OCS Study BOEM 2016-062

Physical and Chemical Analyses of 

Crude and Refined Oils: Laboratory and 

Mesoscale Oil Weathering

Final Report

US Department of the Interior 

Bureau of Ocean Energy Management 

Alaska OCS Region

Physical and Chemical Analyses of Crude and 

Refined Oils: Laboratory and Mesoscale Oil 

Weathering

Final Report

Author

Kristin. R. Sørheim

Prepared under BOEM Award M14PC00012

by

SEA Consulting Group

325 Mason Ave. 

Cape Charles, VA 23310

AND

SINTEF Materials and Chemistry 

Postboks 4760 Sluppen

7465 Trondheim, NORWAY
i

DISCLAIMER

Study concept, oversight, and funding were provided by the US Department of the Interior, Bureau of Ocean 

Energy Management (BOEM) Bureau of Ocean Energy Management, Environmental Studies Program, 

Washington, DC, under Contract Number M14PC00012. This report has been technically reviewed by

BOEM and it has been approved for publication. The views and conclusions contained in this document are

those of the authors and should not be interpreted as representing the opinions or policies of the US 

Government, nor does mention of trade names or commercial products constitute endorsement or

recommendation for use.

REPORT AVAILABILITY

To download a PDF file of this BOEM Alaska OCS Region report, go to the US Department of the 

Interior, Bureau of Ocean Energy Management, Environmental Studies Program Information System

website and search on OCS Study BOEM 2016-062.

This report can be viewed at select Federal Depository Libraries. It can also be obtained from the National

Technical Information Service; the contact information is below.

http://www.ntis.gov/products/publications.aspx OR

US Department of Commerce

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

Phone: (703) 605-6040

Fax: (703) 605-6900

CITATION

Sorheim, K.R. 2016. Physical and Chemical Analyses of Crude and Refined Oils: Laboratory and 

Mesoscale Oil Weathering. OCS Study BOEM 2016-062. Prepared by SINTEF Materials and Chemistry 

and SEA Consulting Group for USDOI, Bureau of Ocean Energy Management, Alaska OCS Region, 

Anchorage, AK. 106 pp.

CONTRIBUTING AUTHORS

Per Daling – SINTEF Materials and Chemistry

Jon Olav Bjørgum – SINTEF Materials and Chemistry

CJ Beegle-Krause – SINTEF Materials and Chemistry

Ann Hayward Walker – SEA Consulting Group

Melinda McPeek – SEA Consulting Group

ABOUT THE COVER

Cover photo courtesy of SINTEF Materials and Chemistry.
ii

EXECUTIVE SUMMARY

Spilled oils undergo changes when weathering on the sea surface that affect behavior and oil spill 

countermeasures in various ways. Oil weathering varies over time and with different 

environmental conditions. The objectives of this study were to:

(1) To obtain weathering characteristics of crude oils representative of the Alaska OCS (Outer 

Continental Shelf) and typical refined products transported in offshore waters; 

(2) To expand libraries of oil compositions of existing weathering models such as the SINTEF 

Oil Weathering Model (OWM) and the Automated Data Inquiry for Oil Spills (ADIOS) model 

from the National Oceanic and Atmospheric Administration (NOAA). 

This report covers the physical and chemical analyses of six oils including: 

 Three crude oils from Alaska North Slope: Alpine, Kuparuk and Northstar, and

 Three refined products of ADO (Automotive Diesel Oil, also called Ultra-Low-Sulphur 

Diesel (ULSD)) and MGO (Marine Gas Oil) from the Esso Slagen Refinery Norway, and 

a WRG (Wide Range Gasoil) from Mongstad Refinery Norway. 

The six oils from this study were analyzed for their weathering properties in a standardized benchscale methodology. In addition, the weathering was studied in the meso-scale flume basin as a

supplement to the bench-scale testing for all oils. Dispersant effectiveness testing was beyond this 

study’s scope, however, SINTEF added Corexit 9500 to the emulsified oils at the end of the testing 

to obtain a visual assessment of potential dispersibility in their weathered state. The resulting 

laboratory data from this study will be input into oil weathering models, i.e., the OWM and 

ADIOS, to predict the weathering properties of oils at sea. Including the data in these models will 

enable evaluation of the experimental data generated both by the bench-scale and meso-scale 

experiments to consider the most robust oil weathering predictions.

Properties of crude oils from Alaska North Slope:

Alpine is a paraffinic crude oil with a density of 0.832 g/mL (corresponds to API° 38.4). The fresh 

unweathered oil has a very low pour point (<-36 °C), but increases rapidly with the evaporative 

loss. The oil has a medium to low wax content of 2.1 wt. %, and has asphaltene content of 0.46 

wt. %. The laboratory study showed that the oil forms stable water-in-oil (w/o) emulsions when 

weathered. However, the emulsion effectively released water when adding the emulsion breaker 

(Alcopol O 60 %) with a concentration of 2000 ppm. Emulsion breaker may be used during an oil 

spill operation to remove or reduce water from the emulsion, normally applied after recovery, prior 

to transfer to storage tank to minimize the storage volume. After three days weathering in the flume

basin (meso-scale experiments) Corexit 9500 (in-situ application) was added to the emulsion to 

finalize the testing. The oil/emulsion showed a significant potential for dispersant use as a response 

option. However, effectiveness testing and determining the specific time-window, or window of 

opportunity, for dispersant use was not part of this project.

Kuparuk is categorized as a high-density 0.917 g/mL (API° 22.7) asphaltenic (4.7 wt. %) crude oil 

with a relatively low wax content of 1.3 wt. %. Kuparuk has a low pour point and solidification on 

the sea surface is not anticipated since solidification typically arises with pour points 10-15 °C 

above the sea temperature. The crude oil formed stable w/o-emulsions particularly for the 200 and 

250°C+ residues with high viscosities. In general, the emulsions require a high dosage of emulsion 

breaker (Alcopol O 60 % at 2000 ppm) in cases where emulsion breaker might be added as part of 

a mechanical recovery operation to settle out water and decrease the storage volume needed. After 
iii

three days of weathering in the meso-scale flume basin Corexit 9500 (in-situ application) with a 

cumulative dosage Dispersant-to-Oil (DOR) ratio of 1:50 was added to the oil/emulsion. The 

findings indicate that a higher dosage (DOR > 1:50) is recommended to be applied to a slick in an 

oil spill situation for higher effect, since the efficiency of adding dispersant (DOR 1:50) was not 

optimal. However, the window of opportunity for use of dispersant as a function of effectiveness 

and viscosities, and dosage testing for optimal DOR, was not determined in this study.

Northstar is a very light paraffinic crude oil with a density of 0.779 g/ml (API° 50), and exhibits 

low content of wax (1.7 wt. %) and asphaltenes (0.03 wt. %). The oil is a low-emulsifying crude 

oil that forms loose emulsions and easily released water with the addition of a concentration of 

500 ppm of the emulsion breaker (Alcopol O 60 %). The oil showed high potential for application 

of dispersant agent (Corexit 9500) based on the results from the meso-scale flume basin. However, 

no laboratory study was conducted to assess the window of opportunity for using chemical 

dispersant on this oil.

Properties of refined products:

The ADO (Automotive Diesel Oil) has a density of 0.830 g/mL (corresponds to API° 38.8). The 

ADO oil has a very low content of wax and asphaltenes; less than 0.05 wt. %. The diesel oil has a 

very low pour point (<-36 °C) and remained low with evaporative loss. The weathered oil residue 

did not emulsify during the bench-scale emulsifying testing and showed no water uptake. Based 

on visual inspection during the meso-scale flume experiment a great majority of the oil was 

naturally dispersed into the water column, and only a minor amount of the oil was observed on the 

surface after three days of weathering (~ 3 % of the total released oil into the flume). The remaining 

oil on the surface became darker with a "slimy" characteristic. The dispersant Corexit 9500 (insitu application) was added and visually showed that the dispersant was effective. 

The MGO (Marine Gasoil) has a density of 0.849 g/mL (corresponds to API° 35). The MGO oil 

has a higher wax content (1.96 wt. %) compared with the ADO. The asphaltene content of the 

diesel oil is less than 0.05 wt. %. The MGO has a low pour point similar to the ADO. The oil did 

not emulsify (no significant water uptake) in the bench-scale laboratory testing. During the mesoscale testing, most of the oil was easily naturally dispersed and diluted into the water column 

during the two days of weathering, and no dispersant agent was therefore applied onto the surface 

in the flume due to insignificant amount of available surface oil.

The WRG (Wide Range Gasoil) has a density of 0.892 g/mL (corresponds to API° 27) with a 

medium content of wax (4.8 wt. %) and with low content of asphaltenes (0.05 wt. %). The WRG 

oil has a low pour point (<-24 °C). Due to lack of lighter compounds, less than 250 °C, the fresh 

oil was assumed to have similar weathering properties as for the 250°C+ residue. The oil showed 

emulsifying properties during the bench-scale testing, but the emulsions were very unstable and 

easily broke up after standing less than an hour. Based on the meso-scale flume experiment a larger 

amount of the oil was naturally dispersed into the water column, and only a minor amount of the 

oil was observed on the surface after two days weathering. However, the dispersant agent Corexit 

9500 (in-situ application) was added on the surface slick and visually showed high efficiency.
iv

TABLE OF CONTENTS

1. Introduction................................................................................................................................1

2. Oil Samples/Materials................................................................................................................5

2.1 Alpine crude oil........................................................................................................................5

2.2 Refined diesel products (ADO, MGO).....................................................................................6

2.3 Kuparuk crude oil ....................................................................................................................7

2.4 Northstar crude oil ...................................................................................................................7

2.5 Wide Range Gasoil (WRG) .....................................................................................................8

3. Bench Scale Laboratory Testing Results ....................................................................................9

3.1 Pre-handling and analysis .......................................................................................................9

3.2 Chemical composition and physical properties .....................................................................12

3.2.1 Gas chromatographic (GC/FID) characterization .........................................................12

3.2.2 Asphaltene and wax content ........................................................................................20

3.2.3 Physical properties of fresh and weathered residues...................................................21

3.3 Emulsifying properties ...........................................................................................................23

3.3.1 Water uptake ................................................................................................................23

3.3.2 Stability and efficiency of emulsion breaker .................................................................29

3.3.3 Viscosity of water-free residues and emulsified residues.............................................31

4. Meso-scale Flume Laboratory Testing results .....................................................................34

4.1 Alpine crude oil......................................................................................................................34

4.2 Refined product ADO ............................................................................................................41

4.3 Refined products MGO..........................................................................................................48

4.4 Kuparuk crude oil ..................................................................................................................54

4.5 Northstar crude oil .................................................................................................................62

4.6 Wide Range Gasoil (WRG) ...................................................................................................67

5. Conclusions .............................................................................................................................73

6. Quality Assurance ...................................................................................................................73

7. References................................................................................................................................74

Appendix A Experimental setup..................................................................................................76

A.1 Bench-scale laboratory methodology ................................................................76

A.1.1 Evaporation.................................................................................................76

A.1.2 Physical and chemical analysis ..................................................................76

A.1.3 Emulsification properties ............................................................................77

A.2 Meso-scale flume basin.....................................................................................78

A.2.1 Description of the flume basin ....................................................................78

A.2.2 Oil weathering in the flume basin ...............................................................79

Appendix B Table Format-Input to Oil Weathering Models ........................................................81

Appendix C Categorization Map of Alaska North Slope Crude Oils ...........................................90
v
vi

LIST OF FIGURES

Figure 1.1. Location of Alpine in red circle to the left. Alpine is located in the on Alaska’s

western North Slope, west of the Kuparuk River Field (Kuparuk)............................ 2

Figure 1.2. Alpine production site in Alaska.............................................................................. 2

Figure 1.3. Location of Esso Slagen Refinery in the South-East of Norway situated on the

west bank of the Oslo fjord.. ................................................................................... 3

Figure 1.4. Location of Alpine and Kuparuk in red circles to the left. Alpine and Kuparuk are

located in the on Alaska’s Central North Slope................................................3

Figure 1.5. On Alaska's North Slope, ConocoPhillips Alaska, Inc. operates the Kuparuk River 

Unit (Kuparuk), North America’s second largest oil field....................................4

Figure 1.6. Northstar production site in Alaska operated by Hilcorp Alaska, LLC. ..................... 4

Figure 1.7. Location of Statoil Mongstad Refinery at the west coast of Norway......................... 5

Figure 2.1. Oil samples of Alpine crude oil upon arrival at SINTEF laboratory, 19th of March 

2015. ...................................................................................................................... 6

Figure 2.2. Oil samples of ADO upon arrival at SINTEF laboratory, 23rd October 2014............. 6

Figure 2.3. Oil samples of MGO upon arrival at SINTEF laboratory, 23rd of October, 2014. ...... 7

Figure 2.4. Oil samples of Kuparuk crude oil upon arrival at SINTEF laboratory, 19th of 

March 2015. ........................................................................................................... 7

Figure 2.5. Oil samples of Northstar upon arrival at SINTEF laboratory, 2nd June 2015............. 8

Figure 2.6. 1000 liters container of WRG (right). 25 liters aliquot of WRG ready for analysis 

(left)........................................................................................................................ 8

Figure 3.1. GC/FID chromatograms of the fresh and its evaporated residues of Alpine crude 

oil...........................................................................................................................14

Figure 3.2. GC/FID chromatograms of the fresh and its evaporated residues of ADO..............15

Figure 3.3. GC/FID chromatograms of the fresh and its evaporated residues of MGO.............16

Figure 3.5. GC/FID chromatograms of the fresh and its evaporated residues of Northstar 

crude oil.................................................................................................................18

Figure 3.6. GC/FID chromatogram of the fresh Wide Range Gasoil.........................................19

Figure 3.7. Distillation curves of Alpine, Kuparuk and Northstar crude oils in comparison 

with previously tested oils from Alaska North Slope (Leirvik et. al., 2002)..............22

Figure 3.8. Distillation curves of WRG (Year Two) in comparison of ADO and MGO (Year 

One), and other refined products of marine gas oil and wide range gas oil 

(Sørheim and Daling, 2015)...................................................................................23

Figure 3.9. The rotating cylinders of water-in-oil emulsion of Alpine crude oil after 24 hours 

of rotation at 10 °C.................................................................................................24

Figure 3.10. The rotating cylinders of ADO (left) and MGO (right) after 24 hours of rotation at 

10°C. No emulsification was observed for ADO and MGO....................................25

Figure 3.11.The rotating cylinders of water-in-oil emulsion of Kuparuk crude oil after 24 

hours of rotation at 10 °C, given as example for the 200 and 250°C+ residue .......26
vii

Figure 3.12.The rotating cylinders of water-in-oil emulsion of Northstar crude oil after 24 

hours of rotation at 10 °C, given as example for the 150 and 200°C+ residues 

above, and for the 200 and 250°C+ residue, below ...............................................27

Figure 3.13. Unstable emulsion formation of WRG after 24 hours large droplet incorporated 

in the oil phase (left) and totally broken emulsion (left) after 48 hours without 

emulsion breaker...................................................................................................28

Figure 4.1. Estimated mass balance for Alpine crude oil in the meso-scale flume basin at 

10C, before dispersant application. ......................................................................36

Figure 4.2. Visual observation of Alpine crude oil before and after treatment of dispersant.....40

Figure 4.3. Estimated mass balance for ADO in the meso-scale flume basin at 10C, before

dispersant application............................................................................................42

Figure 4.4. The oil-samples P1 (0.5 hour) – P8 (48 hours) from left to right with observed 

changes in the color appearance over time ...........................................................43

Figure 4.5. Visual observation of ADO before and after treatment of dispersant agent............48

Figure 4.6. Estimated Mass balance for MGO in the meso-scale flume basin at 10C. ...........49

Figure 4.7. Visual observation of MGO....................................................................................53

Figure 4.8. Estimated mass balance for Kuparuk crude oil in the meso-scale flume basin at 

