In the wake of every failed attempt to stem the gush of oil spewing from the bottom of the Gulf of Mexico, the one option that is almost unanimously recommended is the use of relief wells. But such a procedure has its own safety risks and has the potential to actually increase the impact of the spill, say scientists and researchers.
BP is drilling two relief wells, one at 12,090 feet and another at 8,576 feet, which are expected to be done in August. The oil giant's CEO Tony Hayward told reporters that "the relief wells ultimately will be successful," also adding his belief that building back-to-back relief wells "will assure ultimate success."
On its website, BP describes the process of building the relief wells as "drilling a second well to intersect the original, flowing well as deeply as possible. A specialized heavy liquid is then pumped into the flowing well to bring it under control. This liquid is denser than oil and so exerts pressure (known as hydrostatic pressure) to stem the flow of oil. Once the flow is stopped, the well can be returned to a safe condition."
Although Hayward expresses confidence in the procedure, BP has acknowledged the razor-thin margin for error. In a regulatory filing, BP estimated that a blowout resulting from a failed relief well would increase the amount of oil released to a stunning figure, approximately 240,000 barrels a day, nearly 50 percent more than its worst-case scenario estimate for the original well, reports Bloomberg News.
The risks are higher with relief wells because BP will be tapping into an already-flowing pocket of oil and natural gas, Fred Aminzadeh, a research professor at the University of Southern California, tells Bloomberg:
"It's potentially the case that you'd see a larger volume of oil because in effect you're puncturing two holes rather than one hole" in the formation, he said.
Though drilling a relief well is similar to drilling a normal well, the procedure is more difficult because the target is much smaller. Richard Charter, a senior policy adviser at the nonprofit Defenders of Wildlife which plans to file suit against BP over the spill, compares the tedious and precise nature of constructing a relief well at any depth to "trying to hit something the size of a dinner plate miles into the Earth."
Last summer, the Montara oil spill in Australia's Timor Sea posed a similar threat to the environment and could serve as a cautionary tale. PTT, the Thai oil and gas company that owned the rig, also chose to construct a relief well -- but with disastrous results. After 10 weeks and several attempts, they were finally able to pinpoint the right spot and drill the well but ended up causing another explosion, which destroyed a $250 million rig, reports the New Orleans Times-Picayune.
The Australian government was eventually forced to abandon it and begin the process again. Unlike the leak in the Gulf region, which occurred 5,000 feet below the ocean's surface, the Montara oil rig leak was only 250 feet below, validating Charter's assertion regarding the dangers of relief wells at any depth.
Back in 1979, it took 10 months for Pemex, the Mexican state oil company, to use relief wells to help stop up the Ixtoc I well in Mexico's Bay of Campeche, at a platform in only 150 feet of water. Just like BP, Pemex tried a variety techniques -- including a containment dome, junk shot and top kill -- to no avail.
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