200736 Close approach with oil rig

A drilling rig was engaged in operations in a designated offshore oilfield. Its location had remained unchanged for more than four months and a two-mile radius safety zone had been established. This information was adequately promulgated to mariners. Despite these measures, on a clear day, the rig's crew was alerted to a cargo vessel that was approaching with a closest point of approach (CPA) of 0.3 nautical miles. It was observed that the ship's AIS was not operational, and general calls on the VHF went unanswered.

The rig's standby vessel was then sent off to intercept the cargo vessel and after closing with her, called her by name and also sounded the danger signal of several rapid short blasts at close range. The cargo ship made no attempt to respond and continued on her dangerous course, passing about two cables off the rig despite there being unrestricted sea room to seaward of the rig.

Root causes/contributory factors
Inattentive bridge watch on the cargo ship;
Passage plan did not take into account local navigation warnings.

Corrective/preventive actions by rig
Maintain proper look-out by sight and hearing as well as by all available means.
Deploy standby vessel to patrol safety zone of a two mile radius and warn vessels in vicinity.
Report incident to coastal authorities and to MARS (The Nautical Institute).

Editor's note: Regardless of whether a safety zone has been established around a rig, it is prudent to lay courses keeping well clear of charted oilfield boundaries. In any case, the appropriate radio watch must be maintained at all times, safety-related calls must be responded to and the OOW must ensure that the AIS is correctly set up and is operational.