Page 42: of Offshore Engineer Magazine (Jan/Feb 2021)

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FEATURE GREEN RIGS available energy. Integrating these technologies has provided a holistic solution, now deployed on board the semi-submers- ible drilling rigs COSLPromoter and COSLInnovator, which achieves far greater energy savings than could be attained by focusing on a single area.

Learning from the past

The challenge was significant, as COSLPromoter and

COSLInnovator already claimed record low emissions for a 6th generation harsh environment semi-submersible

DP3 rig. Historical data provided the key to the savings delivered by both NOV and Kongsberg. The rigs are both powered by six Wärtsila Vasa 12V32 diesel generators de- veloping 4,800kW each. These previously ran all the time during drilling operations, but analysis showed that full capacity was rarely used. NOV examined historical data for parameters such as rig movement, hook load, and the number of generators, and delivered a software update based on this information to optimize energy utilization for large consumers.

Figures for estimated maximum power consumption drawn from this historical data were sent to the team at Kongsberg, who, based on these estimates, developed advanced, targeted solutions to control energy production and distribution on board. The net result allowed them to shut down – on aver- age – three of the six diesel engines. COSL can now deliver full DP3 drilling operation with fuel consumption of less than 20 tonnes per day, and – as COSLPromoter and COSLIn- novator are certi?ed to operate in 2 split mode for DP3 and

Posmoor/anchor operations – the possibility exists to deliver

Predicting the future even greater ef?ciency and sustainability by running on just

While the additional generators remain available for use in two generators.

To service the needs of the rig, the remaining generators adverse conditions, the aim of the Kongsberg/NOV solution is work at higher loads, which is highly bene?cial to the diesel to avoid using them when not required. Kongsberg Maritime engines, with more ef?cient fuel consumption and reduced helps to achieve this by improving how ef?ciently the installed thrusters are used via a dynamic load prediction strategy, built carbon build-up. This has a positive knock-on effect in terms of both working environment, noise, and reducing required on the company’s decades of experience in Dynamic Position- ing (DP). Just as a driver might accelerate a car as they ap- maintenance.

proach a steep hill in order to avoid making a reactive response

Reducing the number of running generators and increas- which consumes more fuel, Kongsberg’s patented system an- ing the ef?ciency of operation of the remaining units pro- duces dramatic savings both in costs and emissions. Annual ticipates thruster requirements to virtually eliminate spikes in fuel consumption is cut by approximately 2,300 tonnes, demand, similar to a peak shaving application.

CO2 emissions by 7,300 tonnes and NOx by 125 tonnes,

Measurable success representing an overall saving in both fuel and emissions of

To quantify the savings delivered, Kongsberg uses an In- more than 25%.

The project is approved and supported by the NOx Fund, formation Management System (K-IMS) that collects perfor- a Norwegian Government initiative for reducing NOx mance data from the rig and uploads it to the cloud, allowing information to be viewed in a dashboard environment and emissions.

42 OFFSHORE ENGINEER OEDIGITAL.COM