Our main interest was in the flow path and BOP issues:
Flow path:
The investigation team concluded that hydrocarbon ingress was through the shoe track, rather than through a failure in the production casing itself or up the wellbore annulus and through the casing hanger seal assembly.
BOP:
- The explosions and fire very likely disabled the emergency disconnect sequence
- The condition of critical components in the yellow and blue control pods on the BOP very likely prevented activation of another emergency method of well control, the automatic mode function (AMF), which was designed to seal the well without rig personnel intervention upon loss of hydraulic pressure, electric power and communications from the rig to the BOP control pods. An examination of the BOP control pods following the accident revealed that there was a fault in a critical solenoid valve in the yellow control pod and that the blue control pod AMF batteries had insufficient charge; these faults likely existed at the time of the accident.
- Remotely operated vehicle intervention to initiate the autoshear function, another emergency method of operating the BOP, likely resulted in closing the BOP’s blind shear ram (BSR) 33 hours after the explosions, but the BSR failed to seal the well.
BP’s flow path assessment is consistent with our expectations. Early on, while most of the attention was focused on the annulus, we thought that flow inside the production casing was a distinct possibility. With regard to the BOPs, BP’s explanation is a more complete than we expected at this time, given that the stack has just been recovered.
More to follow.
