In view of gas hydrate formation in the containment of deep water oil/gas blowout, the evolution of methane hydrate films on gas bubbles rising naturally in deep water was simulated and observed by visual microscopy. The results reveal that hydrate films on gas bubbles formed at conditions corresponding to deeper depths (higher pressure) rose intact for longer distances and showed more pronounced fractures on the film. Secondary hydrate growth happened along the cracks of the hydrate film as the hydrated bubble rose upward. The fractured hydrate films were more likely to close with secondary growth when formed at subcoolings higher than 3.0 K. The strength of methane hydrate film formed on the surface of a suspended gas bubble was examined by rapidly decreasing the external pressure of the hydrate film soon after its formation. The maximum tension that the hydrate film could withstand without fracturing as well as the tensile strength were evaluated for hydrate films formed at 277.2 K and different subcoolings. It was found that the tensile strength of hydrate film increased with increasing subcooling at the formation conditions. (C) 2014 Elsevier Ltd. All rights reserved.