(a) The heating value of the gas sampled must be calculated as follows:

(1) Gross heating value is defined by API 14.5, Subsection 3.7 (incorporated by reference, see § 3175.30) and must be calculated under API 14.5, Subsection 7.1 (incorporated by reference, see § 3175.30); and

(2) Real heating value must be calculated by dividing the gross heating value of the gas calculated under paragraph (a)(1) of this section by the compressibility factor of the gas at 14.73 psia and 60 °F.

(b) Average heating value determination. (1) If a lease, unit PA, or CA has more than one FMP, the average heating value for the lease, unit PA, or CA for a reporting month must be the volume-weighted average of heating values, calculated as follows:

(2) If the effective date of a heating value for an FMP is other than the first day of the reporting month, the average heating value of the FMP must be the volume-weighted average of heating values, determined as follows:

Where: HVi = the heating value for FMPi, in Btu/scf HVi,j = the heating value for FMPi, for partial month j, in Btu/scf Vi,j = the volume measured by FMPi, for partial month j, in Btu/scf Subscript i represents each FMP for the lease, unit PA, or CA Subscript j represents a partial month for which heating value HVi,j is effective m = the number of different heating values in a reporting month for an FMP

(c) The volume must be determined under § 3175.94 (mechanical recorders) or § 3175.103(c) (EGM systems).