http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/05/challenges_involved_in_drillin.html
By Rebecca Mowbray, The Times-Picayune
May 30, 2010, 10:07PM
JOHN MCCUSKER / THE TIMES-PICAYUNE
Ships surround the Deepwater Horizon rig Saturday at the site of oil spill in the Gulf of Mexico 50 miles from Louisiana. 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. A BP spokesman said the company is making progress on the two wells.
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.
BP has been attempting to contain or stop the flowing oil since its Macondo well exploded April 20, killing 11 people. But the ultimate solution to permanently cap the well is to inject concrete from wells drilled in from the side.
With short-term efforts failing, officials locally and in Washington are beginning to contemplate that the oil could spew until the height of hurricane season.
“There could be oil coming up until August, when the relief wells are dug, ” White House energy and climate change adviser Carol Browner said on NBC’s “Meet the Press” Sunday morning. “We are prepared for the worst. … We will continue to assume that we move into the worst-case scenario.”
Plaquemines Parish President Billy Nungesser said he got weak in the knees at the Plaquemines Parish Seafood Festival when he saw the news on a Blackberry that efforts to plug the raging well with drilling mud and rubber pieces had failed.
“We’re not counting on anything until this relief well is drilled, ” Nungesser told CNN Saturday night.
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.
Making progress
The company appears to be making progress. Spokesman Graham MacEwen said Friday that the first relief well has now reached 12,090 feet below the floor of the rig, 5,000 feet from the sea floor.
BP interrupted drilling last week to install a blowout preventer, the safety device that’s supposed to seal a well in an emergency, but which failed to do so on the main well.
The second relief well, MacEwen said, is 8,650 feet below the floor of the rig.
The relief wells start about a half mile from the original site and try to meet the original at a diagonal.
Drilling a well involves using a pipe that unfolds section by section like an antenna, only upside down.
With each section, the company drills and then pulls out the pipe and puts in casings to form the sides of the well.
Drills are equipped with directional sensors that do three-dimensional surveys to help workers see where the drill bit is and what it’s encountering, while metal detectors help guide it toward the metal in the original well.
Once the drills intersect with the original well, typically just above or below where the problem occurred, cement is pumped in to seal it.
Dave Rensink, president-elect of the American Association of Petroleum Geologists, said that drilling a relief well is not that different from drilling a regular well, except that the target is much smaller.
“The only problem is really finding it, ” Rensink said of the original well. “You’re trying to intersect the well bore, which is about a foot wide, with another well bore, which is about a foot wide. The probability of finding it the first time … is probably pretty low.”
When the company drills into the well casing but misses the right spot, it will need to set a cement plug.
As BP tries to meet the original well, it will need to have plenty of mud on hand, because when the drill actually connects, the mud from the relief well will have a tendency to get sucked into the lower pressure of the original well, and drillers could lose control of the relief well.
“That clearly is a risk. They need to be very specifically prepared when they penetrate the existing well bore, ” Rensink said. “You want to make sure you’re not creating a problem in your relief well that’s the same problem as on your existing well.”
No guarantee on timing
With the failure of the top kill, BP plans to cut off the broken riser pipe and install a cap with a “straw” in it that could siphon oil up to a drill ship.
The company may also try installing a new blowout preventer on top of the broken one and using it to try to shut off the well.
Even if the company goes that route and it succeeds in stemming the flow of oil, BP will still move forward with drilling the relief wells because it will enable the company to seal off the top and bottom of the well, making the fix more durable.
But examples from elsewhere in the world show there’s no guarantee on the timing, and that drilling a relief well can be dangerous.
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.
‘More caution’ needed
Certainly, the technology today is much more advanced than when engineers fought to shut down Ixtoc, but even in modern context, relief wells don’t always go smoothly.
Last August, the Thai company PTT Exploration and Production Co. was drilling the Montara well in 260 feet of water in the Timor Sea off of Australia when it well blew up and began leaking oil into the ocean.
It took 10 weeks and five tries for the drilling rig brought in to drill the relief well to hit its target about 8,600 feet below the sea floor. On the last try, there was another rig explosion, which burned for two days.
The oil was finally stopped on Nov. 3, and it took until mid-January to cap the well, according to news reports.
A final report from the Australian government on the Montara incident is due June 18.
Like the Montara well, BP’s Macondo well has already shown itself to have pockets of gas big enough to interrupt drilling.
Weeks before the April 20 Deepwater Horizon rig explosion, workers on the rig experienced a gas kick so intense that they abandoned any “hot work” — smoking, welding, cooking or any other use of fire — for fear of an explosion.
Don Van Nieuwenhuise, a University of Houston geologist, said that BP will have to tread carefully to avoid the problems encountered at Montara.
“You have to be very careful, because you don’t want to have another blowout if you hit petroleum or gas in another level, ” Van Nieuwenhuise said. “Any relief or kill well needs to be drilled with more caution than the first well, because you don’t want a repeat performance.”
Van Nieuwenhuise speaks from experience. In 1979, he worked on killing a gas well in the Gulf of Mexico that blew up when workers ran out of drilling mud. Even though it was only in about 60 feet of water, it took about four and a half months to cap the well by drilling a relief well because of concerns about pockets of gas. “We had to stop drilling every 500 feet, ” said Van Nieuwenhuise, who was working for Mobil in New Orleans at the time.
Better drilling technology today, Van Nieuwenhuise said, should make the job easier, but the key is to know where the drill bit is in relation to formations of oil and gas in the area.
BP said it’s mindful of the risks and is proceeding cautiously with the relief wells.
“We’ve got many many safety systems in place, both procedural and technical, ” MacEwen said. “We’re constantly measuring the pressure in the well.”
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Rebecca Mowbray can be reached at rmowbray@timespicayune.com or 504.826.3417.
WHAT TO KNOW ABOUT RELIEF WELLS
Q: What is a relief well?
A: It’s a well drilled in from the side to intercept the original well, fill it with cement and shut it down. It is considered to be a permanent way of closing off a well.
Q: How are things going so far on the relief well?
A: BP is drilling two relief wells in case it encounters any problems along the way. The first well is at 7,090 feet beneath the ocean floor, and the second well is 3,650 feet below the ocean floor. BP plans to drill to about 18,000 feet, or 13,000 feet into the earth.
Q: What’s so hard about drilling a relief well?
A: It’s basically the same as drilling a regular well, except that engineers have to hit a very specific target. They’re using a drill pipe that’s about a foot wide, and trying to hit another pipe that’s about a foot wide about 3 miles away. Experts say it is likely to take several tries to hit the well at the right spot.
Q: Is it risky?
A: When BP hits the well in the right spot, there will be a tendency for the drilling mud from the relief well to get sucked into the lower pressure of the original well. To make sure the company doesn’t lose control of the relief well, it will need to have huge amounts of drilling mud on hand. In a rig blowout last fall off of Australia, engineers did lose control of the relief well, which started a fire and consumed the original rig.
Q: When will the relief wells be completed?
A: BP predicts in early August, but sometimes it takes longer. When engineers tried to shut down the Ixtoc I well in the Gulf of Mexico in 1979, they thought it would take about three months, and it took almost 10. But technology is a lot better now.
Special thanks to Richard Charter