This is a legitimate question, not a criticism: why do you think that you, specifically, will be the scapegoat?
Is it possible that you can find a way to not work 15 hours straight? Since you know that the project will crash and burn anyway, this effort will be meaningless. Trying to carry the weight of a doomed project by yourself is not a good idea.
Now, if the project is a high-profile one, expect that some management cuts will happen. In some companies, but not all, this also means "pruning" all the reporting tree. Is the company big enough that you could move to another division, or whatever they call it? If so, you should focus on that.
The ship is sinking and all you have is a bucket. Start sending signal flares.