pipeline corrosion in Alaska ? ? 5

[danw2]

I wondered if anyone had heard what type of corrosion caused the problem on the pipeline.

I read one or two references to a smart pig having discovered corrosion, indicating it's internal, but given how news stories get screwed up, wondered if anyone had a link to reliable info.

This is outside my field. Is 30 years the life expectancy on above ground pipelines?

Dan

 

[mcguire]

It appears that BP removed sludge buildup this time before running the pig and thus found thinning that wasn't detectable while a thick sludge covered the ID.

It seems that the pipeline steel, which was adequate for the orignal crude, could not stand up to the mixture of water, gas, and oil currently produced. Acidity and sulfur make the mixture much more corrosive. They tried using inhibitors but this could not reach the pipe wall because of the buldup, so corrosion went unchecked.

The life expectancy was apparently calculated to be finite but adequate. It seems, however, that it was incorrectly based on projected acceptable corrosion rates with the caveat that inhibitors could be used to compensate for errors or changes in the projected rate. The sludge defeated that option.

I am waiting to see if they use a weldable 13Cr plus Mo, Ni, Cu line pipe to replace this section. There are such alloys which would have essentially zero corrosion compared to carbon steel. Maybe it wouldn't pay since they need to continue to inhibit the for the rest of the line. One wonders how long the rest of the Alaska pipeline will last if this occurrence was a surprise. You can bet that new pipelines won't escape having to justify their use of finite-lived materials when dealing with corrosive crude.

I expect that the publicity of this Prudhoe Bay failure will cause some pipeline specifiers to get out their metallurgy books and see what one needs to obtain correct corrosion resistance. BP probably did what was right in the 1960's, but that won't work in the future.


Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[EdStainless]

After all, isn't this why the Alaska Pipeline is mostly 2205?

I'll wager that in the end we find out that cleaning, inspection and inhibition were all limited by buget constraints.

My guess is that they will go back with 2 1/2 Cr. It will have good resistance and survive a long time with very little care.

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Rust never sleeps
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[mcguire]

Do you think the failed pipe is 2205?

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[EdStainless]

I don't think so. The lines that I heard ref. to are in the field proper. I believe that all of those are CS.
The only 2205 that I know of is the transmition line.

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Rust never sleeps
Neither should your protection

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[swall]

According to an article in today's WSJ, the corrosion was found in a section of the 22 miles of feeder lines around Prudhoe Bay, not the main Prudhoe to Valdeze pipline.

 

[stanweld]

Some of the later 1980s to early 1990s gathering pipe was 2205 based on the unusually high expected corrosion rates but all of the initial gathering systems were carbon steel pipe of various API and ASTM specifications. The Alyeska pipeline was constructed fom API 5LX 65/70. Whereas water production has been much greater than the originally designed seperators could remove, I suspect that the that is the principal problem. It was also well understood that the formation would eventually be poisoned during treated sea water injection and I would suspect an H2S environment as well.

 

[unclesyd]

A little further information.

http://www.phmsa.dot.gov/news/BarretttoDingell07-26-2006.pdf

There was a report on CNN that showed a section of pipe during a report on the problem that showed as section of pipe. The pipe showed 100% corrosion coverage with a surface morphology of sandpaper.

A later report from a reporter at the scene mention that bacteria was cause of the corrosion.

 

[ggrindle]

I'm thinking that there were micro-environments where the attack was more severe due to the build-up.

 

[kenvlach]

Bugs creating acid were under the buildup, which consisted largely of waxy petroleates and carbonate. The pipe had never been pigged by BP since they took over operation in 1992.
News articles have mentioned that BP tried boosting inhibitor (from 20 to 200 ppm?), but too little, too late -- and I don't see how inhibitors would help considering the buildup.

A section of the corroded pipe, after cleaning, is shown in the ABC News story:

http://abcnews.go.com/Business/wireStory?id=2283370

 

[EdStainless]

BP has had a lot of anti-corrosion activity in the field. It looks like their risk/severity estimates were way off though.

