The sheer expanse of the world’s oceans is beyond the realm of comprehension for most. Only those have crossed oceans from a sea-level perspective, or perhaps long-haul airline pilots, can really begin to have an appreciation of it.
Beneath the waves are thousands upon thousands of cubic miles of seawater, moving constantly about via the great ocean currents.
The vast ocean also provides the perfect medium to host some of the world’s largest man-made objects.
The longest moving object on earth is undoubtably a 35,000+ foot-long drill string hanging from the derrick of an ultra-deepwater drilling vessel.
At the moment, the most massive moving object on earth is likely a fully-laden Floating Storage Offloading vessel such as the FSO Africa pictured above.
From a sheer dimensional standpoint however, there is an even larger man-made object moving about in the ocean, one towed by a particularly odd-shaped vessel.
Extending beyond the stern of the Polar Duchess, one of the world’s most powerful 3D seismic survey vessels, is an array of 14 seismic streamers, each separated laterally by 100 meters and extending 8 kilometers behind the ship.
This “wide tow” array results in an apparatus covering 11.2 square kilometers of ocean, or the surface area of of three Vatican Cities, two Principalities of Monaco and two Cities of London.
In short, the operator of the vessel, Dolphin Geophysical – a relative newcomer to the world of offshore seismic exploration, had created the world’s largest floating object.
In 2012, the company won their first contract with Royal Dutch Shell to take full advantage of this vessel and her capabilities.
But why such an array?
Phil Suter, VP Marketing and Sales for Dolphin Geophysical notes that Shell won an exploration license off the west coast of South Africa, an area renowned for bad weatherband in order to maximize the operational window of opportunity available to them, “we needed to come up with a radical solution.”
With 8,000 square kilometers of seafloor to survey, the company was able to complete the job in only 4 months while utilizing the Polar Duchess.
“Oil companies are now contending with increasingly short exploration licenses for larger and larger swathes of the seafloor, so they have to act quickly, “ adds Suter.
Large 3D seismic vessels such as the Polar Duchess are purpose-built for the task.
The distinctively wide stern is designed to permit the deployment of a wide array, and within her engine room is a 2 x 7100 kw power plant to handle the extreme frictional resistance created by such a large object moving through the water at around 4.5 knots.
The power is similar to that of a large ocean-going tugboat actually. In the case of the Polar Duchess, she is rated for 210 tons of bollard pull.
While towing the array, she’ll likely only need half that power, or roughly 90 tons, but with plenty of extra should it be needed due to bad weather or adverse currents.
The business of Seismic
Although Dolphin Geophysical is a relatively new company, having been established in 2010, they have already gained significant market share and are now the 5th largest such company in the world, a position which continues to rise.
In a recent presentation in Houston, company founder and Chairman Tim Wells notes that their fleet of eight ships are on a long term charters from GC Reiber and Sanco Shipping AS. On board those vessels however, all the seismic survey equipment is owned by them.
The ships are utilized on specific seismic survey contracts for their clients – which include nearly all of the world’s top energy firms, or they conduct their own seismic surveys and license the data they collect for use by these same energy firms.
The recently delivered Sanco Sword was delivered a few weeks ago to Dolphin Geophysical and is on a multi-client contract in the Barents Sea.