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assorted dry and liquid additives. After BP approved the design, Halliburton
began pumping the cement.

In addition to cementing, the process of preparing a well for temporary
abandonment includes further procedures to secure the well so that the rig’s BOP

stack and riser can be removed as the rig prepares to move off the location. BP
engineers in Houston developed temporary abandonment procedures (different
from the MMS‐approved procedure) for the Macondo well that included the
34
following steps: performing a positive pressure test; displacing mud in the well
from 8,367 feet to the wellhead; performing a negative pressure test; setting a
35
300‐foot cement plug in the well approximately 3,300 feet below the sea floor and
36
setting a lock‐down sleeve to lock the final casing into place. BP engineers
changed the order of these steps several times in the days before the temporary
abandonment.

During all well activities, including temporary abandonment, crew
members monitor various sensors on the rig that show fluid volumes and well
pressures. These sensors provide real time data to the crew, which monitors
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and analyzes the data on electronic displays to identify potential kicks, among
other things. Early kick detection is critical to maintaining well control.

On April 20, the crew conducted tests to evaluate the integrity of the
production casing cement job. The tests were based on MMS‐approved
procedures that a BP drilling engineer had sent to the rig that morning. The
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crew first conducted a positive pressure test to evaluate whether the well casing
could sustain pressure exerted on it from the inside of the well and received
39
favorable results. On the same afternoon, the crew circulated mud up from the

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Additives are used to tailor the cement to the needs of a well. For example, a weighting
material might be added to a cement slurry when a higher density cement is needed.
34 A positive pressure test is conducted by pumping fluid into the well after sealing the blind
shear rams. The rig crew monitors the well to determine whether pressures in the well remain
static.
35 A negative pressure test seeks to create conditions that simulate what will occur when the well
is abandoned. The rig crew displaces drilling mud with other fluids, resulting in the wellbore
being underbalanced against the formation pressures. The rig crew then monitors pressures and
flow to determine the integrity of the barrier being tested.
36 BP‐HZN‐MBI‐00129108. Each of these steps is discussed in detail in Section I of the findings
and conclusions in this Report.
37 Fluid includes any fluid (mud, spacer, seawater) coming out of the well or across the rig.
38 BP –HZN‐MBI‐00021237.
39 BP‐HZN‐MBI‐00136947.

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