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The Panel found additional evidence that a blockage may have been
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present at the beginning of the production casing cement job. Earlier in the
procedure, the crew landed a bottom wiper plug on the float collar in order to
establish a separation between fluids (spacer and mud) already present in the
well and in order to prevent contamination of the cement. After the wiper plug
landed on the float collar, pressure was applied to rupture a burst disk in the
wiper plug, which would allow circulation of the cement job to continue. The
burst disk was designed to rupture at between 900 psi and 1,100 psi, but the disk
did not actually rupture until the pressure reached 2,900 psi.

BP might have been able to reduce the likelihood of float collar blockage
by installing a float collar that was more debris‐tolerant than the float collar used
on the Macondo well. Because of the numerous lost circulation events in the
well, BP had to use lost circulation material several times. When there is such
material in the well, drillers sometimes use debris‐tolerant float collars to reduce
the chances that the material might lead to a blockage. Indeed, during the
attempted float collar conversion, one of BP’s contractors suggested to Mark
Hafle, a BP drilling engineer, that BP use a more debris‐tolerant float collar in the
future. Hafle’s response was that the float collar “shifted at 3140 psi. Or we
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127
hope so.” This response suggests that Hafle could not verify that the float
collar had converted, nor could he explain why it took so many tries to convert
the float collar.

The Panel did not find sufficient evidence to determine what caused the
blockage that affected the float collar.

F. Cementing the Macondo Production Casing

The April 19cement job was performed according to the procedures

detailed in the April 18 OptiCem report. However, BP used only six
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centralizers in the well, rather than the seven centralizers recommended and

assumed in the April 18model. Prior to cementing, BP did only a partial

A reamer shoe is a piece of equipment that guides casing towards the center of the hole as it is
lowered down the wellbore.
125 IADC report 4/19/10; Sperry Sun rig data.
126 BP‐HZN‐MBI00257031.
127 Id.
128 BP‐HZN‐CEC000011406.

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