How do you stop an oil spill that is the result of offshore drilling gone awry? As it turns out, you drill some more. A couple of weeks after the Deepwater Horizon exploded on April 20, creating the worst oil spill in U.S. history, BP began drilling a relief well a parallel pathway to the oil reservoir deep beneath the floor of the Gulf of Mexico that will eventually intersect with the original well. (At the insistence of U.S. officials, the company began drilling a backup relief well later in May.) When the linkup is made, BP will be able to pour mud and then concrete into the original well, finally cutting off the flow of oil for good.
While BP and the government have struggled during the past three months over attempts to temporarily stop the spill top hats, containment domes, top kills, junk shots the relief wells have made quiet and steady progress. The drilling begins vertically, pushing down some 10,000 ft. below the surface of the Gulf. That's the easy part. Then the drill's path has to curve into the original well. The companies involved use sophisticated sensors to determine the correct angle of the hole, steadily threading the drill toward the blown well. Magnetometers in the drill help guide the way. They can detect the electromagnetic field created by an electric current that runs down the original well's casing. As of July 20, the main relief well was less than 5 ft. from its target: the original well's 7-in.-diameter steel casing, more than 3 miles below the surface of the water. "We're absolutely perfectly positioned," said BP senior vice president Kent Wells, who is leading the effort.
Of course, little in the spill response has gone as planned, though so far BP's latest containment cap seems able to stanch the flow of oil without damaging the sensitive wellbore. But even if the cap remains sealed, the only way to ensure that the well never bleeds again is to finish the relief drilling, which could be done by the end of the month. "The relief well," said retired Coast Guard admiral Thad W. Allen, in a July 16 briefing, "is the final solution." It's about time.