[trek]

The fluids in the well/riser complex are circulating not static. So gas can easily leak in from the surrounding formations if the well is not properly cased and sealed. This is undoubtedly what happened. And the gas which is under tremendous pressure in situ, expands dramatically as it rises up to the surface. So once the mud was removed from the improperly sealed well the rig was doomed.

[HoustonCurmudgeon]

I UNDERSTAND what likely happened. What I am TRYING to make others understand is that IF you fired a torpedo into a riser, full of mud, it would NOT blow up. IF I were going to blow one up I would pick one full of gas and crude. There is NO WAY anyone could have known that at just that moment there would/might be gas present.