In my world, petrol will not be available anymore and there will have been a crisis ending its availability (the story is set after the crisis).
The consequences will be these:
Developing and poor countries will regress to some sort of medieval era while stable countries will survive and become independent from the petrol by successfully moving to other sources of energy and advancing the civilization.
Basically the world will breakdown in 2 parts. A "futuristic part" with advanced technology composed of the countries that have survived the petrol crisis and another part with poor countries that become more poor due to the petrol crisis.
I know that people in some poor countries already live in a similar way but how much can hold done in fiction?
I took a look atthe map of the developing countries (Wikipedia) and everything seems OK with what I want to write but I'm not sure about the 2 type of countries. Is this realistic?