Robots Run Free at OTC
Robots may not be ready to take over the world just yet, but they are making great strides in the offshore industry. A technical session at this year’s Offshore Technology Conference presented some of the advances, including untethered ROVs and subsea broadband communications.
Remotely operated vehicles (ROVs) are frequently used to inspect offshore and subsea facilities. Typically, these ROVs are tethered to vessels to transfer the data they have collected and receive control commands. This tethering limits the vehicles and adds the expense of the control vessel to the inspections. OneSubsea, a Schlumberger company, is working to remove the tether and unlock the benefits of autonomous underwater vehicles (AUVs).
AUVs have their own set of challenges, especially when operating around producing fields where a certain amount of supervision is necessary, so OneSubsea is working on a platform it calls uROV, or untethered ROV. The uROV has a “person in the loop” to review real-time images and make adjustments but still operates autonomously. OneSubsea calls this compromise “supervised autonomy.”
“This is the idea that you have the best of both worlds,” said Jack Vincent, product champion at OneSubsea, while presenting paper OTC 29586. “You have a fully autonomous vehicle that does everything. But you watch everything that it does. You can intervene, and you can change things. … That’s where the value comes in.”
Although the uROV has no tether, communication is critical, and wireless communication makes the whole platform possible.
“This is the key enabler to supervised autonomy,” Vincent said. “If you don’t have the wireless, you really can’t enable the supervised autonomy framework.”
Optical and electromagnetic communications, although frequently used, have range limitations that make them less than ideal for communicating with uROVs. Once the distance is greater than 200–500 m, often outside the drill center, “you really have to leverage acoustics,” Vincent said. “This is all for communicating with a moving vehicle. … If I want to go to much range, I have to go with acoustics.”
Acoustics, however, has a challenger for effective underwater wireless communication. The underwater laser telemetry and remote access (ULTRA) system, presented by Ishan Mons, who works for Oceanit Laboratories, uses optical encoding to transmit data through a variety of media, including seawater. Mons presented paper OTC 29303.
“What ULTRA is essentially is a point-to-point laser communications network,” Mons said. “The idea behind it is setting up an in-place undersea broadband network. I hope everyone here is familiar with Netflix. This is essentially the transformation we are trying to enable, where, instead of going and getting the one thing that you maybe thought you wanted, you have access to everything that you have connected on the seafloor at any given moment in time.”
The idea behind ULTRA is to have a resident network that “is always there and always on,” Mons said, that allows for monitoring of subsea facilities without manual inspections.
“The thing we want to do is instrument everything all the time,” Mons said. He pointed out that many communications technologies have limitations in the number of channels they have available and the amount of bandwidth available per channel. “But, if you can hook up hundreds of sensors and have them not interfere with each other so they’re all talking … if everyone in this room is talking at the same time, no one would be able to hear anything. But, if you could understand everyone in the room at the same time, you would have a massive amount of information changing hands simultaneously.”
Another major limitation for subsea wireless communication is the condition under the water, such as reflections or particulates, which scatter signals. ULTRA has been demonstrated at greater than 100 Mbs for about 30 m. “That was dominated by the water conditions at the time,” Mons said, “so, hopefully, with a little luck and some more-representative water conditions for open ocean, we should be able to push that out beyond 100 m.”
Mons said the goal is for ULTRA to be 1,000 to 10,000 times faster than acoustic, noting that will be for only one length. Hooking up multiple devices to a hub, he added, would increase the bandwidth capacity of all of them.
“We’re really looking forward to getting out to some clear ocean water where we can really stretch our legs and see how far this system can go,” he said.
ULTRA testing has shown that the underwater network interface, at full duplex, was 100 Mbps in both directions, “essentially equivalent to your home Internet,” Mons said. “Obviously, our goal is really gigabit per second. That is just the network standard for local area networks. We’d be interested to see what can be done with that much bandwidth on the bottom of the ocean.”
Oceanit already has been thinking about how its ULTRA platform could be used with AUVs. The challenge presented by the narrow beam of data could be addressed with acoustic beacons and retroreflectors. “Once you have a general idea of where something is, you can do a raster pattern or even a deep focus to localize where you want your beam to hit and use a retroreflector to focus the beam there and gauge whether you are on target,” Mons said.
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03 July 2019