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XVIII. Conclusion

As detailed in this Report, the blowout at the Macondo well on April 20,
2010 was the result of a series of decisions that increased risk and a number of
actions that failed to fully consider or mitigate those risks. While it is not
possible to discern which precise combination of these decisions and actions set
the blowout in motion, it is clear that increased vigilance and awareness by BP,
Transocean and Halliburton personnel at critical junctures during operations at
the Macondo well would have reduced the likelihood of the blowout occurring.

BP well designers set the casing in a location that created additional risks
of hydrocarbon influx. Even knowing this, BP did not set additional cement or
mechanical barriers in the well. BP made two additional significant decisions
that further increased risks – first, it decided to have the Deepwater Horizon crew
install a lock‐down sleeve as part of the temporary abandonment procedure.
Second, BP decided to use a lost circulation material as spacer, which risked
clogging lines used for well integrity tests.

BP personnel and Transocean personnel failed to conduct an accurate
negative test to assess the integrity of the production casing cement job. The
Deepwater Horizon rig crew, therefore, performed temporary abandonment
procedures while unaware of the failed cement job beneath them and the
looming influx of hydrocarbons. Unfortunately, the rig crew then limited its kick
detection abilities by deciding to bypass the Sperry Sun flow meter when
displacing fluid from the well overboard.

The Deepwater Horizon rig crew missed signs of a kick and thus was
delayed in reacting to the well control situation. Once the flow reached the rig
floor, the crew closed the upper annular and upper variable bore ram and
diverted the flow to the mud gas separator. The mud gas separator could not
handle the volume of the blowout and explosions followed. Additionally,
forensic analysis by DNV strongly suggests that by the time a crew member on
the bridge activated the emergency disconnect system, the explosions had
damaged the Deepwater Horizon’s multiplex cable and hydraulic lines, which
rendered inoperable the BOP stack’s blind shear rams.

The force of the blowout, and possibly the force from drill pipe in the
riser, buckled the drill pipe and placed it in a position where it could not be
completely sheared by the blind shear ram blades. As a result, the blind shear

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