Originally posted by Christopher Helman - Forbes - April 30, 2010
The speculation continues about what happened on the Deepwater Horizon and why. Facts are few, but more are emerging. So let's sum up what we think we know based on our own interviews, reports, deducations, and even the comment sections on countless internet sites.
First of all, it's likely that BP knows precisely what occurred. According to this 2002 article in Offshore, the Deepwater Horizon was set to be outfitted with a system called E-drill, which continuously beams data from rig operations to a monitoring center in Houston. This data is certainly logged. Until BP and Transocean show what they know, we're left with a lot of speculation.
We know with some certainty that workers were in the final stages of setting the final sections of pipe (production liner) in the hole and cementing it in place. Industry insiders speculate that the workers were in the process of setting cement plugs in the wellbore. The plan was to plug the well, temporarily abandon it, and move the Deepwater Horizon off to a new drilling site within a couple days.
Instead, it appears that those plugs failed, or the cement hadn't set when a gas bubble got into the well bore. Even a relatively small amount of gas a can cause big problems because a gas bubble will expand massively as it moves from high pressure at the seafloor to lower pressure at the surface. 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.
Blowout preventers (BOPs) are designed to deal with bubbles. Different control valves and rams can close in the well to various degrees (i.e. think of the difference between a sphincter and a guillotine). Why wasn't the BOP engaged at the time of the "kick." Perhaps there wasn't enough time to act. Even then, the big mystery is why the BOP still can't be activated now by the robotic submarines (ROVs) sent to the scene.
Some scenarios. Assume the workers did try to engage the BOP, but it didn't work. Why? One analyst I spoke with suggested that it could be that the kick pushed newly poured cement out of the casing, gumming up the controls. I ran that idea by a subsea engineer who has been responsible for BOPs in deepwater drilling offshore Brazil, and he felt it could be within the realm of possibility.
Another possibility--they tried to engage the BOP's shear ram (which is supposed to slice through the riser and seal off the hole) but there was something too big to shear. That could have been a solid steel joint between two sections of drill pipe. These joints come along about one foot in every 30 feet of pipe, so it would have been very unlucky for such a joint to be sitting right where the shear ram would try to cut--but possible.
Video shot by the robotic submarines (a.k.a. remote operated vehicles or ROVs) seems to indicate that oil is leaking from three spots in a pipe that is laying on the seafloor. The pipe would have to be a portion of the riser, which would have to still be attached to the BOP, but crimped and bent over. An uncuttable piece of joint lodged in the shear ram would perhaps explain why the ROVs haven't been able to subsequently engage the ram.
Something else to consider: it's been said that the workers were in the final stages of casing and cementing the hole and that within a couple days the Deepwater Horizon was to leave that spot to go drill a new prospect. My deepwater engineer source explains that the closer a rig gets to the end of a job like this, the more pressure there would be (from supervisors, etc) to not take a drastic step like engaging the BOP's shear ram. If they had suddenly disconnected the rig from the well at that point in the cementing process, "they might have lost the whole thing." On a well that cost BP and its partners $100 million to drill, none of the nine ill-fated Transocean and two Smith International employees on the rig floor would want to make that call.
Especially if they couldn't even imagine the scope of the disaster that unfolded. It's been 40 years since a blowout of this magnitude occurred in the Gulf of Mexico. None of those 11 workers who died on the rig floor could have imagined that this would happen to them. "We train people to cope with the unusual, but they very seldom see it," says the subsea engineer. "The equipment is designed to cope, but it very seldom needs to."