10C, before dispersant application. ......................................................................55

Figure 4.9. Visual observations of Kuparuk Crude Oil with and without dispersant 

application .............................................................................................................61

Figure 4.10. Estimated mass balance for Northstar crude oil in the meso-scale flume basin 

at 10C, before dispersant application. ..................................................................63

Figure 4.11. Visual observations of Northstar Crude Oil with and without dispersant 

application .............................................................................................................67

Figure 4.12. Estimated mass balance for Wide Range Gasoil (WRG) in the meso-scale 

flume basin at 10C, before dispersant application ................................................68

Figure 4.13. Visual observations of WRG with and without dispersant application ....................72

Figure A.1. Bench-scale laboratory weathering flow chart of oil ...............................................76

Figure A.2. Principle of the rotating cylinder after Mackay and Zagorski (1982) .......................78

Figure A.3. Schematic drawing of the meso-scale flume..........................................................79

Figure C.1. Categorization of Alaska North Slope crude oils into four main groups; 

Naphtenic, Paraffinic, Waxy, and Asphaltenic oils. ................................................91
viii

LIST OF TABLES

Table 3.1 Pre-handling and analysis of water content and density of Alpine crude oil. ..........10

Table 3.2 Pre-handling and analysis of water content and density of ADO diesel oil .............10

Table 3.3 Pre-handling and analysis of water content and density of MGO diesel oil ............10

Table 3.4 Pre-handling and analysis of water content and density of Kuparuk crude oil ........11

Table 3.5 Pre-handling and analysis of water content and density of Northstar crude oil.......11

Table 3.6 Pre-handling and analysis of water content and density of WRG...........................12

Table 3.7 Asphaltene (“hard”) and wax content of Alpine, ADO MGO (Year One), and 

Kuparuk, Northstar and WRG (Year Two)..............................................................20

Table 3.8 Physical properties of Alpine crude oil and refined products of ADO and MGO 

(Year One).............................................................................................................21

Table 3.9 Physical properties of Kuparuk and Northstar crude oils and refined products 

WRG (Year Two)...................................................................................................21

Table 3.10 Water uptake of the evaporated residues of Alpine crude oil at 10 °C....................24

Table 3.11 Water uptake of the evaporated residues of Kuparuk crude oil at 10 °C. ...............26

Table 3.12 Water uptake of the evaporated residues of Northstar crude oil at 10 °C...............28

Table 3.13 Water uptake of the fresh oil of WRG at 10 °C.......................................................29

Table 3.14 Stability of Alpine emulsions (no emulsion breaker) and efficiency of emulsion 

breaker at 10 °C ....................................................................................................30

Table 3.15 Stability of Kuparuk emulsions (no emulsion breaker) and efficiency of emulsion 

breaker at 10 °C ....................................................................................................30

Table 3.16 Stability of Northstar emulsions (no emulsion breaker) and efficiency of 

emulsion breaker at 10 °C .....................................................................................31

Table 3.17 Stability of WRG (no emulsion breaker) and efficiency of emulsion breaker at 10 

°C ..........................................................................................................................31

Table 3.18 Viscosity of Alpine water-free residue and their emulsified residues at 10 °C ........32

Table 3.19 Viscosity of Kuparuk water-free residue and their emulsified residues at 10 °C .....33

Table 3.20 Viscosity of Northstar water-free residue and their emulsified residues at 10 °C....33

Table 4.1 Tabulated results from the meso-scale weathering experiment of Alpine crude 

oil at 10oC..............................................................................................................35

Table 4.2 Tabulated values of the estimated mass balance for Alpine crude oil. Example 

after 24 hours weathering in the meso-scale flume................................................36

Table 4.3 Results from the meso-scale weathering experiment of ADO. ...............................41

Table 4.4 Tabulated values of the estimated mass balance for ADO.....................................42

Table 4.5 Results from the meso-scale weathering experiment of MGO ...............................48

Table 4.6 Tabulated values of the estimated mass balance for MGO....................................49

Table 4.7 Results from the meso-scale weathering experiments of Kuparuk crude oil...........54

Table 4.8 Tabulated values of the estimated mass balance for Kuparuk crude oil.................55
ix

Table 4.9 Results from the meso-scale weathering experiment of Northstar .........................62

Table 4.10 Mass balance for Northstar during the meso-scale laboratory test at 10 °C...........63

Table 4.11 Results from the meso-scale weathering experiment of WRG 10 °C .....................67

Table 4.12 Mass balance for WRG during the meso-scale laboratory test at 10 °C.................68

Table A.1 Analytical methods used to determine the physical properties ...............................77

Table A.2 Analytical methods used to determine the chemical properties..............................77

Table A.3 Methods used to determine the physical properties of the surface oil/emulsion. ....80

Table B.1 Physical and chemical properties of the fresh oils for Alpine crude oil, ADO and 

MGO (Year One) ...................................................................................................81

Table B.2 Physical and chemical properties of the fresh oils for Kuparuk and Northstar 

crude oils and WRG (Year2)..................................................................................82

Table B.3 True boiling point (TBP) curve for Alpine crude oil .................................................82

Table B.4 True boiling point (TBP) curve for ADO .................................................................83

Table B.5 True boiling point (TBP) curve for MGO.................................................................83

Table B.6 True boiling point (TBP) curve for Kuparuk crude oil..............................................84

Table B.7 True boiling point (TBP) curve for Northstar crude oil ............................................84

Table B.8 True boiling point (TBP) curve for WRG.................................................................85

Table B.9 Summary lab weathering data of Alpine crude oil, 10 °C of fresh oil and its 

residues.................................................................................................................86

Table B.10 Summary lab weathering data of ADO, 10 °C of fresh oil and its residues .............86

Table B.11 Summary lab weathering data of MGO, 10 °C of fresh oils and its residues ..........87

Table B.12 Summary lab weathering data of Kuparuk crude oil, 10 °C of fresh oils and its 

residues.................................................................................................................87

Table B.13 Summary lab weathering data of Northstar crude oil, 10 °C of fresh oils and its 

residues.................................................................................................................88

Table B.14 Summary lab weathering data of WRG, 10 °C of fresh oil due to lack of lighter 

components with boiling point lower than 250 °C...................................................89
x

ABBREVIATIONS, ACRONYMS, AND SYMBOLS

~ approximately

C celsius

cP centipoise

m3cubic meter

° degree

g gram

> greater than

h hour (s)

< less than

m meter

mg milligram

mL milliliter

min minute

mPa.s millipascal second

n normal

ppm parts per million

% percent

s

-1

reciprocal second

rpm rotation per minute

vol.% volume percent

w/o water-in-oil

wt.% weight percent

ADIOS Automated Data Inquiry for Oil Spills

ADO Automotive Diesel oil

ASTM American Society for Testing and Materials

API American Petroleum Institute

BSEE Bureau of Safety and Environment Enforcement

BOEM Bureau of Ocean Energy Management 

DCM Dichloromethane

DER Dispersant-to-emulsion Ratio

DM (DMA, DMB, DMC) Distillate Marine (Marine Fuel ISO 8217)

DOR Dispersant-to-oil Ratio

DWT Deadweight tonnage

GC/FID Gas Chromatography/Flame Ionization Detector

HSE Health, Safety and Environment

ID Identification

IFT Interfacial tension

ISO International Organization for Standardization

MGO Marine Gas Oil

MSDS Material Safety Data Sheet

NCA Norwegian Coastal Administration

NOAA National Oceanic and Atmospheric Administration

T1/2 (Half) Time

TBP True Boiling Point

OCS Outer Continental Shelf

OWM Oil Weathering Model

UCM Unresolved Complex Mixture
xi

ULSD Ultra-Low-Sulphur Diesel

UV Ultra Violet

WOR Water-to-oil Ratio

WRG Wide Range Gasoil
1

1. INTRODUCTION

SINTEF Materials and Chemistry, Department of Oil Spill Research (hereafter referred as 

SINTEF) was asked by SEA Consulting Group (hereafter referred as Client) to conduct weathering 

studies of six oils. A total of three oils were studied in Year One and three additional oils were 

studied in Year Two. The six oils included:

 Year One: One crude oil supplied from Alaska North Slope from ConocoPhillips Alaska, 

Inc. (Alpine), and two light refined products of ADO (Automotive Diesel Oil, also called 

Ultra-Low-Sulphur Diesel (ULSD) and MGO (Marine Diesel Oil). The refined products 

(diesel oils) were supplied from the Esso Slagen refinery in Norway. 

 Year Two: The three oils in Year Two included two crude oils supplied from Alaska North 

Slope from ConocoPhillips Alaska, Inc. (Kuparuk) and Hilcorp Alaska, LLC (Northstar), 

and one refined product of WRG (Wide Range Gasoil) produced in Norway. The WRG 

refined product was supplied from Statoil Mongstad refinery in conjunction with another 

project that SINTEF is conducting (2014-2016) for the Norwegian Coastal Administration 

(NCA). The NCA project is a weathering and dispersibility study, with screening of 

dispersant agents for diesel products, including WRG. Findings from a pre-study of 

weathering properties of another batch of WRG can be found in Sørheim and Daling, 2015 

(open report in Norwegian language).

The bench-scale and meso-scale flume laboratory testing of the six oils were conducted at 10 °C,

reflecting relevant sea temperature in Alaskan waters, and was defined in agreement with the 

Client. The experimental data were further customized in tables for use as input to numerical Oil 

Weathering Models (OWMs), in order to obtain reliable and robust weathering predictions of spill 

scenarios. 

Year One: North Slope Alpine crude oil.

The Alaska oil and gas production is concentrated in three main regions: North Slope Offshore

(Nikaitchuq and Northstar), Central North Slope, and Southcentral Alaska, as shown in Figure 1.1. 

The same figure shows the location of Alpine (CD1) on Alaska’s Central North Slope. Figure 1.2

shows the Alpine crude production site (plant) in Alaska.
2

Figure 1.1. Location of Alpine in red circle to the left. Alpine is located on Alaska’s 

Central North Slope, west of the Kuparuk River Field (Kuparuk). 

Source: http://www.eia.gov/todayinenergy/detail.cfm?id=21632. 

Figure 1.2. Alpine production site in Alaska.

Source: http://alaska.conocophillips.com/PublishingImages/SMID_003_Alpine_BannerHero.jpg

Year One: Refined products from Esso Slagen Refinery.

The two refined oils, ADO (Automotive Diesel Oil, also called Ultra-Low-Sulphur Diesel (ULSD) 

and MGO (Marine Diesel Oil), from the Esso Slagen Refinery in Norway were chosen as 

representatives for refined products in Year One. These diesel oils are specified according to the 

international standard of EN 590 and ISO 8217 Fuel Standard (Distillate Marine fuels /Grade A, 

or DMA grade). Figure 1.3 shows the refinery situated in the South-East of Norway in the Oslo 

fjord. The marine terminal consists of a pier about 500 m long with loading/discharging berths on 

both sides, as shown in Figure 1.3. At present time, the terminal has approximately 800 tanker 

calls a year with size variation 100 to 250,000 DWT (Deadweight tonnage). The annual import of 

crude oil and blend stocks is about 6.5 mill. m3 whereas about 5.7 mill. m3 petroleum products are 

shipped out.
3

Figure 1.3. Location of Esso Slagen Refinery in the South-East of Norway situated on the 

west bank of the Oslo fjord. 

Source: http://www.businesswire.com/multimedia/home/20140903006720/en/

Year Two: North Slope Kuparuk and Northstar crude oils.

As mentioned above in Year One, the Alaska oil and gas production is concentrated in three 

main regions: North Slope Offshore, Central North Slope, and Southcentral Alaska, as shown in

Figure 1.4. The same figure shows the location of Kuparuk and Northstar on Alaska’s Central 

North Slope in red circles. 

Figure 1.5 shows the Kuparuk crude production site in Alaska. Northstar is an offshore 

installation located on an artificial island in the Beaufort Sea, as shown in Figure 1.6.

.

Figure 1.4. Location of Kuparuk and Northstar in red circles to the left. Kuparuk and Northstar

are located on Alaska’s Central North Slope. 

Source: http://www.eia.gov/todayinenergy/detail.cfm?id=21632. 
4

Figure 1.5. On Alaska's North Slope, ConocoPhillips Alaska, Inc. operates the Kuparuk River 

Unit (Kuparuk), North America’s second largest oil field.

Source: http://www.conocophillips.com/newsroom/PublishingImages/Kuparuk.jpg

Figure 1.6. Northstar production site in Alaska operated by Hilcorp Alaska, LLC. Northstar is 

located on an artificial island. It is located 6 miles offshore in water that experiences significant ice 

formation. Product flows through a subsea pipeline. Source: http://libertyprojectak.com/
5

Year Two: Refined product from Statoil Mongstad Refinery.

The refined product of WRG (Wide Range Gasoil) from the Statoil Mongstad Refinery in Norway 

was chosen as a representative oil type for testing in Year Two. According to the ISO 8217 Fuel 

standard, the WRG is classified as Distillate Marine, Grade DMB or DMC quality. The Mongstad

oil refinery is located in the western part of Norway. The plant has an annual capacity of near 12 

million tons of crude. Most of the oil refined comes from the Norwegian continental shelf. Most 

of the output from the refinery is exported, particularly to continental Europe. The principal 

outputs are petrol, diesel oil, jet fuel and other light petroleum products. Figure 1.7 shows the 

refinery area situated in the western part of Norway.

Figure 1.7. Location of Statoil Mongstad Refinery at the west coast of Norway. 

Source: 

http://www.statoil.com/en/ouroperations/terminalsrefining/prodfacilitiesmongstad/pages/energiver

kmongstad.aspx

2. OIL SAMPLES/MATERIALS

2.1 ALPINE CRUDE OIL

The Central North Slope Alpine crude oil arrived at the SINTEF laboratory on the 19

th of March, 

2015 via air cargo from DHL. The oil sample was registered in the SINTEF laboratory database

system, and given a unique identification number: SINTEF ID: 2015-0258. SINTEF received the 

Material Safety Data Sheet (MSDS) and a crude assay of the boiling point curve of Alpine. Figure 

2.1 shows the barrels upon arrival and a sample description.
6

Sample description:

4 x 20 liter barrels

Alpine sales crude

Sampled December 20, 2014 at 12:59

Figure 2.1. Oil samples of Alpine crude oil upon arrival at SINTEF laboratory, 19th of March 2015.

2.2 REFINED DIESEL PRODUCTS (ADO, MGO)

The two refined diesel products of ADO (Auto diesel base = Ultra-Low-Sulfur Diesel (ULSD)) 

and MGO (Marine Gas Oil) arrived at the SINTEF laboratory on the 23rd of October, 2014 from 

the Esso Slagen refinery in Norway. The samples were registered in the SINTEF laboratory 

database system, and were given the following identification numbers: SINTEF ID: 2014-0491 

(ADO) and 2014-0492 (MGO). The material safety data sheet (MSDS) and certificate of quality 

were given from the refinery. Figure 2.2 and Figure 2.3 show the barrels upon arrival and sample 

descriptions.

Sample description:

2 x 25 liter barrels

Sent from Esso Norge AS, Slagen

Type: ADO

Shore tank no: 801

Unit: OMS

Date: 20/10-14

Time: 13:45

 Sample no: 141015108

Figure 2.2. Oil samples of ADO upon arrival at SINTEF laboratory, 23rd October 2014.
7

Sample description:

2 x 25 liter barrels

Sent from Esso Norge AS, Slagen

Type: MGO

Shore tank no: 803

Unit: OMS

Date: 20/10-14

Time: 15:35 and 15:55

 Sample no: 141019027

Figure 2.3. Oil samples of MGO upon arrival at SINTEF laboratory, 23rd of October, 2014.

2.3 KUPARUK CRUDE OIL

A total of 80 liters of Central North Slope Kuparuk crude oil arrived at the SINTEF laboratory on 

the 19th of March, 2015 via air cargo from DHL. The oil sample was registered in the SINTEF 

laboratory database system, and given a unique identification number: SINTEF ID: 2015-0259. 

