Deepwater Oil Spill - of plumes, and drillships, FPSOs and the ASJ

The National Oceanographic and Atmospheric Administration (NOAA) has now tested water samples from oil plumes at three sites in the Gulf of Mexico, at varying distances from the Deepwater Horizon oil spill.

NOAA Administrator Jane Lubchenco said that the tests conducted at three sites by a University of South Florida research vessel confirmed oil as far as 3,300 feet below the surface 42 miles northeast of the well site. Oil also was found in a sub-surface sample 142 miles southeast of the spill, but further tests showed that oil is "not consistent" with oil from the spill.

Lubchenco said the water analysis "indicate there is definitely oil sub surface. It's in very low concentrations" of less than 0.5 parts per million. Additional samples from another research vessel are being tested, she said.

To place these samples in context, consider first the locations at which they were taken.

Locations of the oil sampling sites reported by NOAA The red star is the well, and the oil from the well was found at the two sites (surface and sub-sea) North of the well, while the green spot which marks the site South of the well which was contaminated with oil from another source.


The oil in the southern location may potentially come from a source which also generated the tar balls on the Florida keys recently. This was the map of natural seeps that I put up the other day.

Reported natural seep locations in the GOM.

It is germane to also note that the concentrations of oil in the plume are at a level of 0.5 ppm. In context that means that there is 0.5 cc (or roughly 0.4 gm) of oil in a cubic meter of seawater. This is not discernable to the naked eye. Thus when a news report (such as that from Sam Champion on the ABC World News) talks of the oil plume and shows the blobs of oil that he saw subsurface in a dive some weeks ago, it is effectively deceptive, since the correlation of the plume with that visual conveys the impression that the plume contains a high concentration of oil. In fact the water appears clear, and were this fresh water and the oil were instead Benzene, EPA would let you drink it. At this level, if it takes 3.43 grams of oxygen to biodegrade a gram of oil, then it will only require about 2.7 gms of oxygen to treat the cubic meter of seawater. Since oxygen is somewhat scarcer deeper in the ocean it may much slower that the 100 gm/cu m/day that I mentioned as the top rate in an earlier post But on the other hand it is not likely to take months.

This relatively short-life for the oil after it is dispersed contrasts with the remnants of the oil that was not dispersed, in the colder waters of Alaska, after the Exxon Valdez oil spill. Remnants of that oil still remain 21 years later, and can be found as emulsions, tar balls, and trapped liquid. The suggestion by Jean-Michel Cousteau that the oil should have been left untreated, so that it could rise to the surface and be collected by skimmers, does not recognize that in many conditions skimmers are only able to collect about 15% of the oil, and that in large volumes (as with the Alaskan example) oil, once it reaches the shore, can survive for decades. Better surely to break it into small droplets that are degraded and disappear. And in that regard one of the benefits of adding Corexit to the oil is that it both breaks it into these small droplets, and that in the process it reduces their chance of floating on the surface and contaminating surface dwelling fauna. Corexit even works in cleaning marshes.

In other current developments, the flow of oil from the LMRP and cap over the well, continues to increase.

For the first 12 hours on June 8th (midnight to noon), approximately 7,850 barrels of oil were collected and 15.2 million cubic feet of natural gas was flared.

That increased flow (achieved by reducing the choke on the outflow pipe) can be seen indirectly by comparing the current picture from the Skandi ROV 2 with that earlier.

The small triangular pieces at the bottom of the cap are now well clear of the plume, showing the reduced flow.

As a result this increased flow is exceeding the capacity of the existing fleet sitting over the well. Upstream Online is reporting that as a result BP is bringing a Floating, Production Storage and Offloading (FPSO) vessel and a shuttle tanker, the Loch Rannoch, from its station off Shetland to the Gulf. (The Loch Rannoch was involved in another BP accident, a collision that stalled production at the Schiehallion field at the end of last year.

“The crash happened when the 130,000 tonne tanker was docking to take oil from the 144,000 tonne BP platform for transfer to the Sullom Voe terminal, off Shetland. Its only hose-reel used for exporting the oil was damaged in the collision,” the newspaper reported.

And a BP spokesman was quoted as saying that the Schiehallion FPSO was not back in production yet. (November 3rd).

The Loch Rannoch is an 850,000 barrel shuttle tanker, that carried oil from the FPSO at Schiehallion to Sullom Voe in Shetland.


