With BP trying to stop the gushing oil leak in the Gulf of Mexico with a "top kill," we look at how we ended up here: what BP has tried and why it has yet to succeed.
End of April
Solution: Robots to shut blowout preventer
The rig’s blowout preventer, a 48-foot-tall, 450-ton apparatus that sits atop the well 5,000 feet underwater, failed to automatically cut off the oil flow after the April 20 explosion of the Deepwater Horizon rig. BP attempted to use remote-controlled submarines with robotic arms to reach access portals and activate the valve.
Expectation
The highly complex task was to take 24 to 36 hours, said Doug Suttles, chief operating officer of BP's global exploration and production business.
Outcome
Failed. "We've tried many different ways. Some things have showed promise; some haven't," BP spokesman Daren Beaudo said. "We don't know why the remote-operated shutdown systems haven't worked."
May 4, 2010
Solution: Drilling a relief well
The second well joins the failed well at the bottom, in rock 13,000 feet below the ocean. Once contact is made, drilling fluid and concrete will be put into the first well.
Expectation
This will lower the pressure on the failed well, enough to allow a concrete plug to be placed into it and permanently shut it down. The relief well could also be used for future oil and gas production. BP began drilling the second well this month, but it will take three months to complete. Weather conditions could prolong the process, Beaudo said.
Outcome
The well is expected to be completed by August. It would be a permanent solution to cap the leaking well.
May 7, 2010
Solution: First containment dome
BP lowered a massive four-story containment vessel over the well to cap the larger of two leak points. The hope was that the container would collect the leaking oil, which would be sucked up to a drill ship on the surface.
Expectation
"If all goes according to plan, we should begin the process of processing the fluid and stop the spilling to the sea," Suttles said. But the method had not been done at such depths before.
Outcome
The plan was thwarted after ice-like hydrate crystals formed when gas combined with water to block the top of the dome and make it buoyant. The dome was moved off to the side of the wellhead and is resting on the sea floor, Suttles said. He declined to call it a failed operation but said, "What we attempted to do ... didn't work."
May 12, 2010
Solution: Second containment dome or “top hat”
The "top-hat" cofferdam is a 5-foot-tall, 4-foot-diameter structure that weighs less than 2 tons and would be injected with alcohol to act as an antifreeze and keep its outlet clear.
Expectation
BP built the smaller dome after the containment vessel, designed to cap the larger of two leaks in the well, developed glitches. The new device would keep most of the water out at the beginning of the capping process and allow engineers to pump in methanol to keep the hydrates from forming, Suttles said. Methanol is a simple alcohol that can be used as an antifreeze.
Outcome
BP abandoned the idea of using the “top hat” and opted to proceed with an insertion tube technique instead. It wasn’t clear why BP made that choice.
May 14, 2010
Solution: Riser insertion tube
The riser insertion tube tool is a temporary solution that involves inserting a 4-inch-diameter tube into the Deepwater Horizon’s rise, a 21-inch diameter pipe, between the well and the broken end of the riser on the sea floor.
Expectation
The insertion tube connects to a new riser to allow hydrocarbons to flow up to the Transocean Discoverer Enterprise drill ship. The oil will be separated and shipped ashore.
Outcome
This seems to be the most successful effort thus far in containing some of the spill. The system was able to capture some of the leaking oil and pipe it aboard a drill ship, burning off some of the natural gas released in the process, according to a statement from the joint BP-Coast Guard command center leading the response to the oil spill.
The flow rate from the tube reached 3,000 barrels of crude (126,000 gallons) and 14 million cubic feet of gas a day as of May 20. BP’s Suttles said the company is "very pleased" with the performance of the tube. However, Gov. Bobby Jindal of Louisiana says the efforts haven't stopped oil from reaching his state's coastline.
May 25, 2010
Solution: "Top kill"
The "top kill" involves pumping heavy drilling fluid into the head of the leaking well at the sea floor. The manufactured fluid, known as drilling mud, is normally used as a lubricant and counterweight in drilling operations. The hope is that the drilling mud will stop the flow of oil. Cement then would be pumped in to seal the well.
Expectation
Top kill has worked on above-ground oil wells in the Middle East but has never been tested 5,000 feet underwater. BP Chief Executive Officer Tony Hayward has given the "top kill" maneuver a 60 percent to 70 percent chance of success.
Work is under way, and BP is setting equipment into place. A team of experts will examine conditions inside the five-story blowout preventer to determine how much pressure the injected mud will have to overcome. The company then will perform diagnostic tests to determine whether the procedure can proceed.
