If i remember correctly, the WWIII scenario is set up to have an 80-85% world petrol supply. If you have no options to build offshore platforms or inland derricks, then you must either conquer a supply, or develope more and more technology to replace oil in power generation and transportation. There are tech advances for advanced clean power sources (wind, solar etc.) advanced coal, oil, and nuclear production (greater output) and a host of advances to reduce population and transportation use of oil. Also eventually Fusion is available to research. You might be able to trade diplomatically for some of these to ease the situation quickly.
Hope that helps.