Key Parameters Affecting the Dispersion of Viscous Oil

Abstract

Oil viscosity has been perceived as a major factor affecting the dispersibility of oil. Very high viscosity oils—20,000 centistokes (cs) or more—can readily be observed as resisting the breakup of the oil into dispersed droplets. However, there are instances where a relatively viscous oil will disperse much more readily than another oil of similar viscosity. An extensive study has been conducted at ExxonMobil Research facilities in New Jersey to define the molecular makeup of 14 viscous heavy fuel oil products and determine the property of the viscous oils, besides viscosity, that influences dispersibility. Dispersibility was measured by a standard laboratory dispersant test using a COREXIT dispersant selected from the U.S. Environmental Protection Agency (EPA) National Contingency Plan (NCP) Product Schedule. Initially, IATROSCAN (TLC) and gas chromatography data failed to show any correlation between chemical properties, such as sulfur, aromatics, paraffins, resins, vanadium, nickel content, etc., and dispersibility. However, the analysis did identify a statistically significant relationship between a parameter based on normal paraffin content and dispersibility, which helps explain anomalies such as low viscosity oils that do not disperse. These results are expected to aid in guiding oil spill response for viscous oils.

Comparative Laboratory-Scale Testing of Dispersant Effectiveness of 23 Crude Oils Using Four Different Testing Protocols*

“…However, our laboratory BFT ( Figure 6) agrees with previous research from field studies showing that dispersibility of oil is inversely proportional to viscosity [3] A correlation for DE with the paraffin content of heavier oils has been reported [26]. There are instances where oils of similar viscosity disperse quite differently.…”

Comparative Laboratory-Scale Testing of Dispersant Effectiveness of 23 Crude Oils Using Four Different Testing Protocols*

“…However, our laboratory BFT ( Figure 6) agrees with previous research from field studies showing that dispersibility of oil is inversely proportional to viscosity [3] A correlation for DE with the paraffin content of heavier oils has been reported [26]. There are instances where oils of similar viscosity disperse quite differently.…”

Oil Irradiation Experiments Document Changes in Oil Properties, Molecular Composition, and Dispersant Effectiveness Associated with Oil Photo-Oxidation

“…Finally, we examined the role of viscosity in reducing the observed dispersant effectiveness. It is known from bench-scale, tank-based, and field tests that viscosity can affect the dispersibility of fresh and weathered crude oil. ,, In line with these studies, we also observed a decrease in dispersant effectiveness with increasing viscosity of irradiated oil residues (Figure C). Our data showed similar dispersant effectiveness–viscosity relation as a study that also used the Baffled Flask Test to measure the dispersant effectiveness of 23 different (non-photo-oxidized) crude oils (Figure C) .…”

“…It has been suggested that high paraffin contents in oil residues can be inversely correlated with dispersant effectiveness. 52 Previous studies found this correlation to be applicable for low-viscosity oils and not for oils with viscosities >1000 cP. 8 In line with these studies, we did not find an inverse correlation between the paraffin content of the oil residues (total mass of n-alkanes per mass unit of total oil; Table S3) and measured dispersant effectiveness values (Figure S9).…”

“…In our test, sunlight exposure of 200–350 μm films of HOOPS oil (original viscosity 6 cP) for 3 days still had Baffled Flask Test-dispersant effectiveness values larger than 60%, compared to 87% for the fresh oil. Considering that bench-top tests produce lower dispersant effectiveness than large-scale tank tests , or field conditions (Figure ), our results imply that even though photochemistry will change the chemical composition and physical properties of a low-viscosity oil slick that would be targeted by aerial dispersion applications, the slick would still be amenable to chemical dispersion when applied within the typical “window of opportunity”, which is within 2–4 days of the onset of an oil spill.…”

Effect of Oil Composition on Chemical Dispersion of Crude Oil

“…When the composition was measured using an analytical method that separates the oil into four SARA fractions similar to those used in this study, the concentration of the saturates fraction was positively correlated with the performance of Corexit 9500, but the concentrations of the aromatics, resins, and asphaltenes fractions were negatively correlated (Fingas et al , 2003). Canevari et al (2001), on the other hand, observed a negative effect of the saturates fraction on dispersibility of 14 heavy fuel oils by Corexit 9500 but could not discern effects due to the aromatics, resins, or polars (asphaltenes) fractions.…”

Comparative Laboratory-Scale Testing of Dispersant Effectiveness of 23 Crude Oils Using Four Different Testing Protocols*

“…However, our laboratory BFT ( Figure 6) agrees with previous research from field studies showing that dispersibility of oil is inversely proportional to viscosity [3] A correlation for DE with the paraffin content of heavier oils has been reported [26]. There are instances where oils of similar viscosity disperse quite differently.…”

Oil Irradiation Experiments Document Changes in Oil Properties, Molecular Composition, and Dispersant Effectiveness Associated with Oil Photo-Oxidation

