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Figure 12 – Off‐center drill pipe (Source: DNV)

2. Activation of the Casing Shear Rams

During intervention efforts, on April 29, the drill pipe was sheared using
345
the casing shear ram (“CSR”). DNV found that the shearing of the drill pipe
changed the flow pattern within the wellbore. At the BSR, the flow had been
through the partially sheared drill pipe; the new path allowed flow up the entire
wellbore, starting at the CSR through the 2.8 inch gap along the entire length of
the block faces.

3. Automatic Mode Function

DNV concluded that it could not rule out the possibility that the BSR was
346
closed through activation of the automatic mode function circuits. DNV found
that there was evidence that “conditions necessary for AMF/Deadman (loss of
power, communication and hydraulic pressure) existed immediately following
347
the explosion/loss of rig power and prior to ROV intervention.” DNV stated
that its function testing demonstrated that the AMF circuits within both pods
activated when the loss conditions were simulated. Function testing on the blue

345 DNV Report, Vol. 1 at 5.
346 Id.
347 Id. at 169. Modifications to the BOP stack are included in a timeline at Appendix F of the DNV
Report, Vol. 2 (Appendix D of this Report).

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