The need for enhanced redundancy and proper deck arrangements to ensure continuous operation of seismic vessels without loss of speed is the backbone of new technical requirements developed by DNV in consultation with key industry players such as WesternGeco, PGS and Fugro-Geoteam.
With its high-end computerised technology, sudden loss of service speed may damage a seismic vessel’s cables, causing complications in seismic data processing. DNV’s new notation, released this summer, focuses on the increased availability of the vessels during critical phases of seismic operations. The key issue is maintenance of propulsive power. The class notation has taken the DNV concept for redundant propulsion one step further so that any failure onboard will not lead to loss of more than 50% forward trust. This rate is sufficient to maintain a minimum speed of a few knots, which will protect any deployed air guns and streamers.
Seismic vessels typically operate for many months continuously without seeking harbour. The class notation requires a deck arrangement that facilitates side-by-side transfer for crew and resupply from a seismic support vessel. Beyond this, the class notation also sets a requirement for the bridge arrangement to ensure good view to the streamers and any workboats that are close by during normal operation. High-pressure systems are also addressed in the class notation to ensure the crew can safely carry out deck operations.