Remotely operated vehicles (ROV) technology has made steady progress since deployment in the 1970s. Vehicles are much stronger, more maneuverable, able to complete a multitude of tasks, and much smarter. Now, on the brink of a new millennium, market forces rather than technology may drive the next generation of remotely operated vehicles.
The first ROVs were very simple. They could swim down and retrieve video images from below the surface. The vehicles could see problems, but couldn't do much about them. As demand increased, technology answered the call with more advanced work class ROVs that could perform basic manipulations, installations, and intervention work.
The logical progression would be toward more skilled vehicles that can perform a greater number of tasks. Ironically, Bill Tink with Canyon Offshore believes dumb may be the wave of the future. With costs taking a front seat over research and development, the ROV industry is looking to its customers to provide the next level of advancement.
Tink's point is that smarter subsea design will allow simpler ROVs to be more effective. Of course, simpler often means less expensive, which is definitely a priority for ROV companies.
Every aspect of the petroleum industry has been hit hard by the recent dip in oil prices, but for ROVs, the day rates were already too low. With a retreat in both exploration and production projects, there is a glut in the market. ROV producers are hesitant to pump a lot of their own money into new research and development (R&D) when there is no financial incentive from the customer for the development of new technology. Faced with the responsibility of paying for new R&D, customers re-think their relationship with suppliers.
Many companies who are former ROV customers have recently become manufacturers. They decided that instead of spending money to lease ROVs, they could build their own ROVs with the technological advances needed to assist vessels working in the deepwater market. Saipem's Sonsub is a good example of this strategy. Alan Chafin, Superintendent of Sonsub International, said his company is building 11 new ROVs to support the company's floating assets. Those not destined for Saipem vessels will be rented out to the industry.
Allen Leatt, CEO for Perry Tritech, said the involvement of integrated contractors in the manufacturing end of the ROV business is not new, and part of a broader trend toward deepwater subsea projects. As ROV operations become an essential ingredient in contractor operations these contractors are moving to shore up control of the ROVs they use. "They want to control this technology so they are not competitively disadvantaged," Leatt explained. As the market moves to a smaller number of integrated contractors these firms are perhaps less likely to subcontract this service since it is a key driver for the commercial success of these ultra deepwater projects.
ABCs of ROVs
Chafin explained there are four basic components to an ROV system. An ROV requires a launch and recovery system (LARS) to lower it into the water and return it to the vessel. There is a control van from which the ROV is operated. A maintenance van keeps the ROV running. The top hat or side entry cage tether management system (TMS) goes into the water with the ROV and acts as a landing point for the vessel. From this launch point, the ROV makes excursions on a tether.
In a sense, there are two umbilicals involved in controlling and communicating with the ROV. The main cable runs from the LARS to lower the ROV and the TMS into the water. Recent advances in design have changed this system to make it more reliable in heavy seas.
For example, an Oceaneering design runs the ROV and TMS down a cursor system on the side of the deepwater vessel so it is stable until it enters the safety of the water. This eliminates the risk that an ROV launched in heavy seas might be damaged by swinging into the side of the vessel.
Sonsub has developed a LARS that is not only a pivotable boom, but also telescopes in and out to offer operators more freeboard during launch. The telescoping boom also allows operators to set down the ROV and TMS on the deck without swinging in heavy weather. A control system can orient the swing frame to accommodate currents moving around the ship and avoid damage to the umbilical.
Regardless of how it enters the water, the TMS carries the ROV from the vessel to the depth that it will be operating. Once the TMS is at the proper depth, the ROV is launched on its tether to do the work. The tether spools out from the TMS and is lighter in construction than the heavy cable that lowers and raises the ROV and TMS. Sonsub has designed a top hat TMS with a soft docking system and a constant tensioning device that monitors the tension on the tether to avoid overstressing it. The length of the cables and the tether impose limits on the depth and range of an ROV. Even if the vehicle is designed to operate in higher pressures, if it is out of cable, it stands to reason that it can go no deeper.
