Alberta Innovates report shows more study is needed to assess corrosivity of tar sands and Canadian heavy crude
Posted November 29, 2011
A report on pipeline corrosion released by Alberta Innovates recently evaluated evidence of diluted bitumen’s corrosivity relative to conventional crude. The Alberta Innovates report noted that there is no peer reviewed research on this issue, identified gaps in safety data kept by regulators, and found that many of the corrosive properties of diluted bitumen are shared by certain blends of very heavy Canadian crudes. However, the report went one step too far when it assumed that corrosive properties diluted bitumen shares with certain very heavy Canadian crudes do not present increased risks to pipelines. Like diluted bitumen, the production and export in pipelines of large volumes of heavy Canadian crudes is a relatively recent development which has not been accompanied by adequate due diligence on the part of regulators and the industry. The fact that pipelines are moving increasing volumes of unconventional crudes which share some of diluted bitumen’s corrosive characteristics only increases the urgency for appropriate scientific study.
In the report Tar Sands Pipelines Safety Risks, NRDC compared diluted bitumen to the West Texas Intermediate (WTI), the benchmark crude of North America. The reason that NRDC chose WTI as a point of reference is that it is similar to the conventional crudes historically moved on the U.S. pipeline system. These conventional crudes are lighter and less viscous, and therefore can be transported at lower temperatures and pressures than thick tar sands crude.
The Alberta Innovates report compared diluted bitumen with five blends of very heavy Canadian crude. These blends of heavy crude differ significantly from the lighter oil pipelines were designed for – even from conventional heavy crude. Like diluted bitumen, these heavy Canadian crudes require unconventional production methods, must be mixed with diluents to move in a pipeline and have been transported on some of the same pipelines which have shown signs of wear and tear in the United States. In many cases, these heavy Canadian crudes have to be upgraded into synthetic crude before being processed by conventional oil refineries. Simply stated, the blends of Canadian heavy crude that Alberta Innovates considered are far more similar to tar sands diluted bitumen than they are to the lighter crudes that historically have been moved by the onshore pipeline system.
Also like tar sands diluted bitumen, the production and export of significant quantities of heavy Canadian crude on the U.S. pipeline system is a recent development. Combined exports of heavy crude and diluted bitumen have increased over four-fold over the last fifteen years, from less than a quarter million barrels per day (bpd) in 1995 to over a million bpd last year.
This development has been accompanied by early warning signs. The pipelines moving the bulk of this crude in the United State’s upper Midwest spilled nearly three times as much crude per mile as the national average between 2007 and 2010. Enbridge’s line 6B, which spilled over 840,000 gallons of diluted bitumen in Michigan and on which hundreds of corrosion abnormalities have been identified, has been used to move large quantities of Canada’s heavy crude and diluted bitumen exports.
The Alberta Innovates report also noted that large diameter pipelines in Alberta have rates of internal corrosion that are comparable to those in the United States. This is actually a sign of trouble, as the U.S. pipeline system is on average twice as old as the Alberta pipeline system. Because the risk of internal corrosion increases with pipeline age, the newer Alberta pipeline system should also have a significantly lower rate of internal corrosion. That it doesn’t is evidence of a potential problem.
There is significant evidence that more study and enhanced safety standards are needed for the pipeline transport of viscous, unconventional crudes like diluted bitumen. Alberta Innovates identifies some of these gaps and and urges Alberta's regulator, the Energy Resources Conservation Board, to start separating safety and operating statistics for pipelines that carry tar sands crude from those that ship conventional oil to allow better information gathering. NRDC agrees that this better collection of information is an important first step.
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