OIL PLATFORM ACCIDENT INVESTIGATION – OVER-PRESSURIZATION OF THE WELL ANNULUS
On August 17, 2014, an incident occurred that resulted in
significant damage to the lower annular. This was an exploratory drilling
operation. The lower annular operating
chamber was prepared for pressure testing on the surface. The target pressure
for this test was 3000 psi. Once the lower annular was prepared, the Subsea
Engineer started applying pressure to the operating chamber using a test pump.
At this time, with the pump still running the Subsea Engineer decided to put
away some tools, leaving the test pump unit unmanned.
The Subsea Supervisor
arrived at the test unit to find the test pump unattended. He then left the
testing area to look for the other Subsea Engineer. He found the Subsea Engineer
in their shop and informed him that the test pump should never be left unattended.
The Task Based Risk Assessment did not address the monitoring of the running pump.
The Subsea Supervisor also informed the crew they should be testing the upper
annular operating chamber and not the lower annular operating chamber.
At this time
a loud bang was heard coming from the testing area and the test pump was then immediately
shut down. Further investigation by rig personnel found that the lower annular
operating chamber that has a (MAWP) Maximum Allowable Working Pressure of 3000
psi, was overpressurized to at least 10,000 psi.
LIST THE PROBABLE
CAUSE(S) OF ACCIDENT:
1)
Poor
communication between all personnel involved in the testing procedure.
2)
Leaving the
test pump running while unattended allowing the component being tested to over
pressurize.
3)
Nothing notated
in the Task Based Risk Assessment about leaving the test pump running without
properly trained personnel monitoring the pressure.
4)
The Subsea
Supervisor failed to secure the test pump prior addressing the Subsea Engineer
about leaving pump running and unattended.
LIST THE CONTRIBUTING
CAUSE(S) OF ACCIDENT:
1)
Miscommunication
and not being focused on the task at hand.
2)
Initial
documentation showed the upper annular operating chamber should have been tested
and not the lower annular operating chamber.
3)
Not
double-checking with Subsea Supervisor prior to commencing testing.
DAMAGED PROPERTY
Lower Annular
COST OF DAMAGE
Sheared inner cylinder studs. Pusher plate blown out of annular
housing. Broken shuttle valve on choke
isolation valve. Also support ring and
inner piston dislodged due to over pressurization causing significant damage to
lower annular.
Sevan Drilling has been forced to halt operations on a well
being drilled in the Gulf of Mexico due to a technical glitch with newbuild
cylindrical rig Sevan Louisiana.
