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BP Likely to Attempt Top Kill Procedure Late This Week or Over the Weekend to Stop Flow from Deepwater Horizon Well; NOAA Cautions on Conclusions About Subsurface Oil Plumes
18 May 2010
|The top kill procedure. Click to enlarge.|
BP is likely to attempt the top kill procedure late this week or over the weekend to stop the flow of oil from the Deepwater Horizon well, according to BP Chief Operating Office Doug Suttles during a press conference on Monday, 17 May.
The top kill procedure involves uses the choke and kill lines on the blowout preventer to pump at high velocity heavyweight fluid (“mud”) to overcome the pressure of the flow coming up well, thereby stopping the flow. Once the flow is stopped, BP would follow that with cement.
The top kill option is one of several that BP is working on to stop the flow from the well, and is currently the one they are hoping will close off the flow the soonest. Should the top kill procedure not work, a “junk shot”—attempting to plug the well with a volume of debris—would still be possible. Work on the two relief wells continues, and will continue to do so even if the top kill is effective.
In selecting options to shut off the flow, Suttles said, BP and the advising engineers and scientists from other oil companies and the Departments of Energy and Interior have been concerned with (a) not making the situation worse and (b) not doing something that would preclude other options. For example, Suttles said, leading off with the junk shot could have precluded subsequent possibilities.
In order to perform the top kill procedure, BP needed to reconfigure one of the control pods on the BOP to gain control of the valves on the choke and kill lines, as well as get several critical pieces of data.
We had to get certain diagnostic information and measurements across the BOP and damaged riser. We have been gathering that data over time. We think we have the information we need, and we are finalizing the required equipment to do the work. We had to measure the pressure at which the well was flowing to determine the likely pressure required for top kill operation.
We managed to get the pressure from the bottom of the BOP and the top of the BOP. The pressure is pretty low, compared to what we worried about, and is dropping. We needed that data before making the assessment. That was the primary piece of data that we needed.
While a successful top kill procedure would stop the flow, that is not, Suttles noted, the end of procedures on the well.
[Top kill] should stop the flow. It doesn’t end the well. We will finish the relief well and pump cement into the bottom of this well. There is absolutely no intent to ever, ever produce this well. We intend to fill up the bottom portion of this well with cement. It will never be produced.
|The drillship Discoverer Enterprise flares gas brought up from the wellhead via the riser insertion tube. USCoast Guard photo by Petty Officer 3rd Class Patrick Kelley. Click to enlarge.|
Suttles also said that the riser insertion tube (earlier post), was taking up more than 1,000 barrels per day. BP will gradually open it up to increase the flow, to perhaps some 2,000 barrels per day, but needs to be careful about introducing water into the pipe lest hydrates form, he said. The purpose of the tube is not to stop the flow, but to prevent hydrocarbons from escaping into the water. BP is storing the oil on the drillship and flaring the gas.
The “oil plumes”. Prior to the press conference, NOAA Administrator Jane Lubchenco had issued a statement saying that media reports claiming the existence of massive subsurface oil plumes based on research conducted aboard the R/V Pelican were “misleading, premature and, in some cases, inaccurate”. The independent scientists have clarified three important points, Lubchenco said:
No definitive conclusions have been reached by this research team 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.
While oxygen levels detected in the layers were somewhat below normal, they are not low enough to be a source of concern at this time.
Although their initial interest in searching for subsurface oil was motivated by consideration of subsurface use of dispersants, there is no information to connect use of dispersants to the subsurface layers they discovered.
At the press conference, both US Coast Guard Rear Adm. Mary Landry and Charlie Henry from NOAA referenced Lubchenco’s statement. Henry noted that NOAA was eagerly awaiting data from the analysis, but said that the notion that there were solid plumes of oil suspended beneath the surface was incorrect.
NOAA is not saying that there are not hydrocarbons from the well in the water. The NOAA statement is that the information was taken out of context... Using different types of instruments, [the researchers on the Pelican] were able to detect what they think is hydrocarbons in water column, but not oil you can see. That information has not been analyzed. We don’t even know what for sure is in those samples. A lot of reports came out and were taken to another level, but we don’t have the quantitative information on that.
Almost 19,000 people are involved in the response, and some $500 million has been spent to date. Admiral Landry noted that even once the well is capped, the response will continue on for a very long time, both in terms of cleanup as well as in trying to gain a better scientific understanding of the impacts.
The Admiral also noted that, contrary to some reports, the oil has not entered the Loop Current yet, although there might be some leading edge sheen closer to the current now.
The important thing is to focus on the volume of oil on the surface—that is being reduced. We are confident that we can continue to fight this spill offshore.
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