BP’s Deepwater Horizon Accident Investigation (BP,RIG)

I thought it would be nice of me to share some excerpts from  BP's Macondo accident report. Clearly what happened on that well was product of negligence and mechanical failure.  Clearly BP is liable and the finger pointing game is clearly evident in the report quoted below. The report lists a number of "Findings" we took the liberty of highlighting a few.

From a  source from within the industry:

"Mud and gas on the rig floor….that is an oh shit moment if ever there is one. Tragedy all the way around and especially for our colleagues who lost their lives in the accident…..sort of forgetting about that I think. My gut still says bad cement job on the backside combined with bad TA decisions on deck…..usually the simpler explanations prove more plausible. BP is trying hard to divert attention from the fact that they really don’t know if they had a bad cement job or not."

Use the quote above to help draw a mental picture of the platform while reading Finding #5 below.

Lets focus on Finding #5 – Well control response actions failed to regain control of the well

(Excerpt from BP Deepwater Horizon Accident Report)

"At approximately 21:40 hours, witness accounts indicated that mud flowed uncontrolled onto the rig floor. Real-time data and further witness accounts suggest that the rig crew attempted to control the well by closing an annular prevent-er in the bop at approximately 21:41 hours. This first action was too late to prevent the release of hydrocarbons, which were already in the riser. Modeling suggest that the annular preventer did not fully seal around the drill pipe, allowing hydrocarbons to continue entering the riser.

The rig crew  diverted hydrocarbons coming through the riser to the mud gas separator (MGS), which was quickly overwhelmed and failed to control the hydrocarbons exiting the riser. The alternative options of diversion overboard through the 14 in. starboard divert er line did not appear to have been chosen, this action would probably vented the majority of the  gas safely overboard.

Real-time data indicated that at 21:47 hours, drill pipe pressure rose from 1,200 PSI to 5,730 psi within one minute. This was likely caused by the closure of one or two variable bore rams (VBRs), which sealed the annulus. AT approximately 21:49 hours, rig power and real time- data were lost. Witnesses recall an explosion on the rig, followed closely by a larger explosion. After the explosions, fires continued on the rig.

The sub sea supervisor attempted to activate the emergency disconnect sequence (EDS) some time after the explosion. This would have sealed the well and disconnected the riser from the BOP stack. There Were no indications that the sequence activated.

BP Conclusions:

No apparent well control actions were taken until hydrocarbons were in the riser. The actions that were taken after that did not control the well.

The annular preventer was likely activated at 21:41 hours, and it closed around the drill pipe. It failed to seal the annulus for approximately five minutes, allowing further floor of hydrocarbons into the riser until the annulus was sealed at 21:47, likely by the closure of a VBR.

The diversion of fluids overboard, rather than to the MGS, may have given the rig crew more time to respond and may have reduced the consequences of the accident.

Transocean's shut-in protocols did not fully address how to respond in high flow emergency situations after well control has been lost. Well control actions taken prior to the explosion suggest the rig crew was not sufficiently prepared to manage an escalating well control situation"

Tudor Pickering Holt's conclusion from this finding - "the annular BOP was apparently successful for a brief moment of time.  This may take some of the heat off RIG regarding BOP modifications, functioning and maintenance."

Posted in: BP,RIG