Slitherine

I'm currently playing Cyrene. Next to me there is one no oases and two shifting dunes. It is stated that they can be removed by an oases. The AI put an oases in all three of them almost at the beginning of my game. After over 120 turns nothing has happened. If I invade the oases will disappear. Will any of those impediments ever disappear?
Thanks for any opinions.

Only the desert nomadic Culture can create Oases. Egypt can become Oases, but only as a lucky Event.
But for you, the Desert is a perfect Shield for you. No Roads, no Food and two Region with 6 Step to go. Every Army is dead befor she reach Kyrene.

I use this Tactic in one of my Multiplayergames.