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 Nathaniel Chaisson, a cementing engineer, stated that “poor centralization
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does not equate to complete blowout;”
 Jesse Gagliano, a cementing engineer, stated that “channeling does not
equal a blowout;” and
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 Vincent Tabler, a cementer, stated that, in a meeting on April 19, no one
raised concerns about the risk associated with the production casing
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cement job.

It is not common for operators in the Gulf of Mexico to complete cement
jobs that present a severe gas flow potential, although cement jobs with these
conditions have been completed successfully in the past. Halliburton provided
the Panel with information about the number of cement jobs it conducted
between January 1, 2005 and April 20, 2010 where the gas flow potential was
calculated to be severe. The Panel reviewed records for jobs performed in the
Gulf of Mexico, and offshore in Brazil, Norway and the United Kingdom, which
showed that 53 of these jobs had severe gas flow potential. Eleven of these 53
cement jobs were performed in the deepwater of the Gulf of Mexico. BP was the
operator on two of Halliburton’s severe gas flow potential cement jobs
conducted in the deepwater Gulf of Mexico.

D. Centralizers

A centralizer is a device that fits around a casing string or liner to ensure
centering of the casing in an open hole. Centralization of casing strings and
liners facilitates the efficient placement of cement around the casing string. Even
though the Macondo well was a straight hole, BP used centralizers because the
diameter of the production casing does not always align exactly with the center
of the wellbore and, therefore, without centralizers the production casing could
rest along the sides of the wellbore. Casing string contact with the side of the
wellbore can lead to void spaces in the cement job (referred to as “channeling”).

On April 14, four days before the production casing was scheduled to be
run, BP had only six centralizers available on the Deepwater Horizon for the
production casing cement job. The six centralizers already on the rig had built‐in
stop collars. Stop collars prevent a centralizer from moving up and down the
casing and built‐in stop collars are integrated into the centralizer. Other

103 Testimony of Nathaniel Chaisson, Joint Investigation Hearing, August 24, 2010, at 419.
104 Gagliano, testimony at 264.
105 Testimony of Vincent Tabler, Joint Investigation Hearing, August 25, 2010, at 12‐13.

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