I have been posting the past few days as well as reading a lot of the posts on this blog & I have to say the one posted a couple above this one is the scenario I agree with the most. I don’t believe the hanger seals were ever set in the casing head fully. Due to the shear weight of the casing the seals could have been set in the head just one inch or less& still tested perfectly. I say this with 15 years experience as a previous tool hand having set hundreds of sets of seals in packers & casing heads. I believe there had to be retardant placed in the cement to keep it from setting prematurely & this cement should have been given 24 hours at least to harden before performing a negative test & displacing out with seawater. I also believe that a tool joint was spaced out in the shear rams. This is a no-no in spacing out for any type of dispalcement procedure, but may have been permitted due to the point in the process the rig was in ( displacing the riser with seawater to disconnect). I also believe the casing seals did not blow until there was a sufficient amount of time in an underbalance condition like until the riser had just about been completely circulated out before the caing seal blew & allowed a massive amount of gas to expand & blow the riser dry & explode. As for the BOPs not working, it is possible that everyone responsible for operating them was either killed or injured in the blast & any others who may have had the opportunity to shut in the well may have assumed the other person on duty ( who was already hurt or killed) was possibly involved in well control or would surely close the shear rams. Anyone knows that on a job like this you better be sure of what you are doing or functioning the shears can do more harm than good.
Having speculated all this & understanding that this crew was topnotch at doing their jobs, I have to say it was a confluence of all the right circumstances happening together that contributed to this disaster. So what can be done to prevent this type of future occurrance? First, all subsea casing heads should have a polished bore at least 4’ long so that while it is being stung in it can be circulated & after there is a positive indication from pressure build up the pressure can be bled & the casing slacked off enough to ensure that it is positively seated in place. 2nd, on a deep hole such as this a sufficient amount of time should be given for the cement to set. at least 24 hours to give any retardants sufficient time to deactivate & allow the cement to harden & form a sufficient bond with the hole. Then secondary testing & negative tests should be performed. 4th & certainly not least, the deeper we have to go to explore for oil the more risks we run of having somehting like this happen. When it does the costs are insurmountible. BP will pay an extremely heavy price for this well. Maybe so heavy it will bankrupt their company. However, we all pay when something like this happens in our industry. Therefore, we should have two sets of shear rams in all deep water wells. There has been much talk about the redundancy of safety systems on this rig, yet they are dependant on a safety system with only one “surefire failsafe valve”. If a tool joint happens to be in the the way of the shear rams anytime when a well takes a kick, then they become useless as they can not shear a 3" thick solid piece of pig iron such as a tool joint or other x-overs & subs that are run into the wells of today. Therefore, double shear rams spaced out 10’ apart allowing for tool joint spacing should be used.
I know some of these things sound tedious, costly, & unneccessary, but when you count them against the cost of just one catastrophe like this, they are a small price to pay for prevention. It is my fervent hope that an engineer with some considerable amount of stroke with a major oil company or the IADC or a ranking member of the MMS will read these recommendations & make them SOP for future deep water operations as I can’t due to my position in this business. Rant over.