Digital twins and hardware-in-the-loop simulations are improving the workability and safety of gangway-based access systems
The walk-to-work (W2W) market continues to see strong demand in both traditional offshore oil and gas and the offshore renewables environment, as operators recognise the cost and safety benefits it can bring
It was a hot topic at OSJ’s sister title’s Offshore Wind Journal Conference in London on 5 February 2019, where the “Walk-to-work vessels and access systems” panel addressed issues such as key trends in the market, cost benefits, safety and workability, and innovation in offshore access. The role of technology, especially in the form of simulation software, played a major part in the discussion.
“Our more experienced clients ask us to have more transparency for our performance,” said Acta Marine general manager commercial offshore Simon Anink, explaining that his company is being asked to provide increased predictability of operations, requiring improved upfront modelling of systems.
Damen Shipyard Group business development manager for offshore wind Peter Robert highlighted the use of digital twins – simulations of systems based on sensor data from the physical system – to predict the workability of vessels, which he described as “the next step in this industry”.
He explained that Damen has a full simulation setup, incorporating multiple pieces of equipment such as the DP system and gangway into a full hydrodynamic model of the vessel. When combined with metocean data about the area in which a vessel will work, this allows for accurate predictions to be made of the vessel’s workability.
“You cannot comment on performance if you just look at the gangway itself, or the DP system itself, or the platform itself; if you have that isolated approach you’re not going to get real workability”
The system relies on hardware-in-the-loop technology, which the company used on service operations vessel Bibby Wavemaster 1. This involves replacing a physical part of a system with a simulation, allowing for testing and improvement of integration and controls design before construction begins. For example, a digital twin of a new gangway can be integrated into an existing vessel’s control system to see how it works and to identify issues before installation.
Using these methods, Damen compared the workability of a converted PSV with a dedicated W2W vessel design, Mr Robert said. The result was that by using a fit-for-purpose, dedicated design, operators would gain 70 additional working days over the course of the year.
“You cannot comment on performance if you just look at the gangway itself, or the DP system itself, or the platform itself; if you have that isolated approach you’re not going to get real workability,” he said.
“You need a combination of systems to simulate the task [a vessel is] designed for.”
“If you’re bringing a new design to the market with a dedicated purpose you need to have something extra. With the hardware-in-the-loop simulator, we are able to supply the market with real assessments in a three- or four-hour simulation run, where we can guarantee the performance of the vessel.”
Mr Robert said: “More and more, we are using simulation technology for existing or new products to bring to the market”
Uptime International director of sales and business development Bjørnar Huse also noted: “We see end-users like Shell building that [technology] into their requirement for any walk-to-work vessel or floatel they want to hire in.
“They require the gangway vendor, the ship vendor, equipment vendors [all] work together to make a complete digital simulation of the whole vessel before they actually enter into a contract."
Added Mr Huse: “In the future, we will see more use of advanced simulations and advanced computer simulations, to ascertain that operations can be done in the planned timeframe."
Also at the Offshore Wind Journal Conference, Equinor marine department manager Morten Sundt and marine department advisor Ole Steinar Andersen discussed Equinor’s experiences using W2W vessels in projects on the Norwegian continental shelf, and their plans for the future in this area.
Mr Steinar noted Equinor’s experiences using a W2W system to gain access to an unmanned platform for commissioning. The platform, Oseberg H, was installed in mid-2017, but delivery of Askepott, a new jackup vessel intended to be used for commissioning work, was delayed.
Equinor therefore chartered Island Offshore’s installation support vessel Island Crown on a two-month basis to provide accommodation for the approximately 35 workers needed to finalise Oseberg H’s commissioning activities. As the platform is unmanned and does not have a helipad, a W2W vessel was the only suitable access method.
Island Crown was fitted with a crane for logistics purposes and an Uptime gangway for personnel transfer. The personnel worked daytime shifts, with the gangway permanently connected in passive mode while work operations were under way, serving as the main evacuation route to Island Crown in significant wave heights of approximately 2.5 m.
Askepott is now drilling wells, but once this activity is completed, Equinor will have further need of a W2W solution for maintenance campaigns on the platform. These will take place semi-annually and will require a vessel to be on station for about 10 days at a time, said Mr Steinar.
Island Clipper can transform from PSV to W2W vessel, by mounting a gangway at 48 hours' notice
Having a vessel dedicated to this purpose would be too expensive, Mr Steinar said, so the decision was taken to charter Island Offshore’s platform supply vessel (PSV) Island Clipper. The PSV will spend most of its time as a pool vessel carrying out platform supply activity, but an Uptime gangway will be stored at the vessel's Mongstad base, capable of being fitted at 48 hours’ notice to transform it into a W2W vessel. Currently, this gangway is a 23.4 m model, capable of operating in significant wave heights of 2.5 m, but in 2020 this will be replaced with a 30 m solution that can operate in significant wave heights of 3.5 m.
Mr Sund and Mr Steinar noted that Equinor plans to increase the number of unmanned platforms in Norwegian waters, and is also considering a project for a windfarm to produce energy for the Snohvit and Gulfaks oil fields, which would also need W2W access. Equinor will therefore need to a new solution to handle W2W demand from these new windfarms and platforms post-2022. It will look to have a purpose-built vessel engineered with these duties in mind, rather than modify an existing one.
To keep costs to a minimum and ensure utilisation, such a vessel would need to be able to undertake other roles in addition to W2W duties, said Mr Steinar. Equinor is considering a high-spec PSV as one option, or a multirole emergency response and rescue vessel capable of operating in significant wave heights between 4-4.5 m. Such a vessel would require an active stabilisation system and good station keeping abilities, together with a W2W system with additional roll and heave compensation.