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 Technology Assessment & Research (TA&R) Program
Project Number 617
Date of Summary September 22, 2009
Subject Employing Chemical Herders to Improve Oil Spill Response Operations
Performing Activity S.L. Ross Environmental Research Ltd.
Principal Investigator Mr. Ian Buist
Contracting Agency Minerals Management Service
Estimated Completion March 3, 2010
Description The objective of this research program is to extend the research on herders in pack ice conditions, in open water and in salt marshes. This proposed project is a continuation of TAR Project 554 “Mid-Scale Test Tank Research on Using Oil Herding Surfactants to Thicken Oil Slicks in Broken Ice”. There are two tasks in this project.

Task 1: Using Herders to Enhance Mechanical Recovery of Oil in Pack Ice

Field deployment tests of booms and skimmers in broken ice conditions in the Alaskan Beaufort Sea highlighted the severe limitations of conventional containment and recovery equipment in even trace ice (Bronson et al. 2002). The main problem is that booms, deployed to collect and concentrate oil for effective skimming, also collect and concentrate ice pieces that quickly render the skimmers ineffective. The research on using herding agents to thicken slicks for in situ burning has shown that they can significantly contract and thicken oil among ice, without concentrating the surrounding ice. This could be beneficial to mechanical recovery. In fact, as a skimmer removes oil from the center of a herded slick, the action of the herding agent may cause the slick to continuously contract towards the skimmer, eliminating the need to move the skimmer around to contact all the oil. However, it has been observed that the active ingredient in herding agents (the surfactant) renders sorbent pads less hydrophobic and their water retention increases considerably. This could be a significant detriment to oleophilic skimmers such as drums, discs and rope mops whose recovery surfaces contact herding agent. This should not be an issue with other skimmers types such as weirs and vacuums.

Experiments will be conducted in the laboratory and at Ohmsett – The National Oil Spill Response Test facility to explore the capabilities and limitations of using herding agents to thicken oil in loose pack ice for recovery by skimmers.

Task 2: Using Herders to Clear Oil Slicks in Salt Marshes

A parallel to the situation in pack ice exists in salt marsh environments: access for mechanical recovery equipment is almost non-existent due to concerns over damaging the marsh substrate. This task will involve preliminary laboratory experiments in small-scale simulated marshes to determine if chemical herders might play a role in clearing spilled oil from the marsh. The existing contract has been modified to include the following task.

Task 3: Herders to Improve Operational Efficiency of Dispersant Operations The application of a herding agent around the periphery of a slick just prior to it being treated with dispersant would cause the slick to contract into much thicker oil, covering a much smaller area with a more uniform, and predictable, thickness. This would allow more precise application of dispersant to a smaller area of oil at a more predictable dosage. Herders will contract free-spreading oils with thicknesses ranging from <1 µm to 1+ mm into slicks of ~1 to 4 mm thickness, eliminating the sheen overdosing problem and greatly aiding the thick slick under-dosing problem. This offers the possibility of significantly improving dispersant targeting. Slicks that have spread to «1 mm thickness could be shrunk and thickened with a chemical herder applied with a helicopter-slung bucket delivery systems, or vessel-based delivery systems, then treated with dispersant from ships or aircraft. Another possibility is the application of herding agents around slicks in calm seas to prevent them from spreading until the wind picks up and breaking waves (necessary for effective chemical dispersion) appear. Experiments will be conducted in the laboratory and at Ohmsett – The National Oil Spill Response Test facility to explore the capabilities and limitations of using herding agents to improve the operational efficiency of dispersant operations.

Progress Task 1. Using Herders to Enhance Mechanical Recovery of Oil in Pack Ice - In late May 2008, the principal investigator participated in an intentional oil spill offshore Svalbard, Norway. Approximately 1,500 liters of crude oil were released onto the waters surface and allowed to spread for one half hour. A small amount of chemical herder was applied on the outside of the slick and allowed to contract the slick. The slick was intentionally ignited and allowed to burn. It is estimated that the burn efficiency was approximately 90%. Experiments were successfully conducted February 9-20, 2009 at the Ohmsett facility. The MMS has accepted the summary report for this task.

Task 2: Using Herders to Clear Oil Slicks in Salt Marshes - Experiments using small scale simulated marsh environments were successfully conducted in September 2008 to determine if chemical herders might play a role in clearing spilled oil from the marsh. MMS has accepted the summary report for this task.

Task 3: Herders to Improve Operational Efficiency of Dispersant Operations - In October 2009, experiments will be conducted in the laboratory and at Ohmsett - The National Oil Spill Response Test facility to explore the capabilities and limitations of using herding agents to improve the operational efficiency of dispersant operations.

Last Updated: 10/05/2009, 03:14 PM