Nasa’s adventure at the bottom of the sea

With the Brent field stopping production, decisions had to be made about what to do with the structures. Shell needed to find out more about the sediment at the bottom of those vessels.

“There was a plan to drill through the top of the vessels,” remembers Roddy MacFarlane, who works on Shell’s Brent decommissioning team, “but they are at the bottom of the sea and are made of metre-thick reinforced concrete. Drilling through was going to be difficult and risky.”

A group of Shell staff who meet in their own time to hunt out solutions to the company’s biggest challenges – the Hunters Network – thought Nasa might have the expertise to send a probe through the existing 10-inch network of pipes. 

And that’s where Magruder came in. 

“As soon as Shell told me the challenge I thought about our AERCam – something we invented to float around the Space Shuttle to inspect it without having to do spacewalks,” says Magruder, who is Deputy Chief of Robotic Systems Technology at the Johnson Space Center. 

He took time away from some of his Nasa projects – which include building humanoid robots to set up a base on Mars – and got to work making a bowling ball-sized scanning device that could get through the Brent pipes.

Building the probe

It needed lights, cameras, control systems and, of course, sonar. And it had to be gold-coloured, a reference back to the Apollo missions.

Nasa built a replica of the Brent pipe system in its Neutral Buoyancy Lab – a vast swimming pool used to simulate the weightless conditions in space – to test that the Sonar Sphere prototype worked. It did.

But Magruder also wanted to see if it could scan effectively inside the vessel. So he found an abandoned US nuclear missile silo.

“One of my colleagues is a diver and he knew of this silo, which is largely flooded, in Texas,” said Magruder. “It is almost exactly the same shape and size as the Brent vessels. So we tested the probe there too.”

But despite all the preparation, the North Sea had some surprises in store. On the first attempt, the tether attached to the probe snapped. On the second, the probe got through the pipe but wouldn’t go into the vessel itself. And on the next attempt, the probe struggled to see through a layer of mixed oil and water.

The fourth attempt was different.

To get access to the pipes Magruder had to climb down inside one of the legs supporting Brent Bravo. He worked in a room 71 metres under the surface.

“We had breathing gear on and special suits, we were weighed down with so much stuff and monitoring equipment,” recalls Magruder. “The attention to safety was really strong, very similar to Nasa.

“To get into position we even had to go through a huge blast door. It was cold too. It was just like being an astronaut. I loved it.”

Once the probe got in and data started coming through, Magruder cried tears of joy.

Back on shore, MacFarlane punched the air in celebration.

The probe went on to produce a detailed map of the amount and distribution of sediment in the vessel. Another technique, developed by a separate team, was used to get a sample of the sediment so its composition could be analysed. 

With the project now nearing its end, Magruder has hopes the Sonar Sphere could find yet another use: back up in space. 

“We are looking at dragging an asteroid into the Moon’s orbit to investigate it,” he says. “With a little modification, the Sonar Sphere could be at the forefront of space exploration, telling us what the asteroid is made from.” 

Not bad for a little gold ball.

Story by Lech Mintowt-Czyz