I'm getting confused by the OP.
You mention: When we were applying for work permits, we got refused.
Then you continue with saying you want to finish your study.
I would say your chances are probably very low, it really looks like you just take whatever you can to stay in Canada (not blaming you or something), but for the VO that might be reason to just reject you. Don't apply unless you can present them a strong case. If you give it a go and they refuse your study permit, I believe you've 0% chances.
Currently I think you still might have a chance, not a big one, but I wouldn't say 0% since you're 18 now and never applied on your own, or did you? Since your family is no longer in the country you have ties to the original place. NOt trying to give you false hope here though, I think your chances are slim, but not 'non-existant'