Section 6-8-1-5 - "Petroleum", "natural gas", "oil", and "barrel of oil" defined(a) As used in this chapter, "petroleum" means all hydrocarbons produced at a well in a liquid or gaseous state.(b) As used in this chapter, "natural gas" means petroleum that maintains a gaseous state at atmospheric conditions.(c) As used in this chapter, "oil" means petroleum that maintains a liquid state at atmospheric conditions.(d) As used in this chapter, "barrel of oil" means forty-two (42) U.S. gallons of oil at sixty degrees Fahrenheit (60 ° F).(Formerly: Acts 1947, c.278, s.5.) As amended by P.L. 109-1988, SEC.9.