ACCIDENT
INVESTIGATION REPORT- APACHE DEEPWATER ALLOWED DISCHARGE OF DRILLING FLUID INTO
THE GULF OF MEXICO
INVESTIGATION FINDINGS
At approximately 23:00 hours on 23 May 2014, the Diamond Ocean Onyx
semi-submersible, moored, drilling rig under contract to Apache Deepwater LLC
(Apache) reported an initial loss of 107 barrels (bbl) of 16.9 pounds per
gallon (ppg) of synthetic base mud (SBM) during abandonment operations on Well
#1 (Bimini Well) permitted at the subsurface location of Garden Banks (GB)
Block 213; surface location at GB Block 169. However, after strapping calculations were
completed, the SBM discharge amount was revised from 107 bbl to 61 bbl. There were no injuries or property damage
during this incident.
Prior to the SBM spill, the mud line from the Mud Pit Room to
the auxiliary recirculation line on the Schlumberger Cement Unit had blockage
and required cleaning. Several attempts
to remove the blockage between Batch Mixing Tank #2 and Cement Unit by flushing
with water were unsuccessful; therefore, the line was removed, cleaned out and
reinstalled. While cleaning out the
line, the two mud line valves were functioned several times but were left in
the open position.
At approximately 22:45 hours, the Schlumberger Cementer began
mixing cement from Batch Mixing Tank #2 to the Cement Unit Auxiliary Tub. When he began pumping the first 8 bbl of
cement, the Diamond Ocean Toolpusher observed that Batch Mixing Tank #2 was over
flowing and discovered that SBM was spilling into the Gulf of Mexico. The Diamond Ocean Toolpusher responded by
closing the two open valves on the overboard drain line located below the Main
Deck at 23:30 hours that prevented any additional SBM discharge.
On Tuesday 27 May 2014, Bureau of Safety & Environmental
Enforcement (BSEE) inspectors from the Lafayette District mobilized to the
Diamond Ocean Onyx rig located at the surface location of GB Block 169 to
conduct an incident investigation. BSEE inspectors met with representatives
from Apache, Diamond Ocean and Schlumberger and obtained documentation related
to the SBM spill. The Apache Company Man
informed BSEE that a total of 61 bbl of SBM was discharged into the Gulf of
which approximately 26 bbl consisted of synthetic based oil. Apache reported that the preliminary cause of
the SBM spill was attributed to improperly aligned mud line valves on the
Schlumberger Cement Unit. The
Schlumberger Cement Unit mud line valves were left in the open position that
allowed the SBM to overflow from the 50 bbl Batch Mixing Tank #2 and the Cement
Unit 15 bbl Auxiliary Tub. The SBM
spilled into the secondary containment areas for both vessels, then flowed into
drains that lead to the overboard discharge line. Since the overboard discharge line valves
were also left in the open position, this provided a conduit for the SBM to
spill into the offshore waters.
Incident investigations conducted by Apache and Schlumberger
have attributed the probable causes of the SBM spill to the Cement Unit mud
line valves that connected the mud line to auxiliary recirculation lines that
were left in the open position after cleaning and were not checked to verify
their position prior to the cement job.
The contributing causes to the SBM spill identified by Apache
and Schlumberger included: 1) the design of the Cement Unit package did not
provide the Cementer with a clear view to monitor Batch Mixing Tank #2 nor was
it equipped with a device to remotely monitor the fluid level in the tank; 2)
inadequate cement unit start-up procedures; 3) the failure to identify risk
associated with handling of SBM with the Cement Unit; and 4) the two valves on
the rig's overboard discharge line were in the open position during the cement
that provided a pathway for the SBM to spill into offshore waters.
LIST THE PROBABLE
CAUSE(S) OF ACCIDENT:
Incident investigations conducted by Apache and Schlumberger
have attributed the probable causes of the SBM spill to the Cement Unit mud
line valves that connected the mud line to auxiliary recirculation lines that
were left in the open position after cleaning and were not checked to verify
their alignment prior to the cement job.
LIST THE CONTRIBUTING
CAUSE(S) OF ACCIDENT:
The contributing causes to the SBM spill identified by Apache
and Schlumberger included:
1)
the design of the Cement Unit package did not
provide the Cementer with a clear view to monitor Batch Mixing Tank #2 nor was
it equipped with a device to remotely monitor the fluid level in the tank;
2)
inadequate cement unit start-up procedures;
3)
the failure to identify risk associated with
handling of SBM with the Cement Unit; and
4)
the two valves on the rig's overboard discharge
line were in the open position during the cement job and that provided a
pathway for the SBM to spill into offshore waters.
SPECIFY VIOLATIONS
DIRECTLY OR INDIRECTLY CONTRIBUTING. NARRATIVE:
Based on the incident investigation findings, a G-110 Incident
of Non-Compliance was issued to Apache Deepwater, LLC (Apache) on 27 May 2014
to document its failure to protect health, safety, property, and the
environment by performing operations in an unsafe and unworkmanlike manner. On
23 May 2014, Apache allowed an unauthorized discharge of 61 bbl of 16.9 ppg SBM
into the Gulf of Mexico from open valves on the Cement Unit mud line and the
overboard discharge line.
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