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when using synthetic oil‐based mud. The study stated that “an important aspect
that should be addressed when drilling with a synthetic fluid is the peculiarities
concerned with well control. Because of the solubility of formation gas in oil‐
based fluids, it could be completely dissolved in the mud at bottom‐hole
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temperature and pressure conditions, making kick detection very difficult.”
The Panel found no evidence that BP and MI‐SWACO discussed whether
the use of synthetic oil‐based mud would affect the rig crew’s ability to detect
kicks during drilling operations at Macondo. Even so, the Panel found no

evidence that the specific mud program used by BP and MI‐SWACO was a cause
of the blowout.

E. Mud Losses

Throughout the drilling of the Macondo well, BP experienced multiple
incidents where mud was lost into the formation. While the loss of mud during
drilling operations is not uncommon, it is a key indicator to drilling engineers
that they must monitor the well closely to ensure that well and formation
integrity are being maintained properly. Abnormal pressure zones identified as
a result of mud loss events often lead drilling engineers to change the well design
and casing setting points.

BP drilled the Macondo well to a measured depth of 18,360 feet. The crew
set a 9‐7/8 inch liner in place at 17,168 feet measured depth prior to drilling the
production section, which was the final section of the well. The last section was
difficult to drill due to a decrease in the fracture gradient at the bottom of the
wellbore. This condition required BP to carefully select the correct mud weight
necessary to maintain overbalance relative to the formation while avoiding fluid
losses to the well.

According to IADC daily reports, the well experienced mud losses of
approximately 3,000 bbls across the hydrocarbon zones of interest during the
drilling of the production casing open‐hole section. The crew controlled these
losses with the addition of lost circulation material (“LCM”) pills and a relatively
small quantity (less than 200 bbls) of a special blend of drilling fluid, which help
retard the loss of mud into fractures and highly permeable formations. From the
time the Deepwater Horizon moved onto location at Macondo, a total of

73 Id.

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