10,000 Feet Under the Sea
Ultra-deepwater rigs get a powerful set of eyes, arms and hands far below the waves with Remotely Operated Vehicles.
By Scott Redepenning Illustrations by Jameson SimpsonThe deeper the water, the farther the rig is from the wellhead. This is a simple relationship that gives rise to some complicated issues. Imagine trying to flip a switch, turn a valve or do a closeup inspection on equipment that’s nearly two miles away, underwater, with 5,000 psi of pressure bearing down. Diamond Offshore ultra-deepwater rigs perform these kinds of tasks routinely by deploying onboard ROVs.
The ROV aboard the newly upgraded Ocean Monarch is an Oceaneering* Hydra Millennium Plus system, fully equipped to operate at the rig’s 10,000-foot water depth rating. From the 8 x 20-foot. control van perched on the Monarch’s main deck, a three-man crew puts the ROV through its paces, assisting with virtually every underwater rig function, from site inspection to subsea equipment deployment to drilling. According to Oceaneering ROV Project Manager Egan Gyldenege, there’s rarely an idle moment.
“As soon as a rig arrives on a worksite, the ROV deployment cage is usually the first thing into the water,” he says. “The unit goes down to help set the rig’s anchors, or the transponders in the case of a dynamically positioned rig. We then take a seabed survey to make sure there are no obstructions or environmental issues to deal with before commencing work.
We take video and sonar the entire time the ROV and deployment cage are at depth to have a recording of everything we see and do. We also repeat this survey when the rig is about to move to another location to verify that we are leaving the site in proper condition–not leaving anything behind that shouldn’t be there.” These pre- and post-drilling surveys are a Minerals Management Service requirement.
After anchorage and site survey, the ROV goes about the various tasks of helping to spud the well–setting the lower marine riser package ( LMRP?), blowout preventer ( BOP?) stack and riser. “You’ll have an ROV deployed at depth around the clock for days and even weeks while doing the initial spud in,” Gyldenege says. “We are 99% of the observation that goes on. We are looking for the right kinds of visual verification
that things are going as they should. We can also see and address any issues that may come up. But we’re not just watching; we’re also doing. We can use the brute strength of the ROV to help land the surface casing strings, BOP and LMRP by grabbing the structures with the unit’s manipulator arms and guiding them into place.”
Once the well is spudded and the drill string begins its jour-ney, the ROV is still ever present, assisting the drilling and subsea crews with both observational and manipulative tasks. The unit’s “eyes” consist of five cameras that record digital video and stills in color and black & white or high definition. One is a low-light camera for situations where the work area isn’t sufficiently illuminated by the ROV’s eight 250-watt light pods. Two hydraulically powered robotic manipulator arms provide seven-way movement that replicates and augments the full functioning of the human shoulders, elbows, wrists and hands, giving the ROV pilot
both formidable strength and precise small-detail coordination simultaneously.
Oceaneering Vice President of Sales and Marketing Charles Royce says the greatest role of an ROV is to speed things up–all things. “We can take care of tasks in minutes that would take days if the rig crew had to pull the equipment out of the water. Say you’re changing a gasket thousands of feet down. You’d spend three days pulling the stack, another day or so working on the equipment and three more days putting it back down. The ROV lets you quickly make the change in situ, giving you back about a week in drilling time.”
Weighty capabilities
The entire ROV system accounts for 150,000 pounds of the Monarch’s total deckload. The ROV and deployment cage weigh 20,000 pounds and the control and work vans 48,000 pounds. The remaining 82,000 pounds is tied up in the deck-mounted hoisting system and the 12,000 feet of steel-armored umbilical cable on which the ROV and cage are lowered to working depth. The umbilical itself is the single most expensive component of the system, costing Oceaneering between $250,000 and $350,000 per cable. It is also the most critical component, says Royce.
“All of the ROV’s power, telemetry and communication fiber optics run through that cable. Without those, it doesn’t matter how sophisticated the vehicle is. It becomes just a hunk of metal in the water.” Royce then takes his analogy to another level. “If you lose the ROV, you can’t see, you can’t work, and you can’t drill. Then the whole rig is just sitting there doing nothing. We can’t have that. That’s why we have over 12,000 feet of umbilical on a rig that plans to drill in up to 10,000 feet of water. As a preventive measure, we periodically slip, cut and reconnect the cable at its highest stress point, where it terminates on the deployment cage.”
When the cage reaches working depth, the 8,800-pound ROV–now neutrally buoyant–is “flown out” via eight vertical and horizontal thrusters to perform its various planned tasks. The vehicle is connected by a 1,000-foot tether that carries power and fiber optics from the deployment cage to the ROV. The cage itself is also equipped with lights, cameras and thrusters, allowing the “garage” to be flown with almost the same deft precision as the vehicle.
“People mostly focus on the ROV itself, but the cage is a pretty amazing piece of equipment,” says Royce. “It pays out and retracts the tether. It can see, it can navigate, and it carries the hundreds of pounds of tools that the ROV typically needs at the worksite.”
Gyldenege adds, “When we deploy the ROV, we’re planning to do multiple tasks that could take days or weeks.
“When we deploy the ROV, we’re planning to do multiple tasks that could take days or weeks. If we’re working at 10,000 feet, it takes about eight hours to pull the ROV out onto the deck, re-outfit the system and send it back down. That’s time taken away from drilling, so we try to be overprepared and send the ROV down with every tool it could possibly need.”
