Existing seafloor asset monitoring warns of danger
Safe, efficient mooring operations present a challenge in deepwater. To protect valuable seafloor assets, rig masters must constantly monitor mooring lines during active mooring and anchor handling operations. Furthermore, accurate site information is essential to successful offshore positioning.
Traditionally, mooring in deepwater is carried out in two stand-alone efforts. Standard positioning software monitors the positioning, and a mooring company engineer monitors the mooring lines. If a mooring line is of particular concern, engineers can monitor the catenary shape in relation to other seafloor assets, though not easily, in a 3D environment.
An operator challenged Fugro Chance Inc. to provide a system that would help to monitor the rig mooring lines in relation to seafloor assets as they are being laid, and that would alert the engineers of close proximity to seafloor assets or hazards. Fugro supplies survey services to the energy industry and positions offshore oil drilling rigs, production platforms, and pipelay barges. Its surveyors have collected data to develop a proprietary Gulf of Mexico comprehensive database, which contains geographic information on wells, pipelines, and other hazards.
“We started kicking around ideas with our research and development group in Lafayette, Louisiana, on how to display both mooring line cantenaries and seafloor assets in relation to one another,” Larry Prewitt, marine manager, Fugro Chance Inc., says. “Our R&D came up with some ideas on how we could marry our existing software with catenary mooring software to provide real-time 3D graphic images of mooring lines as they are laid.”
Diamond Offshore's semisubmersible Ocean Victory tested the system during a deepwater rig move.
Fugro needed to prove the concept with an expert in mooring, so it teamed with Delmar. The mooring company confirmed the concept, informing Fugro that they had the technology needed to integrate with Fugro’s system to make this idea a reality. Delmar offered its mooring software DelCat, allowing the system to be developed with proven mooring software.
Model marriage
Fugro took its Starfix navigation suite, which provides positions and anchor states to model each mooring line in real time, and integrated it with Delmar’s DelCat catenary algorithms to develop Starfix.Moor.
Starfix.Moor is a visual tool that provides an overall scene of the rig, seafloor assets, and mooring catenaries, the company says. The rig master is alerted to a potential problem when moving a rig or setting mooring lines. Prior to this, rig personnel did not have good visualization of catenaries of the anchor mooring lines. They put out wire and chain, but without a mooring engineer offshore, had no idea how it affected the catenary or the shape and clearances of the mooring lines.
More and more often in deepwater, mooring lines will have to be anchored in developed locations where assets already run through the field. Starfix.Moor monitors the rig’s mooring lines relative to these hazards during the mooring operation, which allows the drilling rig operator to move safely on location.
Starfix.Moor also provides 2D profile windows showing calculated catenaries with respect to the seafloor and assets. The tool calculates and displays tension of the rig, anchor handling vessel, and anchor, as well as support of the mid-line buoys, true seafloor definition, and preset anchor hookup operations. Bollard pull and rudder clearance calculations are also displayed.
Delmar’s DelCat algorithms base each mooring line computation on any two of three observables: scope, payouts, and tension. Wireless handheld computers that anchor-handling personnel operate transmit the payout observables into the Starfix.Moor system, which displays the payout information in 3D.
“You are getting all your mooring line components’ payouts from these handhelds that are wirelessly linked back to Starfix.Moor,” Evan Zimmerman, manager of engineering, Delmar Systems, says. “So with position and payout, you can calculate the catenary shape. That is what is done internally and then displayed back in this 3D environment.”
Starfix.Moor’s 3D presentation, HydroVista, displays and tracks rigs, mooring lines, AHVs, and ROVs in real time. Multiple cameras and multiple views, including Orthometric and Profile, can virtually fly or attach to moving or static objects. For example, a rig master could view a mooring line from the vantage point of a wellhead. The system also displays alarms and highlights the areas in danger.
“If any asset gets within 1,000 ft, the screen can be configured to come up with a warning,” Zimmerman says. “An alarm box pops up that might say, ‘line two is close to tree four.’ It alerts them so they know which line and what asset they are close to. If it continues, there is time to react, but as it gets closer, say 500 ft, it goes to a red alarm and tells everyone to start reacting stronger to the warning.”
However, Starfix.Moor is only as good as the input data.
“We have to have buy-in from a lot of people to make it work,” Prewitt says. “The system is updated every 12 seconds. A guy on the rig is running the handhelds. He is punching in numbers and has to be diligent in his job. If he puts in bad data, we get bad answers.”
The tool can alert rig masters to potential problems in the field as they happen, but it can also be used prior to the actual work to illustrate potential problems.
“If there is a mooring line that is critical to us, we can do a run-through in the field to see how it works, then go set the mooring line,” Prewitt says. “Or it can be used as a planning tool in the office weeks or months prior to going out to see if the work can even be done.”
The marriage of these two monitoring tools has significant benefits to the user, Zimmerman says. “First, everybody that is in the field or even in the office planning this job is on the same page; they all can easily visualize what’s going on. Second, it acts as a real-time alarm system that can alert the infield personnel when a potential problem is getting ready to happen or one they need to pay additional attention to.”
Anyone, anywhere
According to Fugro, the modeling tool is applicable to any environment for any operator or drilling contractor. Fugro builds a 3D shape of the vessel, which includes all the mooring line components, chain, size in length and width, connectors, wire, and weight, then goes out to do the work.
The partners introduced its solution, Starfix.Moor, to the operator during a trial run. Diamond Offshore’s semisubmersibleOcean Victory tested the system during a deepwater rig move. The operator was pleased with the results. Since then, Fugro and Delmar have conducted two deployments and one pick-up with the system, and another operator has scheduled two more deployments and one more pick-up.
The initial challenge the operator commissioned Fugro to tackle involved an AHV installing mooring lines, but Fugro says Starfix.Moor can be used to monitor just about any vessel or platform and its umbilicals, risers, flowlines, etc.
Both companies believe this new system will make deepwater anchoring and rig moves safer in the GoM and world wide.•
Editor’s Note: Please view a demonstration of Starfix.Moor at http://www.fugrochance.com/BrochuresHome.html
