Check to make sure the fan is clear of dust and clean accordingly.  If that does not silence the fan, it will need to be replaced. Service manual: [URL]  
Hello,  I've had my Alienware m15 R3 for roughly 2-2.5 years now. As of late the right fan has been making this awful noise that’s like a drill. Is it an issue with the fan itself or is this something I can fix? Here’s a video of the sound 
m15 R3, right fan making drill noise