Autonomous vehicles like this artist's conception may be the future of ROV technology.
ROVs on a leash
ROVs should be on a tether while working for a variety of reasons. First the tether provides power. There currently are no batteries that could produce the energy the ROV needs to do work for extended periods. Currently, an ROV can be deployed and work continually around the clock until it breaks down or the job is done. If it breaks down, the maintenance van is equipped and manned specifically to get the vehicle back on line and back in the water as soon as possible.
Battery power would require the ROV be returned to the surface to charge, which takes a considerable amount of time. The ROV would be out of service while charging and then have to be deployed again to resume work. The retrieval and deployment of the ROV are time consuming.
There also are severe through-water communication limitations that require a physical connection between the ROV and the surface. It is difficult to transmit dense amounts of data through the water column. Thermoclines and impurities in the water deflect transmissions, thinning and dispersing the data. The data that is successfully transmitted moves very slowly.
Even under ideal conditions, a video image would be of very poor quality and have a time delay of several minutes. This makes real-time control of the ROV impossible. The pilot would be reacting to images that are several minutes old. Also, there is the question of orientation. Without a tether, an ROV could lose power and be lost forever or get far enough off course that it could not be recovered. With the current system, there are contingencies for power failure and it is relatively easy to retrieve an ROV that has run into trouble.
More, tougher cables
The focus now is on smaller, tougher tethers and umbilicals that will allow more cable to be stored on the same size spools. In addition, the ROVs themselves are being designed to be smaller and more powerful in terms of the payload they can carry and the conditions in which they can operate.
These adaptations for deepwater are important because they allow an ROV to operate in extended depths without increasing the weight the ROV system places on the rig or the amount of space the ROV systems requires. Innovations in thruster design and the design of syntactic foam for buoyancy allow a more powerful vehicle that takes up the same space as its less powerful predecessors.
Sonsub has developed a new buoyancy system that uses large hollow aluminum spheres cast in syntactic foam. While more expensive than traditional syntactic buoyancy designs at conventional depths, in ultra-deepwater applications the reduced volume of the buoyancy foam is less on a cost per unit of buoyancy basis. This new technology allows for more buoyancy in the same amount of space on the vessel.
While increased efficiency in buoyancy systems is an issue, there is also a horsepower race underway in the ROV market. The new deepwater ROVs have substantially more power than their predecessors, although Chafin said there is some debate over what horsepower numbers mean.
He illustrates his point using Sonsub's new Innovator design. These ROVs boast 150 horsepower. Chafin said this is horsepower measured at the propeller shaft. To generate 150 hp at the shaft, Chafin said it is necessary for the electric engine to generate 200 hp. This along with an enhanced frame design will allow the ROV to carry a greater payload of equipment.
In the case of the Innovator, the frame can carry 6,600 lb beneath the primary lift point. This becomes important for jobs that require a modification of the ROV equipment. A prime example of this is the addition of a pipeline jetting system, which is very heavy and mounted on the bottom of the ROV.
Royce said Oceaneering doesn't buy into the horsepower race. He said many ROV customers focus too much on individual statistics such as horsepower when choosing an ROV. In his opinion, the customer would do better to choose an ROV company based on track record and reputation.
In many cases, Royce said he has been approached by customers who ask about the horsepower of Oceaneering's new Magnum ROVs, which also have 150 hp, and he has to explain that although this is a lot of power, it is not the most important consideration. The hydrodynamics of the ROV as well as the flow path for the thrusters can also make a difference in the amount of power available. This is an example of details a client might not be aware of when inquiring about horsepower.
Leatt, said that in ultra deepwater dedicated ROV support construction vessels will become the norm. These vessels will have dedicated ROV systems installed for operational efficiency. The traditional arguments of vehicle weight and size tradeoff will thus be offset somewhat by the scale of infrastructure needed in ultra deepwater operations. That being said the requirement for small portable systems allowing for rapid intervention is likely to remain strong into the future. He said this is not a contradiction, merely a recognition of the segmentation of very different market sectors in the ROV industry.
