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Halliburton pumped a total of 51 bbls of cement for the production casing
cement job, consisting of 5.26 bbls of lead cement, 38.9 bbls (47.74 bbls when
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foamed) of foamed cement, and 6.93 bbls of tail cement. BP did not plan to
pump cement above the top wiper plug in order to preserve the ability to run a
cement evaluation log (discussed below), if necessary. Cement above the wiper
plug would have provided an additional barrier to hydrocarbon flow.

2. Pump Time and Rate

BP planned to pump the cement into the well at a relatively low rate of
four barrels a minute in order to reduce pressure on the formation that could
result in lost returns. This strategy carried risks since a higher pumping rate
generally would have increased the likelihood that cement would displace mud
from the annulus and thereby would have increased the likelihood of a
successful cement job.

BP was aware that it was using a low pump rate, so it wanted to be able to
maximize the amount of time it could run the pump without the cement setting
up or fracturing the formation. Brian Morel, BP Drilling Engineer, expressed this
in an email to John Guide, BP wells team leader, on April 17, which stated: “I
would prefer the extra pump time with the added risk of having issues with the
nitrogen. What are your thoughts? There isn‘t a compressive strength
development yet, so it’s hard to ensure we will get what we need until its [sic]
done.”
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3. Nitrified Cement

Another way in which BP sought to reduce additional lost returns during
the cement job was by using a nitrified or “foamed” cement slurry in the annular
space (the “tail cement” for the shoe track was unfoamed cement). Cement
specialists make nitrified or foamed cement by injecting cement with nitrogen
bubbles while the cement is being prepared on the rig. Nitrified cement is less
dense than unfoamed cement and therefore exerts less pressure on the formation.
However, the use of foamed cement creates the risk of nitrogen breakout – if the
nitrogen bubbles in the cement “break out” of suspension – which can result in
inconsistent cement placement and densities. The use of nitrified cement in

92 BP‐HZN‐CEC011406.
93 BP‐HZN‐MBI00255923.

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