Yesterday, I received an account from someone who I believe is very close to the events leading up to the blowout of BP’s Mississippi Canyon Block 252 well. This account provides a very detailed, technically correct, yet chilling description of the conditions surrounding this well from drilling through cementing, up to the operations they were undertaking when the well got away from them. Like other accounts I’ve heard, this one leaves questions about key details that only BP and Transocean can answer, if they’ll break their silence about these critical pieces of information only they can provide.
This account begins with a general statement about well conditions when drilling, describing problems very common with big wells. Because of these drilling problems, as well as the well logs they had run, BP knew they had a big discovery. Before I go on with this story, I need to give a little background to those readers not familiar with the oil and gas industry.
Wells capable of big production generally have very high porosity (or pore space in the reservoir rock) that holds oil, gas, and water. It’s important to understand that oil does not sit in caverns underground as is commonly believed. Oil and gas actually reside in the space between sand grains in sandstone; as an analogy, think of the way a sponge holds water. When you encounter high porosity and high permeability (the ability of fluids to flow within the rock) you’ve got potential for big production as long as pressure and, of course, the hydrocarbons themselves are present. In this well, BP had all of these characteristics. In spades.
These high porosity zones, and often sections above them, can be very difficult to drill. These wells are drilled with a weighted drilling mud, designed to keep enough hydrostatic pressure in the hole to keep well pressure back. There is a fine balance, though. Too much mud weight, and the well will start taking fluid, reducing hydrostatic head, then kick when reservoir pressure overcomes the column weight. Too little mud weight, and the well will kick straightway. These are exactly the conditions described in this account. This well required 16 lbs per gallon weight, which likely translates to bottom hole pressure somewhere around 15,000 lbs per square inch (PSI) at 18,000 feet (5,000 feet above the sea floor, 13,000 feet below it). That’s big.
As I’ve talked about before, based, on other accounts, BP ran production casing and cemented with nitrified cement to make a lightweight slurry to keep the well from losing circulation. Remember, the top of the well is at 5,000 below sea level, so it is reached from the surface with drill pipe through the riser. Once the pipe is hung off with a casing hanger and cemented, weight is then set down to seal a “packoff” in the hanger assembly that sits in the casing head. The purpose of this packoff is to seal between the production casing and the surrounding string of pipe. This particular description all squares with other accounts I’ve received. This account describes the setting of the assembly and the successful test to 10,000 PSI pressure.
Here’s where this account varies from others I’ve heard. Apparently, after hanging off the casing, cementing, setting the packoff, and testing, they came out of the hole with drillpipe, then went back with a bridge plug to set in the top of the casing to seal the inside. A bridge plug is a mechanical device, in this case run on drillpipe, that is set with weight from the drill string after it is turned to activate it. With two plugs in the casing, and the packoff outside the casing, the well should have been safe.
The writer of this account is unsure whether the bridge plug was actually set before the rig crew displaced the mud in the riser with seawater. It makes sense to me that it would be, and that they had pulled up into the BOP to displace the mud so the riser and the BOP stack would be clear of mud when they separated to recover the riser. An earlier account said that they had closed the annular preventer at this point, but this description does not include that particular step. Instead, the account writer believes that the casing hanger packoff failed as the hydrostatic weight of the mud was reduced while being replaced with the lighter seawater. If this is true, then there was a catastrophic failure of the hanger packoff, likely because the backside pressure exceeded the rated ability of the assembly to hold. This explains the sudden pressure at the surface and makes more sense than an experienced operator opening a BOP with pressure on it as was told from an earlier account. This description clearly supports a backside blowout around the outside of the production casing.
This next part of the narrative is graphic, describing the tragic and sudden failure of all systems on the rig, but doesn’t explain the failure of the BOP deadman to activate the shear rams in the stack. It was a calm night, so when gas hit surface, it settled, being heavier than air, around the rig floor, even as the blowout strengthened. The air inductions for the deck engines that run the rig are nearby on the floor, so when they breathed in the gas/air mix, the engines ran away with themselves uncontrollably and exploded, lighting off the cloud of gas and the flow from the well. Similar explosions happened in the mud pump room, destroying inner walls, which, according to this account, were unfortunately adjacent to the living quarters. In a strange twist of fate, the off-shift crew was reportedly having a party in the living quarters, celebrating 7 years of accident free performance. Dear God. This writer confirms that there were 7 BP bigwigs visiting on the rig at the time, which we’ve now heard from several sources.
11 crew were killed; 9 on the drilling rig floor, and 2 mud engineers in the mud room. It’s a miracle that the rest got off, including apparently, the BP executives. This writer’s most compelling statement?
“We never have had an accident like this before, so hubris, the folie d’grandeur, sort of takes over. “
Hubris. Illusions of grandeur. I believe that the Deepwater Masters of the Universe had been so
successful lucky that they were over-confident. Having never experienced this kind of failure, it was inconceivable to them that it could happen. It did. They turned their backs on this beast, and it attacked.
With a deadly, disastrous vengeance.
I continue to call on BP and Transocean to publicly disclose their operations that night and to answer the questions that are being asked. Only then do we know what steps we can take to prevent this from ever happening again. This account may not be 100% accurate, but squares with enough of key the facts in other accounts I’ve heard that I have no reason to believe it’s not genuine. I’ll continue to chase this story.