Spills of Diluted Bitumen from Pipelines A Comparative Study of Environmental Fate, Effects, and Response (2016) / Chapter Skim
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2 Chemical and Physical Properties of Crude Oils
2 Chemical and Physical Properties of Crude Oils
Pages 21-34
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From page 21... ...
Such mixtures are called diluted bitumen. Diluted bitumen are engineered to resemble other crude oils that are transported via pipeline and processed in the same refineries.
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From page 22... ...
In Table 2-1 and Figure 2-1, North American crude oils of each type for which data are readily available are provided as representative examples. 22 From light, to medium and heavy crudes, and on to diluted bitumen, the abundance of saturated hydrocarbons drops 4-fold and the combined abundances of resins and asphaltenes increase 50-fold.
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From page 23... ...
For example, the graphs in Figure 2-2 show results of parallel analyses of samples of Cold Lake Blend diluted bitumen and Bakken crude oil.23 The latter is dominated by a strong series of peaks representing its abundant, straight-chain, saturated hydrocarbons. The diluted bitumen, in contrast, is dominated by a hump representing the profusion of branched and cyclic hydrocarbons that are more resistant to biodegradation.
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From page 24... ...
. SOURCE: Swarthout, et al.23 Aromatic Hydrocarbons Crude oils contain aromatic hydrocarbons possessing one or more aromatic rings.
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From page 25... ...
Resins and Asphaltenes The resins and asphaltenes characteristic of heavy crudes and diluted bitumen can precipitate from the oil as black sludge and cause numerous problems: clogging well bores, pipelines, and apparatus.24 Moreover, refining costs increase with the abundances of resins and asphaltenes.24 For all of those reasons, light and medium crudes have been favored. With increasing pressure on supplies, and with continued improvements in refining processes, heavy crude oils have come into broader use.
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From page 26... ...
(µg/g) Total Aromatic 3,504 7947 5,231 5,384 Compounds (µg/g)
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From page 27... ...
The compositions of diluents, however, can strongly affect the weathering behavior of diluted bitumen, chiefly because the evaporation of a highly volatile diluent will more readily produce a heavy residue. The individual selection of diluents varies depending on the desired outcome, the current cost of acquiring and transporting the diluent to the bitumen source, and other internal considerations of pipeline operators.
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From page 28... ...
, it can evaporate more readily in the event of a spill, yielding a dense and viscous residue that must be accounted for in response. WEATHERING AND ITS EFFECTS ON PHYSICAL PROPERTIES The behavior of a crude oil or diluted bitumen released into the environment is shaped not only by its chemical composition but also by its physical properties.
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From page 29... ...
0.98 (19%) Diluted Bitumene 0.92 0.98 (15%)
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From page 30... ...
On the other hand, undiluted bitumen and heavy crude oils typically are not flammable. Table 2-5 provides a quantitative summary of these variations.
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From page 31... ...
TABLE 2-6 Adhesion Comparison of Typical Crude Oilsa Adhesion After Adhesion After Additional Initial Weathering Weathering Adhesion (mass % loss in (mass % lost in Type of Crude Oil Before Release weathering) weathering)
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From page 32... ...
Light Crudea 0 0.77 1 −30 Weatheredb Light Crude 9 0.84 5 95 Medium Crudec 12 0.85 8 −10 Weathered Medium Crude 33 0.90 112 >110 Heavy Cruded 75 0.94 820 −3 Weathered Heavy Crude 600 0.98 475,000 >95 Diluted Bitumene 98 0.92 270 −35 Weathered Diluted Bitumen 1,580 1.002 50,000 >70 aScotiaLight. bAfteradditional weathering.
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From page 33... ...
The distinct physical and chemical properties of diluted bitumen arise from two components: the bitumen provides the highmolecular-weight components that contribute most to density, viscosity, and adhesion; and the diluent contributes the low-molecular-weight compounds that confer volatility and flammability, and that determine the rate at which evaporation increases the density of the residual oil. Because diluted bitumen has higher concentrations of resins and asphaltenes than most crude oils, spills of diluted bitumen products will produce relatively larger volumes of persistent residues.
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