He is only using one of them. Orochimaru knows where Obito's hideout is because if you remember he was inside of Anko when they went to the hideout and Orochimaru revealed that he was able to hear and see everything through Anko. Obviously Obito left the Rinnegan there and for some reason I am sure Orochimaru will go there, it makes sense because Yamato is there as well being held captive. In which Yamato is Orochimaru's creation.