The majority of new work for ROVs will be in deepwater subsea intervention. This is a reflection of the trend among exploration and production companies to install a series of subsea wellheads, tiebacks, and manifolds for deepwater field development. This design, while less expensive than conventional surface systems in deepwater remote areas, often require intervention and extensive installation assistance from an ROV.
This cursor system allows an operator to safely launch an ROV in heavy seas.
Extreme water depths eliminate the options of using either saturation divers or a Wasp suit for this work. Deepwater is actually the hottest market for ROVs because of the limited number of units able to work in these depths. In addition, because the subsea designs vary in how ROV accessible they are, some require very advanced vehicles to perform interventions.
The key to making the most of this market lies not in the design of the ROV but in the design of the subsea systems. This is what Tink is referring to when he says dumber ROVs and smarter downhole engineering. The systems must be designed from scratch with the idea that an ROV will fly in to do installation and intervention work. This means valves that can be opened and closed by an ROV and trees designed to accommodate the bulky vehicles and prevent tangling of umbilicals.
Royce said this last point couldn't be over-emphasized. One of the greatest threats to an ROV is getting hung up on equipment subsea. Oceaneering has equipped its side-entry cages with thrusters and a camera to help avoid these problems, but the key to overcoming this threat is subsea systems designed to be ROV-friendly. Sonsub has redesigned the spooling and tracking mechanism inside the TMS so that it is controlled electronically rather than mechanically. One advantage of the top hat system is that the tether comes out of the top of the vehicle. This means the operator can see the tether at all times and the tether is less likely to become tangles as the vehicle moves.
Royce said his company keeps spare ROVs ready to go into the field to replace those it has working as well as spare umbilicals on winches. At the Sonsub yard in Houston, spools and spare parts of all descriptions line the walls. Chafin said the Innovator system is designed with fiber optics in the umbilical that allow the system to monitor a variety of systems and detect probable problems before they occur. Not only is downtime expensive for the ROV company, but, if the work is occurring on the critical path of an offshore operation, it can mean a delay.
Traditionally, there is a necessary division between the customer for ROVs and the manufacturer. Richard Frisbie, Senior Vice-President for Deepwater Technology with Oceaneering said his company struggled with this years ago when it moved into the ROV manufacturing business.
The problem, as he explained, it is that the operator and manufacturer have different philosophies about the business. The operator is looking at what it takes to get the current project completed, then move on to the next. To be innovative, the manufacturer must take the long view. This involves a focus on planning and design, with little emphasis in the problem at hand.
Oceaneering was compelled to enter the manufacturing business in the early 1990s when it began to look to the deepwater and could not find a manufacturer to work with. Frisbie said this move also gave Oceaneering better control over the supply chain and ownership of the patents that come with innovative design.
Oceaneering was initially cautious in its construction program, but eventually ramped up to two ROVs a month which put it at the head of the market for newbuilds. Previously, Oceaneering had developed a market with the US Navy for the development of very deepwater ROVs. Some systems were tested to 20,000 ft.
ROV pilots have their background in electronics and come to Oceaneering with this training. They then undergo a 32-day special course in either hydraulics or engineering before being sent offshore. Frisbie said the key asset to an ROV technician is the ability to troubleshoot a problem on the fly and get the unit back on line.
Oceaneering, and many other ROV companies recruit from the military, not just for the piloting experience, which translates readily to ROV flight, but the electronic and hydraulic training that make these pilots able to fix a problem and get a vessel back on line in a minimum amount of time.
As the complexity of both ROV design and the tasks required of these vehicles increases, the human factor becomes more important. It is the pilot ultimately who makes the vessel perform, accepting of the design factors, but excluding the visibility, currents, and sea states.;