SINTEF received the Material Safety Data Sheet (MSDS) and a crude assay of the boiling point 

curve of Kuparuk from the Client. Figure 2.4 shows the barrels upon arrival and sample 

description.

Sample description:

4 x 20 liter barrels

Kuparuk sales crude

From CPF-1

 Sampled January 16, 2015 at 3:52 PM

Figure 2.4. Oil samples of Kuparuk crude oil upon arrival at SINTEF laboratory, 19th of March 2015.

2.4 NORTHSTAR CRUDE OIL

A total of 80 liters of Central North Slope Northstar crude oil arrived at the SINTEF laboratory on 

2

nd of June, 2015 via air cargo from DHL. The oil sample was registered in the SINTEF laboratory 

database system, and given a unique identification number: SINTEF ID: 2015-0469. SINTEF 

received the Material Safety Data Sheet (MSDS) and a crude assay of the boiling point curve of 

Northstar from the Client. Figure 2.5 shows the barrels upon arrival and sample description.
8

Sample description:

4 x 20 liter barrels

Chemical Name: Northstar crude oil (from 

shipping pumps)

 Sampled: 3-15-15 

Figure 2.5. Oil samples of Northstar upon arrival at SINTEF laboratory, 2

nd June 2015.

2.5 WIDE RANGE GASOIL (WRG)

SINTEF received in mid-November 2015 a container of 1000 Liters of a batch of WRG produced 

at the Statoil Mongstad refinery in Norway. The sampling and shipment was arranged through the 

Norwegian Coastal Administration (NCA). A total of 200 Liters from the container was transferred 

to a separate barrel, and an aliquot of 25 Liters was further sampled to a separate can. The 25 Liters

sample of WRG was used in this study. The sample was registered in the SINTEF laboratory 

database system, and was given the following identification number: SINTEF ID: 2016-0106. A 

certificate of quality of WRG including the boiling point curve was customized by the refinery. 

Figure 2.6 shows the 1000 Liters container of WRG upon arrival and the aliquots of 25 Liters for 

analysis.

Figure 2.6. 1000 liters container of WRG (right). 25 liters aliquot of WRG ready for analysis (left)
9

3. BENCH-SCALE LABORATORY TESTING RESULTS

The bench-scale methodology is thoroughly described in Appendix A. As some of the tested oils 

exhibit similar properties and characteristics, this section is organized by the various composition 

and property testing conducted and combines and summarizes results. 

3.1 PRE-HANDLING AND ANALYSIS 

Pre-handling and analysis of oils from Year One

The samples of Alpine crude oil and the two refined diesel oils were measured for water content 

and densities upon arrival, and were further homogenized prior to the testing of the chemical 

composition and physical properties related to the weathering study. An overview of the results 

and comments are given in Table 3.1, Table 3.2, and Table 3.3. 

Neither Alpine nor the two refined products showed high level of water content, therefore no extra 

distillation /topping was required. The original barrels containing the Alpine crude were dented 

upon arrival at the laboratory; however, the damage did not influence on the quality of the crude 

oil for the physical and chemical properties and conducting the weathering study.

Pre-handling and analysis of oils from Year Two

Samples of the two crude oils (Kuparuk and Northstar) and the refined WRG were measured for 

water content and densities upon arrival, and further homogenized prior to the testing of chemical 

composition and physical properties related to the weathering study. An overview of the results 

and comments are given in Table 3.4, Table 3.5, and, Table 3.6. 

Some free-water was observed in the bottom of all the barrels of Kuparuk as described in the table 

below. It was decided to remove water/oil from the bottom of each barrel prior to homogenization 

to avoid any free-water from being incorporated into the whole sample. High water content is not 

beneficial for topping/distillation due to a HSE (Health, Safety and Environmental) aspect. 

Neither Northstar crude oil nor the WRG showed any significant level of water content upon 

arrival, and no extra precaution prior to topping/ distillation were required. The original barrels 

containing the Kuparuk crude were dented upon arrival; however, the damage did not influence 

the quality of the crude oil for the physical and chemical properties and conducting the weathering 

study. The color appearance of Northstar was light brown and translucent, and the visual inspection 

indicated a low content of asphaltene. In addition, no visual precipitation of wax in a sample of 

Northstar crude oil, stored at a lower temperature (5 °C), was observed.
10

Table 3.1

Pre-handling and analysis of water content and density of Alpine crude oil.

Barrel Water content 

(vol. %) *

Bottom sample

Density

(g/mL)

Comments Alpine crude oil

(SINTEF ID: 2015-0258)

1 of 4 <0.01 0.835 The original barrel was highly dented upon arrival, but no 

leakage. The sample was transferred to a separate jerry can.

2 of 4 < 0.01 0.831 The original barrel was highly dented upon arrival, but no 

leakage. The sample was transferred to a separate jerry can.

3 of 4 < 0.01 0.831 The original barrel was highly dented upon arrival, but no 

leakage. The sample was transferred to a separate jerry can.

4 of 4 < 0.01 0.832 The original barrel was highly dented upon arrival, but no 

leakage. The sample was transferred to a separate jerry can.

*Measured with KF: Karl Fisher titration methodology

Table 3.2

Pre-handling and analysis of water content and density of ADO diesel oil

Barrel

Water content 

(vol. %) *

Bottom sample

Density

(g/mL)

Comments ADO (Auto diesel)

(SINTEF ID: 2015-0491)

1 of 2 < 0.01 0.830 None

2 of 2 < 0.01 0.830 None

*Measured with KF: Karl Fisher titration methodology

Table 3.3

Pre-handling and analysis of water content and density of MGO diesel oil

Barrel

Water content 

(vol. %) *

Bottom sample

Density

(g/mL)

Comments MGO (Marine Gas Oil)

(SINTEF ID: 2015-0492)

1 of 2 < 0.01 0.849 None

2 of 2 < 0.01 0.849 None

*Measured with KF: Karl Fisher titration methodology
11

Table 3.4

Pre-handling and analysis of water content and density of Kuparuk crude oil

Barrel Water content 

(vol. %) *

Homogenized 

sample

Density

(g/mL)

Comments Kuparuk crude oil

(SINTEF ID: 2015-0259)

1 of 4 0.1 0.918 The original barrel was dented upon arrival, but had no leakage.

Some free-water was observed. Approx.400 mL was removed 

from the bottom of the barrel. The barrel was further 

homogenized and the water content was quantified 

2 of 4 0.1 0.917 The original barrel was dented upon arrival, but had no leakage. 

Some free-water was observed. Approx.400 mL was removed 

from the bottom of the barrel. The barrel was further 

homogenized and the water content was quantified

3 of 4 0.1 0.917 The original barrel was dented upon arrival, but had no leakage. 

Some free-water was observed. Approx.400 mL was removed 

from the bottom of the barrel. The barrel was further 

homogenized and the water content was quantified

4 of 4 0.1 0.917 The original barrel was dented upon arrival, but had no leakage. 

Some free-water was observed. Approx.400 mL was removed 

from the bottom of the barrel. The barrel was further 

homogenized and the water content was quantified

*Measured with KF: Karl Fisher titration methodology

Table 3.5

Pre-handling and analysis of water content and density of Northstar crude oil

Barrel Water content 

(vol. %) * 

Bottom sample

Density

(g/mL)

Comments Northstar crude oil

(SINTEF ID: 2015-0469)

1 of 4 0.14 0.779 The barrel was filled up with oil, and the homogenization was 

performed carefully and pre-heating at 50 °C was not considered 

necessary.

2 of 4 0.23 0.778 The barrel was filled up with oil, and the homogenization was 

performed carefully and pre-heating at 50 °C was not considered 

necessary.

3 of 4 0.31 0.778 The barrel was filled up with oil, and the homogenization was 

performed carefully and pre-heating at 50 °C was not considered 

necessary.

4 of 4 0.1 0.779 The barrel was filled up with oil, and the homogenization was 

performed carefully and pre-heating at 50 °C was not considered 

necessary.

*Measured with KF: Karl Fisher titration methodology
12

Table 3.6

Pre-handling and analysis of water content and density of WRG

Barrel

Water content 

(vol. %) *

Bottom sample

Density

(g/mL)

Comments WRG (Wide Range Gasoil)

(SINTEF ID: 2016-0106)

1 of 1 0.07 0.892 The 1000 litres container of WRG was stored upon arrival in room 

temperature for some weeks before an aliquot of 200 Liters was 

transferred to a separate barrel. The barrel was stored in room 

temperature prior sampling of 25 Liters.

*Measured with KF: Karl Fisher titration methodology

3.2 CHEMICAL COMPOSITION AND PHYSICAL PROPERTIES

3.2.1 Gas chromatographic (GC/FID) characterization 

The gas chromatograms show the n-alkanes as systematic narrow peaks. The first peaks in the 

chromatogram represent components with the lowest boiling points. Some of the more complex 

components, such as resins and naphthenes, shown as a broad and poorly defined bump below the 

sharp peaks, are often described as “Unresolved Complex Mixture” (UCM). Heavier compounds 

such as asphaltenes (> nC40) are not possible to analyze with this technique. The gas 

chromatographic characterization of the hydrocarbon distributing of the fresh oil and its 

corresponding residues (150, 200 and 200°C+) verifies the artificial evaporation of the oil by use 

of distillation (topping) in the laboratory.

GC/FID characterization of oils from Year One

The chemical composition of Alpine crude oil and the two refined products of ADO and MGO 

diesel oil, as characterized by gas chromatography (GC/FID), are shown in Figure 3.1, Figure 3.2, 

and Figure 3.3. No evaporation loss lower than 150 °C was observed. The GC/FID characterization 

indicates that Alpine crude oil is categorized as a paraffinic crude oil reflecting a medium to low 

amount of wax /paraffinic components in the range of nC20-nC30 and a minor content of UCM. 

GC/FID characterization of oil from Year Two

The chemical composition of Kuparuk and Northstar crude oil and the refined product of WRG, 

as characterized by gas chromatography (GC/FID), are shown in Figure 3.4, Figure 3.5 and Figure 

3.6, respectively. The fresh sample of WRG showed insignificant evaporation loss lower than 250 

°C.

The GC/FID characterization indicates that Kuparuk contains a relatively high amount of UCM 

that has possibly been caused by biodegradation in the reservoir. The oil reflects a medium to low 

amount of wax /paraffinic components in the range of nC20-nC30. However, since the oil contains 

high amount of asphaltenes as shown in Table 3.7, the Kuparuk crude oil classifies as an 

asphaltenic crude oil.

The Northstar crude oil is categorized as light paraffinic crude with low content of UCM, reflecting 

a medium to low amount of wax /paraffinic components in the range of nC20-nC30. In comparison, 
13

Kuparuk contains fewer lower molecular weight components and has a larger UCM envelope than 

Northstar and is also the heaviest crude oil (high density).

The fresh samples of ADO and MGO correspond to their 150°C+ residues due to no observed 

evaporation loss lower than 150 °C during distillation, and the corresponding GC-chromatograms

(Figure 3.2 and Figure 3.3) verify that the distillates have minor content of the lightest component. 

However, MGO has a higher amount of n-alkanes in area from nC20 compared with the ADO 

reflecting wax-components.

WRG (Wide Range Gasoil) is a distillate with minor content of the lightest components and 

exhibits a high amount of n-alkanes of nC20-nC26 reflecting wax-components with a well-defined 

UCM in this area.
14

Figure 3.1. GC/FID chromatograms of the fresh and its evaporated residues of Alpine crude oil 

(SINTEF ID: 2015-0258)

Alpine

SINTEF ID: 2015-0258

Fresh oil

Alpine

SINTEF ID: 2015-0258

150°C+ residue

Alpine

SINTEF ID: 2015-0258

200°C+ residue

Alpine

SINTEF ID: 2015-0258

250°C+ residue
15

Figure 3.2. GC/FID chromatograms of the fresh and its evaporated residues of ADO

(SINTEF ID: 2014-0491)

ADO

SINTEF ID: 2014-0491

Fresh ~150°C+ residue

ADO

SINTEF ID: 2014-0491

200°C+ residue

ADO

SINTEF ID: 2014-0491

250°C+ residue
16

Figure 3.3. GC/FID chromatograms of the fresh and its evaporated residues of MGO 

(SINTEF ID: 2014-0492).

MGO

SINTEF ID: 2014-0492

Fresh~150°C+ residue

MGO

SINTEF ID: 2014-0492

200°C+ residue

MGO

SINTEF ID: 2014-0492

250°C+ residue
17

Figure 3.4. GC/FID chromatograms of the fresh and its evaporated residues of Kuparuk crude oil 

(SINTEF ID: 2015-0258)

Kuparuk

SINTEF ID: 2015-0259

Fresh oil

Kuparuk

SINTEF ID: 2015-0259

150°C+ residue

Kuparuk

SINTEF ID: 2015-0259

200°C+ residue

Kuparuk

SINTEF ID: 2015-0259

250°C+ residue

UCM
18

Figure 3.5. GC/FID chromatograms of the fresh and its evaporated residues of Northstar crude oil 

(SINTEF ID: 2015-0469)

Northstar

SINTEF ID: 2015-

0469

Fresh oil

Northstar

SINTEF ID: 2015-0469

150°C+ residue

Northstar

SINTEF ID: 2015-0469

200°C+ residue

Northstar

SINTEF ID: 2015-0469

250°C+ residue
19

Figure 3.6. GC/FID chromatogram of the fresh Wide Range Gasoil (SINTEF ID: 2016-0106)

WRG

SINTEF ID: 2016-0469

Fresh

UCM

WRG

SINTEF ID: 2016-0469

250°C+
20

3.2.2 Asphaltene and wax content

The chemical properties of asphaltene and wax contents of Alpine crude oil and the two refined 

products of ADO and MGO (Year One), and Kuparuk, Northstar and Wide Range Gasoil (Year 

Two) are given in Table 3.7. Kuparuk exhibits a high content of asphaltenes compared with the 

other oils, and is considered as an asphaltenic crude with paraffinic features. Alpine, Kuparuk and 

Northstar crude oils have all low to medium content of wax. The lack of lighter components 

explain the low evaporative loss of Wide Range Gasoil (WRG) and the fresh oil is therefore 

assumed to correspond to the 250 °C+ residue, whilst the fresh oils of ADO and MGO correspond

to the 150°C+ residue.

Table 3.7

Asphaltene (“hard”) and wax content of Alpine, ADO MGO (Year One), and Kuparuk, Northstar and 

WRG (Year Two)

"Hard"*

Oil type Residue asph. Wax

(wt.%) (wt.%)

Alpine Fresh 0.46 2.05

SINTEF ID 150°C+ 0.58 2.61

2015-0258 200°C+ 0.68 3.07

250°C+ 0.78 3.51

ADO** Fresh~150°C+ 0.03 0.04

SINTEF ID 200°C+ 0.04 0.05

2014-0491 250°C+ 0.06 0.08

MGO* Fresh~150°C+ 0.03 1.96

SINTEF ID 200°C+ 0.04 2.16

2014-0492 250°C+ 0.05 2.70

Kuparuk Fresh 4.74 1.32

SINTEF ID 150°C+ 5.21 1.44

2015-0259 200°C+ 5.46 1.51

250°C+ 5.94 1.64

Northstar Fresh 0.03 1.74

SINTEF ID 150°C+ 0.05 2.77

2014-0469 200°C+ 0.06 3.47

250°C+ 0.09 4.82

WRG*** Fresh~250°C+ 0.05 4.84

SINTEF ID

2016-0106

* Hard asphalthenes: Precipitation of asphaltene using n-heptane (nC7) 

** The fresh oils of ADO and MGO correspond to the 150°C+ residue.

*** The fresh oil of WRG corresponds to the 250°C+ residue.
21

3.2.3 Physical properties of fresh and weathered residues

The physical properties of Alpine crude oil and the refined diesel oils of ADO and MGO (Year 

One) and Kuparuk and Northstar crude oils and the refined WRG (Year Two) are listed in Table 

3.8 and Table 3.9.

