Page 54 - test2

additional 10 hours to install 21 rather than 6 centralizers, and he stated that the
earlier decision to use 21 centralizers was made by Gregg Walz, BP drilling
115
engineer team leader, and others in his absence.

The Panel found no evidence that BP’s decision to use 6 centralizers rather
than the 21 recommended by Halliburton was a cause of the blowout.

E. Float Collar

1. Float Collar Function

Float collars are one‐way valves installed at or near the bottom of the
casing string. When a float collar has been successfully “converted” it will allow
fluids to flow in only one direction. A converted float collar allows cement and
other fluids to be pumped down the well without reversing direction and
coming back up the casing. BP used a Weatherford Model M45AP mid‐bore
auto‐fill float collar in the Macondo well, which is depicted in Figure 4 below.

The float collar uses a double‐check valve – a mechanical valve that
permits fluid to flow in one direction – that is held open by an auto‐fill tube.
When running the casing into the well, the auto‐fill tube allows mud to flow into
the casing, thereby reducing the force exerted by the mud on the formation and
helping to prevent loss of fluids into the formation. To convert the float collar, a
ball (in this case an “Allamon ball” because the float collar was manufactured by
Allamon) rests in the auto‐fill tube when running the casing into the well and
when mud pumping starts it restricts the flow of mud by diverting the mud
through two small ports in the auto‐fill tube. Circulation through these ports
creates a differential pressure in the float collar, forcing the auto‐fill tube out of
the float collar and allowing the check valves to close. In doing so, a float collar,
which is set near the bottom of the casing string, acts as a check valve and
prevents cement that is pumped down through the casing from flowing back
into the shoe track (which is the distance between the float collar and end of the
casing) once the cement is in place. If the float collar fails to convert, it is possible
for “reverse flow” or “u‐tubing” flow to occur from the bottom of the casing up
the wellbore toward the rig.

115 BP‐HZN‐CEC022433.

49