Operators looking to increase activity in the Arctic must deal with the harsh environmental issues that make work in the region difficult. In particular, sea spray icing can affect the integrity of offshore structures, posing a significant safety hazard for onsite workers. To help address this issue, DNV GL recently partnered with a handful of operators on the Rig Spray joint industry project (JIP), which seeks to develop a simulation model that bridges functional winterization requirements and real physical conditions for rigs, platforms, and vessels.
“We aim to ensure that the design of icing mitigation measures delivers both safety and cost benefits,” Per Olav Moslet, DNV GL Arctic technology program director, said in a statement.
DNV GL previously released an offshore standard (DNV-OS-A201 “Winterization for Cold Climate Operations”) that addressed the anti- and de-icing procedures used to mitigate ice accumulation. While that standard and others currently available list safety function requirements and mitigation solutions, they do not give specifics on how and where they should be implemented. The Rig Spray JIP aims to reduce the uncertainty related to the prediction of sea spray production by measuring offshore installations. It includes the development of equipment for reliable long-term measurements of sea spray flux, frequency, and duration.
The first step in the process will be to develop a software tool that further understands sea spray icing using mathematical modeling and measurements. This tool should provide a basis for extending local ice estimations to a wider spectrum of metocean and structural conditions, which in turn could lead to cost-effective approaches for handling winter conditions on drilling rigs, production platforms, and vessels operating in cold climates. The rate of ice accretion is determined by the amount of water hitting a surface per time and the heat transfer from the surface, and DNV GL said that both must be accurately predicted for marine icing models to give reliable results. Due to a limited number of available sea spray measurements, all existing models are associated with a large uncertainty in the amount of sea spray.
“Present knowledge of sea spray generation is limited to very local metoocean conditions and sporadic vessel designs. We certainly need to fill this gap with more experimental and modeling studies, RigSpray project manager Olga Shipilova said.
Among the JIP’s secondary objectives are the measurements of sea spray on offshore structures such as semisubmersibles, and the study and quantification of uncertainties in the sea spray icing model for areas such as water transport and heat transport.
The project is scheduled to last until 2019 and has a budget of NOK 18.6 million, with financial support from Statoil, Eni, OMV, Aker, and Lundin. DNV GL is managing the project and executing it in collaboration with Sintef ICT and the University of Oslo.