At the end of last episode, Wells said
There are other speedsters in this Universe, and my thinking is that Wells is already at war with them. What if, for example, Wells and Reverse Flash are enemies in the future (which makes Wells sort of an antihero, as I've already mentioned before) and for whatever reason Wells is in the past, he's trying to keep Barry alive to help him take down RF. And now that he took Blackout's blood, he potentially has a weapon for disarming RF.
This theory is still also compatible with my Wells = Barry theory, though doesn't have to be