Behaviour of Crude Oil Under Fresh-Water Ice

Abstract

Abstract Experiments were carried out in a cold room at −15 °C to investigate the behaviour of Norman Wells crude oil under fresh water ice. The crude, when injected in water under the ice, separates into droplets and rises to the ice-water interface, where the oil droplets coalesce to form a slick. The spreading of oil under ice is complicated by the coalescence of oil drops at the ice-water interface, and the spreading process is found to be different from that of oil on water or on ice. If sufficient turbulence exists in the water, both oil-in-water and water-in-oil emulsions are formed. An oil lens sandwiched between the ice acts as an insulating layer and thus increases the temperatures drop cross the ice. Introduction The discovery of oil in commercial quantities in Northern Canada could lead to the construction of oil pipelines to the southern markets. Such pipelines would cross many rivers and streams that are subjected to ice conditions of varying seasonal length. It is conceivable that oil spills under ice-covered rivers may result from such pipeline crossings, The spills can be large, such as those caused by a major pipeline fracture, or they can be small, such as those developing through holes of a few centimeters diameter in the pipe. In addition, accidents involving oil tankers, storage tanks and tank trucks may also result in oil spills in ice-covered rivers. Although results on oil pollution research are published in an increasing number, available information on the behaviour of oil spilled under ice is limited. The only systematic study reported in the literature is by Wolf and Hoult(1). They investigated the effects of crude and diesel oils on the porous substructure of Arctic sea ice and found that the oil, when injected under the ice, was pocketed below the ice surface. They also reported that as freezing continued, more ice formed beneath the oil and that the oil acted as an insulating layer impeding the flow of heat- However, in order to assess the effect of an oil spill under ice-covered rivers and to help in developing clean-up techniques for such an oil spill, more must be understood about the behaviour of oil under ice, The present work investigates the behaviour of crude oil under fresh-water ice, Parts of the work were presented at the 1975 Conference on Prevention and Control of Oil Pollution(2). Experimental A circular aluminum basin, 150 cm in diameter and 70 cm deep was installed in a cold room where the temperature was maintained at −15 ±2 °C. Heating tapes were glued to the outside of the tank and covered with 10 cm of polystyrene insulation. The heating tapes were connected to variacs set at very low power to cancel out the bottom and side heat losses. This arrangement resulted in one-dimensional freezing in the basin, A stirrer was mounted on the side of the basin and a circular boom installed to prevent the oil from rising up the tank walls.