'Top hat' oil spill containment device in gulf

An oil spill containment device that BP PLC calls the “top hat” sat on the seabed near a deepwater blowout off Louisiana on May 12, BP PLC spokesmen said.

This story was updated May 12 following afternoon news conferences in Robert, La., and Washington, DC.

Paula Dittrick
OGJ Senior Staff Writer

HOUSTON, May 12 -- An oil spill containment device that BP PLC calls the “top hat” sat on the seabed near a deepwater blowout off Louisiana on May 12, BP PLC spokesmen said.

US Secretary of the Interior Ken Salazar and US Secretary of Energy Steven Chu met with scientists and engineers from industry and government at BP’s offices upon the request of President Barack Obama.

“This is a vital national priority and we cannot and will not rest until BP has capped the well and controlled the spill,” in the Gulf of Mexico, Salazar said.

Chu noted, “Department of Energy scientists from the National Laboratories have been working with the operations experts at the BP command center on ways to determine what is happening inside the BOP (blowout preventer) atop the damaged wellhead.”

Work includes using supercomputers to assist with imaging and sampling of the seafloor, measuring pressures in the BOP, and analyzing fluid flows, Chu said.

“Putting our best scientific minds together with BP’s deepwater drilling engineers will enable these dedicated professionals to examine every feasible means and practical solution to this environmental crisis,” Chu said.

Marcia McNutt, director of the US Geological Survey, arrived in Houston on May 7 to help coordinate the joint efforts of federal scientists who are working with BP engineers to stop the oil leak and minimize environmental damages from the spill.

Transocean Ltd.’s semisubmersible rig, Deepwater Horizon, drilled the well in 5,000 ft of water on Mississippi Canyon Block 252. The rig exploded Apr. 20, leaving 11 crew members missing and presumed dead. On Apr. 22, the Deepwater Horizon sank. The oil and gas well is spilling an estimated 5,000 b/d (OGJ, May 3, 2010, p. 31).

BP is the operator with 65% interest. Partners are Anadarko Petroleum Corp., 25%, and Mitsui Oil Exploration Co. Ltd., 10%.

In addition to collecting leaking oil with the containment system, BP is working to stop the flow of oil from the Macondo well by plugging up the BOP on the seabed and then sealing the wellhead using a technique know as the top kill or junk shot (OGJ Online, May 10, 2010).

Two top hat versions
Doug Suttles, chief operating officer of BP Exploration and Production, said the top hat system involves two possible options, one is the collection device and the second involves the use of a riser insertion tube.

The riser insertion tube would be inserted into the damaged Deepwater Horizon riser that is leaking oil, Suttles said during a May 12 news conference from Robert, La.

The riser insertion tube would prevent leaking hydrocarbons from contacting seawater and forming gas hydrates, which was a problem with an earlier large containment dome (OGJ Online, May 10, 2010).

All equipment related to the top hat was being put in place while engineers and scientists determined exactly how they were going to implement the system, Suttles said.

The US Minerals Management Service has approved the use of methanol in conjunction with the top hat to prevent the formation of hydrates.

Warm seawater from the surface also is going to be pumped along the riser bringing the collected oil and gas to the surface where it will go into Transocean’s Discoverer Enterprise drillship for processing and storage.

Dispersant testing
Environmental Protection Agency Administrator Lisa Jackson told reporters in a news conference from Washington, DC, that 28,709 gal of dispersants had been applied to oil leaking on the seabed.

EPA authorized the application of dispersants at the subsea level for three tests. Jackson said the first two tests were inconclusive and a third test recently was done.

The first two tests had “logistical problems” in getting the needed information from 5,000 ft of water, Jackson said.

“The effect of underwater dispersant still is unknown,” Jackson said. “We are awaiting results of the third test…. Dispersants are not the silver bullet.”

The National Oceanic and Atmospheric Administration is working with EPA on water sampling to determine the effectiveness of the subsea application of dispersants.

Jane Lubchenco, a NOAA undersecretary of commerce for oceans and atmosphere, said dispersants being used both on the surface and at the seabed are less toxic than the spilled oil.

“This oil spill is unprecedented and dynamic,” Lubchenco said.

The US Coast Guard on May 12 reported more than 517 vessels were involved in the cleanup response. More than 1.5 million ft of boom was deployed, and about 4 million gal of oily water has been recovered.

EPA’s Dana Tulis, acting director of the EPA Office of Emergency Management, said no dispersants were being applied within 3 miles of shore.

Teams have used about 436,250 gal of chemical dispersants, with most of that being applied on the water’s surface. Some 13,000 people are involved in the oil spill response.

Leaders of the National Park Service and the National Wildlife Refuge system worked from command centers along the Gulf Coast to protect the shoreline. Oil from the spill has been confirmed washing up in Alabama’s Dauphin Island as well as on Chandeleur Islands, a chain of barrier islands off Louisiana.

Contact Paula Dittrick at paulad@ogjonline.com.

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