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after the displacement of the mud from the wellbore. The plan also increased the
depth of the cement plug to be set in the well as a barrier to flow. BP chose to
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hang 3,000 feet of drill pipe below the lock‐down sleeve to weigh it down.
Having chosen to do this, BP believed that it needed to set the cement plug
deeper than normal to increase the amount of weight on the lock‐down sleeve.
The approved plan also called for two negative tests. The first negative test was
to be to the wellhead with a seawater gradient on the kill line. The second
negative test was to be conducted after displacing with seawater down to 8,367
feet. Further, the approved plan called for the cement plug to be set in seawater
after displacement of mud from the wellbore.

BP’s temporary abandonment plan also called for the cement plug to be
set in seawater after displacement of mud to 3,300 feet below the mud line. This
created a risky situation – after displacement of the mud, the well would be in an
underbalanced condition and at risk of a well control event. In addition, BP had
already eliminated the second cement barrier that would normally be set above
the top cement wiper plug. This further increased the well control risks.

C. The Use of Lost Circulation Material as Spacer

BP’s plans for displacement of the mud from the riser at the Macondo well
called for the use of spacer fluid, which is used to separate the drilling mud from
the seawater during displacement. The plans included the use of two different
“pills” of spacer. The pills to be used were a blend of leftover lost circulation
material that had been mixed on the rig. The lost circulation material (material
provided by MI‐SWACO with the trade names Form‐A‐Set and Form‐A‐
Squeeze) had been primarily used to prevent additional lost returns at the well.
BP had never used this type of spacer before, and it did not know whether the
spacer would be compatible with the synthetic based mud that it was displacing.
BP also did not have any information about the long‐term stability of the
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interface between the spacer and the seawater. The Panel found no evidence
that BP had provided the rig crew with design specifications for the spacer.

The Panel reviewed evidence, including BP internal emails, that indicated
that BP chose to use the lost circulation materials as a spacer to avoid having to
dispose of the materials onshore. If the materials were circulated through the
205

203 Testimony of Ronald Sepulvado, Joint Investigation Hearing, July 20, 2010, at 145.
204 Testimony of Steve Robinson, Joint Investigation Hearing, December 8, 2010, at 114.
205 BP‐HZN‐MBI00262887.

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