The U.S. Bureau of Safety and Environmental Enforcement (BSEE) and the U.S. Coast Guard have issued a joint safety alert addressing a dynamic positioning incident involving an offshore supply vessel (OSV) which resulted in a loss of position while conducting a critical outer continental shelf activity.
The OSV was attached to a wellhead, lost position and severed the wellhead tree causing a lubricant release on the platform deck and to the environment. Immediately prior to the position loss, the OSV had multiple DP system alarms and failures, including loss of bow thruster and engine control.
No attempt was made to identify or correct the causes of these failures and the operations continued. At the time of the position loss, the OSV was being utilized to support pump and electric line equipment which was connected to the well at the time of the incident.
Specifically, when the vessel lost position, the vessel operator was in the process of removing a downhole DX plug from the well via wireline. High pressure pump lines were also connected to the well, although actual pumping operations were not in progress. When the vessel lost position, the Christmas tree was sheared from the well because of the force exerted on it by virtue of the connected high pressure lines. Severe consequences were averted because a subsurface safety valve was activated and there was an absence of hydrocarbon flow from the well.
The incident highlights the following critical issues:
Alarms: The Coast Guard and BSEE stress the importance of properly acknowledging and investigating all alarms
SMS: The OSV was not required to and did not have an International Safety Management (ISM) Code certificate. The Coast Guard reminds OSV owners and operators that an effective SMS is essential to safe operations.
Dynamic Positioning: The Coast Guard strongly recommends owners and operators of OSVs using DP to follow DP Marine Technology Society DP operations guidance when conducting critical activities.
The alert is available here.