Okla. Stat. tit. 52, § 472

The term "cubic foot of gas" or "standard cubic foot of gas" means the volume of gas, including both natural gas and casing head gas, contained in one cubic foot of space at a standard pressure base and at a standard temperature base. The standard pressure base shall be fourteen and sixty-five hundredths (14.65) pounds per square inch absolute and the standard temperature base shall be sixty (60) degrees Fahrenheit. Whenever the conditions of pressure and temperature differ from the above standard, conversion of the volume from these conditions to the standard conditions shall be made in accordance with the Ideal Gas Laws corrected for deviation from Boyle's Law, which correction must be made unless the pressure at the point of measurement is two hundred (200) pounds per square inch gauge or less; all in accordance with methods and tables generally recognized by and commonly used in the natural gas industry.