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Canadian diluted bitumen study is a missed opportunity

Anthony Swift

Posted November 23, 2012

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The Globe and Mail recently reported on a study by Natural Resources Canada which evaluating the corrosivity of a variety of crudes, including diluted bitumen. In many ways, this study represents a missed opportunity. In Tar Sands Pipeline Safety Risks, NRDC advocated that regulators "analyze and address potential risks associate with the transport of diluted bitumen at the high temperatures and pressures at which those pipelines operate." However, by choosing room temperature, rather than the higher temperatures commonly found in diluted bitumen pipelines, to evaluate the corrosivity of diluted bitumen, researchers limited the value of their results. Because internal corrosion is catalyzed by either higher temperatures or sulfide fixing bacteria, it's not surprising to find that all crudes in low temperature lab settings aren't particularly corrosive. It's not particularly useful either.  

In addition to an inadequate evaluation of internal corrosion, it appears that this study did not evaluate the higher risks that external corrosion pases for high temperature diluted bitumen pipelines. While most crude pipelines do operate at ambient temperatures, we know from a study of high temperature pipelines in California that pipelines operating above 129 F have nearly ten times the external corrosion failure rate when compared to ambient temperature pipelines. The Keystone XL tar sands pipeline has an expected temperature range which goes well above that level while Keystone 1 was listed with a maximum operating temperature of 158 F. The National Transportation Safety Board (NTSB) faulted Enbridge in its investigation of Kalamazoo because the company didn't consider how two separate risks, external corrosion and stress corrosion cracking, interacted to create a much more significant risk. Understanding how diluted bitumen behaves in high temperature pipeline conditions is critical to evaluate the risks of these pipelines.

It is encouraging that regulators are beginning to due due diligence to evaluate the risks of diluted bitumen pipelines - NRDC has been asking for this for several years. However, not only do researchers need to consider the high temperatures of diluted bitumen pipelines as they evaluate internal corrosion risks, they also need to evaluate external corrosion risks, leak detection issues, and the greater challenges that diluted bitumen poses during spills. It's important that regulators have an accurate understanding of the risk of internal corrosion in diluted bitumen pipelines. However, stopping there would be akin to a pilot stopping after the first item in his checklist. You wouldn't want to fly on that plane - and folks have the right to expect the same level of due diligence by companies proposing to build tar sands pipelines through their communities.

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Mike HolmstromNov 23 2012 07:33 PM

Very basic chemistry ignored in this study. Two reaction rates may look close at room temperature & pressure could be much different inside a pipeline.

Some years ago, I called up Colonial Pipeline to ask about why they had cooling facilities. Petroleum products they get from refiners are warm to begin with, like 90 degrees F. As the products are pumped, liquid temperatures go up, so just the Houston to Atlanta section goes from 90 degrees to 107 degrees, and, that's not from a lot of uphill pushing. Refined products are much easier to pump, than tar sands crude is, so the temperature rise for tar sands will be even higher.

Some pipeline coatings are temperature sensitive. A Mobil Co. crude oil pipeline from Kern Co. CA to the Los Angeles basin had several external corrosion failures from coating break down, due to the temperature of the product., in the 1980's & 90's. This was when cheaper, but heavy, Kern Co. crude started to be produced & refined more.

All pipeline corrosion types are made worse by higher temperature.

Michael BerndtsonNov 23 2012 07:37 PM

Here's an old study from Society of Petroleum Engineers (SPE) from the mid 1990s that may be of interest to you on corrosion of steel pipe w.r.t temperature of full pipe fluid flow. Test fluids included saltwater, crude oil, CO2, oil/water mixtures. It seems that corrosion rate increases with increasing fluid temperature. Old study and not on Bitumen so who knows. From Google keyword search.

D TrahanNov 25 2012 06:28 PM

Those interested should go to NACE and look at the many volumes of reports on internal corrosion on pipe from crude pipelines. The majority (+99%) of the major crude pipelines continuously inject corrosion inhibitors to prevent failure.

Corrosion is something we slow down but never totally halt. The highest potential for corrosion is when there is water present in the crude oil which is always. Even at pipeline specifications of 0.2 % BS&W the water will collect in low areas (river and road crossings). This water provides a great breeding ground for Sulfate Reducing Bacteria and can lead to microbiologically induced corrosion (MIC).

Temperature for oil pipelines is always low given the fact the pipeline is in the ground and no matter how hot the crude is going in, it will normalize to a low temperature within a short distance of pump station.

Corrosion can be controlled effectively and has been for many many years in all major pipelines crossing our country. The Keystone XL is no exception.

Just a correction point, you speak about external failure. This is a whole different sort of mechanism and has nothing to do with the content of the pipeline.

Also, a reference to the "toxic" characteristic of the pipeline's oil content is sort of confusing in that all crude oil contains toxic substances, so goes the name "crude" oil.

Michael BerndtsonNov 26 2012 11:06 AM

D Trahan, with all due respect I believe you missed the point of the post. The issue is investigation results as addenda pursuant to permit submission. The issue isn't corrosivity - but the temperature of the trials upon which the tests were run. Were they performed at intended operating conditions? Corrosivity maybe a given - the operator is responsible for demonstrating how it intends to deal with it - given assumed operating conditions.

Here's my guess regarding the issue of Bitumen. Oil sands may be "under cooked" compared to other fossil fuel matrices such as coal and crude oil. My gut tells me that the anaerobic bacteria that produces hydrogen sulfide is more prevalent in oil-sand Bitumen then say crude oil and may become more active with temperature rise. The general chemistry, bio-chemistry and physical properties may be just different enough from that of crude oil - that the crude oil comparison may not be appropriate. Again, my statement is simply a guess. I'd be interested in a rebuttal and corrected if I'm simply wrong, crazy or paranoid.

Hugh KerrNov 26 2012 07:42 PM

Corrosion, like all "thermally -activated processes", does get faster at higher temperatures. The proposed Northern Gateway pipeline to the BC coast has a maximum design temperature of 50C. But general corrosion seems to be less of a problem than "underdeposit" corrosion. It occurs under the water + sand (0.5%) which deposits at protrusions and "overbends", etc, anywhere where the flow is interfered with, akin to a log piling up sand at a beach. MIC corrosion is one possibility. Some "pigs"might remove the deposits, but they reoccur in the same locations. Inhibitors do not reach under the deposits. The chemistries of the deposits is complex, and variable, depending on the crude or bitumen source.

Victor A. DelgadoNov 29 2012 01:42 PM

With all due respect, to name only some of the possible factors that could cause other damage to the inside of the pipe such as: a) a major factor at the time of the design of the pipes is the fluid velocity, as a result of the content of solid particles and liquid that this type of heavy crude (bitumen), just to name some of them (solids: heavy metals + sand + salts) and (liquids: water and salt mixed); the solid elements mentioned above could cause abrasion/erosion, increase the temperature of the inner walls of the pipe and decrease in the thickness of the pipe too; b) the temperature of the bitumen in pipes is also critical, since temperature decreases viscosity increases and greater power (greater capacity pumps) is required to move the same volume of crude considered in the original design; c) if do not exist a suitable design of the speed of the bitumen in the pipe, leads to problems such as: accumulation of fluid in the lowest points of pipelines and with the presence of H2S, salts, wet sand and temperature,, which could be accelerating a corrosive process in those sites. Also, running tools to internally clean pipes often do not eliminate the presence of impurities on the lowest points of the pipelines.

Additionally, there are many other issues to be considered. Also, !!!!congratulations to all of you for the interested comments about this important matter!!!!!!

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