Below is the TransOcean rig data on the wellbore from two hours out until blowout.
This from what was filed with the US government investigators. So what does it say?
It says that the well wasn't drilling (no ROP (or Rate of Penetration), no Torque or RPM data which measures how smoothly and quickly the drill string turns).
It shows that the fluid had a constant mudweight of 16 lbs per gallon, which is probably in error. The mudweight was reported to be 14 lbs per gallon, and the replacement of mud with seawater is reported to have started at 8:00 p.m. (20:00).
You see an immediate increase in Flow In (fluids flowing up inside the casing) as well as Stand Pipe Pressure, with a dramatic increase in Pit Volume Change beginning at 8:10 (this means that what is coming out of the hole has more volume than what was put in the hole, and a true indicator that the reservoir was NOT isolated by the cement job), along with a gas kick within the mud (coming out between casing and hole) beginning at 8:16. All of this points to the fact that the reservoir was not controlled by the cement job in place. Presumably, they must have felt they could control it with the BOP.
It looked like they tried to control it and probably felt like they had a handle on it by about 9:10, as the pit volumes dropped, perhaps indicating they began mudding up to stop flow, but they were still circulating it looks like.
It took a secondary kick from around 9:14 to around 9:30 and settled down.
Then, at 9:47, the well took a dramatic kick, and blew out at 9:50.
By. Allen Gilmer