Important to note, Saudi Arabia has basically the lowest cost of extraction in the world. While other places need to perform complex engineering and invest huge amounts of capital to extract oil, Saudi Arabia can basically just stick straws in the ground and watch it flow.

So if oil prices decline, Saudi Arabia will be one of the last profitable producers.

http://graphics.wsj.com/oil-barrel-breakdown/

https://knoema.com/rqaebad/cost-of-producing-a-barrel-of-cru...