The FPSO is a different sort of vessel. This is the one at Schiehallion (And I don’t think it is coming since it still has an oilfield to service).

The Schiehallion FPSO

At a top speed of 14 knots, and having left last Wednesday, with a stop in Rotterdam, it may still be a while. That will free up the drillship to move on to other things, providing they have an FPSO by then.

And one last point in this series of shorter items that has filled the news today, I had mentioned using an ASJ to cut outwards from the inner pipe of a series of casings, but the illustration I gave earlier had the pipe cut from the outside. This one (the outer casing diameter is 26 inches) was cut from the inside.

(Courtesy ANT)

And this shows the relative sizes and where the cut was made. It is needed as one of the final steps in the abandonment of the well.

(Courtesy ANT)

Perhaps BP might use it when they finally abandon the well.
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Deepwater Oil Spill - the end of Top Kill

BP and Admiral Landry just held a Press Conference in which they said that, based on a decision 90 minutes ago, by the “best and brightest minds” that it was time to move on the next option, the Lower Marine Riser Package (LMRP). BP was unable to block sufficient flow out of the well to make the injection of cement possible, and thus to kill the well. They had made, I believe he said three attempts to inject material (the junk shots) without being able to get that material to block the passages through the Blow-Out Preventer (BOP) . (Unfortunately I missed a large part of his opening remarks, and thus have only the question response to go on at present). The volume of mud used did not appear to have changed from earlier reports at some 30,000 barrels.

Mr Suttles said that they had given the technique every chance, but could not get it to start to provide an effective seal. They had, however, determined that the majority of the pressure restrictions to the flow of oil was coming from some resistance within the well itself, and from the BOP. Since the riser above the BOP was not contributing much to the resistance, and thus to control of the oil flow, the next plan is to remove it, using a band saw device (of which pictures will be available) and then to lower the LMRP onto the existing BOP. They intend cutting the surface that the LMRP will sit on flat, so that it will give a good, but not perfect seal. Thus there will be some leakage around the joint, and they will monitor that and use dispersant as appropriate.


The new change should take somewhere between 4 and 7 days to implement. The assembly, which has been constructed, and is not the Top Hat assembly built earlier, to fit on the bottom of a riser. Flow of oil from the LMRP will rise up a 6 7/8 inch drill pipe within the riser (the same size as the one currently fitted to the RIT). The riser will also carry hot water down to the LMRP to protect against the formation of hydrates.

He noted that their inability to stop the well “scares everybody” but is reasonably confident (no success percentage estimates) that this will collect the majority of the oil and gas. Because they do not know the flow path of the oil below the seabed it is difficult to estimate what is actually going on in terms of oil path below the BOP. Thus they are, again, trying something that has never been done before, but expect, based on the RIT, that it will work.

On being asked about the cleanup of the dispersed oil – he pointed out that the reason that the dispersant was used was to break the oil into small droplets. These are small enough to be consumed by the microbes in the sea, and thus there is no plan to do other than let nature take its course. For the oil on the surface, they are getting better at spotting oil pools and sending skimmers to deal with them.

The Admiral drew attention to the article on Hurricanes and the Oil Spill which is available at the Unified Command We site.

The relief well is about half-way through the rock it must drill (about 6,000 ft below sea level) but progress will slow as the well deepens.

The Lower Marine Riser Package (LMRP) option

The Gulf oil spill, recovery and cleanup - Monday's Press Conference

Today’s press conference in Louisiana began with an update on the use of the riser insertion tool. However Coast Guard Admiral Landry cautioned that this only treated part of the spill, and that they were looking forward to the “top kill” program that would follow. The weather is now good enough that four controlled burns are planned, as well as a strong skimming program. To date there has been a minimal impact on the shore from the spill, but teams are in the field ready to react as this becomes more severe. Further the high flow rates from the Mississippi River are helping keep the larger volumes of the spill out in the Gulf. Both NOAA and the EPA are monitoring the use of dispersants recognizing the tradeoff between its use and the damage that it is mitigating.

The Admiral drew attention to the statement by Jane Lubchenco, the head of NOAA, who had said, in regard to the many reports of large underwater oil plumes and their causes and likely effects

"Media reports related to the research work conducted aboard the R/V Pelican included information that was misleading, premature and, in some cases, inaccurate," Lubchenco said in a statement. She was referring to research, including water sampling, done by the National Institute for Undersea Science and Technology.



