Don't fanny around with it, get a pair of pliers push the carpet down in the corner and pinch it, pull it back and it will lift with out any damage, even if a few tufts come out it will not be noticeable.
If your worried about doing that then get a nail lifter (a tool that looks like a screw driver but has an open end) slide it down behind the carpet and ease it up.
The only thing I would say about pulling it back from around the central heat pipe is the backing can get very brittle here due to the heat, so be very carefull the backing can split SURPRISINGLY easy.