Experimental investigation on the oil permeation mechanism of underwater oil storage method with flexible oil bladder

A novel underwater oil storage method with flexible oil bladder is developed in this study. The polymer flexible bladder is used to replace the rigid storage tanks, and is restrained by a shed with anchor cables underwater. To avoid environmental pollution due to the oil permeation is essential to the practical use of the proposed underwater oil storage method. In this study, the mechanism of the permeability of the polymer flexible bladder is investigated by indoor experiment and numerical analysis. The factors including oil types, test environments and pressure differences are considered. The results reveal that the olefins and aromatics are the major controlling components. The pressure gradient in the permeation path is mainly provided by the remaining buoyancy of the oil bladder, which is linearly related to the permeation rate. When the pressure gradient is opposite to the permeation direction, the oil still diffuses with the concentration gradient. An empirical formula for calculating the oil permeation rate is presented to conveniently and directly evaluate whether the oil bladder meets environmental protection and oil loss standards. This study provides a theoretical basis for the application of the present method, and has important significance for the development of underwater oil storage. •A new oil storage method with a flexible oil bladder is proposed.•A series of factors are considered to study the mechanism of oil permeation across polymer membranes.•An empirical formula for calculating oil permeation is presented to evaluate its environmental performance and oil loss.