Deep Problems from the Deepwater Horizon

Two weeks ago tomorrow, on Apr. 20, an explosion and fire on the oil-drilling platform Deepwater Horizon off the Louisiana Coast resulted in the presumed deaths of eleven people and the sinking of the structure two days later. Initially, it was thought that an automated device called a "blowout preventer" (BOP in petroleum-engineer speak) would shut off the high-pressure oil from the well, which is about a mile below the ocean's surface. But soon after the structure sank, oil started showing up on the surface. British Petroleum, the owner of the well, and Transocean Inc., the operator hired by BP, initially estimated that 1,000 barrels a day were leaking out. More recently the number has risen to 5,000 barrels a day, and the slick has come within nine miles of the Louisiana coastline by today (Monday morning May 3). Already the federal government has prohibited all fishing operations for the next ten days in the region, and things look like they will get worse before they get any better.

There are nearly 4,000 offshore oil rigs in the Gulf of Mexico, most of them concentrated south of Louisiana, and as long as things operate smoothly, they are out of the public consciousness despite the fact that almost a third of our domestic oil production originates there. Partly because there have been no major headline-grabbing spills in recent years, President Obama recently called for increased offshore drilling in selected areas. The Deepwater Horizon disaster has put that on hold, and threatens to turn public opinion against offshore drilling for a long time.

Out of the 4,000 or so offshore oil rigs that operate without major problems, why did the Deepwater Horizon explode and sink? And even more urgently now, why didn't the blowout preventer work? These are technical questions that will require months of investigation to answer, although computerized logs and telemetry from the platform should help considerably. The blowout preventer, a three-story-high assemblage of hydraulic equipment designed to withstand the tremendous pressures five thousand feet underwater, is a sophisticated multi-stage system that sits on top of the ocean floor and surrounds the well pipe assembly. It is essentially a large automatic shutoff valve, using hydraulic pressure to acivate guillotine-like rams or rubber-and-steel rings that impose enough counterpressure to block the several-thousand-pounds-per-square-inch pressure behind the oil emerging from the ocean floor. Normally it is activated by remote control from the platform, but before the platform sank, operators tried to activate it without success. When underwater remotely operated vehicles (ROVs) reached the BOP's control panel and flipped the control switches, nothing happened. According to online discussions, in the event of a major disaster such as the loss of the platform, stored hydraulic energy in devices called accumulators should be sufficient to make the BOP do its job. But this didn't work, for reasons that are not yet clear.

Time is now critical, but unless something on the shrinking list of things British Petroleum engineers haven't tried on the BOP works, the other options to shut off the increasing flow of oil from the well will take at least weeks, if not longer. A risky idea that has apparently never been tried at such depths involves lowering large metal cans or funnels over the leaks (there are apparently at least two in the broken and twisted riser pipe) and trying to "vacuum" up the oil that way. All sorts of complications and challenges attend this approach, from the buoyancy of oil that might literally float the cans away to the differential pressure that could crush pipes and disable suitable submersible pumps, only a few of which exist anywhere in the world. The third way, which is going to be done sooner or later in any event and is pretty likely to work, is to drill a relief well, which could be better understood as a capping well. This involves drilling sideways at some safe distance to hit the exact location of the original well in order to send mud or cement into it and stop the flow. For the relief well to work, pinpoint accuracy is required, somewhat like hitting a rain gutter on the side of a building from half a mile away. While accuracy like this can be achieved, it takes two to three months to do it. And by that time, the oil could have reached Gulf shores all the way from Louisiana to Florida.

By now, British Petroleum is the poster child of the Petroleum Industry Hall of Infamy. The Houston refinery explosion that killed about two dozen people five years ago happened largely due to BP's lax safety standards, and while it is too soon to assess BP's culpability for the initial explosion and fire on the Deepwater Horizon, which was operated in any event by Transocean, no amount of feel-good institutional advertising is going to overcome the public perception that BP is careless about safety. In the meantime, let's hope that the effort to stop the oil leak is managed safely, efficiently, effectively, and fast.

Sources: I used information from the following websites: http://en.wikipedia.org/wiki/File:Gulf_Coast_Platforms.jpg has a map of oil platforms in the Gulf, http://www.timesonline.co.uk/tol/news/world/us_and_americas/article7114487.ece is an article in The Times of London about attempts to shut off the oil flow, and attached to the photo of the ROV shutoff attempt at http://www.flickr.com/photos/uscgd8/4551846015/ is a long thread of discussion among engineers about the problems surrounding the disaster and how to shut off the well flow. Also, CNN has a good graphic of the three major approaches to shutting it off at http://www.cnn.com/2010/US/05/01/explainer.stopping.oil.leak/index.html.