During the pumping and displacement of the heavyweight spacer used to displace the mud, a breach in pressure integrity resulted in the undetected loss of drilling mud into the probably uncemented well-bore.
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When the heavy drilling mud that provides the pressure needed to keep things from coming up the well was removed, first as a test, then as part of a procedure for closing down the well and moving the rig, telltale signs that something was wrong were missed.
As the drill progresses through the rock and sand below the seabed, the pressure of the mud in the drill string must be kept within a limited range.
The friction caused by the gas bubble pushing up the pipe and displacing the drilling mud used to control the pressure could have created a static charge that ignited the gas into a fireball.
At 8:20 p.m. on the day of the explosion the pressure data suggest there was a constant flow of sea water being pumped into the drill pipe that was displacing the heavier mud system which was the primary pressure control for the well.
And following the intersection of the well bore with those relief wells, they will put heavy mud down there to suppress the pressure of the oil coming up from the reservoir, put a cement plug in and effectively do what I would call a bottom kill, as opposed to the top kill, which was not successful a couple of weeks ago.
Given the two red flags that had been thrown up previously, one would have expected that as a precaution a cement plug would have been placed somewhere in the wellbore as a secondary pressure seal before this primary pressure control system (heavy mud) was evacuated from the wellbore.
Transocean engineers wanted to keep the pressure in the borehole under control with heavy mud while Halliburton set the cement plugs.
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The denser mud had been, up until this time, the primary pressure control and was keeping the hydrocarbons in place despite the lack of an adequate cement job at the casing shoe.
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