Lubchenco said those scientists have clarified that (in regard to the plumes) they have not reached "definitive conclusions ... about the composition of the undersea layers they discovered. Characterization of these layers will require analysis of samples and calibration of key instruments. The hypothesis that the layers consist of oil remains to be verified."

This has been later qualified by Vernon Asper, one of the scientists involved who said, among other things:

1) We are not 100% sure that the plumes are oil. We have NOT analyzed the samples yet and won’t know what’s in them until we do. That will take at least a few days or even a week or more and we don’t want to rush these results. The sensor we used is not definitive for oil and other compounds do respond in a manner that is similar to oil and could be confusing us.

2) I NEVER said that these “plumes” could cause a dead zone! It’s really important that you correct that! Consider:

a. We don’t even know if there is any oil in the plumes so the oxygen signal we’re seeing could be due to something else that is going on near the well and, if so, it could disappear overnight (we just don’t know

b. The oxygen levels we saw are lower than “normal” but are no where near the danger zone! For the most part, they are not even as low as the layer above them that we call the “oxygen minimum zone.”)

The NOAA Administrator was also on PBS where she again said that it was too early to speculate on what was in the plumes, and that there was a light oil sheen on the surface that might reach Florida in 9 – 12 days, but that it would be very dilute, and may just show up as tar balls, with little prospect of significant damage to distant beaches. She noted that the threat sounds scarier than it is.

MMS confirmed that the permit for the second well has been approved, and is in process. They pointed out that any procedure being carried out has first to be reviewed and permitted by MMS after ensuring that it will have minimal environmental impact and be safe. They also emphasized that the monitoring and regulatory side of MMS will be strengthened.

For their part Doug Suttles of BP noted that at the time of the briefing on the afternoon of the 17th, they were getting a little over 1,000 bd up through the Riser Insertion Tube (RIT). And they are now slowly opening the choke to ensure no hydrate formation.

Later this week they will run the top kill procedure, that will start to close out the well sealing process. The use of the RIT and of dispersant has reduced the size of the oil slick appearing on the surface.

In response to questions from the floor Mr Suttles said that if the RIT could recover more than half the flow out of the riser (which he characterized as a 2,000 bd target) that they would all be very pleased. He stressed that they did not want to draw too much fluid into the system, since that would lead to hydrate formation and another blockage of the line. And later he noted that they hadn’t decided yet what to do with the oil that they are capturing. (Though he also ducked a more definite confirmation of the actual volume that is leaking).

Admiral Landry said that the oil had not entered the Loop Current at this time. The larger volumes of oil are several miles from it, while there is a surface sheen that is getting closer.

Doug Suttles further explained the top kill by pointing out that the mud will be introduced at high velocity through the two 3-inch diameter choke and kill lines into the BOP. However he also clarified the position of the RIT, which I had thought was close to the BOP. It is, however, almost 5,000 ft up the riser, at the open end. The top kill is anticipated to stop the flow, after which cement will be injected. That will stop the flow, but BP will go ahead with a relief well to reach, and then pump cement into the bottom of the well which will finally secure it. He stressed that there was no intent ever to produce oil from this well. (Because the oil-bearing formation around the well is now degraded into a condition that is no longer controllable). The final decision as to whether to use “top kill” or “junk shot” first has not been made, but the inclination is to use top kill since it has less risk of precluding the alternate technique if it should not work.

Before they committed to the top kill they had to know the pressure on both sides of the BOP. They now have that data, and found that the pressures were quite low, less than expected, and were falling. They then had to remove the “yellow pod” on the BOP sine this carries the controls for the valves to the choke and kill lines, and these controls had to be modified to allow the top kill to take place. The pod has been prepared, but has not yet been taken underwater and replaced. That will happen soon.

The Admiral also emphasized that even though the oil may stop flowing out of the well at the end of the week, the studies and investigations of what is going on will continue for a long time. Further all the steps that are being made are being reviewed at several levels in different government agencies to ensure that they do what is needed, with minimal impact, while working out where all the oil and dispersant has gone.

Charlie Henry of NOAA clarified the comments about the “oil plumes” noting that the samples were so clear that you could not, by eye, see anything in the water. To find out what really is in the water will require an analysis, that has not yet been done, of what is actually there. There is also a lot of research and monitoring to see where the oil is going, and in what condition. This is the adaptive management of the process which must change as results come in on what is going on.