Variation of stretching tension and breaking tendency of floating fresh South Louisiana crude oil with slick thickness

Abstract

Floating crude oil patches can separate from the main oil slicks depending on oil characteristics and sea conditions. The breaking tendency of smaller oil patches from the fresh crude oil slicks vary depending on oil type and thickness of the oil slick. Some oil slicks have high breaking tensions that can support significant weight. We investigated the breaking tension of fresh crude oil (South Louisiana crude oil (MC 252)) floating on water in relation to oil layer thickness. We observed that there is a critical thickness (CT) at which the floating oil exhibits significantly high breaking tension, and it becomes difficult for oil patches to break off. Below the CT, the floating oil layer was too thin and broke off easily. Above the CT, the oil layer was too thick, and external forces caused larger oil to stretch to form larger globules that broke off from the main floating oil until the oil layer thickness was reduced to CT. For the fresh crude oil tested, we estimate the maximum breaking tension as 0.23 ± 0.02 N/m and occurred at oil layer thickness of 0.16 mm. When the oil layer was thicker than the CT, the breaking tension was significantly lower (0.03 ± 0.02 N/m) and larger oil globules separated from the floating oil easily. These observations explain the conditions that lead to formation of highly stable oil patches at sea that can remain floating and travel long distances, some eventually depositing at beaches and in shallow waters as large oil patches.