For O&G Person,
Trying to be gracious, I’ll point out that a little knowledge isn’t nearly as good to have as a lot of knowledge.
Who has said the BOP failed ?
There are dozens of scenarios that one could cobble together that could bring gas to the surface in an uncontrolled fashion, several of which will include a successful BOP test a few steps prior to the blowout. Cruise some of the drilling boards for complex plausible scenarios that end with a complete surprise for the crew.
If normal tests following downhole equipment installation show the well to be killed and then - for example - a plug (or packer) fails or a liner collapses - during some subsequent operation that includes tripping out of the hole, the combination of rapid gas expansion and an uncorked drill string could unload the DP very quickly. A BOP stack has to be TOLD to close, it’s not an automatic function. If the crew was killed or equipment (including the deadman) is destroyed by the blast, then the BOP will just sit there, which is what it’s supposed to do.
As explained (and illustrated) earlier, a blowout from a sandstone reservoir usually carries a lot of sand up the hole along with the fluids. If the BOP can’t close completely (during an after-the-fact effort) due to some odd geometry of stuff that has been dislodged and moved uphole then the sand will wash out the metal of the rams and/or the bore diameter and the BOP will never seal correctly. That’s probably where we are today.
Regards.