ASSESSMENT OF THREE SURFACE COLLECTING AGENTS DURING TEMPERATE AND ARCTIC CONDITIONS

Abstract

ABSTRACT Laboratory and field tests were conducted to evaluate the effectiveness of using surface collecting agents in cold weather oil recovery and in situ burning operations. In a small laboratory test tank, the surface areas and equilibrium thicknesses of three Alaskan North Slope crude oils were observed before and after the application of three different surface collecting agents to each oil. Numerous small bench-top tests also were conducted to further support the observations made in the test tank. Ambient air temperatures were varied from 23° C to −17° C, while the temperatures of fresh water and laboratory-prepared sea water were varied from 15° C to 0° C. The three surface collecting agents used (Corexit OC-5, Nalco 3WP-086, Shell Oil Herder) were equally effective in concentrating the areas of thin films by as much as 95 percent within a minute or less. The efficiencies of the surface collecting agents were observed to decrease only slightly with air temperatures below 0° C. Equilibrium thicknesses and areas before and after collectant application were determined using standard photometric techniques. In addition, two field tests were conducted to evaluate the effectiveness of collecting agents on large experimental oil slicks in an onshore pit at Prudhoe Bay. In each test, approximately 1 m3 of fresh Prudhoe Bay crude oil was released and allowed to come to an equilibrium thickness. In each test, the oil was concentrated with Corexit OC-5 and Shell Oil Herder and then ignited. Winds of 4-to-6 knots (2-to-3 m/s) herded the slicks into one corner of the pit and produced an average slick thickness of 9.5 mm. The use of collectants resulted in a 5 percent reduction of the wind-herded slick areas, thus increasing the thicknesses to approximately 10 mm.