Offshore Marine Technology: 2nd Quarter 2017
On the face of it, the offshore oil and gas sector currently seems an unlikely breeding ground for autonomous vessels – and yet that’s precisely the market that Rolls-Royce is targeting with two unmanned vessel concepts. Rolls-Royce VP for innovation Oskar Levander says: “The offshore oil and gas industry is very risk-averse. It’s not the first place you’d look for users of autonomous ships; anyone who picks up on these concepts would be considered the ‘early adopters’ of this sector.” However, he reckons: “When the offshore market bounces back, it won’t look exactly the same as it did before.” Most owners/operators won’t forget the impact of this downturn and will be hesitant to return to pre-crash levels of spending. At the very least, unmanned vessels present the possibility of significantly reducing crew-related expenditure.
Take PSVs, for instance. Rolls-Royce has calculated that the owner of a typical PSV can break down his/her per-vessel costs as roughly comprising: 35% on capex; 32% on manning; 20% on bunkering; and just 4% on maintenance. Levander comments: “Obviously, more of the budget can be allocated to maintenance if you significantly cut manning expenses.”
Rolls-Royce has now unveiled two compact concepts for the offshore sector’s consideration. Inspiration for these vessels came from the most unlikely of places – namely, online retailer Amazon’s autonomous aerial delivery drone, which is designed to drop packages at customers’ houses using parachutes.The compact nature of the flying drone struck a chord with Rolls-Royce. “The fact we are cutting crew numbers at sea means we can have a small vessel – we can really scale the thing down,” Levander recalls. As a safety bonus, a small unmanned vessel would also pose far less of a threat to offshore platforms, rigs and sites in the event of a collision or accident.
The first proposal is for a small PSV, designed in the style of an open-top container vessel, carrying deck cargo only. The proposed ‘drone PSV’ would be equipped with redundant hybrid machinery, an autonomous navigational system, permanent magnet (PM) azimuthing thrusters and a dynamic positioning (DP) system, Levander says. The basic model has been designed with a load equivalent to 8teu, he adds.
The autonomous mini-PSV could be used to drop off supplies to offshore personnel on a weekly or even daily basis, creating an integrated logistics system with a corresponding decrease in fuel and energy consumption, as well as reduced vessel charter rates and crewing costs. Compared to the reference PSV’s cost breakdown of 35% capex / 32% manning, the PSV drone could slash manning costs to 17%, Levander estimates, which would free up more resources for capex – which could now, theoretically, be increased to 41% – or enable the owner to realise a substantial decrease in overall costs.
The second proposal concerns an autonomous surface vessel dedicated to ROV support. “Typically, ROV operations are supported by a large mothership at the surface, which costs a lot to rent,” says Levander. “You have highly trained ROV operators on the mothership, but they have nothing to do while the vessel is in transit and/or repositioning.” Instead, Rolls-Royce proposes a small, remote-controlled surface vessel, which, along with the ROV, would be managed from a shore-based control centre. In this way, the operator can forego the cost of deploying ROV specialists at sea and instead use skilled personnel, working in shifts at the control centre. Similarly, the need to build crew accommodation blocks (which bump up vessel weight) is reduced.
For the ROV surface support vessel, Rolls-Royce envisages a 20m x 6m unit – possibly fashioned from GRP – which would carry up to 99tonnes, including 4,000m of cable. The vessel would be powered by twin MTU 8V4000 gensets driving two US 105-P6 thrusters, resulting in a top speed of 14knots. The crew-free vessel would also offer an endurance of 25 days when operating at 30% MCR, and its size would make it easy for technicians to lift it onto offshore construction vessels (OCVs) or rigs.
