US, GoM -- During an unplanned disconnect of the lower marine riser package from the subsea BOP on a semisubmersible drilling rig, 710 bbl of mud was released into the Gulf of Mexico, according to the MMS.
The rig involved in the accident was engaged in exploratory activities, when shifting loop currents coupled with quickly deteriorating met-ocean conditions from tropical storm developments, pushed the rig's DP system beyond its capacity, leading to a loss of position, says the MMS.
While the riser volume was being displaced with seawater in preparation for the disconnect operation, the rig was no longer able to maintain station. As a result, the riser was disconnected from its lower marine riser package, and synthetic mud was released.
An MMS investigation concluded in part that the inability of the rig to maintain station adequately, resulting in the subsequent release of synthetic mud into the Gulf, was primarily the result of inappropriate DP rig selection for the environment in which it was to operate.
Procedures onboard the vessel at the time of this incident did not adequately take into account the proper watch areas and appropriate T-times for certain action items to be taken during deteriorating sea conditions, it adds. These procedures were revised after the incident to reflect loop currents and associated eddies in the GoM.