If we’re working at 10,000 feet, it takes about eight hours to pull the ROV out onto the deck, re-outfit the system and send it back down. That’s time taken away from drilling, so we try to be overprepared and send the ROV down with every tool it could possibly need. Sometimes we’ll even launch a day or so ahead of time if rougher seas are in the forecast. We’re equipped to launch in high seas, but if we can avoid it, we’ll just park the unit at depth and wait for the rig to be ready for the tasks to commence. Obviously, full preparation is key.”
Tooling packages typically sent down include wire and fiber rope cutters, ring-gasket replacement tool, trash pump for vacuuming or blowing debris from a work surface, rotary grinder/cutter/buffer, hot stabs for actuating various components on the subsea equipment and an assortment of wrenches and other rotary tools.
The manipulator arms that wield these tools run on a 200-horsepower hydraulic pump system, which also powers the thrusters. Two electric motors aboard the ROV drive the hydraulics at 480 volts AC, which must be stepped up in three phases to nearly 3,000 volts on deck before the electricity is sent down the umbilical, ensuring that the required power gets to the ROV at depth to perform all functions.
In the pilot’s seat
On the Ocean Monarch, ROV personnel are vital players in the rig’s functioning. Although direct Oceaneering employees, they in effect become members of the Monarch’s drilling, subsea and station-keeping teams. They are integral to task planning and are in constant communication with key rig personnel during operations. A live video feed from the ROV is also sent to monitors throughout the Monarch, so all crewembers can see what’s going on in real time. “I think the best part of the job is that no matter what needs to be done down there, the whole rig crew is looking to the ROV people to be the eyes of the operation,” says Royce. “It can’t happen without you.”
Three Oceaneering crewmembers are constantly in charge of the ROV–an electronic technician, mechanical technician and supervisor. Although each has specialized skills and duties, all three are trained to do every job, including piloting the ROV. The pilot flies the vehicle from a multifariously complex control chair that puts a button-bedecked joystick in each hand. Several other toggles, minor joysticks, foot pedals and a touch screen add more functions. The pilot simultaneously controls tether payout and retraction, thruster up, down, forward and back, and port and starboard lateral travel and hard turns. All manipulator arm functions are controlled–shoulder, elbow, forearm, yaw, wrist rotation and claw open and close. Camera controls such as tilt, pan and zoom are also at the pilot’s fingertips, and everything the ROV sees, as well as key operational data, is displayed on several monitors arrayed before the pilot.
Controlling these some two dozen variables at once becomes second nature to pilots, and difficult tasks are made to look simple. Yet this skill level does not come easy. Oceaneering spends $10 million a year on simulator and on-the-job training for ROV personnel. Gyldenege points out the high level of sophistication of Oceaneering’s simulators. “These are extremely realistic, much like a flight simulator,” he says. “They replicate all of the forces at work in the ocean, including current and the heaving of the rig in the waves.
A new recruit spends about 10 hours on a simulator before ever touching a real ROV. Then we begin to give them live experience on an ROV doing real work. However, they will not be involved with critical portions of tasks until they’ve flown the ROV a minimum of 200 hours.”
Gyldenege says that simulators are also used by seas-oned pilots to practice unfamiliar tasks before attempting them in the real world. “We use our simulators to ‘do the job’ before we do the job. We can replicate the tasks and conditions our pilot will face and end up saving everyone lots of time. Tasks that were taking days and days in the simulator we’ve been able to knock down to hours by doing them again and again and getting really good at it.”
Looking at the ROV control chair, one imagines that the best pilots would be arcade dwellers who grew up mastering video games. This is a common misperception. “We don’t look for joystick jockeys. We seek out people who have strong electronic or mechanical backgrounds.”
Royce puts it into financial perspective. “Simulation is a must. With rigs already costing operators up to a million dollars a day, we just don’t have the luxury of on-the-job training,” he says. “Our ROV systems typically cost operators between $9,000 to $12,000 a day. We have to be the best we can be the minute we begin work. When we perform a task, our clients want us to be as good on the first time as on the 10th time. Getting it right, right away, saves a lot of money.”
Crewing up
Looking at the ROV control chair, one imagines that the best pilots would be arcade dwellers who grew up mastering video games. Gyldenege says this is a common misperception. “We don’t look for joystick jockeys. We seek out people who have strong electronic or mechanical backgrounds.
We get some ex-Navy people who are used to working offshore. But we also get the guy who turned a wrench on his car every weekend, or someone from a farm who is really good with equipment, or an electrician who worked on residences, or a commercial diver who wants to stay dry now.
We just look for bright people and then we train them for what we want them to do.”
Although the Monarch is only now working its maiden assignment since being upgraded in Singapore, the ROV crew has built considerable longevity with the rig. “We got involved with Diamond Offshore way ahead of time on the Monarch,” says Royce. “We went out to Singapore and had the actual crew who works the ROV on the Monarch install the system. That way they would know it inside and out and be ready to work the ROV immediately.”
Gyldenege says that upcoming tasks for the Monarch’s ROV system could be virtually anything that Diamond Offshore and its clients want to do. “I really believe that ROVs are an outgrowth of necessity. Their only limitation is the imagination. When a client says, ‘Hey, it would be great if…’
we are great at coming through on those ‘ifs.’”
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