With the offshore sector booming, the marine seismic fleet has been busy acquiring new surveys and delineating existing fields. Given the size of the fleet, it’s interesting to note that none of these vessels were actually designed with marine seismic surveys in mind. Military boats, work boats and even fishing trawler hulls have been fitted with streamer spools and airgun arrays to meet demand.

The reason is simple—the industry is cyclical. When demand goes up, clients aren’t content to wait for a new vessel to be designed and built. It’s quicker and cheaper to build a vessel based on existing designs. But there are certain requirements for marine seismic surveys that often aren’t satisfied when using these boats.

“A lot of these hulls were designed for speed,” said Rajeev Tooteja, vice president, marine operations for WesternGeco. “A seismic vessel operates 90% of its life at 5 knots. It’s not really about speed; it’s about stability and efficient thrust at 5 knots.”

WesternGeco decided to go back to the drawing board, he said, to determine the functional requirements of a designed-for-purpose seismic vessel. The first of the Amazon class of vessels, named Amazon Warrior, is being delivered this quarter in time for the beginning of the North Sea season in May.

Several considerations have gone into the design of the new vessel. One is its size—it will be about 50% larger than any of WesternGeco’s current fleet. The wide back deck will provide an efficient platform that will aid in safe and efficient deployment and recovery of the in-sea equipment, Tooteja said. The vessel has been designed to tow 18 streamers, with more than 200 km (124 miles) of streamer capacity, in anticipation of future market demand.

The Amazon class also features two separate propulsion systems, allowing seismic operations to continue normally during engine repairs or maintenance mid-survey.
Additionally, the vessel was designed to withstand two types of movement that can affect data quality—rolling and pitching. Rolling occurs when the vessel lifts sideways, whereas pitching occurs when the bow moves into the waves, which can introduce slamming as weather worsens. Slamming can cause tugging on the steamers, also introducing noise and control issues.

Part of the design consideration was to have vessels that can operate anywhere in the world. Not only are the Amazon class of vessels defined as special-purpose ships, but they also have a Polar Class 7 specification, making them eligible for longer, safer Arctic operations.

“There is not a market I can think of that we would not be able to address with these vessels,” Tooteja said.

Overall, the Amazon vessel class is designed to complement all of WesternGeco’s technologies, including the new IsoMetrix streamer technology, a multimeasurement system that constructs an entire wavefield, not just the image below the streamer. “With that best-in-class technology, we need to have a best-in-class operating platform,” he said. “The vessel not only builds on our technology but ensures our clients can use this technology cost-effectively.

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