As Rachel notes the "top kill" was just "the latest failure in a long line of failures to plug the Deepwater Horizon rig" and reminds us that if history is any indication, the relief wells that they are drilling that they keep calling "the ultimate solution" to the oil well disaster are hardly assured to work on the first attempt.
Drilling relief wells to stop Gulf oil leak poses challenges:
With the "top kill" declared a failure and BP moving on to less-desirable options to stop its well from continuing to shoot thousands of barrels of oil each day into the Gulf of Mexico, the grim reality set in that the company may be unable to stop the oil until it completes the first of two "relief wells" in August.
...But relief wells are something that, fortunately, engineers don't have to do very often. Drilling the relief well also can be fraught with challenges -- especially working in deep water on a well that has already had problems with gas bubbles.
"You have to hit something the size of a dinner plate miles into the earth, " said Richard Charter, a senior policy adviser at the nonprofit Defenders of Wildlife, who follows spills around the world. "Even in a shallow-water blowout, the drilling of a relief well can be complicated and problematic."
On Sunday, the White House said the government had insisted that BP drill two relief wells instead of one to ensure that it can reach the original well without problems.
...The world's worst well blowout and oil spill, the Ixtoc I well in Mexico's Bay of Campeche, was ultimately stopped with a relief well after a containment dome, junk shot and top kill failed, but it took nearly 10 months.
The oil platform sat in about 150 feet of water and blew out in early June 1979 at a depth of 11,625 feet.
According to a 1981 report from the Society of Petroleum Engineers detailing how Pemex, the Mexican state oil company, stopped the well, engineers decided to start drilling two relief wells at the end of June.
Progress was slow. It took one well until Nov. 20 to reach the original well, and the second took until Feb. 5, 1980.
Shutting down the main well took multiple attempts in February and March 1980 as Pemex shot drilling mud through both wells and gradually decreased the flow of oil.
The oil stopped flowing on March 17, and then it took a few more weeks to plug the wells with cement, wrapping up the operation in early April.
The blowout, according to the Society of Petroleum Engineers, lasted for nine months and 22 days.
Tyler Priest, a historian at University of Houston who has written a book about the history of offshore drilling, said Pemex thought it would go a lot faster. He cited a headline in the Aug. 6, 1979, issue of Oil & Gas Journal that reads, "Pemex: Ixtoc may flow until Oct. 3."
"They initially estimated three months. It took them almost 10, " Priest said. Read on...
