Mechanical Recovery of Oil in Ice

The goal of mechanical recovery is to remove oil from the surface of water using specially designed recovery (skimming) devices and to store the recovered fluids until they can be safely disposed or recycled. Recovery devices are most effective on thick slicks; hence containment booms are used in open water and very open ice cover to contain and concentrate and oil slick. In higher ice concentrations, the ice itself acts as a barrier to limit the spreading and contain the oil.

Many decades of experience with mechanical recovery under cold-climate conditions around the world have advanced the understanding of the recovery process and led to the development of proven response tactics and specialized equipment. Several configurations of ice-capable response vessels, both with built-in and over-the-side or stern recovery equipment are currently in operation. Azimuthal Stern Drive (ASD) vessels are invaluable for arctic oil spill and emergency response due to their high manoeuvrability in ice and ability to effectively support both mechanical recovery and vessel-based dispersant operations.

Project Reports

ACS Mechanical Recovery of Oil in Ice Feasibility Report

High-capacity arctic skimmers have been developed and tested for the recovery of oil in ice while operating at low temperatures. Advances with specialized cold climate skimmers include improved oil and ice processing, the ability to handle larger volumes of cold viscous oils and oil/ice mixtures with low water uptake, and the heating of critical components to prevent freezing. Various viscous oil pumping systems and techniques have also been developed to facilitate efficient transfer of cold and viscous mixtures of oil water and small ice pieces.

Planning for mechanical recovery in arctic waters should consider the logistical and environmental impacts associated with all phases of the response operations. Mechanical recovery is one of several viable response techniques available for arctic spill response when used appropriately.

As with any other tool, any final decision on its use needs to balance potential effectiveness against possible impacts, while recognizing the inherent limitations associated with variable ice conditions, remote area logistics and waste disposal sensitivities.

Mechanical recovery is a well-practiced response technique used under a variety of conditions around the world. Success depends upon the availability and rapid deployment of appropriate equipment and personnel, as well as an ability to gain safe access to the oil to allow recovery. This technique is most suited for small to moderate sized operational spills under relatively calm weather conditions in open water or very open drift ice as well as small localized small spills contained in closer pack ice. Considering that the vast majority of spills are small, and that most areas being considered for petroleum exploration and development have long periods of ice-free conditions, mechanical recovery will continue to serve as an important response tool in the Arctic.

The aim of the JIP’s mechanical recovery initiative was to examine results from previous research projects and operational experience with mechanical recovery in ice to identify any opportunities to substantially improve recovery performance.

Shortly after the JIP launch in early 2012, a dedicated workshop took place in London, UK.

Highly experienced researchers, responders, mariners, and manufacturers evaluated ideas beyond conventional booming and skimming equipment as well as vessel design, focusing on selected Arctic response scenarios and identifying promising tactics or equipment designs that could enhance mechanical recovery under Arctic conditions.

The workshop evaluated approximately 50 ideas from which several concepts were selected for further feasibility analysis to gauge their probability of success. Concepts were grouped into four key focus areas:

  1. New recovery vessel designs.
  2. Remote recovery units operating from a “mother ship” /support vessel.
  3. On-board oil-water-ice separation devices.
  4. On-board oil incinerators.
The JIP brought together many of the leading experts in the world to study the challenge of developing new, improved mechanical systems to work in ice covered waters.

Novel concepts were put forward but none demonstrated the necessary potential to justify further development.

A comprehensive evaluation confirmed that the efficiency of mechanical recovery in ice is primarily controlled by the physics of oil spreading and an inability to efficiently encounter large volumes of recoverable oil, rather than any intrinsic limitations in equipment design. The existing skimming systems are already operating at close to their maximum attainable recovery rate in ice. This analysis further confirmed that better integrating mechanical containment and recovery operations with advanced support tools like real-time remote sensing could lead to greater improvement by enhancing the performance of existing recovery systems, for example making sure they are positioned in the thickest oil films to maximise encounter rates.