ROVs shine in work on runaway Macondo well

Crews working on the runaway deepwater Macondo well use remotely operated vehicles to perform a wide-ranging multitude of tasks. About 12 ROVs are at the wellhead in 5,000 ft of water where no human diver can venture.

Although the overall oil spill response effort has been marred by disappointments, the ROVs and their operators score fairly high on successful operating performance and on safety since the Apr. 20 Deepwater Horizon drill rig accident.

Each ROV is controlled via a tether going up to a vessel on the Gulf of Mexico. Macondo is operated by BP PLC, whose executives say choreography ensures ROV tethers do not tangle with other equipment in the congested area.

In their most-publicized chore, ROVs provide the lights and cameras that enable the public to watch a live video feed of oil and gas spilling from the failed blowout preventer on Mississippi Canyon Block 252. Some ROVs ran the saws to cut off a portion of the riser while other ROVs kept up the live video feed for a public audience.

Most of the time, the ROVs work smoothly without attracting attention, although the undersea robots are believed responsible for one, possibly two, mishaps. During May, an ROV temporarily dislodged a riser insertion tube that collected leaking oil and gas. In June, an ROV might have bumped a containment cap, forcing BP to temporarily suspend some collection operations.

"There are an unbelievable amount of ROVs operating down there," National Incident Commander and retired US Coast Guard Admiral Thad Allen told reporters during a June 23 conference call. "I think the fact that we've had two bumps that have had some kind of a consequence associated with them in the 60-plus-days response is a pretty good record."

Spilled oil being burned on open water, EPA monitoring

Oil spill response officials are using controlled burns to eliminate some of the crude oil spilled off Louisiana. They say burning crude oil offshore has been effective elsewhere in the past.

Meanwhile, federal officials are monitoring air quality and testing water samples. Officials say it will take some time to measure the effectiveness of the controlled burns in the Gulf of Mexico.

US Coast Guard Rear Adm. Mary Landry said a controlled burn off the coast of Newfoundland in 1993 proved very effective at eliminating oil trapped in special containment booms and set on fire.

The majority of the spill on the gulf’s surface is an oil-water mixture called a rainbow sheen with some areas of emulsified oil. The spill is moving closer to the shore and to Louisiana’s wetlands.

The controlled burn eliminates the emulsified oil, leaving a waxy substance that can be picked up by skimming vessels.

“If we don’t secure this well, this could be one of the most significant oil spills in US history,” Landry said during an Apr. 27 news conference. An estimated 5,000 b/d is leaking from a BP PLC well drilled by Transocean Ltd’s Deepwater Horizon.

An Apr. 20 explosion and fire on the semisubmersible left 11 crew members missing and presumed dead. The semi sank on Mississippi Canyon Block 252 on Apr. 22. Efforts continue to stop the leaking oil.

The controlled burn practice does involve tradeoffs in that it creates air pollution, said Charlie Henry, a scientific support coordinator with the National Oceanic and Atmospheric Administration.

Meanwhile, other scientists say warm water temperatures, strong sunshine, and microbial action will help the oil degrade and evaporate. The spill involves light, sweet crude so it will degrade faster than did the heavy oil spilled from the Exxon Valdez tanker. An API spokewoman says a controlled burn was used on the Valdez spill and was effective.