“…Finally, we examined the role of viscosity in reducing the observed dispersant effectiveness. It is known from bench-scale, tank-based, and field tests that viscosity can affect the dispersibility of fresh and weathered crude oil. ,, In line with these studies, we also observed a decrease in dispersant effectiveness with increasing viscosity of irradiated oil residues (Figure C). Our data showed similar dispersant effectiveness–viscosity relation as a study that also used the Baffled Flask Test to measure the dispersant effectiveness of 23 different (non-photo-oxidized) crude oils (Figure C) .…”

“…It has been suggested that high paraffin contents in oil residues can be inversely correlated with dispersant effectiveness. 52 Previous studies found this correlation to be applicable for low-viscosity oils and not for oils with viscosities >1000 cP. 8 In line with these studies, we did not find an inverse correlation between the paraffin content of the oil residues (total mass of n-alkanes per mass unit of total oil; Table S3) and measured dispersant effectiveness values (Figure S9).…”

“…In our test, sunlight exposure of 200–350 μm films of HOOPS oil (original viscosity 6 cP) for 3 days still had Baffled Flask Test-dispersant effectiveness values larger than 60%, compared to 87% for the fresh oil. Considering that bench-top tests produce lower dispersant effectiveness than large-scale tank tests , or field conditions (Figure ), our results imply that even though photochemistry will change the chemical composition and physical properties of a low-viscosity oil slick that would be targeted by aerial dispersion applications, the slick would still be amenable to chemical dispersion when applied within the typical “window of opportunity”, which is within 2–4 days of the onset of an oil spill.…”

Effect of Oil Composition on Chemical Dispersion of Crude Oil

“…When the composition was measured using an analytical method that separates the oil into four SARA fractions similar to those used in this study, the concentration of the saturates fraction was positively correlated with the performance of Corexit 9500, but the concentrations of the aromatics, resins, and asphaltenes fractions were negatively correlated (Fingas et al , 2003). Canevari et al (2001), on the other hand, observed a negative effect of the saturates fraction on dispersibility of 14 heavy fuel oils by Corexit 9500 but could not discern effects due to the aromatics, resins, or polars (asphaltenes) fractions.…”

Comparative Laboratory-Scale Testing of Dispersant Effectiveness of 23 Crude Oils Using Four Different Testing Protocols*

“…However, our laboratory BFT ( Figure 6) agrees with previous research from field studies showing that dispersibility of oil is inversely proportional to viscosity [3] A correlation for DE with the paraffin content of heavier oils has been reported [26]. There are instances where oils of similar viscosity disperse quite differently.…”

Oil Irradiation Experiments Document Changes in Oil Properties, Molecular Composition, and Dispersant Effectiveness Associated with Oil Photo-Oxidation

“…Finally, we examined the role of viscosity in reducing the observed dispersant effectiveness. It is known from bench-scale, tank-based, and field tests that viscosity can affect the dispersibility of fresh and weathered crude oil. ,, In line with these studies, we also observed a decrease in dispersant effectiveness with increasing viscosity of irradiated oil residues (Figure C). Our data showed similar dispersant effectiveness–viscosity relation as a study that also used the Baffled Flask Test to measure the dispersant effectiveness of 23 different (non-photo-oxidized) crude oils (Figure C) .…”

“…It has been suggested that high paraffin contents in oil residues can be inversely correlated with dispersant effectiveness. 52 Previous studies found this correlation to be applicable for low-viscosity oils and not for oils with viscosities >1000 cP. 8 In line with these studies, we did not find an inverse correlation between the paraffin content of the oil residues (total mass of n-alkanes per mass unit of total oil; Table S3) and measured dispersant effectiveness values (Figure S9).…”

“…In our test, sunlight exposure of 200–350 μm films of HOOPS oil (original viscosity 6 cP) for 3 days still had Baffled Flask Test-dispersant effectiveness values larger than 60%, compared to 87% for the fresh oil. Considering that bench-top tests produce lower dispersant effectiveness than large-scale tank tests , or field conditions (Figure ), our results imply that even though photochemistry will change the chemical composition and physical properties of a low-viscosity oil slick that would be targeted by aerial dispersion applications, the slick would still be amenable to chemical dispersion when applied within the typical “window of opportunity”, which is within 2–4 days of the onset of an oil spill.…”

Effect of Oil Composition on Chemical Dispersion of Crude Oil

“…When the composition was measured using an analytical method that separates the oil into four SARA fractions similar to those used in this study, the concentration of the saturates fraction was positively correlated with the performance of Corexit 9500, but the concentrations of the aromatics, resins, and asphaltenes fractions were negatively correlated (Fingas et al , 2003). Canevari et al (2001), on the other hand, observed a negative effect of the saturates fraction on dispersibility of 14 heavy fuel oils by Corexit 9500 but could not discern effects due to the aromatics, resins, or polars (asphaltenes) fractions.…”