Testing of a High Seas Oil Recovery System

Abstract

ABSTRACT A system for recovery of petroleum products from accidental offshore spills has been developed and tested. The testing has included both model testing and full-scale testing of a 60-foot long system capable of recovering oil at a rate of 2000 gallons per minute. The tests have shown the system capable of recovering spilled oil at high efficiencies (less than ten percent water in the recovered oil) at the 2000-gpm rate under environmental conditions ranging from calm to low state 5 Seas (eight-foot significant wave height) and in currents up to three knots. The system efficiency (percent of oil in the recovery stream) is relatively independent of oil specific gravity, viscosity, oil film thickness, wind and wave conditions, oil-water interfacial tension, surface temperature and variation in significant oil type when towed at speeds of one to three knots. As indicated, efficiencies of 90-100 percent can be expected under these conditions. The oil recovery rate is relatively independent of wind and wave conditions, surface temperature, oil specific gravity, oil-water interfacial tension and significant oil type variation. It is not affected by viscosity except for discharge hose pressure limitations above 10,000 SSU. The oil recovery system is air and truck transportable for rapid deployment to a remote spill location. It is completely self-contained having its own power unit, control system, and pumps. In its preferred deployment configuration it is used with oil containment booms for funneling the oil to the recovery system. A double weir system is employed to obtain the high performance of the system. The system is operated in such a way that oil thickens in front of the primary weir and then further thickens in front of the secondary weir, where it is withdrawn. Typically, the system concentrates free slicks from a thickness of 0.1 inches or less to a depth of approximately two feet front of the secondary weir. The testing reported upon includes both model testing and full scale testing of the system. The work reported upon was partially supported by the U. S. Coast Guard. INTRODUCTION Accidental oil spills on coastal and ocean waters are a matter of increasing concern. It has been recently estimated(1) that over 200,000 metric tons of oil are annually discharged into the world's waters from accidental spills. This spillage not only represents a loss of product but also represents substantial cleanup costs and potential liability. When the spillage occurs offshore in a wave environment the oil spreads fairly rapidly and cleanup becomes a major problem. Only recently have methods been developed for cleanup of oil spills in an offshore environment. This paper deals with one of those methods. There are two major elements to any successful cleanup operation which must be carefully coordinated: containment and recovery.