Cable protection is stronger, lighter and more versatile

Paul Boughton
With environmental issues and energy saving being hot topics in our current climate, you would not think that a cable fairing would be something that would spring to mind in either of those categories. Alan Cooper reports.

Current seismic vessels have reached a peak in performance. When you weigh up the size of a seismic vessel against the volume of equipment towed behind it, it is amazing to think just how far this industry come in the past 15 years.

From a normal footprint width of about 400m in 1993, up to 850m in today's market. And getting every last metre in spread width can make a difference to the length a contract takes to shoot, and with the rising costs of fuel also making a difference to weather a contract is profitable or not.

CWA has developed a Rigid Cable Fairing that helps reduce the drag on the 'Tag line ropes', which can increase the width of the tow by up to 25m, and with a drag co-efficient (CoD) of 0.13 it is one of the most efficient fairings ever tested. This reduced drag can save thousands of dollars in diesel fuel. And considering the low cost of the equipment, it is an investment in equipment that should not be ignored. The materials used to make this product have been designed around reclaimed polyethylene's, to help with environmental impact.

Following extensive testing at an independent tow test tank, and a number of years of manufacturing refinement, the product available today looks quite different from the one we first started with in 1999, but the outline profile and the performance are exactly what we had hoped to achieve all those years ago.

CWA first started working in the seismic market in 1992, working with companies like Haliburton and Digicon. And it's only when you look back at the sort of equipment required by our customers back then, that you realise how far both the industry and CWA have come. In those early days and large seismic vessel would tow up to six streamers, each 5km in length, these days vessels towing 16 streamers 7km in length is more commonplace.

As the years have rolled by, and the demands from the industry have lead to longer, stronger, smaller diameter cables, so CWA have had to adapt to be able to provide the market leaders with cable protection which is stronger, lighter and more versatile. One of our first designs was a bend stiffener 1.5m in length, 150mm diameter and taking loads of up to 3000 lbs. Just five years later, and the bend stiffener is up to 2.5m in length, 200mm diameter and taking loads of 5 tons. We had to source strong polyurethanes to be able to give the product maximum performance, but the customers had restrictions on the size of the items we could provide. Now wind the clock forward to 2008, and we have now had to stop using polyurethane for the high strength systems, the loads our equipment is now being asked to perform to can be as much as 15 tons standard load, with a peak load of over 20 tons.

So, our latest lead-in protection system is now produced entirely from alloy's, a combination of high strength bronze and stainless steel, castings and solid billets. With input from our customers and our own experience of the market, we have produced the Helical Tow System, which has been specifically designed to be used on the 'Wide tow/high load' applications of today's seismic market.

Today's seismic vessels have such a staggering output, that they can gain as much data as a fleet of vessels could 15 years ago.

Small refinements are going to be the way forward, tweaking the system to get the maximum from the equipment. CWA plan to be around to help with all those tweaks.

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Alan Cooper is a director of CWA Products Ltd, Hook, Hampshire, UK.


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