One problem is that they have no holding facility for the sludge that they push out of these lines. And the pipeline guys sure don't want it.

I wish that petrol products were a consumer commodity. If so then there would be less price swing and BP would stand to loose tens of millions due to lost capacity.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[swall]

Put in a blender/mixer, mix the sludge with diesel fuel and then send it through the pipeline.

 

[rustbuster]

I've heard from a reliable source that bacteria is the cause, apparently the presence of SRB's has been known for a number of years but nothing was done to mitigate / control them.

 

[danw2]

AP ran a photo of a section of pipe from the pipeline - looks pretty pitted

 

[ndeguy]

http://usresponse.bp.com/posted/1249/BP_Corrosion_Monitoring_Report.127827.pdf

This is a link to BP's Corrosion Management report for 2005 for Alaska to the Alaskan Department of Environmental Protection. 200 pages of a supposed comprehensive corrosion management. I wonder if they will ever be believed again!

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

 

[rorschach]

Quick question, Is BP doing water injection on these reservoirs to boost output? If so, are they treating the injected water with biocides? In my oilfield corrosion class from the local chapter of ASM, one of the metallurgists teaching the class mentioned the fact that in some wells where water injection is taking place, no biocides are being used and the wells that used to be "sweet" are becoming sour due to injected SRB. Another thing that can cause that kind of pitting is wet CO2, especially in the HAZ of welds. Are these wells producing CO2?

 

[danw2]

"Is BP doing water injection on these reservoirs to boost output?"

According to the news story (by an AP writer) cited below, yes.

Bacteria can hitch a ride into the pipeline in the cold salt water that is sucked from the nearby Beaufort Sea and injected into the ground to coax the field's dwindling supply of oil up to the surface.

Oil, gas and water all exit the permafrost together and are separated out at flow stations scattered throughout the North Slope, the nation's most remote oil region. In addition to seawater, the fresh water and natural gas are pumped back down to help maintain the underground pressure that pushes the hot oil to wellheads, which from a distance resemble red Christmas trees.

Microbes can enter any groundwater that contacts air before flowing back into the layer of gravel and sandstone 9,000 feet beneath the spongy tundra.

More and more water has come up from the ground as production rates have fallen from a 1989 high of 1.5 million barrels per day to 400,000 barrels before the shutdown. The water was most likely siphoned off before oil reached the corroded section of pipeline, but BP is looking into the possibility that some got by, according to Copeland.

"As the field has declined the water sitting underneath the oil has increased," Copeland said. "The ratio of water to oil coming out of the ground is higher."

http://seattlepi.nwsource.com/local/6600AP_WST_Prudhoe_Bay.html

 

[stanweld]

The original system was designed for "Sweet" CO2 corrosion.
As I stated previously, it was well known in the early 1980's when sea water injection was introduced that the formation would be "poisoned" with introduction of SRB and H2S would be created. Unfortunately, MIC was not as well understood at that time.

 

[ndeguy]

With regards the BP 2005 Corrosion Management report and my comment, now comes this:

http://seattlepi.nwsource.com/business/282056_bpalaska22.html

Nigel Armstrong
Karachaganak Petroleum
Kazakhstan

 

[oldcorreng]

danw2

rorschach hit the nail on the head. It could be a case of SRB (sulfate reducing bacteria) attack, Desulfovibrio desulfuricans. I have seen cases of this attack in oil well casings, sucker rods and some cooling water systems contaminated by small amounts of crude oil. It is seen as a a series of shiny concentric rings inside of pits on the metal surface of typically carbon steel and it's alloys. There are tests for the bacteria, biocide treatments and monitoring methods. I'm surprised that with all the new technology for monitoring pipelines that such an old villian was not detected if SRB attack is the case. It is also prevalent under many other conditions. There is much information on the internet on this subject.