BP tries new response to gulf spill

June 7, 2010
BP PLC gave up "top kill" efforts to halt the leaking Macondo oil and gas well in the Gulf of Mexico, instead moving to install another collection system pending completion of at least one of the two planned relief wells, not expected before August.

BP PLC gave up "top kill" efforts to halt the leaking Macondo oil and gas well in the Gulf of Mexico, instead moving to install another collection system pending completion of at least one of the two planned relief wells, not expected before August.

As OGJ went to press last week, BP was making the second of two cuts in the damaged Deepwater Horizon riser on the seabed, but crews reported a diamond-wire saw was binding as remotely operated vehicles tried to cut horizontally through a damaged riser in 5,000 ft of water.

National Incident Commander and Adm. Thad Allen expected the saw problem would be resolved, enabling a lower marine riser package (LMRP) containment cap to be put on the LMRP at the top of the failed blowout preventer (BOP) stack.

"The cleaner the cut, the tighter the seal we can make," Allen said June 2. Crews tried to reposition the riser so the saw could move better, he said, adding the tool might have to be brought to the surface to resolve the problem.

Government scientists estimated the flow of oil and gas could increase 20% between the time the riser was cut off and the time that a containment system would be installed.

BP said of the LMRP cap: "Successful deployment of the containment system cannot be assured." Once a containment system is installed, oil and gas will be diverted into a drillship instead of spilling in the gulf.

An Apr. 20 fire and explosion on Transocean Ltd.'s Deepwater Horizon semisubmersible, which was drilling for BP and its partners, left 11 crew members dead. The Deepwater Horizon sank Apr. 22 on Mississippi Canyon Block 252 (OGJ, May 3, 2010, p. 31).

LMRP cap explained

As part of the LMRP cap containment system, two caps, each with a different sealing design, sat on the seabed. If the horizontal cut is made to be flat and smooth enough, an LMRP cap is expected to seal on top of the riser stub. The LMRP cap has a thick rubber grommet.

A second similar device would perform basically the same function, but the second cap is wider than the LMRP cap and is not expected to provide as good of a seal, Allen said.

Lines carrying methanol will be connected to the system to help stop gas hydrate formation. A drill pipe within a new riser would take collected oil and gas to Transocean's Discoverer Enterprise drillship.

Plans call for warm surface water to be poured down the outside of the drill pipe to help prevent hydrates.

While trying to install the containment system, crews first used a hydraulic shear to vertically cut through the damaged riser at a point out from the BOP. While this was done, slings supported the riser still attached to the BOP.

Crews using ROVs and the diamond-wire saw then intended to sever the rest of the riser from the top of the failed BOP.

A riser insertion tube tool, previously used to collect leaking oil and gas, was pulled from the riser during the top kill operation. It will not be used again because the end of the riser already was cut off.

Meanwhile, the first relief well, which started on May 2, had reached 12,090 ft as of June 1. The second relief well, which started on May 16, had reached 8,576 ft before drilling was temporarily suspended during top kill operations. It resumed drilling on May 30.

As of June 1, the estimated cost of the spill was nearly $1 billion, BP said.

LMRP enhancements

BP consulted with federal officials and decided to enhance its LMRP containment system.

The first addition will be to use the hoses and manifold implemented for injections during the top kill operation. Toward mid-June, BP hopes to be able to use these hoses and manifold to help take oil and gas to the surface.

"This system…is intended to increase the overall efficiency of the containment operation by possibly increasing the amount of oil and gas flow that can be captured from the well," Kent Wells, BP senior vice-president of exploration and production, said during a technical briefing.

Plans also are being implemented so spill-containment equipment on the surface could be moved if a hurricane enters the gulf. June 1 marked the start of the Atlantic hurricane season.

BP plans to use a free-standing riser ending 300 ft below sea level. A flexible hose then will be attached from the riser to a containment vessel, possibly a floating production vessel that would be moved into location, Allen said.

"This long-term option is designed to permit the system to more effectively disconnect and reconnect the riser to provide the greatest flexibility for operations during a hurricane," BP said. "Implementation of this enhancement is expected in late June or early July."

Top kill fails

Numerous specialized vessels were involved in the top kill procedure, which started about 1 p.m. on May 26 only to be called off late on May 29. The effort failed to sustainably halt the flow from the blowout.

BP Group Chief Executive Officer Tony Hayward said, "We worked the top kill procedures hard for 3 days. We pumped more than 30,000 bbl of mud at high pressures through the system. We fired 16 different bridging material shots."

The bridging materials involved various items such as rubber balls, tire pieces, and knotted rope, that were pumped inside the BOP.

Before the top kill started, BP reconfigured a control pod on the failed BOP and also reconfigured the BOP's choke and kill lines to use them to inject the mud.

"This scares everybody, the fact that we can't stop this flow," Doug Suttles, chief operating officer of BP Exploration & Production, said May 29 in a news conference from Robert, La. "We are going to keep after it until we get it fully contained, fully stopped, and until we get this relief well down."

Obama returns to Gulf Coast

US President Barack Obama visited Louisiana May 28 in his second trip to the Gulf Coast to inspect oil spill response efforts.

"We're hoping for the best but preparing for the worst," Obama said during a May 27 news conference from Washington, DC, regarding the oil spill. "It is my job to make sure that everything is done to shut this down."

Meanwhile, oil has reached the shoreline in Louisiana, Alabama, and Mississippi, Allen said. More than 100 miles of Louisiana shoreline has been polluted.

In response, federal officials approved part of Louisiana's proposal to build temporary barrier islands to stop oil from coming ashore.

The state's original proposal called for dredging more than 92 million cu yards of material over 6-9 months to build temporary barrier islands.

Construction of a prototype berm was approved while federal officials considered possible implications that construction of a series of berms might have on sea currents, Allen said.

A diamond-wire saw is used to sever the damaged Deepwater Horizon riser in 5,000 ft of water using remotely operated vehicles. Still photo taken from live-feed video posted online by BP PLC.

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