Deep-Sea Command: From shipboard control rooms, ROV pilots use joysticks to steer robots through deep water and maneuver their plierlike mechanical hands.
In the weeks following the explosion of BP's Deepwater Horizon oil rig on 20 April, a dozen robots the size of moving vans descended into the Gulf of Mexico. Each tethered to a ship by a combination electrical and optical cable, the remotely operated vehicles (ROVs) formed a fleet of unprecedented size.
Deep-water-drilling companies routinely enlist ROVs to maintain and assemble equipment underwater. But in the aftermath of the explosion, BP's attempts to contain the gushing well have pushed these machines to the limits of what they were built to do.
"No one's ever seen anything like this before—that many ROVs simultaneously working on one project," says Tyler Schilling, president and CEO of Schilling Robotics, based in Davis, Calif., which manufactured four of the ROVs in the Gulf and all the robots' manipulator arms. But if predictions about the growth of deep-water drilling prove accurate, big fleets of robots will become the norm, and with that will come the need for much better automation.
Experts mostly agree that the ROVs in the Gulf have carried out their tasks with impressive success, and it is unlikely that better ROVs would have solved the crisis sooner. They have provided the hands and eyes of the entire underwater response operation. For example, when a device inside the rig's blowout preventer failed to automatically seal off the spewing drill pipe, engineers sent ROVs down to jam it into place. When that didn't work, they sent ROVs to saw off the busted pipe, position a four-story dome over the well, and later install a smaller oil-collecting cap in its place. "In those kinds of water depths, nothing happens without an ROV," Schilling says.
Sending human divers below 200 meters is risky and expensive. BP's gusher sits at 1500 meters—easily reachable by ROVs, which can work at depths as great as 7000 meters when equipped with blocks of syntactic foam. The blocks, made of epoxy and glass microspheres, compose much of the robot's bulk and keep it buoyant.
A "work-class" ROV requires a lot of power to drive its hydraulic pumps, which spin thrusters and animate manipulator arms and tools, allowing the robot to haul half a metric ton. Electricity, at as many as 3600 volts, flows from a generator on board a surface ship to the ROV through its massive tether. Unwieldy and cumbersome beasts, tethers stretch as far as 8 kilometers and weigh up to 15 metric tons, about three times the weight of the ROV itself. "Most of the energy in piloting an ROV goes into moving the cable through the water," says Craig Dawe, chief ROV pilot at the Monterey Bay Aquarium Research Institute (MBARI), in California.
Work-class robots make up less than a third of the world's ROVs, but they are the industry's fastest growing sector. Since shortly after the Arab oil embargo in 1973, the global work-class ROV fleet has grown from just three to more than 700. Texas-based Oceaneering International dominates the market with 253 ROVs and is supplying most of the robots at the spill site in the Gulf. Despite the BP disaster, analysts expect deep-water oil production worldwide to rise from 6 million to 10 million barrels a day within five years. And that will drive the total number of work-class ROVs to 1250 by 2014, according to market analysts at Douglas-Westwood, in Canterbury, England. By then work-class ROV manufacturing and services will be a US $3.2 billion business, says the firm.
Almost all such ROVs serve oil and gas companies. (The remainder maintain subsea telecom cables, aid scientific research, and mine for diamonds.) Most offshore operations need just a few robots for construction and maintenance—laying cables, operating valves, and anchoring equipment, among other tasks.