How To Design an Unmanned Minimal Floating Platform
A fully unmanned minimal floating platform may be a cheaper, more efficient option for operators looking to develop small- or medium-sized fields where a long subsea tieback or a host facility with full processing capacity is not economically feasible. Advancements in technology and design principles have made these platforms a more realistic possibility. Evolution in some areas, like subsea processing equipment and robot-supported operations, may make the installation and maintenance of these platforms even easier.
“This is where the future is going, to not put people offshore and in harm’s way,” said Eleni Beyko, director of platform life services at TechnipFMC.
Beyko spoke at a technical session held during the 2019 Offshore Technology Conference, presenting a paper (OTC 29648) she co-wrote with Anil Sablok and Mathew James Pegg on the design of unmanned minimal floating platforms. The paper reviewed different platform configurations, looking at functionality, construction, installation, operations, and maintenance.
Unmanned floating facilities eliminate the need for people offshore, reducing exposure to the possible hazards of offshore operations. While they have been around for several years, their success has been somewhat mixed for a number of reasons, much of them centering on the visitation frequency and intervention needs of the facility greatly exceeding the original intent. The maintenance workload is often higher than what was anticipated during the design phase. Operational requirements sometimes need additional human intervention to allow for recovery from transient events. Unmanned platforms are often designed to be accessible, so operators often find it easier to resolve issues by visiting the facility instead of attempting to solve them remotely.
Regardless, because of the potential safety benefits of keeping people onshore, Beyko said, “We’re looking for lower capital expenditure, lower OPEX, and minimal maintenance requirements. Definitely it is safer to operate if we don’t have as many people offshore than a conventional host platform. [Unmanned platforms] can help better enable phased field developments and enable marginal field developments as well,” she said.
The paper outlined how designing a successful platform requires the operator to consider functional requirements at an early project phase, and that unrealistic or overly rigid requirements will constrain the design process. Among the requirements that should be considered are those for health, safety, and environment (HSE); government regulations; maintenance; facility access, whether through a motion compensated gangway, aircraft, or some other method; operational mode; and availability.
Beyko discussed the ESSA (eliminate, simplify, standardize, automate) principle and how it could apply to designing more cost-efficient topsides. An unmanned platform would likely necessitate the elimination of systems and design elements suited for people, like living quarters and a helideck. Utility and support systems can also be optimized. Choosing the simplest, most robust, and most reliable equipment is also important; the paper highlighted material selection, particularly corrosion resistant alloys, as a key area of focus. Standardized equipment allows for optimized maintenance inventories, and without automated remote operation, an unmanned facility is impossible to design.
“We are eliminating systems that are not required when humans are not permanently present on the facility. We need to simplify the equipment, utilize simple, advanced, and valuable equipment,” she said.
The ESSA principle also applies to the substructure. In fact, it is generally easier to apply ESSA to the substructure because there are fewer systems that can be designed for minimal maintenance and inspection.
The paper outlined TechnipFMC and Genesis’s work on developing minimal unmanned floating substructures for several applications including platforms for production, compression, power, and wind turbines. They used a spar platform for each application, in part because it is an inherently stable platform that becomes more stable after compartment flooding. This stability enables the elimination of permanent ballast and bilge pump systems, which can provide significant benefits for inspection, maintenance, and operations. With limited systems in the substructure, the scope of integrating the hull and topsides is smaller.
“It is a simpler hull design than some of the other semisubmersible-type platforms, and it has a smaller number of compartments, so it is a much more cost-efficient application,” Beyko said of spar platforms.
TechnipFMC and Genesis also studied alternatives to the spar for an unmanned platform, like the EDP (extended draft platform) buoy. An EDP buoy can be used for a number of applications, like supporting the low-cost subsea development of a marginal field or gathering long-term oceanographic and geotechnical data. The columns and pontoon of an EDP buoy are raised, which allows for equipment to be installed in the deck box when it is at ground level or floating in a collapsed configuration. The shape of the deck box also provides sufficient area for processing, power, communications, instrumentation, and material-handling equipment.
While onshore personnel would still be needed to monitor fully unmanned platforms, optimizing existing drone technology and other unmanned vehicles, like remotely operated vehicles (ROVs) or autonomous underwater vehicles, will help ease the demands of physical inspections. They can also help simplify design of the substructure, as the stairs and elevators normally needed to allow people to access the inside of the substructure can be replaced with ladders and ropes that require less space.
“The technology exists, and it is in different levels of readiness. We already use ROVs for subsea operations. But, they can be used on the platforms for routine walk-arounds, observation, inspections and assessments, maintenance support. These are currently under development,” Beyko said.
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18 June 2019
19 June 2019