Table 3.8

Physical properties of Alpine crude oil and refined products of ADO and MGO (Year One)

Oil type Residue

Evap.

(vol. 

%)

Res.

(wt. %)

Dens. 

(g/mL)

Flash

point 

(°C)

Pour

point 

(°C)

Visc.

mPa.s

10°C

10 s-1

IFT 

(ini.)

(mN/m)

IFT 

(eq.)

(mN/m)

Alpine

Fresh 0 100 0.832 - <-36 8 30 15

150 oC + 25.5 78.5 0.877 40 0 43 30 14

200°C+ 37.9 66.8 0.896 87 9 204 28 13

250°C+ 46.6 58.4 0.906 113 12 688 30 15

ADO*

Fresh~ 

150 oC+ 0 100 0.830 59 <-36 5

24 12

200 oC + 15.9 84.7 0.835 74 <-36 6 23 9.5

250 oC + 47.5 53.4 0.845 107 -33 10 21 8.3

MGO* Fresh~ 

150 oC+ 0 100 0.849 62 <-36 7

27 17

200 oC + 9.7 90.9 0.854 78 <-36 9 29 13

250 oC + 28.5 72.8 0.864 108 -30 14 28 11

* The fresh oil of ADO and MGO corresponds to the 150°C+ residue.

- = Not analyzed

Table 3.9

Physical properties of Kuparuk and Northstar crude oils and refined products WRG (Year Two)

Oil type Residue

Evap 

(vol. 

%)

Res.

(wt. %)

Dens.

(g/mL)

Flash

point 

(°C)

Pour

point 

(°C)

Visc.

mPa.s

10°C

10 s-1

IFT 

(ini.)

(mN/m)

IFT 

(eq.)

(mN/m)

Fresh 0 100 0.917 - -33 143 19 7

Kuparuk 150 oC + 11 92 0.941 57 -27 630 20 8

200°C+ 16 87 0.950 81 -21 1242 21 9

250°C+ 23 80 0.962 115 -12 4420 26 11

Northstar Fresh 0 100 0.779 - -9 1 29 10

150 oC + 42 63 0.838 33 9 20 30 8

200 oC + 54 50 0.852 71 15 249 30 7

250 oC + 68 36 0.869 116 21 409 31 9

WRG* Fresh~ 0 100 0.892 106 -24 85 19 12

250 oC +

* The fresh oil of WRG corresponds to the 250°C+ residue.

- = Not analyzed

Distillation curve (True Boiling Point Curve -TBP)

The distillation curve, which is obtained by measuring the vapor temperature as a function of the 

amount of oil distilled, shows the relative distribution of volatile and heavier components in the 

oil. The boiling point of a particular chemical component depends on its vapor pressure, which is 
22

a function of its molecular weight and chemical structure. Low molecular weight oil components 

have a higher vapor pressure, thus lower boiling points than higher molecular weight components 

of a similar type. Aromatic compounds boil at a higher temperature than paraffinic compounds of 

the same molecular weight, and iso-alkanes boil at a lower temperature than the equivalent nalkanes. Hence, the distillation curve is an indicator of the relative amount of different chemical 

components, principally as a function of molecular weight, but also as determined by the chemical 

composition. 

Figure 3.7. Distillation curves of Alpine, Kuparuk and Northstar crude oils in comparison with 

previously tested oils from Alaska North Slope (Leirvik et. al., 2002). Northstar lab data is based 

on the topped oil, and the TBP is therefore adjusted to fit the lab data as input to model tools
23

Figure 3.8. Distillation curves of WRG (Year Two) in comparison of ADO and MGO (Year One),

and other refined products of marine gas oil and wide range gas oil (Sørheim and Daling, 2015)

3.3 EMULSIFYING PROPERTIES 

The emulsifying properties were studied using the rotating cylinders method as detailed in Hokstad 

et al., 1993. The parameters for kinetics (rate of water uptake) and maximum water uptake were 

studied to define the emulsification characteristics of oils selected for this study as described in 

Appendix A, section A.1.3. The T1/2 value derived from kinetics is defined as the consumed time 

in hours needed to incorporate half of the maximum water uptake. In general, residues of 150°C+, 

200°C+ and 250°C+ are made for each oil in order to produce data for stability, viscosity, water 

uptake and effectiveness of application of an emulsion breaker. Four cylinders of each residue of 

each oil, e.g., 150°C+, are prepared to study in parallel: stability testing and water uptake (rotating 

cylinder 1); viscosity / water update (rotating cylinder 2); effectiveness of emulsion breaker at 

dosage of 500 ppm (wt.%) (rotating cylinder 3); and effectiveness of emulsion breaker at dosage 

of 2000 ppm (wt.%) (rotating cylinder 4).

3.3.1 Water uptake 

Emulsification is the mixing of seawater droplets into spilled oil at the water’s surface (water-inoil emulsion), forming a weathered oil product that tends to be relatively resistant to other 

weathering processes such as evaporation, and also increases the total volume of oil due to the 

uptake of water into the oil. Highly emulsified oil can be more difficult to recover and also be 

difficult to chemically disperse.
24

Alpine Crude Oil

The Alpine crude oil formed water-in-oil (w/o) emulsions mixing with seawater as shown in Figure 

3.9 The oil showed both a rapid and high water uptake for all the residues. The tabulated water 

uptake as a function of time and the calculated T1/2 values is shown in Table 3.10.

Figure 3.9. The rotating cylinders of water-in-oil emulsion of Alpine crude oil after 24 

hours of rotation at 10 °C

Table 3.10

Water uptake of the evaporated residues of Alpine crude oil at 10 °C

Mixing 

time

*150°C+ 

(Vol. % water)

*200°C+ 

(Vol. % water)

*250°C+ 

(Vol. % water)

Start 0 0 0

5 min 33 28 15

10 min 45 39 23

15 min 54 45 25

30 min 69 54 37

1 hour 77 63 78

2 hours 91 69 79

4 hours 90 78 79

6 hours 89 82 79

24 hours 84 81 79

T1/2 0.16 0.23 0.38

 * Depending on weather situation and release rate, the residues correspond to 

 approximately 0.5-1 hour, 0.5-1 day and 0.5-1 week of weathering on the sea surface.

 
25

ADO and MGO

Neither the ADO nor the MGO emulsified when mixed with seawater, where no water uptake 

during the testing in the rotational cylinders was measured, as shown in Figure 3.10. The stability 

and effectiveness of emulsion breaker was therefore not evaluated for these oils.

Figure 3.10. The rotating cylinders of ADO (left) and MGO (right) after 24 hours of rotation at 10°C. 

No emulsification was observed for ADO and MGO

Kuparuk Crude Oil

The Kuparuk crude oil formed water-in-oil (w/o) emulsions mixing with seawater as shown in 

Figure 3.11 after 24 hours of rotation. The oil showed a slow emulsification rate and relatively low 

maximum water uptake after 24 hours, as shown in Table 3.11.

A

DO

B

GO
26

Figure 3.11. The rotating cylinders of water-in-oil emulsion of Kuparuk crude oil after 24 hours 

of rotation at 10 °C, given as example for the 200 and 250°C+ residue

Table 3.11

Water uptake of the evaporated residues of Kuparuk crude oil at 10 °C.

Mixing 

time

*150°C+ 

(Vol. % water)

*200°C+ 

(Vol. % water)

*250°C+ 

(Vol. % water)

Start 0 0 0

5 min 8 3 2

10 min 13 7 4

15 min 19 7 4

30 min 31 18 7

1 hour 41 26 12

2 hours 48 33 12

4 hours 52 40 14

6 hours 55 43 14

24 hours 58 49 21

T1/2 0.52 1.10 1.50

* Depending on weather situation and release rate, the residues 

are corresponding to approximately 0.5-1 hour, 0.5-1 day and 0.5-1

week of weathering on the sea surface.
27

Northstar Crude Oil

Northstar crude oil showed almost no emulsification for the 150°C+ residue where the emulsified 

residue almost corresponded to the water-free fresh oil, whilst the 250 °C+ residue developed a 

very high water uptake, but the emulsion was unstable with large water droplets and easily released 

water when settled under static conditions. Figure 3.12 shows the rotating cylinders of water-inoil (w/o) emulsion of Northstar crude oil after 24 hours rotation time at 10 °C.

Figure 3.12. The rotating cylinders of water-in-oil emulsion of Northstar crude oil after 

24 hours of rotation at 10 °C, given as example for the 150 and 200°C+ residues above, 

and for the 200 and 250°C+ residue, below.
28

Table 3.12

Water uptake of the evaporated residues of Northstar crude oil at 10 °C.

Mixing 

time

*150°C+ 

(Vol. % water)

*200°C+ 

(Vol. % water)

*250°C+ 

(Vol. % water)

Start 0 0 0

5 min 3 47 81

10 min 3 44 88

15 min 3 44 89

30 min 3 39 90

1 hour 3 33 90

2 hours 3 33 90

4 hours 3 31 90

6 hours 3 26 90

24 hours 3 26 90**

T1/2 0.01 0.01 0.03

 * Depending on weather situation and release rate, the residues are corresponding 

to approximately 0.5-1 hour, 0.5-1 day and 0.5-1 week of weathering on the sea surface.

**~ 90 vol. % due to supersaturation in rotating cylinders and the very high water uptake is unlikely to happen 

in a spill situation at sea.

Wide Range Gasoil (WRG)

The Wide Range Gasoil product showed emulsifying properties at 10 °C, but the oil formed very 

unstable emulsions with large water droplets, and the emulsion was quickly broken upon standing 

(within 1 hour), where most of the water was separated from the oil phase, as shown in Figure 3.13

below.

Figure 3.13. Unstable emulsion formation of WRG after 24 hours large droplet incorporated in the oil 

phase (left) and totally broken emulsion (left) after 48 hours without emulsion breaker
29

Table 3.13

Water uptake of the fresh oil of WRG at 10 °C

Mixing time Fresh oil~250 

°C+ residue

(Vol. % water)

Start 0

5 min 41

10 min 82

15 min 91

30 min 91

1 hour 91

2 hours 91

4 hours 91

6 hours 91

24 hours 91*

T1/2 0.15

*Unstable emulsion after 24 hours rotation. The emulsion was easily broken due to large

droplet incorporated in the oil phase. 91 vol. % due to supersaturation- the very high water uptake

is unlikely to happen in a spill situation at sea.

3.3.2 Stability and efficiency of emulsion breaker

Overall, the findings of stability and the efficiency of emulsion breakers is important in a 

mechanical recovery situation because separating the oil from water enables optimal use of 

available storage facilities/tankers. The emulsified oil volume decreases considerably with 

treatment of an emulsion breaker as water is removed.

Alpine Crude Oil

The emulsion stability of Alpine crude oil was studied by quantifying the amount of water released 

from the emulsion during 24 hours settling time. In addition, the efficiency of adding emulsion 

breaker (Alcopol O 60 %) to the emulsion was evaluated. The results are shown in 

Table 3.14. The results indicate that Alpine crude oil forms very stable water-in-oil emulsions 

when spilled at sea and weathered. The effect of applying chemical emulsion breaker was most 

efficient by using the highest dosage of 2000 ppm (0.2 wt. %).

Kuparuk Crude Oil

The emulsion stability of Kuparuk was studied by quantifying the amount of water released from 

the emulsion during 24 hours settling time and the efficiency of adding emulsion breaker (Alcopol 

O 60 %) to the emulsion was evaluated. The effect of applying the highest dosage of 2000 ppm 

(0.2 wt. %) was slightly more efficient compared with the lower dosage of 500 ppm of the emulsion 

breaker. The results are shown in Table 3.15.

Northstar Crude Oil

The emulsion stability of Northstar was studied by quantifying the amount of water released from 

the emulsion during 24 hours settling time. In addition, the efficiency of adding emulsion breaker 

(Alcopol O 60 %) to the emulsion was evaluated. Northstar formed loose emulsions that were

easily broken with the lowest dosage of 500 ppm of the emulsion breaker. The results are shown

in Table 3.16.
30

Wide Range Gasoil

The stability of WRG emulsion was studied by quantifying the amount of water released from the 

emulsion during 24 hours settling time. In addition, the efficiency of adding emulsion breaker 

(Alcopol O 60 %) to the emulsion was evaluated. The emulsion was easily broken with or without

the addition of emulsion breaker; i.e. the effect of adding emulsion breaker was insignificant. The 

results are shown in Table 3.17.

Table 3.14

Stability of Alpine emulsions (no emulsion breaker) and efficiency of emulsion breaker at 10 °C

Residue Emulsion breaker Water-in-oil emulsion (vol.%) at 10 oC

Reference 24 hours * Stability ratio**

150oC+ none 84 86 1.00

200oC+ none 81 80 0.95

250oC+ none 79 77 0.94

150oC+ Alc. O 60 % 500 ppm 84 - -

200oC+ Alc. O 60 % 500 ppm 81 71 0.57

250oC+ Alc. O 60 % 500 ppm 79 72 0.70

150oC+ Alc. O 60 % 2000 ppm 84 12 0.02

200oC+ Alc. O 60 % 2000 ppm 81 35 0.12

250oC+ Alc. O 60 % 2000 ppm 79 39 0.17

 - Not measured

* w/o emulsion after 24 hours rotation and 24 hours settling

** Stability ratio of 1 implies a totally stable emulsion during 24 hours settling. Stability ratio of 0 (zero) 

implies a totally unstable emulsion; all the water is settled out during 24 hours settling.

Table 3.15

Stability of Kuparuk emulsions (no emulsion breaker) and efficiency of emulsion breaker at 10 °C

Residue Emulsion breaker Water-in-oil emulsion (vol.%) at 10 oC

Reference 24 hours * Stability ratio**

150°C+ none 58 6 0.05

200°C+ none 49 17 0.21

250°C+ none 21 19 0.87

150°C+ Alc. O 60 % 500 ppm 58 12 0.10

200°C+ Alc. O 60 % 500 ppm 49 12 0.14

250°C+ Alc. O 60 % 500 ppm 21 17 0.75

150°C+ Alc. O 60 % 2000 ppm 58 12 0.10

200°C+ Alc. O 60 % 2000 ppm 49 6 0.07

250°C+ Alc. O 60 % 2000 ppm 21 9 0.37

 * w/o emulsion after 24 hours rotation and 24 hours settling

 ** Stability ratio of 1 implies a totally stable emulsion during 24 hours settling. Stability ratio of 0 (zero)

 implies a totally unstable emulsion; all the water is settled out during 24 hours settling.
31

Table 3.16

Stability of Northstar emulsions (no emulsion breaker) and efficiency of emulsion breaker at 10 °C

Residue Emulsion breaker

Water-in-oil emulsion (vol.%) at 10 °C

Ref. 24 hours * Stability 

ratio**

24 hours + 

10 rotations 

***

Stability 

ratio***

150°C+ none 3 3 - 3 -

200°C+ none 26 19 0.67 19 0.67

250°C+ none 90 90 0.93 51 0.11

150°C+ Alc. O 60 % 500 ppm 3 3 1.00 3 1.00

200°C+ Alc. O 60 % 500 ppm 26 3 0.10 3 0.10

250°C+ Alc. O 60 % 500 ppm 90 23 0.03 23 0.03

150°C+ Alc. O 60 % 2000 ppm 3 3 1.00 3 1.00

200°C+ Alc. O 60 % 2000 ppm 26 12 0.38 6 0.19

250°C+ Alc. O 60 % 2000 ppm 90 14 0.02 14 0.02

* w/o emulsion after 24 hours rotation and 24 hours settling

** Stability ratio of 1 implies a totally stable emulsion during 24 hours settling and stability ratio of 0 (zero)

implies a totally unstable emulsion; all the water is settled out during 24 hours settling

*** w/o emulsion after 24 hours rotation and 24 hours settling + 10 rounds of rotation is expected to be most 

reliable with respect to a field operation.

