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production casing. When BP drilled out the cement job on the 16‐inch
intermediate long string, it discovered that the condition of the shoe track
suggested that the cement had not set up properly, leading the cement to channel
and result in lost returns.
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5. Cement Modeling

Offshore operators use cement models to calculate real‐time equivalent
circulating densities based on actual cement volumes, rates and fluid densities.
By modeling various inputs, operators can assess, among other things, the
likelihood that channeling in the cement will occur as it sets up. Channeling in
cement is a problem because it can provide an opportunity for gas to flow
through the cement, which is quantified as gas flow potential.

For the Macondo well, BP used Halliburton’s OptiCem program to model
pumping sequences of various fluid densities and volumes to determine whether
the minimum formation fracture pressure would be exceeded. In all, Halliburton
developed at least 30 to 40 models for the cement to be used with the Macondo
production casing. In developing these models, BP and Halliburton frequently
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changed assumptions about the casing string and number of centralizers to be
used. For example, Halliburton generated an OptiCem model on April 15 at 3:30
p.m., which showed that channeling could result if only ten centralizers were
installed in the well. The model called for ten centralizers to be installed between
18,300 feet and 17,811 feet measured depth, using approximately 45‐foot spacing
and an approximate 80% standoff. The resulting gas flow potential (“GFP”)
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was moderate at a reservoir zone of 18,200 feet measured depth.

Later on April 15, Halliburton ran a second model using 21 centralizers
installed between 18,300 feet and 17,400 feet measured depth, using 45‐foot
spacing with a 70% top of centralized interval standoff. This model predicted
that channeling would not occur; the resulting gas flow potential was minor.
Based on this report, BP ordered 15 additional centralizers to supplement the six
centralizers already on the Deepwater Horizon. BP’s decision‐making with respect

96 BP‐HZN‐MB100036098. Cement channeling is a failure during the cementing of the casing to
the formation in which the cement slurry leaves open spaces where hydrocarbons can potentially
flow. The shoe track is the space between the float collar and a piece of equipment called a
reamer shoe (located at the bottom of the casing).
97 Testimony of Jesse Gagliano, Joint Investigation Hearing, August 24, 2010, at 245.
98 Standoff is the smallest distance between the casing and the wellbore wall. The standoff ratio is
the ratio of the standoff to the annular clearance for a perfectly centered casing.

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