Sep 09, 2010– BP released their own internal investigation report yesterday into the Deepwater Horizon oil rig explosion, fire, sinking and then massive oil spill caused by the rupturing of the pipeline riser several thousand meters below the ocean surface of the Macondo well. However, there is no one cause that has been listed, but rather several contributing causes have been mentioned. Some of the key noteworthy points in the report are listed below.
Our own comments are highlighted below (in bold italics).
1. Weaknesses in cement design and testing.
2. Failure of the shoe-track barrier in isolating hydrocarbons. The investigation team has reportedly found some clues that identify how the shoetrack cement and the float collar allowed hydrocarbon ingress into the production casing.
3. Acceptance of the negative pressure test before establishing the well integrity-here BP has pointed fingers at the Transocean rig crew as well as at BP’s own rig leadership which “incorrectly” interpreted the test results.
4. Influx was not recognized until the hydrocarbons were in the riser.Apparently almost 40 minutes before the crew started taking action, increase in drill pipe pressure data could be seen-which was not apparently noticed.
5. Wrong actions on diverting the fluids exiting the riser to the Mud-Gas separator, rather than to the overboard diverter line.
6. Once diverted to the Mud-Gas Separator, the fluids got vented onto the rig itself, where it these fluids may have found an ignition source and exploded
7. Failure of the Fire & Gas System to prevent ignition-this point seems a bit debatable, because an F & G system cannot “prevent” a fire from occuring really- all it does it to measure any gas leaks or fires and extinguish them. Apparently the hydrocarbons went into unclassified areas like engine rooms where it could find potential sources of ignition.
Incidentally this is a similar phenomenon that was observed in the infamous Buncefield, UK accident where a large explosion took place.
8. Lastly the Blow Out Preventer (BOP) did not seal the well. The control pods that were supposed to act did not work, a guess is that they got damaged due to the fire and explosion. Consequently a critical solenoid operated valve did not operate. What is more startling and damning however, is that the control pod batteries had inadequate charging, due to which the Solenoid valve did not operate-this is most certainly an oversight by the maintenance personnel who were in charge of the Control & Instrumentation systems on the rig.
Finally the report mentioned that the investigation revealed potential weaknesses in the inspection and maintenance regimes.
Though there will be several more investigation reports from different agencies like the Coast Guard, the US Chemical Safety Board and others, the initial BP investigation does seem to have covered a lot of ground. It raises questions about hazardous area classification, especially on an oil rig where the classification of areas that are classified and “safe” or “non-hazardous” seems a bit arbitrary. If one cannot know which areas of the rig would have the presence of hydrocarbons then there is no point in classifying-one should designate all areas as hazardous, although with different risk profiles such as Zone 1, Zone 2 and so on.
Have a look at the excellent training resources for both of these crucial topics here.