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occurred between April 19 and April 20 was a possible contributing cause of
the blowout.

D. Flow Path Cause

1. Production Casing Annulus Cement Barrier and the 9‐7/8 Inch

Wellhead Seal Assembly

As discussed above, the following evidence weighs against the possibility
that hydrocarbons flowed through the production casing annulus cement barrier
and the 9‐7/8 inch wellhead seal assembly:

1) On September 9, 2010, Dril‐Quip technicians confirmed with a lead
impression tool that the 9‐7/8 inch wellhead seal assembly remained
properly seated in the 18‐3/4 inch high pressure housing, where it had
been placed on April 19, 2010 prior to the flow of hydrocarbons.
2) On September 10, BP conducted a 30‐minute pressure test of the 9‐7/8 inch
production casing annulus that confirmed the lack of annular
communication.
3) On September 11, the lock‐down sleeve seal was successfully pressure
tested to 5,200 psi, which tended to prove that the hanger was properly
seated.
4) On September 22, Schlumberger’s logging data determined that “free” gas
was not present below the BOP to 9,318 feet measured depth.
5) On October 7, BP’s perforation of the 9‐7/8 inch casing between 9,176 feet
and 9,186 feet found that no u‐tube flow occurred from the casing to
annulus.
6) During well intervention operations, ROV observation determined the
wellhead seal assembly was intact. In addition, subsequent to removing a
portion of the 9‐7/8 inch production casing, original 13.8‐14.0 ppg mud
was discovered between the 16 inch intermediate casing and 9‐7/8 inch
production casing.
7) Pictures taken from the DDII relief well rig at the time the hanger and seal
assembly were extracted from outside hanger and seal assembly showed
no signs of erosion from annular flow.

Based on this evidence, the Panel concluded that hydrocarbons did not flow
from the production casing annulus cement barrier and the 9‐7/8 inch wellhead
seal assembly during the blowout.

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