A post from one of the rig guys over at theoildrum.com
No oil and gas well ever drilled has gone exactly to plan, or without mistakes being made. The Upstream Industry has learned the hard way. The path to todays drilling (well construction) approach is littered with terible loss events, and awash with lessons. But the fact is that todays drilling approach allows for mistakes to be made, simply because wells do not always behave as planned, and the execution of each step of the well construction plan relies on people. Contingency measure after contingency measure is layered over the average well construction plan such that if one, two, three, or even more consecutive issues occur and stack up against the well construction team there remains the cability on hand to identify there is a problem, to secure the well, and to plan and effect an appropriate remedial plan.
Yes a number of issues were stacking up against the well contruction team on Mississippi Canyon 252 #1-01 well on the night of the tradgey. Issues such as a communication path between the reservoir (oil and gas) and the well bore, the choice of casing plan and related well barriers, etc. However up until around 21:45 there remained the cability on hand to identify there was a problem, to secure the well, and to plan and effect an appropriate remedial plan to deal with the issues that had stacked up.
Unfortunately, at around 21:47 the Annular BOP opened releasing the immense energy that had accumulated beneath it (gas), energy that on release evacuated (ejected) the drilling riser of fluids in seconds. Thousands of gallons of fluids entering the workspace (drill floor) at almost jet force would have made any subsequent action to try to regain control of the well very difficult.
Much has been made about the issues that stacked up against the well construction team on that night, the cement program, the cement quality, the casing program, the testing program, etc etc, however the point remains that until around 21:45 the team still had the ability on hand to identify there was a problem, to secure the well, and to plan and effect an appropriate remedial plan to deal with the issues that had stacked up. The BOP Annular was closed and was capable of containing pressure build up as a result of the leak path between the reservoir and the well bore. There were other BOP Ram Preventers available of high pressure rating than the BOP Annular Preventer to call upon if required. With this contingency at hand (the last layer of contingency in any well construction plan), why did it still go so wrong?
I would offer that the real question is why did the BOP annular open? Did it fail? Was it opened by mistake? Was it opened thinking there was no hazardous gas build up below it? The investigation team will undoubtedly determine the truth.
I can also offer that in the Drilling Industry the Driller (the man that operates the drilling machine integrated into the rig structure) has two Golden Rules when it comes to well control:
#1, if there is any doubt whatsoever about a possible influx of formation fluid into the well bore then the well must be shut in (close the BOP), he requires approval from no-man for this action
#2, if the BOP has been closed for whatever well activity the Driller must be assured that doing so will not result in a hazardous situation for him, his team and all with him at the worksite. He requires approval from the worksite supervisors for this action.
The mud logger charts (main drilling parameter record) for the period 20:00hrs through 21:50hrs as presented at the Senate hearing show clear indicators of a problem with the well. There was more flow coming back from the well than going in, there was additional pressure where there should not have been. Evaluation and interpretation of these charts is an essential part fo providing the Driller the assurance he needs that opening the BOP Annular will not result in a hazardous situation.
If the BOP Annular was opened by the well construction team the other question undoubtedly being asked by the investigation team is whether suitable and sufficient evaluation and interpretation of the drilling parameter records was undertaken prior to authorising the opening of the BOP Annular?
The time line on the mud logger chart suggests around 15 minutes (from 21:30hrs to around 21:45hrs) may have been available for the well construction team to evaluate and interpret why there was pressure under the BOP Annular when there shouldnt have been.
15 minutes is not a long time to consider this kind of situation. Given that there had been a number of issues going on with this well since the casing was run and cemented (a lot of red flags were flying) there should have been the highest degree of awareness on every subsequent step of the operation. This means the full attention of all supervisors at all times. So, assuming again that the BOP Annular was opened by the team, why was there only a few minutes spent deciding the next step when the biggest red flag of them all (pressure under the BOP Annular) was waving.
