Studies find oil sands-derived crude oil no more corrosive in pipelines than other crudes
21 November 2012
Both scientific research and industrial experience have found that bitumen-derived crude oil (i.e., crude from the oil sands) is no more corrosive in transmission pipelines than other crudes, according to Natural Resources Canada (NRC).
ASTM International recently published a guide (G205) for measuring the corrosivity of crude oil under pipeline conditions, based on research conducted by several organizations including the CANMET Laboratories of NRC.
Guide G205 is a step toward the creation of an industry-wide standard test to measure the corrosivity of different crude oils under pipeline conditions, since it describes test methods that enable a direct comparison of the corrosivity of crude oils from various sources.
Measurements obtained from these tests indicate that the corrosivity of oil sands-derived crudes is no different than that of other crudes.
In the absence of water, the crude oil is noncorrosive. The presence of sediment and water makes crude oil corrosive...The corrosivity of crude oil containing water can be determined by a combination of three properties: the type of emulsion formed between oil and water, the wettability of the steel surface, and the corrosivity of water phase in the presence of oil.—ASTM G205
The low corrosivity of crude oils—including bitumen-derived crude in transmission pipelines regulated by Canada’s National Energy Board—is due to the fact that corrosive (water) and erosive (mud, sand) constituents are largely removed upstream of the pipelines as part of achieving transport quality specifications. For transport in transmission pipelines, the sand and water content of the oil is controlled, and the combined basic sediment and water content must be less than 0.5% by volume.
Crude oils, including bitumen-derived crudes, contain little or no carbon dioxide (CO2) or hydrogen sulfide (H2S), noted NRC. Furthermore, these transmission pipelines operate at temperatures below 60°C. Consequently, naphthenic acid and sulphur compounds that can cause corrosion under refinery conditions (>200°C) do not cause corrosion in pipelines.
Pipelines carrying bitumen-derived crude oil operate at approximately the same pressure levels as pipelines carrying other crude oils, Canada’s NRC said.
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