Dispersant Testing Under Realistic Conditions

Scope of Work

SINTEF, Trondheim, Norway is the contractor for this project. Subcontractors are SL Ross Environmental Research Ltd., Ottawa Canada and Cedre, Brest France.

KEY COMPONENT 1 – STATE OF KNOWLEDGE REVIEW

The objective was to understand the existing knowledge base on dispersant use in ice in order to define additional research needs. This effort ensured that Project 2 studies only those areas of dispersant efficacy that have not been adequately studied in the past. This component is complete. The report “Dispersant Testing Under Realistic Conditions: State of the Knowledge Review”, summarized the scientific literature and identified previous research of dispersant effectiveness under arctic conditions. Important parameters assessed were oil type (naphthenic, asphaltenic, paraffinic, waxy crude or fuel oil), oil viscosity, oil weathering degree, dispersant type, dispersant to oil ratio, salinity, ice coverage, mixing energy, and temperature. The main findings from the report are:

  • Dispersants can work in the Arctic and will, under certain conditions, be more effective in the presence of ice than in open water.
  • The presence of ice can also increase the time window within which dispersants can be used effectively.

KEY COMPONENT 2 – BASIN TESTS IN ICE-CONDITIONS

The objective is to build on the knowledge base defined in the State of Knowledge Review to further understand the boundaries of when dispersants can be effective in different ice conditions. SINTEF, SL Ross and Cedre have the same type of meso scale flume basin, of which the flumes at SINTEF and SL Ross have exactly the same dimensions, while CEDRE’s flume is larger.

Before full testing, an inter-basin calibration study was completed to determine consistent test protocols and energy conditions for each basin.  For a test basin to be acceptable, the standard deviation of the triplicate dispersant-effectiveness tests at each energy condition should be no more than ± 20% of the average for the test basins.

Dispersant effectiveness of one oil‐dispersant combination was performed using the pre‐weathered Norwegian crude oil Grane and Corexit 9500 as the dispersant. Three different energy conditions (low, medium, high) were established. Triplicate dispersant effectiveness tests were conducted at each energy condition. Results show there is very good correlation between the dispersant efficiency in the flumes at SINTEF and SL Ross at all three energy levels. Although the Cedre flume is different than the flumes at SINTEF/SL Ross, the correlation in dispersant efficiency was good, especially at low and high energy conditions. The dispersant efficiency in all energy levels performed in the flumes at SINTEF, SL Ross, and Cedre were within the ±20% of the average dispersant efficiency. The final report “Test tank inter‐calibration for Dispersant Efficiency”, recommended that all three flumes are accepted for further testing of dispersant/OMA efficiency in component 2.

Mesoscale flume tank experiments were conducted in Canada and Norway 2015-2016 to establish boundaries for dispersant efficiency testing using three commercial dispersants (Corexit 9500, Dasic, and OSR‐52), five different oils (Alaska North Slope (paraffinic), Grane (asphalthenic), Troll Blend (mixture of naphthenic and paraffinic), and Oseberg Blend (paraffinic) were estimated using flume‐based experiments varying parameters such as mixing energy, weathering time, and seawater salinity. Preliminary results indicate:

  • That the ice cover did not influence the results significantly.
  • Water salinity influences the results significantly with the poorest dispersant efficiencies found for the 5 ppt salinity water.
  • Dispersant effectiveness varied with both oil type and dispersant type applied.
  • Effectiveness increased when higher mixing energy conditions were used.

Additional flume tank experiments are being conducted in Norway to confirm experimental test results and strengthen the final report.

KEY COMPONENT 3 –DISPERSANT INJECTION FOR WELL CONTROL EVENTS

Dispersant injection during well-control events is a significant advance for offshore contingency plans, including in the Arctic. This technique can pre-place dispersants into oil during these events to either keep oil dispersed subsea or allow dispersion at the surface when the oil is impacted by mixing energy from waves or ice motion. The objective of this component is to evaluate the potential for injecting dispersants during well-control events to understand the fate of dispersed oil under conditions representative of the Arctic.

Initial subsea dispersant modelling was performed in 2013.  The JIP was aware of other subsea modelling efforts in progress, particularly further development of the dispersed oil droplet size algorithm, i.e., the modified Weber number algorithm. These subsea modelling research projects are now complete with new information and algorithms generated. The JIP believes that the algorithms have changed enough to warrant re-running the scenarios performed in 2013. This research will be performed in August-September 2016.

KEY COMPONENT 4 – BENCH-TOP TESTING OF DISPERSANT EFFECTIVENESS

The goal of this research is to conduct dispersant effectiveness testing under conditions that are not possible in meso-scale basins, e.g., conditions that require oil to be weathered on, in, or amongst ice pieces. The JIP is interested in studying other credible Arctic oil spill scenarios considering the various oil exploration and production operations.

As part of JIP Environmental Effects Project 2b Unique Arctic Communities and Oil spill Response Consequences Oil Biodegradation and Persistence, eight mesocosms were fabricated and installed in the sea ice of van Mijen Fjord, Svea, Sval­bard in January 2015 and remained in place until July 2015. Oil was introduced into two mesocosms to follow natural attenuation. In two other mesocosms oil mixed with dispersant was intro­duced and another set contained burned residues mimicking an in situ burn response. The two remain­ing mesocoms served as controls (no oil).  Samples of all mesocosms were taken directly in the icepack. The JIP is conducting research on the oil+dispersant ice cores to examine efficiency of the dispersant and determine if the dispersant is still efficient after a stay trapped of several months in the icepack.

KEY COMPONENT 5 – REGULATORY REQUIREMENTS AND PERMITTING PROCESSES

The objective was to identify and define the regulatory requirements and permitting processes for use of dispersants and mineral fines in each Arctic nation/region and summarise current technical and policy obstacles. This component is complete. The report “Dispersant Use in Ice Affected Waters: Status of Regulations and Outreach Opportunities” identified and summarized the regulatory requirements and permitting process for using dispersants and mineral fines for each arctic nation. The main finding from the reports is:

  • With a few exceptions, where good regulatory models have been established for dispersant use, and credits are in place, there is generally an absence of national policies and procedures to pre-approve the use of dispersants and additional effort is needed to persuade decision-makers about the importance and effectiveness of dispersants and thus the need for such procedures.