Chevron’s Lew Dennis has spoken about how a new type of autonomous underwater vehicle (AUV) promises a step change in subsea decommissioning operations.
Describing Chevron’s seven-year restoration program following hurricanes Katrina, Rita, Ike and Gustav, Lew Dennis, the operator’s US offshore decommissioning manager, told a conference that new technologies played a decisive role in improving safety and efficiency.
Key among these was a new type of AUV that shaved weeks off the surveying of subsea structures. Last year the “Marlin” (pictured), a 10-foot long AUV developed recently by Lockheed Martin in part for defence applications, logged more than 62 hours of submerged operations, covering 72 miles of seabed.
While under the waves, Marlin generated 3-D geo-referenced models of Chevron’s platforms, creating an accurate view of the area.It was “truly amazing,” Lew Dennis told attendees at DecomWorld’s 5th Annual Gulf of Mexico Decommissioning & Abandonment Summit in Houston in March.
Chevron surveyed 14 sites with Marlin in a series of operations with Fugro, Mr Dennis said. Two sites were part of the hurricane restoration program, while the rest were routine.
Marlin, Mr Dennis said, “could swim over to a structure in 200 feet of water and it would be back at the boat in lessthan one hour having created a fairly detailed, 3-D model with minimal risk to humans”. “That’s truly a step change during the course of the project,” he said. “We spent literally weeks [before] mapping those with ROVs and divers.”
Lockheed Martin says Marlin is highly manoeuvrable and has a sprint speed of four knots. It can operate for up to 24 hours at a time while its high-resolution optical and acoustic sensor package provides 3-D pictures up to 1,000 feet beneath the surface.
“Marlin is an example of how we can apply existing technologies to solve new problems in adjacent markets,” said Dan McLeod, Lockheed Martin’s Marlin program manager. “Our systems can allow the industry to conduct more frequent and higher quality inspections at lower costs than traditional methods.”