MacBook Pro crashed and won't turn on

MBP crashed mid session whilst typing document on word. Assumed it was battery but hadn't had any low battery warnings. Power supply was not plugged in. Plugged in and it wouldn't start. Realised it was making odd noise when power supply plugged in. Green light was on but fans were making a repetitive noise as if trying to start up but can't. I have taken the back off to see what was going on and sure enough the fans appear to be struggling. Can't take battery out as don't have tri head screw.

Any ideas or suggestions? Is it the battery struggling or fans? What can I do?

MBP is 15" and purchased in 2011. Charger is correct model. No other known issues.