Probably not, but I'd guess even one supertanker would be more effective than one might expect. We're talking about vessels that are nearly half a kilometer long. Note that the tankers transiting the Strait have very limited maneuverability; it is difficult to turn on a dime when you're carrying half a million tons of cargo. Moreover, tanker captains are a very conservative lot: they will be reluctant to make a transit even if there is room if there are not sufficient margins of error for fear of further jamming the channel.