Outcome
Undetermined.
End of April
Solution: Robots to shut blowout preventer
The rig’s blowout preventer, a 48-foot-tall, 450-ton apparatus that sits atop the well 5,000 feet underwater, failed to automatically cut off the oil flow after the April 20 explosion of the Deepwater Horizon rig. BP attempted to use remote-controlled submarines with robotic arms to reach access portals and activate the valve.
Expectation
The highly complex task was to take 24 to 36 hours, said Doug Suttles, chief operating officer of BP's global exploration and production business.
Outcome
Failed. "We've tried many different ways. Some things have showed promise; some haven't," BP spokesman Daren Beaudo said. "We don't know why the remote-operated shutdown systems haven't worked."
May 4, 2010
Solution: Drilling a relief well
The second well joins the failed well at the bottom, in rock 13,000 feet below the ocean. Once contact is made, drilling fluid and concrete will be put into the first well.
Expectation
This will lower the pressure on the failed well, enough to allow a concrete plug to be placed into it and permanently shut it down. The relief well could also be used for future oil and gas production. BP began drilling the second well this month, but it will take three months to complete. Weather conditions could prolong the process, Beaudo said.
Outcome
The well is expected to be completed by August. It would be a permanent solution to cap the leaking well.
May 7, 2010
Solution: First containment dome
BP lowered a massive four-story containment vessel over the well to cap the larger of two leak points. The hope was that the container would collect the leaking oil, which would be sucked up to a drill ship on the surface.
Expectation
"If all goes according to plan, we should begin the process of processing the fluid and stop the spilling to the sea," Suttles said. But the method had not been done at such depths before.
Outcome
The plan was thwarted after ice-like hydrate crystals formed when gas combined with water to block the top of the dome and make it buoyant. The dome was moved off to the side of the wellhead and is resting on the sea floor, Suttles said. He declined to call it a failed operation but said, "What we attempted to do ... didn't work."
May 12, 2010
Solution: Second containment dome or “top hat”
The "top-hat" cofferdam is a 5-foot-tall, 4-foot-diameter structure that weighs less than 2 tons and would be injected with alcohol to act as an antifreeze and keep its outlet clear.
Expectation
BP built the smaller dome after the containment vessel, designed to cap the larger of two leaks in the well, developed glitches. The new device would keep most of the water out at the beginning of the capping process and allow engineers to pump in methanol to keep the hydrates from forming, Suttles said. Methanol is a simple alcohol that can be used as an antifreeze.
Outcome
BP abandoned the idea of using the “top hat” and opted to proceed with an insertion tube technique instead. It wasn’t clear why BP made that choice.
May 14, 2010
Solution: Riser insertion tube
The riser insertion tube tool is a temporary solution that involves inserting a 4-inch-diameter tube into the Deepwater Horizon’s rise, a 21-inch diameter pipe, between the well and the broken end of the riser on the sea floor.
Expectation
The insertion tube connects to a new riser to allow hydrocarbons to flow up to the Transocean Discoverer Enterprise drill ship. The oil will be separated and shipped ashore.
Outcome
This seems to be the most successful effort thus far in containing some of the spill. The system was able to capture some of the leaking oil and pipe it aboard a drill ship, burning off some of the natural gas released in the process, according to a statement from the joint BP-Coast Guard command center leading the response to the oil spill.
The flow rate from the tube reached 3,000 barrels of crude (126,000 gallons) and 14 million cubic feet of gas a day as of May 20. BP’s Suttles said the company is "very pleased" with the performance of the tube. However, Gov. Bobby Jindal of Louisiana says the efforts haven't stopped oil from reaching his state's coastline.
May 25, 2010
Solution: "Top kill"
The "top kill" involves pumping heavy drilling fluid into the head of the leaking well at the sea floor. The manufactured fluid, known as drilling mud, is normally used as a lubricant and counterweight in drilling operations. The hope is that the drilling mud will stop the flow of oil. Cement then would be pumped in to seal the well.
Expectation
Top kill has worked on above-ground oil wells in the Middle East but has never been tested 5,000 feet underwater. BP Chief Executive Officer Tony Hayward has given the "top kill" maneuver a 60 percent to 70 percent chance of success.
Work is under way, and BP is setting equipment into place. A team of experts will examine conditions inside the five-story blowout preventer to determine how much pressure the injected mud will have to overcome. The company then will perform diagnostic tests to determine whether the procedure can proceed.
Outcome
Undetermined.
No comments:
Post a Comment