| #3 Generally makes sense. I don't know about the explanation of the surface plug (cement just below the sea floor) - yes, cement generates heat when it cures, and yes, slushy methane occurs and could get melted. But that slushy gas (methane hydrate, or clathrate) is not deep below the seafloor, but fairly close to the sea floor, and in a zone of rock that already had several strings of casing and cement settings across it. Yes, a rapidly rising and expanding gas bubble does seem to have been the primary culprit - but where did it come from? Oil contains quite a lot of dissolved gas, and as pressure drops that gas comes out of solution and as the gas separates it will rise and expand faster than the oil. But neither oil nor gas was supposed to be inside the casing - which had been set, cemented, and supposedly tested - so should not have even been anywhere it could have been able to expand, exsolve gas, and make a bubble when the crew lightened the mud weight to set the surface plug. If the gas came from somewhere else it could have caused the explosion, but the oil should still be behind cemented pip, so somehow that cement (the cement near the bottom of the well) failed. And it should have been, and supposedly was, tested. It's all very strange to me - the tricky bits (drilling, casing, cementing) were all done, with nothing but fairly benign operations remaining (which is why the safety celebration was going on) when everything went to Hell. |
