OTC | Offshore Technology COnference

Amid the global energy expansion, where diverse energy sources are needed to meet rising demand, minerals like nickel, cobalt, and lithium become imperative for the renewable energy supply chain. While these minerals are almost exclusively mined from land, when utilizing offshore industry expertise, these critical minerals become accessible by deep sea minerals harvesting of the seabed, where vast reserves of such minerals remain untapped. This paper highlights a test of the feasibility of side-by-side mooring for offloading such minerals in the offshore environment. The study employs frequency and time domain simulations to evaluate the operation of a two-vessel system. The setup involves a production vessel with dynamic positioning (DP) and a transport vessel moored side-by-side, connected with mooring lines and fenders. Simulations span various wave heights, periods, and directions. Critical metrics like line tensions, fender loads, and vessel motions are then contrasted against predefined criteria, pinpointing scenarios where the operation could be viable.

The simulations revealed that the primary determinant of operability is line tensions. Factors such as the direction of incident waves, wave period, and the shielding effects from the DP vessel also significantly influence outcomes. Particular care should be taken to manage the drafts of the vessels to prevent thruster impact on the transport vessel, which would elevate line loads. The DP settings of the production vessel should also be tuned to account for the vessel moored alongside.

Additionally, the paper discussed further work needed to establish guidance on the approach and departure of the transport vessel. The maneuvering characteristics of the transport vessel will be pivotal during its approach and departure, especially given the operations’ remote open water location and unpredictable tug support availability as a result thereof.