Table 3.17

Stability of WRG (no emulsion breaker) and efficiency of emulsion breaker at 10 °C

Residue Emulsion breaker

Water-in-emulsion (vol. %) at 10 °C

Reference 24 hours* Stability ratio*

Fresh none 91 6 0.01

Fresh Alc. O 60 % 500 ppm 91 14 0.02

Fresh Alc. O 60 % 2000 ppm 91 0 0.00

 * w/o emulsion after 24 hours rotation and 24 hours settling

 ** Stability ratio of 1 implies a totally stable emulsion during 24 hours settling and stability ratio of 0 

(zero) implies a totally unstable emulsion; all the water is settled out during 24 hours settling

3.3.3 Viscosity of water-free residues and emulsified residues

Alpine Crude Oil

Table 3.18 gives the viscosities of water-free residues and the corresponding residues after 

emulsification at 10 °C with 50 vol. %, 75 vol. % and the maximum water. As a non-Newtonian 

fluid, the viscosities of Alpine oil residues and emulsions are dependent on the shear rate; the 

viscosities are higher at a lower share rate (10 s-1) compared to higher shear rate (100 s-1). This 

decrease in viscosity with increasing shear rate is likely caused by breaking up the wax lattice 

structure with increased mechanical force. In general, Alpine shows an increasing emulsion 

viscosity with increasing degree of weathering (evaporating and water uptake).
32

Table 3.18

Viscosity of Alpine water-free residue and their emulsified residues at 10 °C

Residue

Water 

content

(vol. %)

Viscosity (m.Pas)

10 s-1 100 s-1

Fresh 0 8 7

150°C+ 0 43 39

200°C+ 0 204 159

250°C+ 0 688 447

150°C+ 50 358 281

200°C+ 50 1128 736

250°C+ 50 2386 1370

150°C+ 75 2214 825

200°C+ 75 5760 1885

250°C+ 75 10481 3266

150°C+ 83 24104 3802

200°C+ 80 26059 5485

250°C+ 77 33720 3650

ADO and MGO

The viscosities of the water free residues of ADO and MGO are given in Table 3.8. None of these 

oilsshowed emulsifying properties. The refined products also behaved as a Newtonian fluid, where 

the viscosity is not dependent on its shear rate.

Kuparuk and Northstar Crude Oils

The viscosities of the water free 150, 200 and 250°C+ residues and the corresponding emulsions 

are shown in Table 3.19 and Table 3.20 for Kuparuk and Northstar. The viscosity of Northstar for 

maximum water content of the 250°C+ residue was regarded as uncertain due to the low stability 

of the emulsion.

Wide Range Gasoil

The viscosities of the water free residues of WRG is given in Table 3.9. The emulsion of WRG 

was very unstable, and the very low viscosities measured were not tabulated.
33

Table 3.19

Viscosity of Kuparuk water-free residue and their emulsified residues at 10 °C

Residue

Water 

content Viscosity Viscosity

(m.Pas) (m.Pas)

(vol. %) (10 s−1) (100 s−1)

Fresh 0 143 134

150°C+ 0 630 613

200°C+ 0 1242 1230

250°C+ 0 4420 4410

150°C+ 50 3799 1978

200°C+ 50 7380 3379

250°C+ 50 22497 1867

150°C+ 75 6546 767

200°C+ 65* 14306 2736

250°C+ 27* 9758 4977

150°C+ 60 4979 2049

200°C+ 52 7045 2975

250°C+ 23 8497 4524

 * The residue did not reach 75 % vol. water uptake and hence influence the viscosities.

Table 3.20

Viscosity of Northstar water-free residue and their emulsified residues at 10 °C

Residue

Water 

content Viscosity Viscosity

(m.Pas) (m.Pas)

(vol. %) (10 s−1) (100 s−1)

Fresh 0 1 2

150°C+ 0 20 10

200°C+ 0 249 57

250°C+ 0 409 152

150°C+ < 50* 16 8

200°C+ <50* 81 24

250°C+ <50* 60 39

150°C+ <75* 14 8

200°C+ <75* 55 18

250°C+ <75* 104 33

150°C+ 3 17 8

200°C+ 6 87 25

250°C+ - - 8

 *The residue did not reach 50 and 75 % vol. water uptake.

- Unstable emulsion
34

4. MESO-SCALE FLUME LABORATORY TESTING RESULTS

The description of the meso-scale flume is given in Appendix A.2. This section is organized by oil 

type and provides an overview of the tabulated results of the meso-flume testing, visual 

observations, and estimated mass balance of each of the six oils that were tested.

The estimated mass balance of each oil is presented for each oil in Figures 4.1, 4.3, 4.6, 4.8, 4.10, 

4.12. 

The main processes of the mass balance for oil spilled at sea are:

 Evaporative loss

 Surface oil 

 Dispersed oil into the water column

In addition, the mass balances from the flume basin also includes the estimated parameters: 

 Amount of oil sampled

 Amount of oil sticking to the flume wall

The meso-scale testing provides valuable operational information about the oil's behavior. The 

flume testing is therefore considered a supplement to the bench-scale laboratory testing. The 

experimental results obtained for Alpine crude oil, ADO and MGO (refined products) from Year 

One and Kuparuk and Northstar crude oils, and WRG (refined product) from Year Two conducted 

at 10 °C are presented below. 

4.1 ALPINE CRUDE OIL

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.1 for 

Alpine crude oil.
35

Table 4.1

Tabulated results from the meso-scale weathering experiment of Alpine crude oil at 10oC

Sample no Time Water content Evaporative loss Viscosity Oil in water

(hours) (vol. %) (wt. %) (m.Pas) 10 s-1 ppm*

1 0.5 7 20 NA 69

2 1 28 23 49 62

3 2 32 26 NA 62

4 4 34 29 173 65

5 6 57 31 329 45

6 12 69 33 762 34

7 24 70 35 1587 19

8 48 63 37 2296 17

9 72 56 39 2683 19

 1

st application of dispersants: 49.3g Corexit 9500 (DOR = 1:71)

3 min. disp. 1 - - - - 188

10 min. disp. 1 - - - - 188

60 min. disp. 1 - - - 201

 2

nd application of dispersants: 60.6g Corexit 9500 (DOR = 1:56)

3 min. disp. 2 - - - - 374

10 min. disp. 2 - - - - 334

30 min. disp. 2 - - - - 352

120 min. disp. 2 - - - - 340

- = no measured data. *ppm=parts per million NA: Not applicable

Mass Balance of Alpine Crude Oil

The amount of oil evaporated, oil on surface, naturally dispersed and sampled oil was calculated, 

and the oil adsorbed to the flume walls was estimated by weight. Figure 4.1 shows the estimated 

mass balance before applying dispersant agent into the flume, whilst Table 4.2 shows an example 

of tabulated values of the estimated mass balance after 24 hours weathering. 
36

Figure 4.1. Estimated mass balance for Alpine crude oil in the meso-scale flume basin at 10C, 

before dispersant application.

Table 4.2

Tabulated values of the estimated mass balance for Alpine crude oil. Example after 24 hours 

weathering in the meso-scale flume

Mass balance

(% of initial oil) after 24 

hours

Alpine crude oil

Test temperature

(10 oC)

Evaporated 35

Oil on water surface 55

Dispersed oil 1

Sampled amount of oil* 3

Oil adsorbed to the flume walls* 5

*Estimated values

Visual observations of Alpine crude oil

A selection of pictures taken during the flume experiment at 10 °C is presented below. Figure 4.2

shows the visual observation of Alpine crude oil before and after treatment by dispersant. Artificial 

sunlight simulated using a solar simulator (see Figure A3) was turned on for photographing, but 

otherwise turned off during the weathering time (no photo-oxidation). Note: The oil/emulsion can 

therefore be significantly lighter in appearance /color with the solar simulator turned on.

Sample 0 (Start): The oil spread evenly in a thin dark brown film on the surface. 

Samples 1-3 (First 2 hours): Thin dark brown film on the surface. No emulsification observed.

 
37

Samples 4-5 (4-6 hours): The oil film was getting thicker and had slightly started to emulsify.

Sample 6 (12 hours): The oil is emulsifying.

Sample 7 (24 hours): The oil appeared much thicker as a "real" water-in-oil emulsion. The

appearance /color of the emulsion was now a little bit lighter brown than the 12 hours sample.

Sample 8 (48 hours): Stable homogeneous w/o-emulsion. Minor amount of the emulsion was now 

adsorbed to the flume wall. The appearance of the emulsion was even lighter brown compared 

with the previous samples. 

Sample 9 (72 hours): Less observed changes from the 48 hours weathering. The emulsion became 

a little thicker and more elastic. 

In-situ chemical dispersion of Alpine crude oil.

After 72 hours of weathering in the flume, the dispersant Corexit 9500 was sprayed on the 

remaining w/o-emulsion (in-situ application). Approximately 40 % of the total volume of oil 

(approx. 8.8 liters) was available for chemical dispersion. The treatment of Corexit 9500 was 

sprayed twice on the surface with a dosage-to-oil ratio (DOR) of 1:71 and a dosage-to-emulsion 

ratio (DER) of 1:167 in the first application, giving a cumulative DOR of 1:33 and DER of 1:100 

with the second application. 

The first application of Corexit 9500 showed visually some effect on the surface oil/emulsion as 

the dispersant broke up the emulsion into smaller patches and resulted in less water content and a 

lower viscous emulsion. However, some resurfacing of larger droplets of the dispersed oil was 

observed. The second application of dispersant was considered to be very effective on the 

remaining emulsion with minor observed surface oil after 30 minutes. The emulsion was broken 

into even smaller droplets and was therefore easily dispersed into the water column. No resurfacing 

of oil on the surface was visually observed after 2 hours. The concentration of oil dispersed into 

the water column increased approximately 10 times after the first application and approximately

20 times after the second application compared with no treatment by dispersant.
38

Sample 2 – 1 hour after application of Alpine crude oil.

Sample 5 – 6 hours. The oil is starting to emulsify slightly.

Sample 6 – 12 hours. Emulsion formation.

Sample 7 – 24 hours
39

Sample 8 – 48 hours

Sample 9 – 72 hours. Stable w/o-emulsion.

3 minutes after first dispersant application. 10 minutes after first dispersant application. 

1 hour after first dispersant application. The slick is broken into smaller patches and the emulsion

is now less viscous with less water content. Some resurfacing of the dispersed oil was observed.
40

3 minutes after second dispersant application. The dispersion process is ongoing.

10 minutes after second dispersant application. The major surface of oil/emulsion is dispersed into

the water column.

30 minutes aftersecond dispersion

30 minutes after second dispersant application. Only small patches left on the surface.

2 hours after second dispersant application. Hardly any observed oil/emulsion left on the surface.

Figure 4.2. Visual observation of Alpine crude oil before and after treatment by dispersant
41

4.2 REFINED PRODUCT ADO

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.3 for 

ADO.

Table 4.3

Results from the meso-scale weathering experiment of ADO.

Sample no Time

Water 

content

Evaporative 

loss Viscosity

Oil in

water

(hours)

(vol. 

%) (wt. %)

(mPa.s) 

10 s-1 ppm*

1 0.5 0 3 4 165

2 1 0 5 4 162

3 2 0 8 5 167

4 4 0 14 5 209

5 6 0 18 5 252

6 12 0 24 5 262

7 24 0 32 7 359

8 48 14 42 9 -

9 72 19 47 296 480**

1

st application of dispersants: 10 g Corexit 9500 (DOR = 1:33) 

3 min. disp. 1 - - - - ***

2

nd application of dispersants: 10 g Corexit 9500 (DOR = 1:29)

3 min. disp. 2 - - - - ***

 - = no measured data. *ppm=parts per million **estimated from visual observation

*** An increase of 85 ppm dispersed oil was observed after application of dispersant. This corresponds to

 an oil amount of approximately 400 g and correlates well with the visual observations.

For water samples of dispersed oil, GC/FID was used to quantify oil in water from the water 

samples. The response factor for the fresh oil was used to calculate 'Oil-in-water ppm' for the first 

six samples. 'Oil-in-water ppm' for the last samples was calculated using the 250°C+ residue 

response factor.

Mass Balance of ADO

The amount of oil evaporated, oil on surface, dispersed and sampled oil was calculated, and the 

oil adsorbed to the flume walls was estimated. Figure 4.3 shows the mass balance before applying 

dispersant agent into the flume, whilst Table 4.4 shows values for the mass balance of ADO during 

weathering in the flume experiment after 24 hours. 
42

Figure 4.3. Estimated mass balance for ADO in the meso-scale flume basin at 10C, before

dispersant application.

Table 4.4

Tabulated values of the estimated mass balance for ADO.

Example after 24 hours weathering in the meso-scale flume

Mass balance (% of initial 

oil)

ADO

Test temp 

temperature 10 °C

Evaporated 31

Oil on water surface 29

Dispersed oil 25

Sampled amount of oil 12

Oil adsorbed to the flume walls 3

Visual observations of ADO

A selection of pictures taken during the flume experiment at 10 °C are presented for ADO. Figure 

4.5 shows the visual observation of ADO before and after treatment with dispersant agent (Corexit 

9500). Artificial sunlight simulated using a solar simulator (see Figure A3) was turned on for 

photographing, but otherwise turned off during the weathering time (no photo-oxidation).

Sample 0 (Start): Initially the diesel has little appearance of color and spreads evenly on the 

surface in a thin transparent layer. 
43

Sample 1 (0.5 hour): After 30 minutes the diesel changed its appearance/color to very light

brown. The diesel was still evenly distributed on the surface. No emulsification observed.

Sample 2 (1 hour): Slightly browner than the last sample. Otherwise no significant change.

Sample 3 (2 hours): Slightly browner than the last sample. Otherwise no significant change.

Sample 4 (4 hours): Slightly browner than the last sample. Otherwise no significant change

Sample 5 (6 hours): Slightly browner than the last sample. Otherwise no significant change.

Sample 6 (12 hours): After 12 hours the diesel oil had become darker in color and there was minor

oil on the surface. Some foam was observed, as a mixture of air, water and diesel which was not 

stable.

Sample 7 (24 hours): The diesel and water has now been mixed to a loose emulsion, which was 

very unstable and broke within 15 minutes after sampling, however, slightly more stable than the 

previous sample (P6). 

Sample 8 (48 hours): In the time between P7 (24 hours) and P8 (48 hours) most of the oil had 

been mixed in to the water column and there is not much left on the surface. The remaining residue 

did not form a traditional emulsion, but more like a "slimy material" that seemed to be stable and 

did not separate approx. 30 minutes after sampling. However, when these samples were left over 

night at the ambient testing temperature, most of the water had been drained off. 

Sample 9 (72 hours): Almost all of the surface oil was naturally dispersed into the water column. 

Approximately 300 mL of "slimy material" was left on the surface. These samples did not break 

up when left over the weekend at room temperature. 

The change in appearance/color during the weathering (0.5 - 48 hours) in the flume basin of the 

ADO is shown in Figure 4.4.

Figure 4.4. The oil-samples Sample 1 (0.5 hour) – Sample 8 (48 hours) from left to right with 

observed changes in the color appearance over time
44

In-situ chemical dispersion on ADO

First application: The remaining surface residue estimated to 300 mL was dispersed using 10 

grams of Corexit 9500 with a dispersant-to-oil ratio, DOR of 1:33 (sampling after 3 minutes). 

Second application: Some resurfacing of oil was observed, and the estimated 100 mL remaining 

surface residue was treated with an additional 10 grams of dispersant, which gave a cumulative 

DOR of 1:17. The remaining residue was then totally dispersed into the water column.

Sample 0 (Start)–Application of ADO – Natural dispersion started immediately when wave 

action was turned on.

Sample 1 –30 min.

Sample 2 –1 hour
45

Sample 3 –2 hours

Sample 4 –4 hours

Sample 5 –6 hours

Sample 6 –12 hours
46

Sample 7 –24 hours

Sample 8 –48 hours: Minor residue left on the surface.

