Cal. Pub. Res. Code § 6920

Any person engaged in the production of geothermal resources under a lease issued by the commission may commingle geothermal resources from any two or more wells without regard to whether such wells are located on the lands for which such lease was issued or elsewhere, provided, however, that said lessee shall install and maintain meters or other measuring devices satisfactory to the commission to measure the amount of geothermal resources produced from lands for which leases were issued by the commission.