BP plans 'top kill' as next step to halt oil spill

Numerous specialized vessels will be involved in the “top kill” procedure, scheduled for daylight hours on May 26, to halt the flow of oil and gas from a deepwater blowout.

Paula Dittrick
OGJ Senior Staff Writer

HOUSTON, May 25 -- Numerous specialized vessels will be involved in the “top kill” procedure, scheduled for daylight hours on May 26, to halt the flow of oil and gas from a deepwater blowout. BP PLC, the well’s operator, also worked on other options in case the top kill fails.

Doug Suttles, chief operating officer for BP Exploration & Production, said reporters on May 24 that the company “should know by Wednesday evening,” if the top kill successfully halted the leak at the Macondo well in the Gulf of Mexico off Louisiana.

In the top kill, heavy drilling fluids will be injected into the well to stem the flow of oil and gas and kill the well. If necessary, the top kill could be combined with a “junk shot” in which various items would be pumped inside the blowout preventer (BOP).

The top kill operation involves the use of a command vessel, a mud-pumping vessel, and several backup vessels to pump mud or delivery more mud if needed, Kent Wells, BP senior vice-president of exploration and production, said during a technical briefing in Houston.

“We have a team focused on how do we manage these ships so there are no safety issues,” Wells said. Work on the seabed is “even more complicated” because numerous remotely operated vessels (ROVs) are tethered to vessels on the surface, he said.

“A team will be constantly monitoring where everything is,” Wells said. On May 25, BP said it was still doing “sophisticated diagnostic work” using the ROVs to plan each step of the procedure and in an attempt to ensure that the top kill will go smoothly.

Industry has used top kill operations on wells worldwide with varying degrees of success, Wells said. In this particular case, BP reconfigured a control pod on the failed BOP and also reconfigured the BOP’s choke and kill lines to use the top kill operation.

Transocean Ltd.’s semisubmersible rig Deepwater Horizon drilled the Macondo well on Mississippi Canyon Block 252 for BP and partners. The Deepwater Horizon exploded Apr. 20, leaving 11 crew members missing and presumed dead. On Apr. 22, the Deepwater Horizon sank (OGJ, May 3, 2010, p. 31).

The oil and gas well is spilling an estimated 5,000 b/d. BP holds 65% interest. Partners are Anadarko Petroleum Corp. 25% and Mitsui Oil Exploration Co. Ltd. 10%.

Other options being developed
BP also is progressing with a number of other options in parallel with plans for the top kill. These other plans could be used if the top kill fails to kill the well.

A lower marine riser package (LMRP) cap containment option is being developed to help collect oil and gas from the damaged riser. This would first involve removing the damaged riser from the top of the BOP, leaving a flat-cut pipe at the top of the BOP’s LMRP.

The LMRP cap, an engineered containment device with a sealing grommet, would be connected to a riser from Transocean’s Discoverer Enterprise drillship. The cap would be placed over the LMRP to capture oil and gas flowing from the well and to transport it to the drillship.

The LMRP cap was already on site. Wells said he expected that option will be available for deployment by May 31, if it is needed. Currently, a riser insertion tool is being used to collect oil and gas, which then goes to the Discoverer Enterprise.

Wells said 13,500 bbl had been collected as of May 24 since the riser insertion tool started working on May 16. A second riser insertion tool is available to swap out with the first riser insertion tool if needed, he said.

BP also is working on other options, including lowering a second BOP or possibly a valve, on top of the existing BOP. Two relief wells are being drilled to 18,000 ft. As of May 24, the well being drilled by Transocean’s Development Driller III, which spudded May 2, was at 10,100 ft, and the second well, spudded on May 16 by Transocean’s Development Driller II, was at 8,600 ft.

Contact Paula Dittrick at paulad@ogjonline.com.

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