Sample 9 –72 hours: Collecting oil for surface residue prior to applying the dispersant (Corexit 

9500).
47

Prior to the first dispersion – Estimating 300 mL of the residue described as a "slimy material" 

that was available for chemical dispersion.

Prior to the second dispersion –Estimating 100 mL available for chemical dispersion.
48

After the second dispersion – The residue totally dispersed into the water column. 

Figure 4.5. Visual observation of ADO before and after treatment by dispersant 

4.3 REFINED PRODUCT MGO

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.5

for MGO.

Table 4.5

Results from the meso-scale weathering experiment of MGO

Sample 

no Time

Water 

content

Evaporative 

loss Viscosity

Oil in 

water

(hours)

(vol. 

%) (wt. %)

(mPa.s) 

10 s-1 ppm*

1 0.5 0 1 8 136

2 1 0 3 8 127

3 2 0 4 9 137

4 4 0 7 9 135

5 6 0 10 9 171

6 12 1 13 11 251

7 24 4 17 12 342

8 48 28 24 - 850**

- = no measured data. *ppm=parts per million **estimated from visual observation
49

For water samples of dispersed oil, GC/FID was used to quantify oil-in-water from the water 

samples. The response factor for the fresh oil was used to calculate 'Oil in water ppm' for the first 

six samples. 'Oil in water ppm' for the last samples was calculated using the 250°C+ residues 

response factor.

Mass Balance of MGO

The amount of oil evaporated, oil on surface, dispersed and sampled oil was calculated, and the 

oil adsorbed to the flume walls was estimated. Figure 4.6 shows the estimated mass balance 

for MGO, and Table 4.6 shows tabulated values for the mass balance after 24 hours of weathering 

in the flume.

 Figure 4.6. Estimated Mass balance for MGO in the meso-scale flume basin at 10C.

Table 4.6

Tabulated values of the estimated mass balance for MGO. Example after 24 hours weathering in the 

meso-scale flume

Mass balance (% of initial 

oil) after 24 hours

Test temperature

10 °C, MGO

Evaporated 17

Oil on water surface 45

Dispersed oil 24

Sampled amount of oil 11

Oil adsorbed to the flume walls 3
50

Visual observations of MGO

A selection of pictures taken during the flume experiment at 10 °C are presented. Figure 4.7 shows 

the visual observation of MGO. Artificial sunlight simulated using a solar simulator (see Figure 

A3) was turned on for photographing, but otherwise turned off during the weathering time (no 

photo-oxidation).

Sample 0 (start): The MGO has a light yellow color and spreads evenly on the surface in small

"bubbles". MGO has a blue tint appearance/color under the solar simulator.

Samples 1- 3 (0.5-2 hours): Light yellow color. It was no emulsification and the MGO spread

evenly on the surface. Some natural dispersion and some foam were observed.

Sample 4 (4 hours): The yellow coloring becomes a little darker and more foam was observed. The

oil sample has now formed a very loose "emulsion" that broke easily with very low viscosity. 

Samples 5 - 6 (6-12 hours): Slightly darker yellow appearance/color – some brown "bubbles". 

Sample 7 (24 hours): The water was now whiter /shady, and not much of the diesel remained on 

the surface and the "bubbles" of oil could visually be observed in the water column. The loose 

emulsion was a little harder to break, but still it breaks at the test temperature.

Sample 8 (48 hours): No oil remained on the surface and no sampling was necessary. 

In-situ chemical dispersion on MGO 

Approximately, only 50 mL of the MGO residue remained on the surface. This residue was further 

collected using a stopper and the wave machine was turned off. The sample was "mixed" with a 

slimy consistency (similar observation as for the ADO) that didn’t break easily at the test 

temperature (10 °C). The experiment was finalized without dispersants application because there 

was very little surface oil remaining after two days of weathering in the flume basin.
51

Sample 0 - Application of MGO (note that the diesel appears blue with the solar simulator). 

Sample 1 –30 minutes

Sample 2 –1 hour

Sample 3 – 2 hours
52

Sample 4 – 4 hours

Sample 5 – 6 hours

Sample 6 – 12 hours

Sample 7 –24 hours
53

Sample 8 –48h: no MGO left on the surface – no need for dispersant application.

Figure 4.7. Visual observation of MGO
54

4.4 KUPARUK CRUDE OIL

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.7 for 

Kuparuk crude oil.

Table 4.7

Results from the meso-scale weathering experiments of Kuparuk crude oil

Sample no Time

Water 

content

Evaporative 

loss Viscosity

Oil in 

water

(hours) (vol. %) (wt. %)

(mPa.s) 

10 s-1 ppm

1 0.5 25 6.4 709 423

2 1 43 10.1 2531 286

3 2 46 11.2 3953 261

4 4 61 12.6 6775 125

5 6 68 13.3 8128 106

6 12 70 14.5 10407 60

7 24 72 15.5 11268 69

8 48 68 17.0 14859 57

9 72 65 17.2 17949 77

1

st application of dispersants: 61.6 g Corexit 9500 (DOR = 1:98)

3 min. disp. 1 - - - - 227

10 min. disp. 1 - - - - 219

30 min. disp. 1 - - - - 237

2

nd application of dispersants: 58.4 g Corexit 9500 (DOR = 1:103)

3 min. disp. 2 - - - - 317

10 min. disp. 2 - - - - 448

60 min. disp. 2 - - - - 404

120 min. disp. 2 - - - - 484

 - = no measured data. *ppm=parts per million **estimated from visual observation

Mass balance of Kuparuk crude oil

The amount of oil evaporated, oil on surface, naturally dispersed and sampled oil was calculated, 

and the oil adsorbed to the flume walls was estimated by weight. Figure 4.8 shows the estimated 

mass balance before applying dispersant agent into the flume, whilst Table 4.8 shows an example 

of tabulated values of the estimated mass balance after 24 hours of weathering. 
55

Figure 4.8. Estimated mass balance for Kuparuk crude oil in the meso-scale flume basin at

10C, before dispersant application.

Table 4.8

Tabulated values of the estimated mass balance for Kuparuk crude oil after 24 hours weathering.

Example after 24 hours weathering in the meso-scale flume

Mass balance (% of initial oil)

Test temperature

10 °C, Kuparuk 

crude oil

Evaporated 16

Oil on water surface 72

Dispersed oil 4

Sampled amount of oil 3

Oil adsorbed to the flume walls 5

Visual observations of Kuparuk crude oil

A selection of pictures taken during the flume experiment at 10 °C is presented. Figure 4.9 shows 

the visual observations of Kuparuk crude oil with and without dispersant application. Artificial 

sunlight simulated using a solar simulator (see Figure A3) was turned on for photographing, but 

otherwise turned off during the weathering time (no photo-oxidation).

Sample 0 (start): The oil spread evenly on the surface when applied onto the water surface. 

Sample 1 (30 min.): The oil did not change significantly after 30 minutes of weathering. Low water 

uptake and low viscosity. Easily sampled with a separating funnel. Dark appearance. Most of the 

oil on the surface – minor observed natural dispersion. Thin continuous slick.
56

Sample 2 (1 hour): The oil seemed a bit "thicker" – higher water uptake and increased viscosity. 

Samples 3 - 6 (2 -12 hours): The emulsion steadily got thicker with increased water uptake giving 

a higher viscosity. After 6 hours weathering, it was no longer possible to sample surface oil using

separating funnel. Dark emulsion. Most of the oil is on the surface – minor observed natural 

dispersion. 

Sample 7 (24 hours): The oil/emulsion seemed slightly thicker. Oil moves around the flume as 

balls/lumps of emulsion (diameter ≈ 5 cm) – not a continuous slick. Some emulsion stuck to the 

flume wall, but not more than expected for this kind of crude oil. 

Sample 8 (48 hours): Little or no change visually from sample 7. Thick dark emulsion. Most of 

the emulsion stuck to the wall was now released onto the water surface.

Sample 9 (72 hours): Visually minor changes from Sample 7. Thick dark emulsion. Almost no 

emulsion observed on the flume wall. 

In-situ chemical dispersion on Kuparuk crude oil

After 72 hours of weathering, the dispersant Corexit 9500 was sprayed on the remaining w/oemulsion (in-situ application). Approximately 68 % of the total volume of oil (approx. 8.8 liters) 

was available for chemical dispersion as shown in Figure 4.8. Corexit 9500 was applied twice on 

the surface with a dosage-to-oil ratio (DOR) of 1:98 and a dosage-to-emulsion ratio (DER) of 

1:250 in the first application, giving a cumulative DOR of 1:50 and DER of 1:100 in the second 

application. 

First application: The dispersant (Corexit 9500) broke up the lumps of emulsion in to smaller more 

irregular bits. Some dispersion effect observed, but not much – most of the emulsion was still on 

the surface. After 1 hour, the emulsion started to re-form into balls/lumps again (diameter 3-5cm).

Second application: The dispersant broke the emulsion in to smaller patches (as observed in the 

first application), but still a high amount of emulsion was observed on the water surface. Some 

large droplets were observed in the water column, but those quickly resurfaced. After 30 minutes, 

the emulsion again formed lumps (diameter 2-4 cm). Visually the dispersion was not effective (the 

dispersant gives the emulsion a beautiful blue-green color under the solar simulator). 1 hour after 

the 2nd dispersant application the large lumps generated in the flume broke into smaller 

fractions/patches. The results indicated that Kuparuk is dispersible with Corexit 9500, but requires 

a higher dosage of dispersant (DOR > 1:50; DER > 1:100). Use of artificial turbulence applied on 

the slick after dispersant application in an oil spill situation may also increase the efficiency of 

dispersant use on this oil.
57

Sample 1– 30 minutes continuous slick Sample 2 –1 hour continuous slick

Sample 3 –2 hours Sample 4 –4 hours

Sample 5 –6 hours Sample 6 –12 hours lump formation

Sample 7 –24 hours
58

Sample 8 –48 hours (emulsion color changes due to direct exposure to solar simulator, right)

Sample 9 –72 hours weathering. The blackish lumps observed in the meso-scale flume are 

typical for asphaltenic crude oils.
59

3 minutes after first application of dispersant (broken up lumps)

30 minutes after first application of dispersant (reformed smaller lumps)
60

1 minute after second application of dispersant – picture taken under solar simulator

3 minutes after second application of dispersant – the emulsion breaks down to smaller lumps
61

1 hour after second application of dispersant – lumps reformed into larger lumps

2 hours after second application of dispersant – lump formation

Figure 4.9. Visual observations of Kuparuk Crude Oil with and without dispersant application
62

4.5 NORTHSTAR CRUDE OIL

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.9 for 

Northstar crude oil.

Table 4.9

Results from the meso-scale weathering experiment of Northstar

Sample 

no Time

Water 

content

Evaporative 

loss Viscosity

Oil in 

water

(hours)

(vol. 

%) (wt. %)

(mPa.s) 

10 s-1 ppm

1 0.5 0 36.1 10 105

2 1 0 40.2 16 113

3 2 4 45.6 24 89

4 4 5 48.4 134 -

5 6 22 51.1 213 92

6 12 24 53.1 272 259

7 24 26 55.5 194 283

8 48 16 57.2 416 295

9 72 17 58.3 473 256

1

st application of dispersants: g 55.6 Corexit 9500 

3 min. disp. 1 - - - - 346

10 min. disp. 1 - - - - 292

30 min. disp. 1 - - - - 280

60 min. disp. 1 - - - - 190

 -= no measured data. *ppm=parts per million **estimated from visual observation

Mass Balance of Northstar crude oil

 Figure 4.10 shows values for the mass balance of Northstar crude oil during weathering in the 

flume experiment after 24 hours. Dispersed and sampled oil was calculated, and the oil adsorbed 

to the flume walls was estimated. Table 4.10 shows the estimated mass balance before applying 

dispersant agent into the flume.
63

 Figure 4.10. Estimated mass balance for Northstar crude oil in the meso-scale flume basin at 

10C, before dispersant application.

Table 4.10

Mass balance for Northstar during the meso-scale laboratory test at 10 °C (after 24 hours of 

weathering)

Mass balance (% of initial oil)

Test temperature

10 °C, Northstar 

crude oil

Evaporated 55

Oil on water surface 13

Dispersed oil 20

Sampled amount of oil 8

Oil adsorbed to the flume walls 3

Visual observations of Northstar crude oil

A selection of pictures taken during the flume experiment at 10 °C is presented. Figure 4.11 shows 

the visual observations of Northstar crude oil with and without dispersant application. Artificial 

sunlight simulated using a solar simulator (see Figure A3) was turned on for photographing, but 

otherwise turned off during the weathering time (no photo-oxidation).

Sample 0 (start): The oil spread evenly on the surface. Light brown color. 

Samples 1 - 2 (1 hour): The oil starts to "emulsify" – did not form a true water-in-oil emulsion, 

only unstable "foam". Some natural dispersion.
64

Samples 3 - 4 (2-4 hours): Slightly more stable "emulsion", low water uptake so far more oil

droplets were present in the water column. 

Samples 5 - 6 (6-12 hours): The emulsion appeared darker, but the emulsion was not more stable. 

Sample 7 (24 hours): Less oil on surface, more oil droplets in the water column.

Sample 8 (48 hours): Very little oil left on surface – surface sampling became more challenging. 

Sample 9 (72 hours): Almost no oil on surface available for dispersant application. 

In-situ chemical dispersion on Northstar crude oil

After 72 hours of weathering, the remaining oil was gathered and the dispersant (Corexit 9500) 

was applied onto the water surface on the remaining w/o-emulsion (in-situ application). The 

remaining emulsion dispersed easily into the water column. Less than 10 % of the total volume of 

oil (approx. 8.8 liters) was available for chemical dispersion, and Corexit 9500 was sprayed only 

once on the slick with a dosage-to-oil ratio (DOR) of 1:10 and a dosage-to-emulsion ratio (DER) 

of 1:12.

Sample 1 –30 minutes Sample 2 –1 hour

Sample 3 –2 hours
65

Sample 4 –4 hours Sample 4 –4 hours

Sample 5 –6 hours: "foam" Sample 5 –6 hours

Sample 6 –12 hours Sample 6 –12 hours 
66

Sample 7 –24 hours

Sample 8 –48 hours Sample 8 –48 hours

Sample 9 –72 hours
67

 

Oil before application of dispersant Oil 3 minutes after dispersant application (total 

dispersion)

Figure 4.11. Visual observations of Northstar Crude Oil without and with dispersant application

4.6 WIDE RANGE GASOIL (WRG)

An overview of the tabulated results from the meso-scale flume testing is given in Table 4.11 for 

Wide Range Gasoil (WRG).

Table 4.11

Results from the meso-scale weathering experiment of WRG 10 °C

Sample no Time

Water 

content

Evaporative 

loss Viscosity

Oil in 

water

(hours) (vol. %) (wt. %)

(mPa.s) 

10 s-1 ppm*

1 0.5 58 0.5 465 38

2 1 76 0.9 367 48

3 2 79 1.9 183 73

4 4 83 2.1 207 177

5 6 82 2.8 355 212

6 12 85 4.1 746 148

7 24 80 4.8 978 418

8 48 72 5.8 709 946

1

st application of dispersants: 20.4g Corexit 9500 

3 min. disp. 1 - - - 89 848

10 min. disp. 1 - - - - 1237

30 min. disp. 1 - - - - 1336

60 min. disp. 1 - - - 1191

120 min. disp. 1 - - - - 1327

 -= no measured data. *ppm=parts per million
68

Mass balance of Wide Range Gasoil (WRG)

Table 4.12 shows values for the mass balance of WRG during weathering in the flume experiment 

after 24 hours. The oil adsorbed to the flume walls was estimated. Figure 4.12 shows the estimated 

mass balance before applying dispersant into the flume.

