From the Times-Picayune, via a very good post at Wry Heat:
As the author points out, this is somewhat speculative, but it's the best description and explanation I've seen of how the explosion may have happened.
At this point, some speculation begins. The leading hypothesis is that the cement plugs failed. The drilling crew wouldn’t be expecting a failure and perhaps weren’t monitoring the systems that detect an influx of fluids into the well, drill string, and drill pipe riser. Unbeknownst to those on the rig, a mixture of gas and water was coming up the drill string and riser to the surface and the deck of the Deepwater Horizon. The volatile mixture of high-pressure hydrocarbons likely ignited quickly and unexpectedly, killing the 11 individuals who were on the drilling floor itself.The rig, badly damaged, burned out of control, then later sank. (Quite a number of photos at Americablog, including the following.)
Normally, one of these drillers would have hit the “panic button” that closed the blowout preventers (BOP) on the seabed, but likely didn’t have the time to do it. The toolpusher a bit farther away also has access to a panic button, but he himself may have been incapacitated in the explosion or, if the electrical switches to the BOP were cut when the riser exploded, may have been unsuccessful in his attempt.
Which put out the fire, I guess. But as it sank, it bent, kinked and opened holes in the riser. And it's through those holes the oil is leaking. This is one of the issues I've found confusion over in my discussions with friends. Some have assumed it was a container of oil, like the Exxon Valdez, or an enormous fuel tank. Others have the impression it's leaking directly out of the ground. The following clip from Al Jazeera (of all places) does a good job of looking at the causes of the ongoing gusher, and the solutions that are being implemented:
The official estimate, so far as I've been able to tell, is still 5000 barrels, or 210,000 gallons, of oil leaking per day. Since late last week, I've been seeing reports I didn't consider trustworthy enough to pass along of a "cover up" of the actual amount being leaked. I took these semi-seriously, but chose to wait until I found more credible sources. Then yesterday The CSM posted this story:
Calculating the exact flow of crude out of the bent Deepwater Horizon oil rig "riser" pipe on the bottom of the Gulf of Mexico is difficult. But it's now likely that the actual amount of the oil spill dwarfs the Coast Guard's figure of 5,000 barrels, or 210,000 gallons, a day.(...)
Independent scientists estimate that the renegade wellhead at the bottom of the Gulf could be spewing up to 25,000 barrels a day. If chokeholds on the riser pipe break down further, up to 50,000 barrels a day could be released, according to a National Oceanic and Atmospheric Administration memo obtained by the Mobile, Ala., Press-Register.
A government report obtained by the Mobile, Ala., Press-Register explains that "choke points" in the crumpled riser are controlling the flow from the so-called Macondo well at Lease Block 252 in the Mississippi Canyon. But scrubbing action from sand in the oil is further eroding the pipe. There are likely tens of millions of gallons in the deposit that BP tapped with the Deepwater Horizon.NOAA has claimed the report noted in that quote is a worst-case-scenario, not an official prediction. I haven't seen any confirmation that the "deterioration" is from the "scrubbing action," or whether sand is even present in the oil stream- I suspect that may not be technically possible. [clarification- Meaning I'm not sure it would possible to confirm or observe this with an ROV. The abrasion certainly sounds possible to me, but I don't know.] I'm afraid this is a wait-and-see situation. But the long and short of it is that we may- and I emphasize, may- already be looking at a million-plus gallons per day spill, the equivalent if an Exxon Valdez every ten days. And if the worst case plays out, the same every five days. And though the Al Jazeera clip and the graphic mention 60-90 days for completion of the relief well, most other sources have said something along the lines of "at least 90 days."
"The following is not public," reads National Oceanic and Atmospheric Administration's Emergency Response document dated April 28, according to the Press-Register. "Two additional release points were found today. If the riser pipe deteriorates further, the flow could become unchecked resulting in a release volume an order of magnitude higher than previously thought." An order of magnitude is a factor of 10.
Remember that after oil, the gulf coast's major sources of income are from fishing and tourism. All three of those are going to be mired in mousse for years... maybe decades.
On the other hand, if the dice fall favorably, it's still possible that my gloom and doom is premature. The NYT has a somewhat more optimistic take, also from yesterday. I guess we'll see.
Followup, 7:08: Hmph. One of the sources cited by the above NYT article turns out to be a "non-profit environmental group" whose board of directors consists almost entirely of executives from the... wait for it... oil industry. (H/T)