At its greatest depths, the sea floor is a dark, tranquil, and foreboding place, beyond the reach of both sunlight and human divers. Yet the area around the Deepwater Horizon wellhead, nearly a mile below the surface of the Gulf of Mexico, is busting with activity—robotic activity.
Most of the tools for containing the vast spill on the sea surface—like skimming, burning, and using dispersants—are low-tech and have been in the oil-spill toolbox, mostly unchanged for decades. But efforts to contain and ultimately cap the spill on the sea floor are comparatively high-tech, relying on sophisticated remote-operated vehicles (ROVs) every step of the way. At nearly every press conference, BP officials emphasize the difficulty of working to conduct these operations at such extreme depths, where humans can’t directly interact with the malfunctioning equipment. But how exactly do these ROVs work, what are their true capabilities, and what are their limits?
ROVs are essentially robotic submarines, used for underwater observation and interventions. They can operate miles below the water surface and are tethered to ships on the surface with cables that provide electrical power and allow commands to be sent and data (like video and information from sensors) to be received. They’re operated by human pilots who sit in a command center, see what the ROV is seeing (along with data from other sensors), and can control them accordingly via joystick. ROVs range in size depending on their intended use, but a really large one could be the size of a UPS truck, says Cameron Wallace, director of marketing and investor relations at Helix Energy Solutions Group, one of the companies currently operating ROVs for BP’s spill response efforts.
These vehicles are multimillion dollar tools. They come in many different flavors, some optimized for observation (essentially deep-sea cameramen) and others optimized for intervention work. ROVs designed for intervention are like skilled laborers who never tire, with hydraulic arms called manipulators and other interchangable tooling (saws, cutters, and other specialized equipment) that can be swapped to make them better suited to any given task. They carry video cameras and lights, use fiber optics to transfer data back and forth along the tether to their mothership, and have a tremendous amount of power to apply to the job at hand. “You could argue they’re just as sophisticated as a space probe,” says Glenn Sasagawa, a development engineer at the Scripps Institution of Oceanography. “They allow people to enter an environment that’s hostile to human existence.”
ROVs have been and continue to be critical to every operation performed as part of BP’s undersea spill response. They’re generally used by oil and gas companies for undersea construction and well intervention work, but in the immediate aftermath of the sinking of the Deepwater Horizon rig, ROVs were put to work examining and attempting to activate the malfunctioning blowout preventer, a device that sits atop the wellhead and is supposed to seal off the well in the event of a blowout. Later, they were used to help position the large, 100-ton cofferdam that was supposed to contain the flow and channel it to the surface for collection, but ultimately became clogged with methane hydrate crystals and had to be moved aside. More recently, ROVs successfully inserted the riser insertion tube tool, which, after several failed attempts, is now capturing about 2,000 barrels of oil per day that would otherwise have been leaked into the sea. And currently, they are involved in preparations for a “top kill” of the well, in which heavy drilling mud and concrete will be used in an attempt to seal the well permanently, as soon as later this week.
ROV technology got its start within the Navy in the 1960s, when simple remote vehicles were used as underwater eyeballs to inspect the outsides of submarines without surfacing, says Cliff Chamblee, president of Canyon Offshore, a Helix company involved in ROV operations. Through the ‘70s and ‘80s, ROVs grew progressively larger and more advanced, allowing them to be used for both scientific exploration of the deep sea (the robotic exploration of the Titanic wreckage is a particularly well-known example) and for offshore oil and gas drilling, which has taken the lead in developing new ROV technology as deep-sea drilling has increased.
Of course, these highly advanced machines are not perfect. The robotic arms allow operators to use ROVs for complicated tasks, but are nevertheless nowhere near as capable as the human arm, Chamblee says. Furthermore, they are subject to mechanical failures such as seawater intrusion, which can cause damage severe enough to pull the vehicle back to the surface for repairs, meaning much lost work time; a trip to the surface from such depths can take hours.
“I think that the real point here is that doing things underwater is hard, whether you’re a human diver or whether you’re a robot,” says Andy Bowen, who directs the National Deep Submergence Facility at Woods Hole Oceanographic Institution. “It’s just a really difficult environment to work in.” And at least the robots don’t tire or complain.