Figure 4.12. Estimated mass balance for Wide Range Gasoil (WRG) in the meso-scale flume 

basin at 10C, before dispersant application

Table 4.12

Mass balance for WRG during the meso-scale laboratory test at 10 °C (after 24 hours of weathering)

Mass balance (% of initial 

oil)

Test temperature

10 °C, WRG

Evaporated 4

Oil on water surface 78

Dispersed oil 9

Sampled amount of oil 6

Oil adsorbed to the flume walls 3

Visual observations of Wide Range Gasoil (WRG)

A selection of pictures taken during the flume experiment at 10 °C are presented, below. Figure 

4.13 shows the visual observations of WRG with and without dispersant application. Artificial 
69

sunlight simulated using a solar simulator (see Figure A3) was turned on for photographing, but 

otherwise turned off during the weathering time (no photo-oxidation).

Sample 0 (start): When applied onto the water surface, the oil seemed to solidify in contact with 

the water. Gray/brown color. Within a few minutes, the oil started to make a "foam" with the 

water. 

Sample 1 (0.5 hour): The oil formed a light yellow "foam/emulsion" that covered half of the

flume surface; some oil went into the water (droplet-size: 2-6 mm).

Samples 2-5 (1-6 hours): Minor change between 1 to 6 hours. The emulsion appeared a little 

more yellow and became seemingly thicker and more unstable.

Sample 6 (12 hours): The emulsion became even thicker and more yellow. Minor changes from 6 

hours weathering.

Sample 8 (48 hours): The emulsion seemed smoother and more homogenous. Darker in color/

appearance. Still very unstable emulsion. 

In-situ chemical dispersion on Wide Range Gasoil (WRG)

Corexit 9500 was decided to be applied in one 20.4 g application after 48 hours weathering with 

high dispersant to oil ratio (DOR). The "emulsion" broke up when the waves were switched off. 

30 minutes after the application of dispersant the oil/emulsion was easily dispersed. It was 

estimated that 80 % of the oil was dispersed into the water column.

Sample 0 (start): Wax solidification in contact with water
70

Sample 1–30 minutes (L) Oil droplets in the water (R) "foam"/emulsion under solar simulator

(solar simulator makes oil appear lighter)

Sample 2–1 hour: (L) "foam", (R) "foam"/emulsion under solar simulator

Sample 6–12 hours: (L) "foam", (R) "foam"

Sample 6–12 hours: (L) close-up of foam, (R) emulsion 
71

Sample 7–24 hours: (L) close-up of foam, (R) emulsion

Sample 8–24 hours: (L) close-up of foam, (R) emulsion

Oil before application of dispersant

Oil seconds after application of dispersant
72

3 minutes after application of dispersant

10 minutes after application of dispersant

30 minutes after application of dispersant

120 minutes after application of dispersant

Figure 4.13. Visual observations of WRG with and without dispersant application
73

5. CONCLUSIONS

Overall, the bench-scale weathering studies yielded consistent data for input to oil weathering 

models. The experimental data from the meso-scale flume basin are considered supplemental to 

the bench-scale testing, in addition to providing valuable information related to potential field 

operations, such as the visual assessments of effectiveness after adding Corexit 9500 to five of the 

oils that had weathered for 72 hours. No dispersant was needed to chemically disperse MGO 

because no oil remained on the water surface after 48 hours. SINTEF recommends a total

evaluation of the experimental data generated both by the bench-scale and meso-scale experiments 

to inform a more robust oil weathering prediction. As an example, for Alpine crude oil, the 

maximum water content could be adjusted or reduced from ~ 80 % vol. findings from the benchscale testing to ~70 vol. % as observed in the flume basin. These differences will influence the 

predicted emulsion viscosity. For Kuparuk crude oil, the maximum water content from the flume 

testing was higher compared with the bench-scale testing, and therefore, could possibly be adjusted 

to match the findings from the flume basin. Adjustments of the experimental data to customize the 

most appropriate and best input data to oil weathering models were not a part of this project. 

Therefore, it should be considered to be part of the oil weathering modelling when evaluating the 

output predictions of the oil weathering properties.

6. QUALITY ASSURANCE

Scientific Quality Assurance (S-QA).

Senior scientist Per S. Daling at SINTEF has been responsible for the scientific quality assurance 

and signs the final report. Senior scientist at SINTEF CJ Beegle-Krause had contact with NOAA 

in connection to the ADIOS input data. The information from NOAA (Bill Lehr and Jeff Lankford, 

e-mails 2nd and 14th September, 2015 respectively) indicated that both ADIOS 2 and ADIOS 3 will 

run with only the density and viscosity, and missing fields are approximated by ASTM estimation 

formulas. "For a crude oil you would need the data that for the API or a density value (units of 

measurement and temp), a viscosity either kinematic or dynamic along with related units of 

measurement and temp. For a refined product we need the distillation data. This would consist of 

a volume %, vapor or liquid temperature."

When this project began ADIOS 3 was going to be released in 2015 (Version 2.0.11 of ADIOS 2 

was posted on NOAA’s website on 03/22/2016), and CJ Beegle-Krause (SINTEF) received a list 

of parameters from the ADOIS 3 SQL oil database. However, parameters that would be "nice to 

have" for ADIOS 3 were not possible to include in this project. SINTEF does not conduct these 

analyses on regular basis.

Data Management Quality Assurance (Data QA).

SINTEF Material and Chemistry's laboratories are certified according to NS-EN ISO 9001: 2008 

(Quality Management System), ISO 14001:2004 (Environmental Management System), OHSAS 

18001(Occupational Health and Safety Management System) and Regulations relating to 

Systematic Health, Environmental and Safety Activities in Enterprises (Norwegian Internal 
74

Control Regulations), all which are international accepted standards for management of quality, 

environment and occupational health and safety. 

The laboratory personnel have followed SINTEF laboratory SOP (Standard Operational 

Procedures). Samples and the obtained experimental data were also identified with unique 

identification numbers found in the laboratory database system and/or in the laboratory journals. 

Jon Olav Bjørgum (QA manager at SINTEF Materials and Chemistry) was responsible for 

SINTEF data management in this project, according to procedures in SINTEF ISO certificate 

management system to ensure chain of custody in laboratory reporting. Regular backups of all 

central servers in SINTEF are performed on a daily basis by SINTEF’s CT service contractor, 

EVRY (www.evry.no).

7. REFERENCES

Bridié A.L., T.H. Wanders and W.V. Zegweld, H.B. den Heijde. 1980. Formation, Prevention 

and Breaking of Seawater in Crude Oil Emulsions, Chocolate Mousse. Marine Poll. Bull., vol 

11, pp. 343-348.

Daling, P. S., Brandvik, P. J., Mackay, D., Johansen, Ø. 1990: Characterization of crude oils for 

environmental purposes. Oil & Chemical Pollution 7, 1990, pp.199-224.

Daling, P.S. and Brandvik, P.J., 1991: Characterization and prediction of the weathering 

properties of oils at sea – A manual for the oils investigated in the DIWO project. IKU 

Report No: 02.0786.00/16/91.

Hokstad, J. N., Daling, P. S., Lewis, A., Strøm-Kristiansen, T. 1993: Methodology for testing 

water-in-oil emulsions and demulsifiers Description of laboratory procedures. In: 

Proceedings Workshop on Formation and Breaking of W/O Emulsions. MSRC, Alberta June 

14-15 24p.

Johansen, Ø. 1991. Numerical modelling of physical properties of weathered North Sea crude 

oils. DIWO-report no. 15. IKU-report 02.0786.00/15/91. Open.

Leirvik F, Schrader T and M. Moldestad. 2002: Weathering properties of Endicott, Milne Point 

unit, High Island Composite, the Alpine composite, the Neptune Field Composite and North 

Star oil samples. SINTEF report STF66 A02114, Unrestricted. : 

http://www.boem.gov/BOEM-Newsroom/Library/Publications/2005/2005_020_appB.aspx

Mackay, D. and Zagorski, W. 1982. Studies of W/o Emulsions". Report EE-34: Environment 

Canada, Ottawa.

McDonagh, M, J.N. Hokstad and A.B. Nordvik. 1995. Standard procedure for viscosity 

measurement of water-in-oil emulsions”. Marine Spill Response Corp., Washington, D.C. 

MRSC Technical Report Series 95-030, 36 p.
75

Singsaas, I., Daling, P.S., Jensen, H., 1993: Meso-scale laboratory weathering of oils. IKU 

report 22.2042.00/04/93. 81 p.

Stiver, W. and D. Mackay. 1984. Evaporation rate of spills of hydrocarbons and petroleum 

mixtures. Environ, Sci. Technol., vol. 18 (11), pp. 834-840.

Sørheim, K.R. and P. Daling. 2015. Fysikalsk-kjemiske analyser og emuleringsegenskaper av 

ulike dieselkvaliteter. In English: Physico-chemial analyis and emulsion properties of diesel 

oils. SINTEF report A27122 (Unresricted), ISBN no. 978-82-14-05844-4. 
76

Appendix A

Experimental setup

The testing of the weathering properties was performed at 10 °C in accordance with the Client.

A.1 Bench-scale laboratory methodology

To isolate and map the various weathering processes at sea, the oil was exposed to a systematic, 

stepwise procedure developed at SINTEF (Daling et al., 1990). The weathering process is 

illustrated in Figure A.1.

WOR: Water to Oil Ratio

WOR=1: 50 vol.% water

WOR=3: 75 vol.% water

WOR=max: the maximum 

water content

Figure A.1. Bench-scale laboratory weathering flow chart of oil

A.1.1 Evaporation

The evaporation procedure used is described in Stiver and Mackay (1984). Evaporation of the 

lighter compounds from the fresh condensate was carried out as a simple one-step distillation to 

vapor temperatures of 150C, 200C and 250C, which resulted in condensate residues with an 

evaporation loss corresponding to approximately 0.5-1 hour, 0.5-1 day and 0.5-1 week of 

weathering on the sea surface. These residues are referred to as 150C+, 200C+ and 250C+, 

respectively.

A.1.2 Physical and chemical analysis

The viscosity, density, pour point and flash point of the fresh and water-free residues was analyzed. 

In addition wax content and "hard" asphaltenes was measured for the 250C+ residue. Viscosity 

for all the w/o- emulsions was determined. The analytical methods used are given in Table A.1

and Table A.2.

.
77

Table A.1

Analytical methods used to determine the physical properties

Physical property Analytical method Instrument

Viscosity McDonagh et al, 1995 Physica MCR 300

Density ASTM method D4052-81 Anton Paar, DMA 4500

Pour point ASTM method D97 -

Flash point ASTM D 56-82 Pensky-Martens, PMP1, SUR

Interfacial tension (IFT) - Pendant drop method 

Table A.2

Analytical methods used to determine the chemical properties.

Chemical property Analytical method

Wax content Bridiè et al, 1980

“Hard” asphaltene IP 143/90

Chemical characterization by GC/FID

The distribution of hydrocarbons (nC5-nC40) was analyzed using a Gas Chromatograph coupled 

with a Flame Ionization Detector (GC/FID). The Gas Chromatograph used was an Agilent 6890N 

with a 30m DB1 column. 

A.1.3 Emulsification properties

The w/o emulsification studies were performed by the rotating cylinders method developed by 

Mackay and Zagorski (1982), which is described in detail by Hokstad et al.1993. The method 

includes the measuring of the following parameters:

 Relative water uptake (kinetics)

 Maximum water uptake

 Stability of the emulsion

 Effectiveness of emulsion breaker (Alcopol O 60%)

The principle of the rotating cylinders method is illustrated in Figure A.2. Oil (30 mL) and seawater 

(300 mL) are mixed and rotated with a rotation speed of 30 rpm in separating funnels (0.5 L). The 

emulsification kinetics is mapped by measuring the water content at fixed rotation times. The 

maximum water content is determined after 24 hours of rotation.
78

 Figure A.2. Principle of the rotating cylinder after Mackay and Zagorski (1982)

A.2 Meso-scale flume basin 

In an oil spill situation at sea, the weathering processes will occur simultaneously and affect each 

other. It is therefore very important to weather the oils under realistic conditions when studying 

their behavior when spilled on the sea surface.

A.2.1 Description of the flume basin

A meso-scale flume basin (Singsaas et al. 1993) located at SINTEF’s Sealab is routinely used to 

simultaneously study the weathering processes under controlled conditions. A flume with an 

updated instrumentation was built in 2006, with a schematic drawing of the flume given in Figure 

A.3.

Approximately 5 m3seawater circulates in the 10-metre-long flume. The flume basin is located in 

a temperature controlled room (0C-20C), and two fans placed in a covered wind tunnel control 

the wind speed. The fans are calibrated to simulate an evaporation rate corresponding to a wind 

speed of 5-10 m/s on the sea surface.
79

Figure A.3. Schematic drawing of the meso-scale flume

A.2.2 Oil weathering in the flume basin

The oil sample (~9 L) is carefully released on the seawater surface. In accordance to the standard 

procedure, the oil is normally weathered for three days in the flume. Samples of the surface oil are

taken frequently during the first hours of the experiment and then once a day. The dispersant agent 

will normally be applied to the weathered oil in-situ after Day 3 of the experiment. Water samples 

are taken a few times during the weathering part of the experiment, and at a higher frequency after 

the dispersant application.

The physical properties determined for all surface oil samples during the experiments were:

 Evaporative loss

 Density

 Water content

 Viscosity

Analysis was performed on a limited amount of samples for:

 Emulsion stability

 Oil concentration in the water column (droplets and dissolved components)

Samples of surface oil/emulsion

Samples of the surface oil/emulsion were taken using an aluminum tray and transferred to a 0.5 L 

separating funnel. The free water was removed after settling for 10 minutes in the climate room. 

Solar simulator

Irradiated area

Fan

Wind tunnel

Water

sampling

Wave machine /

breaking board Breaking wave

0.5m

2m

4m

Solar simulator

Irradiated area

Fan

Wind tunnel

Water

sampling

Wave machine /

breaking board Breaking wave

0.5m

2m

4m
80

The oil phase was further handled for an analysis of viscosity, water content of emulsion and 

density.

Analytical methods for surface oil/emulsion

The methods used to determine the physical properties of the surface oil/emulsion are listed in 

Table A.3. 

Table A.3

Methods used to determine the physical properties of the surface oil/emulsion.

Physical property Analytical method Instrument Comments

Viscosity McDonagh et al, 1995 Physica MCR 

300

-

Water content Adding approximately 2000 ppm emulsion 

breaker (Alcopol O 60%) to the sample 

and heating the vial. As the emulsion 

broke, the water height and the total height 

were measured. 

Sample vials

The relative amount of 

water compared to the 

total sample volume 

was calculated.

Density ASTM method D4052-81 Anton Paar, 

DMA 4500

Measured on waterfree samples (after 

removal of the water 

with emulsion breaker 

and heat).

Evaporative loss The density of the oil depends linearly 

on the vol. % of evaporative loss. -

The evaporative loss 

was calculated based 

on the density.

Collection of water samples.

Water samples were taken at a depth of 50 cm through a tap in the basin wall into a Pyrex glass 

bottle (1 L). The sampled water was acidified with some droplets of 10% HCl (pH < 2), and the 

sampling position is shown in Figure A.3. Samples were extracted by liquid-liquid extraction with 

dichloromethane (DCM) and quantified by Ultra Violet (UV) spectrophotometer, unless otherwise

specified in the report.
81

Appendix B

Table Format-Input to Oil Weathering Models

The obtained laboratory data are customized for input into oil weathering models (SINTEF OWM

and ADIOS). The tabulated laboratory oil data for the six oils are given in Table B.1 –Table B.14. 

Note that the tabulated input data are derived from the standard bench-scale weathering study

unless other specified.

