind a vessel in a body of water. In one embodiment, an apparatus includes a signal source coupled to a survey vessel via a source cable, and the source cable includes a plurality of floats along its length. The floats may in some embodiments allow the source cable to be lifted partially, substantially, or entirely above the surface of the water. Lifting the cable above the surface of the water may in turn decrease the amount of hydrodynamic drag on the cable, reducing the force necessary (e.g., from lateral deflectors on the cable or at the signal source) to tow the source and/or the force necessary to attain a desired lateral position for the signal source. The disclosed techniques may in some embodiments be used to tow such sources at relatively wide lateral separations.

Reduced-drag towing of geophysical equipment

A survey method includes towing one or more sources and one or more streamers behind a vessel to acquire geophysical survey data. Steering signals are determined for at least one of: the one or more sources, the one or more streamers, and the vessel. The steering signals minimize an error function having parameters that include a measure of a cross-line position error and a measure of data quality. The cross-line position error may be measured as an offset of the sources or the receivers from their desired paths, or in some embodiments as an offset between midpoints for base survey traces and subsequent survey traces. Some embodiments may employ a maximum spatial cross-correlation coefficient between a newly acquired trace and one or more base survey traces as a data quality measure, while others may employ a time shift, a phase rotation, or a normalized root mean square error. Data quality may indicate sensor noise levels.

Quality-based steering methods and systems for 4D geophysical surveys

Controlling lateral force developed by a paravane system. At least some of the illustrative embodiments are methods including: towing a paravane system through water, the towing by way of a bridle comprising a plurality of fixed-length forward lines coupled to a respective plurality of forward tow points, and a plurality of fixed-length aft lines coupled to a respective plurality of aft tow points; and while towing the paravane system through the water changing one or both of the lateral force supplied by the paravane or the direction of the force supplied by the paravane.

Growing community of inventors

Singapore, Singapore

Anders Goran Mattsson