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Attacking Cross-Cable Strumming

Jun 03, 2016 | Posted in Blog, News, Notes From The Field

Geometrics recently had an opportunity to work on the University of Aarhus’s Aurora Vessel in a joint collaboration P-Cable survey. Naturally, we took advantage of this opportunity and visited Aarhus in Denmark. Dan Shehan and Kolby Pedrie worked with researchers from P-Cable and Per Trinhammer from Aarhus University during the project, with three main objectives: eliminating strumming, field test a new style of paravane doors, and to provide field support to an existing customer.

Geometrics’ primary objective was to characterize and eliminate strumming noise that has been previously observed in the P-Cable data. The project involved deploying 8 different P-Cable setups, and accelerometers were fitted to the equipment in order to measure cable vibration. After monitoring cable vibration with traditional P-Cable configurations, we were able to test a proposed solution by installing and deploying Swallow Tail fairing on our cross cable. We observed a drastic reduction in strumming noise when Swallow Tail fairing was attached, with a drop in max acceleration of approximately 5g. The swallow tails act as a simple solution to the strumming problem, since Swallow Tail fairing require no additional engineering to install, are inexpensive, and have quantitatively been proven to be incredibly effective.

Swallowtail Fairing

Swallowtail Fairing

In addition to analyzing and finding a solution to the strumming problem, we were also able to field test the P-Cable equipped with an innovative new design of paravane doors made by Seismeq. The Seismeq paravane design is more effective and allows for the use of smaller paravane doors. Additionally, Seismeq paravane doors may be deployed from the stern. So, P-Cable deployment can now be done with much smaller vessels and with less expensive paravane handling equipment. This will decrease barriers for new P-Cable owners, since vessels as small as the Aurora can be successfully used for P-Cable surveys. The R/V Aurora has a width of 8.5m a length of 28m, and is extremely small compared to traditional vessels used to deploy similar 8 streamer arrays.

We also carried out support for a recent sale by assisting with a field test of Aarhus P-Cable equipment. The Aarhus P-Cable worked extremely well and was easily and safely deployed from the Aurora Vessel for all 8 deployments.

We were able to solve noise issues on the P-Cable, field test Aarhus gear, field test the new Seismeq paravane doors, all while working with one of the most experienced P-Cable crews to date. Thus, we were able to support our existing P-Cable sale, improve further P-Cable equipment quality, and decrease barriers for future customers. Furthermore, the invaluable hands-on experience our scientists had will allow them to better discuss P-Cable deployment with potential customers and to support sales growth for our marine instruments.

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