Table B.1

Physical and chemical properties of the fresh oils for Alpine crude oil, ADO and MGO (Year One)

* Measured at shear rate 10s-1 ** Calculated based on the measured densities

NA: Not analyzed

Summary properties of the fresh oil Alpine 

SINTEF ID:

2015-0258

ADO

SINTEF ID: 

2014-0491

MGO

SINTEF ID:

2014-0492

Density (60 F/15.5°C) g/mL 0.832 0.830 0.849

API ° ** 38.4 38.8 35.1

Pour point (°C) -36 -36 -36

Reference temperature (°C) 10 10 10

Viscosity at ref. temp. (mPa.s = cP) * 8 5 7

Asphaltenes (wt. %) 0.46 0.03 0.03

Flash Point (°C) NA 59 62

Wax Content (wt. %) 2.05 0.04 1.96

IFT in (mN/m) 30 24 27

IFT eq (mN/m) 15 12 17

Dispersible for visc. < NA NA NA

Not dispersible for visc. > NA NA NA
82

Table B.2

Physical and chemical properties of the fresh oils for Kuparuk and Northstar crude oils and WRG

(Year2)

* Measured at shear rate 10s-1 ** Calculated based on the measured densities NA: Not analyzed

Table B.3

True boiling point (TBP) curve for Alpine crude oil

Temperature 

(°C)

Alpine crude

oil (%)*

47 5

65 10

114 20

170 30

226 40

278 50

329 60

389 70

456 80

547 90

615 95

* TBP based on simulated distillation (SIMDIST). 

Source: Alpine COE-319 received from ConocoPhillips Alaska, Inc. 

Summary properties of the fresh 

oil

Kuparuk

SINTEF ID:

2015-0259

Northstar

SINTEF ID:

2015-0469

WRG

SINTEF ID

2016-0106

Density (60 F/15.5°C) g/mL 0.917 0.779 0.892

API ° ** 22.7 50.1 27.0

Pour point (°C) -33 -9 -24

Reference temperature (°C) 10 10 10

Viscosity at ref. temp. (mPa.s = cP) * 143 1 85

Asphaltenes (wt. %) 4.74 0.03 0.05

Flash Point (°C) NA NA 106

Wax Content (wt. %) 1.32 1.74 4.84

IFT in (mN/m) 19 29 19

IFT eq (mN/m) 7 10 12

Dispersible for visc. < NA NA NA

Not dispersible for visc. > NA NA NA
83

Table B.4

True boiling point (TBP) curve for ADO 

Temperature 

(°C)

ADO 

Volume (%)*

182 5

189 10

196 15

204 20

220 30

237 40

253 50

270 60

288 70

307 80

317 85

328 90

341 95

*Source: ADO-ULSD from Esso Slagen Refinery, Norway

Table B.5

True boiling point (TBP) curve for MGO

Temperature 

(°C)

MGO

Volume (%)*

177 5

191 10

203 15

214 20

238 30

264 40

287 50

304 60

318 70

330 80

336 85

343 90

352 95

*Source: Marine Gas Oil (0.1 % S) from Esso Slagen Refinery, Norway
84

Table B.6

True boiling point (TBP) curve for Kuparuk crude oil

Temperature 

(°C)

Kuparuk crude 

oil

Volume (%)*

99 5

150 10

226 20

281 30

332 40

387 50

444 60

509 70

588 80

658 90

701 95

*Source: "CP1" Crude Assay SIMDIST from ConocoPhillips Alaska, Inc. (2001)

Table B.7

True boiling point (TBP) curve for Northstar crude oil

Temperature 

(°C)

Northstar

Volume 

(%)*

36 8.5

69 14.4

99 25.2

158 40.9

174 45.4

196 50.9

216 55.8

254 64.6

271 67.4

302 73.7

329 77.3

357 82.1

380 84.1

402 87.2

432 90.7

450 92.3

*Source: Northstar Assay Analysis from Hilcorp Alaska, LLC (9.17.13)

The TBP is customized and adjusted to fit the laboratory data as input to OW 

model tools
85

Table B.8

True boiling point (TBP) curve for WRG

Temperature 

(°C)

WRG

Volume 

(%)*

305.8 5

328.5 10

337.9 15

344.7 20

355 30

363.2 40

376.6 60

400** 80**

450** 100**

*Source: WRG TBP from Mongstad Refinery

** Estimated values to fit the input to OW model tools
86

Table B.9

Summary lab weathering data of Alpine crude oil, 10 °C of fresh oil and its residues

Property Fresh 150°C+ 200°C+ 250°C+

Boiling Point Temp. (°C) - 198 260 309

Vol. topped (%) 0 25.5 37.9 46.6

Weight Residue (wt. %) 100 78.5 66.8 58.4

Density (g/mL) 0.832 0.877 0.896 0.906

API ° 38.4 29.7 26.3 24.5

Pour point (°C) -36 0 9 12

Flash Point (°C) - 40 87 113

IFT in. (mN/m) 30 30 28 30

IFT eq. (mN/m) 15 14 13 15

Asphaltenes (wt. %) 0.46 0.58 0.68 0.78

Wax (wt.%) 2.05 2.61 3.07 3.51

*Viscosity of water-free residue (mPa.s =cP), 8 43 204 688

*Viscosity of 50% emulsion (mPa.s = cP) - 385 1128 2386

*Viscosity of 75% emulsion (mPa.s = cP) - 2214 5760 10481

*Viscosity of max water (mPa.s = cP) - 24104 26059 33720

Max. water cont. (vol.%) - 83 80 77

(T1/2) Halftime for water uptake (hrs.) - 0.16 0.23 0.38

Stability ratio - 1 0.95 0.94

* Measured at shear rate 10 s-1

- No data

Table B.10

Summary lab weathering data of ADO, 10 °C of fresh oil and its residues

Property Fresh 

~150°C+

200°C+ 250°C+

Boiling Point Temp. (°C) - 228 270

Vol. topped (%) 0 15.9 47.5

Weight Residue (wt. %) 100 84.7 53.4

Density (g/mL) 0.830 0.835 0.845

API ° 38.8 37.8 35.8

Pour point (°C) -36 -36 -33

Flash Point (°C) 59 74 107

IFT in. (mN/m) 24 23 21

IFT eq. (mN/m) 12 9.5 8.3

Asphaltenes (wt. %) 0.03 0.04 0.06

Wax (wt.%) 0.04 0.05 0.08

*Viscosity of water-free residue (mPa.s =cP), 5 6 10

*Viscosity of 50% emulsion (mPa.s = cP) - - -

*Viscosity of 75% emulsion (mPa.s = cP) - - -

*Viscosity of max water (mPa.s = cP) - - -

Max. water cont. (vol.%) 0 0 0

(T1/2) Halftime for water uptake (hrs.) 0 0 0

Stability ratio - - -

* Measured at shear rate 10 s-1

- No data
87

Table B.11

Summary lab weathering data of MGO, 10 °C of fresh oils and its residues

Property Fresh 

~150°C+

200°C+ 250°C+

Boiling Point Temp. (°C) - 241 281

Vol. topped (%) 0 9.7 28.5

Weight Residue (wt. %) 100 90.9 72.8

Density (g/mL) 0.849 0.854 0.864

API ° 35 34 32.1

Pour point (°C) -36 -36 -30

Flash Point (°C) 62 78 108

IFT in. (mN/m) 27 29 28

IFT eq. (mN/m) 17 13 11

Asphaltenes (wt. %) 0.03 0.04 0.05

Wax (wt.%) 1.96 2.16 2.70

*Viscosity of water-free residue (mPa.s =cP) 7 9 14

*Viscosity of 50% emulsion (mPa.s = cP) - - -

*Viscosity of 75% emulsion (mPa.s = cP) - - -

*Viscosity of max water (mPa.s = cP) - - -

Max. water cont. (vol.%) 0 0 0

(T1/2) Halftime for water uptake (hrs.) 0 0 0

Stability ratio - - -

* Measured at shear rate 10 s-1

- No data

Table B.12

Summary lab weathering data of Kuparuk crude oil, 10 °C of fresh oils and its residues

Property Fresh 150°C+ 200°C+ 250°C+

Boiling Point Temp. (°C) - 227 262 312

Vol. topped (%) 0 10.7 15.6 23.3

Weight Residue (wt. %) 100 91.6 87.4 80.4

Density (g/mL) 0.917 0.941 0.950 0.962

API ° 22.7 18.7 17.3 15.4

Pour point (°C) -33 -27 -21 -12

Flash Point (°C) - 57 81 115

IFT in. (mN/m) 19 20 21 26

IFT eq. (mN/m) 7 8 9 11

Asphaltenes (wt. %) 4.74 5.21 5.46 5.94

Wax (wt.%) 1.32 1.44 1.51 1.64

*Viscosity of water-free residue (mPa.s =cP) 143 630 1242 4420

*Viscosity of 50% emulsion (mPa.s = cP) - 3799 7380 22497

*Viscosity of 75% emulsion (mPa.s = cP) - 6546 - -

*Viscosity of max water (mPa.s = cP) - 4979 7045 8497

Max. water cont. (vol.%) - 60 52 23

(T1/2) Halftime for water uptake (hrs.) - 0.5 1.1 1.5

Stability ratio - - 0.21 0.87

* Measured at shear rate 10 s-1

- No data
88

Table B.13

Summary lab weathering data of Northstar crude oil, 10 °C of fresh oils and its residues

Property Fresh 150°C+ 200°C+ 250°C+

Boiling Point Temp. (°C) - 181 238 297

Vol. topped (%) 0 42.6 54.2 67.7

Weight Residue (wt. %) 100 62.8 50.1 36.1

Density (g/mL) 0.779 0.837 0.852 0.869

API ° 50.1 37.5 34.5 31.2

Pour point (°C) -9 9 15 21

Flash Point (°C) - 33 71 116

IFT in. (mN/m) 29 30 30 31

IFT eq. (mN/m) 10 8 7 9

Asphaltenes (wt. %) 0.03 0.05 0.06 0.09

Wax (wt.%) 1.74 2.77 3.47 4.82

*Viscosity of water-free residue (mPa.s =cP) 1 20 249 409

*Viscosity of 50% emulsion (mPa.s = cP) - - - -

*Viscosity of 75% emulsion (mPa.s = cP) - - - -

*Viscosity of max water (mPa.s = cP) - 17 87 410**

Max. water cont. (vol.%) - 3 6 30**

(T1/2) Halftime for water uptake (hrs.) - 0.01 0.01 0.03

Stability ratio - - 0.67 0.11

* Measured at shear rate 10 s-1

** Adjusted to increase the expected viscosity emulsion and water uptake based on the meso-scale flume basin.

However, the bench-scale testing indicated that Northstar forms unstable emulsions with low viscosities and high 

water uptake of ~ 80 % for the 250°C+ residue. In case of a spill, the oil might therefore show a high water 

uptake with low viscosities at sea, but this is also depending on the release conditions/scenario. Overall, Northstar 

is a "low-emulsifying" crude oil that expects to form unstable emulsions with low viscosities when spilled at sea 

at 10 °C.

- No data
89

Table B.14

Summary lab weathering data of WRG, 10 °C of fresh oil due to lack of lighter components with 

boiling point lower than 250 °C

Property Fresh~250°C+

Boiling Point Temp. (°C) -

Vol. topped (%) 0

Weight Residue (wt. %) 100

Density (g/mL) 0.892

API ° 27

Pour point (°C) -24

Flash Point (°C) 106

IFT in. (mN/m) 19

IFT eq. (mN/m) 12

Asphaltenes (wt. %) 0.05

Wax (wt. %) 4.84

*Viscosity of water-free residue (mPa.s =cP) 85

*Viscosity of 50% emulsion (mPa.s = cP) -

*Viscosity of 75% emulsion (mPa.s = cP) -

*Viscosity of max water (mPa.s = cP) 

Max. water cont. (vol.%)** 70

(T1/2) Halftime for water uptake (hrs.) 0.15

Stability ratio 0.01

* Measured at shear rate 10 s-1

**: Based on the maximum water uptake from the meso-scale flume basin experiment. ~ 90 vol. %

from the bench-scale laboratory testing is too high and not evident in a spill situation. Note that 

WRG exhibits unstable emulsion that easily break with mechanically stress and/or under static 

conditions.

 - No data
90

Appendix C

Categorization Map of Alaska North Slope Crude Oils

A semi-quantitative categorization map of crude oils is developed into four main groups of oil; 

paraffinic, waxy, naphthenic, and asphaltenic oils, based on their typically physio-chemical 

properties, as described below. The categorization of crude oils from Alaska North Slope for Year 

One and Two (2016) and previous studies of crude oils from this region are illustrated in Figure C 

1. The previous studies were part of the OCS Study MMS 98-0031 for MMS (Leirvik et al., 2002), 

and an older SINTEF study funded by MSRC in 1993. The categorization map (Figure C 1) 

illustrates the span in physio-chemical properties within the Alaska North Slope crude oils (blue 

and yellow circles) that can be quite wide, and may change as a function of production time.

Paraffinic crude oils

Paraffinic crude oils are often characterized by low to medium density, which reflects high content 

of light and saturated components, such as paraffins (alkanes). Paraffinic crudes differ mainly from 

the waxy crudes with a lower wax content (typically < 6 wt. %), hence the pour point of the fresh 

crude is often lower compared with waxy crude oils. Paraffinic crudes are characterized with 

medium to high evaporation loss, with rapid and high water uptake and normally form stable w/oemulsions. Rapid initial evaporative loss will result in a relative increase of physiochemical 

properties like pour point, asphaltene and the wax content. Hence, the asphaltenes (polar surfaceactive components) may contribute, together with the wax, to the high stability usually observed 

of the w/o-emulsions formed. 

Waxy crude oils

Waxy crude oils often exhibit high pour points due to large content of wax components (typically 

> 6 wt.%). These oils have a tendency to solidify producing elastic properties on the sea surface, 

particularly observed at low seawater temperatures. Solidification is pronounced if the seawater 

temperature typically is 10-15 oC below the pour point. Waxy crude oils typically exhibit a light 

to medium evaporative loss. The water uptake can vary extensively, whereas the w/o- emulsions 

can be very stable or even highly unstable depending on the content of stabilizing and polar 

surface-active components like the asphaltenes and resins. 

Naphtenic crude oils

Typically, naphtenic oils exhibit disrupted n-alkane (paraffins) patterns due to high degree of 

biodegradation of the oil in the reservoir. The content of paraffins are therefore normally low in 

for these oils, and have low pour points with corresponding low wax content. Such biodegraded 

crude oils may have high densities and a high degree of UCM (Unresolved Complex Mixture) 

consisting of a wide range of complex components, such as resins and naphthenes. Other naphtenic 

crude oils can be only slightly biodegraded and exhibit e.g. paraffinic features. Hence, the 

evaporative loss among this naphtenic crude can vary extensively, depending on its physical 

properties. Naphthenic crudes may form unstable w/o-emulsions with very low viscosities, but can 

also exhibit properties towards asphaltenic features and form stable w/o-emulsions. The water 

uptake may vary among the naphtenic crudes, but generally, they form emulsions with both low 
91

water content (typically 30-50 vol. %) and a relatively slow water uptake rate compared with 

paraffinic crudes.

Asphaltenic crude oils

Typically, features of asphaltenic oils are the high content of heavy components like asphaltenes 

and resins (typically > 0.8 wt. %), while the content of lighter components is correspondingly low. 

This is reflected by high density (typically > 0.9 g/ml) and low evaporation loss. The asphaltenic 

crudes often exhibit low pour points due to the high asphaltene content preventing wax 

precipitation and formation of a wax lattice structure. Compared with paraffinic and waxy crudes 

the asphaltenic crudes usually have both a slower and a lower maximum water uptake. The 

asphaltenic crude oils form stable, highly viscous and persistent blackish water-in-oil emulsions 

with expected long life time on the sea surface. The high stability is caused by the stabilization of 

the w/o-emulsification by the polar material in the oil.

Figure C 1. Categorization of Alaska North Slope crude oils into four main groups; Naphtenic, 

Paraffinic, Waxy, and Asphaltenic oils. The oils in yellow circles are crude oils from Alaska North 

Slope from this project (Year One and Two), while the blue circles indicate crude oils from the same 

region from previous projects at SINTEF for comparison.
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