BP Shuts Well; Skepticism over Claims the Oil Disappeared

Oil Spill at Bon Secour NWR / USFWS Photo

BP announced that its "static kill" was successful in pushing oil farther down into the Deepwater Horizon well. The next step will be to cement the top of the wellbore, and the federal government has given permission for that process to start. There is an explanation of the steps involved in a static kill at The Oil Drum. If the cementing is successful, then no more oil should leak out of that well. A relief well will also close the well bore from the bottom.

Meanwhile, government scientists announced that 75% of the oil that spilled from the well has disappeared from the Gulf of Mexico:

"It is estimated that burning, skimming and direct recovery from the wellhead removed one quarter (25 percent) of the oil released from the wellhead," the scientists said in the report "BP Deepwater Horizon Oil Budget: What Happened to the Oil?"

Another 25 percent naturally evaporated or dissolved and 24 percent was dispersed, either naturally or "as the result of operations," into small droplets, the report said.

The rest of the estimated 4.9 million barrels of crude spilled into the Gulf after the April 20 rig explosion that triggered the leak is either on or just beneath the water's surface as "light sheen or weathered tarballs," has washed ashore where it may have been collected, or is buried in sand and sediments at the sea bottom.

Reading this made me raise an eyebrow, as the claim leaves a lot of questions unanswered. In particular, I would like to know what happened to the large subsurface plumes of oil. The oil that dissolved or was dispersed chemically presumably sank into the water column – is that oil gone or is it still there? Based on the numbers given above, it seems to me that only the 25% burned or recovered and the 25% that evaporated can truly be said to be out of the gulf. Apparently I am not alone in my skepticism, as several scientists are questioning the report.

The scientists and other experts who challenged the government's conclusions warned that painting too rosy a picture could hamper the environmental monitoring and cleanup work that remains to be done in the Gulf.

Marine conservationist Rick Steiner, a retired University of Alaska scientist, said: "Let's look at this another way: that there's some 50 percent of the oil left. It's still there in the environment."

The government report also fails to account for the effect of vast, underwater plumes of microscopic droplets of oil that remain unmeasured, scientists said, and it downplays the potential long-term effects of the release of as much as 4.1 million barrels of oil in the Gulf of Mexico. Some 800,000 barrels were captured at the wellhead.

The remaining 50 percent in the water is the equivalent of almost eight Exxon Valdez oil spills, until now the country's benchmark environmental disaster.

"Now what we're hearing is they don't think the damage will be as bad as they initially thought," Steiner said. "We have to remember that the same thing was said after the Exxon Valdez. But much of the damage didn't become apparent until the second or third year."

Scientists also questioned the report's methodology.

"There is a lot of uncertainty in these figures," said James H. Cowan, Jr., a professor in the Department of Oceanography and Coastal Sciences at Louisiana State University,

For example, the report doesn't explain how its authors decided what was naturally dispersed oil and what was chemically dispersed oil. They gave no details of how they estimated the evaporation rate of oil — something that's difficult to do over large areas of seawater because of the effects of weather and other factors, Cowan said.

Other scientists have also questioned the conclusions. NOAA administrator Jane Lubchenco insists that the report is sound and that its conclusions should not be taken to mean that the danger to wildlife is over. Unfortunately, that is how it is likely to be portrayed in much of the media; the Reuters article I linked does not mentioned any caveats raised by either Lubchenco or the dissenting scientists.

This is a situation where I would like to be able to trust the government's scientists. However, the lack of transparency that has marked the spill response makes that difficult. The lack of transparency also makes it difficult to believe the low numbers of killed wildlife reported by the Fish and Wildlife Service. Even if dead animals were not actively concealed, the official numbers seem far too low given the volume and extent of the spill.