Here is a picture of an Oil Refinery & Derrick. We simplified the rules: Once a derrick is built the IPC value of said territory goes +1. Once a Refinery is built with Derrick then goes up +1 again. Derrick must be placed place one full turn before refinery can be built. Can be bombed and removed or taken over by enemy. We play scorched earth as well, so if you want to burn before its captured you can.