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at about 5:52 p.m. and attempted to bleed‐off the drill pipe pressure. After three
unsuccessful attempts, the crew eventually justified the pressure as a “bladder
effect.” The rig crew did not realize the well was flowing until mud was
discharging onto the rig floor. The Deepwater Horizon crew’s hesitance to shut‐
in the BOP immediately was a possible contributing cause of the kick
detection failure.

The MMS‐approved APM called for two negative tests. This would allow
for the greater opportunity to detect hydrocarbon influx in a staged test since the
first test would have been to the wellhead and the second test would have been
to the depth of 8,367 feet. BP’s failure to conduct the first of the two negative
tests was a possible contributing cause of the kick detection failure.

When the Deepwater Horizon crew resumed pumping the returns
overboard at 9:15 p.m., the flow bypassed the Sperry‐Sun meter due to its
downstream location off the flow return trough. Consequently flow‐out data
could not be adequately monitored by personnel, such as the Sperry‐Sun
mudloggers, who were responsible for monitoring these data. The rig crew’s
decision to bypass the Sperry‐Sun flow meter while pumping the spacer
overboard was a possible contributing cause of the kick detection failure.

Well control training historically has not addressed situations, such as
conducting a negative test in that one is “inviting” a well control event to occur.
Additionally, displacement operations that put the well in an underbalanced
condition should be closely monitored throughout displacement operations. The
failure of BP’s and Transocean’s well control training and MMS requirements
to address situations, such as negative tests and displacement operations, was
a possible contributing cause of the well control failure.

D. Response Failure Contributing Causes

The rig crew’s decision to use the mud gas separator instead of the
diverter accelerated the likelihood that the gas on the rig would ignite. The
decision to use the mud gas separator during the well control event was a
contributing cause of the response failure.

Once members of the drill crew identified the increase in drill pipe
pressure, they checked the well for flow. At approximately 9:42 p.m., the crew
detected flow and diverted the gas to the mud gas separator. The rig crew was
not able to determine the magnitude of the flow when it made the decision to go

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