- The annulus did not isolate the hydrocarbons - Halliburton's fault, though BP should have been more aware.
- The shoe track (bottom section of casing) did not isolate hydrocarbons - Halliburton's and Weatherford's fault.
- The negative pressure test was accepted although well integrity had not been established - Primarily Transocean's toolpusher's fault; BP's fault that company man accepted toolpusher's explanation.
- Influx of hydrocarbons was not recognized until hydrocarbons were in the riser - Transocean's fault.
- Well control response actions failed to regain control of the well - Transocean's fault
- Diversion to the mud gas separator (rather than directly overboard) resulted in gas venting onto the rig - Transocean's fault.
- The fire and gas system did not prevent hydrocarbon ignition - Transocean's fault
- The BOP emergency mode did not seal the well - Transocean's fault
Not on the list were BP's casing design, BP's decision not to run all the centralizers, BP's orders not to circulate bottoms up before the cement job, and BP's decision to displace the riser with seawater prior to running the top cement plug or setting the casinghanger lockdown sleeve. The report, in fact, staunchly defended the casing design calling it standard industry practice that was actually better than a liner, even though other operators, including Shell, disagree . The report concluded that the original influx of gas into the well came up through the production casing, which is the least likely path that required 4 simultaneous failures to occur. The obvious path, up the outside of the production casing to the casing hanger that we've talked about before, was dismissed, though they left the door open to that possibility, buried in the back of the report. As part of their defense of this conclusion was the live feed of pressure readings from the rig up until the explosions; they also cited the pressure behaviors of the well during the static kill, but left that data out of the appendices. They also discounted the lack of centralizers as a cause of the blowout, which I agree with, but for a different reason. They say it's because the gas from the formation actually went DOWN the annulus, into the production casing, through 134 feet of premium cement in the shoe track, through TWO float failed valves, and into the casing. I don't believe the centralizers were a factor because I question their effectiveness, especially in small gauge holes, such as this one.
Two new pieces of information were interesting, though. According to BP's conclusions about pressure data, one of the annular preventer worked, at least partially. They don't explain, though how it ultimately failed. Also, when gas first hit the surface, the crew ran it through the mud gas separator, which was overwhelmed, enveloping the rig in gas. Had they simply diverted it overboard, it could have given them more time to get the well under control. As it happened, the gas flooded the engine rooms with disastrous consequences.
Certainly, running nitrified cement was a factor in this well getting away from them, but that was BP's decision. Not running all the centralizers were BP's decision, and Halliburton's Opti-Cem cement report even warned BP of the likelihood of severe gas flow, which BP promptly ignored. The key mistake here, however, was failure to recognize the influx of hydrocarbons into the well. BP can blame Transocean and the others all it wants, but it was that mistake that lead to the disaster, and that responsibility lay on BP's shoulders as operator. In fact, the influx came to the surface because BP prematurely ordered that seawater be loaded into the riser before the final operations were complete.
It's more than just a coincidence that BP's own conclusions about the causes of this disaster happen to be somebody else's fault, and BP takes little responsibility for key errors that were made. It's also no surprise that the factors BP points to as causes are neither provable or disprovable, because almost everything they point to as causes are still in the hole, never to be recovered. There is plenty of blame to go around here between BP and Transocean. The rig crew should have recognized the kick...but the BP company men should have, too. We all know the BOP failed, and that's on Transocean's shoulders, but the rest? That's on BP as operator.
BP's blatant (some might say cynical) buck-passing calls the validity of the entire report into question, but that's not surprising, with the stakes so high. Rather than getting to the truth, BP's goal here was to spread as much fault as possible and blaming the dead guys is always easiest. The shame is that all this gamesmanship obscures the possible real causes that could help save lives as the industry goes back to work in the deepwater.
I didn't expect that kind of transparency, though, especially based on the experiences of the last 4 months.