Q825. How do I determine the gas to oil ratio (GOR) for my gathering pipelines?

A825. The gathering and boosting system owner or operator can use a direct measurement of GOR through either onsite measurement or by sending samples out for laboratory analysis. The timing and duration of the sampling/measurement program should follow existing regulatory requirements, which include standard methods published by a consensus-based standards organization or industry standard practices. See 40 CFR 98.234(b). The EPA realizes that owners or operators may calculate GOR for other reasons such as documenting fluid quality for financial transactions, equipment optimization or other state/federal reporting requirements. These values can be used where appropriate.A825. 40 CFR Part 98, Subpart W does not prescribe a specific approach to calculate GOR. Gathering and boosting system operators may use the best approach for their facility, including direct measurement, calculation from other measured data, and standard estimation measures. We note that within the EPA’s 2016 updates to New Source Performance Standards for the oil and natural gas sector, GOR is defined as the ratio of the volume of gas at standard temperature and pressure that is produced from a volume of oil when depressurized to a standard temperature and pressure. See 40 CFR 60.5430a.  

The GOR determination should be made at a point along the system so there is no doubt that the value represents the GOR for that pipeline, such as the last custody transfer point upstream of the defined entry point, or at the last separator, processing plant, or wellhead upstream of the defined entry point.

The EPA notes that GOR of the gathering pipeline carrying the hydrocarbon liquids or multiphase flow from a field with a GOR below 300 scf/STB may also be below 300 scf/STB, assuming no additional processing.