USCG: Oil Spill in US Waters Averted

The United States Coast Guard and the U.S. Bureau of Safety and Environmental Enforcement released a joint safety alert today in response to an incident in which an Offshore Supply Vessel (OSV) experienced a loss of position while conducting a critical Outer Continental Shelf (OCS) activity.

The OSV in question was attached to a wellhead, lost position and severed the wellhead tree causing a lubricant release on the platform deck and to the environment, according to the safety alert, which didn't specify the vessel in question or the location of the incident.  Many DP system alarms and failures were activated on the OSV before the incident, which went unheeded. These included the loss of bow thruster and engine control.  Severe consequences were averted, however, because a subsurface safety valve was activated and there was an absence of hydrocarbon flow from the well.

At the time of the position loss, the OSV's 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 through the connected high pressure lines.

The OCS activity performed was critical due to the short time to terminate and the potential uncontrollable release of hydrocarbons from a well with known sustained casing pressure. The OSV was not required to and did not have an International Safety Management (ISM) Code certificate. 

The Coast Guard and the BSEE both share jurisdiction of the OCS, and encouraged operators to properly acknowledge and investigate all alarms, and to take immediate and positive corrective action prior to initiating or proceeding with any critical OCS activity. The alert also expressed the Coast Guard's recommendation to owners and operators of OSVs using DP to follow DP guidance provided in reference 3 (Marine Technology Society (MTS) DP operations guidance) when conducting critical activities on the U.S. OCS.  The Coast Guard also encouraged OSVs to have a defined Critical Activity Mode of Operation (CAMO).