I would like to see some advanced refining. As the oil processing is now, my greatest issue is refinery deleting mass and naphta and now sour gas being useless.
What I would suggest is, making refinery to have aditional output for naphta. And output half of it's input there. Cut the nat gas output or at least add gas pipe output for it.
For naphta I would add new building, some cooker with liqiud input and gas output, producing hot sour gas.
Finally for the sour gas I would add filtering building, taking in sour gas and filtration medium or water and piped sour gas and outputing natgas and some solid waste or p. water.
This will stop the mass deletion of current buildings and keep oil boilers still viable option but keep everything in check, since more processing and more power would be needed to reach usefull product.