Research / Research

OSRR-568-Research at Ohmsett on the Effectiveness of Chemical Dispersants on Alaskan Oils in Cold Water

Project Number
568
Program
Category
Project Initiation Date
09/07/2006
Performing Activity
Principal Investigator
Mr. Randy Belore
Contracting Agency
Minerals Management Service
Description

The U.S. Minerals Management Service (MMS) funded and conducted two series of large-scale dispersant experiments in very cold water at Ohmsett The National Oil Spill Response Test Facility, located in Leonardo, New Jersey in February-March 2006 and January-March 2007. Alaska North Slope, Endicott, Northstar and Pt. McIntyre crude oils and Corexit 9500 and Corexit 9527 dispersants were used in the two test series. The crude oils were tested fresh, weathered by removal of light ends using air sparging and weathered by placing the oils on water in both breaking wave and non-breaking wave conditions.

In February-March 2006, a total of twenty-five large-scale DE experiments were successfully completed at the Ohmsett facility. Ten control experiments (no dispersant) and fifteen Corexit 9527 dispersant application experiments were completed in the test program. The total quantity of crude oil used in the 2006 test program was approximately 1,600 liters and between 65 and 80 liters of oil were used in each experiment. In a few cases where a limited amount of oil was available, smaller volumes were discharged. The estimated average oil thickness for the oil slicks was 1 to 4 mm depending on the experiment being conducted. The total quantity of dispersant used in the 2006 test program was approximately 150 liters and between 4 and 16 liters of dispersant (including overspray) was used in each experiment.

In January-March 2007, a total of twenty-one large-scale DE experiments were successfully completed at the Ohmsett facility. Nine control (no dispersant applied), ten Corexit 9500 dispersant applied experiments and two Corexit 9527 dispersant applied experiments were completed in the test program. Thirteen of the experiments were conducted between January 30 and February 6 and the remaining eight experiments were completed between March 13 and March 15, 2007. The air temperature at the end of the first week of testing dropped dramatically and the tank surface water froze. The ice was broken up using wave action but a layer of frazil ice built up in the tank and the main test program had to be suspended until the onset of warmer weather. One test (No.13) was completed in the frazil ice conditions to investigate the use of dispersants in these conditions while the opportunity presented itself.

The total quantity of oil used in the 2007 test program was approximately 1,560 liters and between 70 and 85 liters of oil were used in each experiment. The estimated average oil thickness for the slicks was 1-2 mm depending on the experiment being conducted. The total quantity of dispersant used in the 2007 test program was approximately 90 liters and between 7 and 12 liters of dispersant was used in each experiment (including overspray).

Latest progress update

Results from the 2006 and 2007 Ohmsett test series demonstrated that both Corexit 9500 and Corexit 9527 dispersants were 85 to 99% effective in dispersing the fresh and weathered crude oils tested. There were no significant differences found in the oil drop size distributions measured in the dispersions generated by the two dispersants. The volume median diameters of the oil drop distributions generated by these dispersants were less than 50 microns indicating that the majority of the oil in these dispersions would persist in the water column and not rise to the surface in moderate sea states. All of the experiments were videotaped from the observation tower located on the main bridge. The video was edited to show the progression of the test from the beginning to the end.

The final reports from both test series have been accepted by MMS. This project is complete. There are film clips embedded into both final reports. When reading the final report, click on the blue icon to see the desired film clip.

Status
Completed
Associated Attachments
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Belore, R..