Yes, it is possible. However I wouldn't recommend it unless you're ok with losing the data (which may actually be ok in some cases).

If you run with only 2 replicas in your swift cluster, you are at a much higher chance of losing data (or at least for it to be unavailable). The chances of losing three drives that share the same data at the same time are very low, and therefore three replicas are recommended.

But in your case, you are proposing that you have only two replicas and that they are separated geographically. In addition to the durability issues of only having two replicas, this means that any time a "local" replica is unavailable (either on a temporary or permanent basis), you will consume bandwidth on the WAN (ie between the regions).

If you have two regions, I'd recommend using either three or four replicas. Three replicas will give you very high durability overall, but it still may cause too much traffic over the WAN. Four replicas (ie 2 replicas in each of 2 regions) will give you high durability and also allow a much higher chance of being able to recover data from a local replica.