NOTE 22. SUPPLEMENTAL OIL AND GAS INFORMATION (UNAUDITED)

The following information is provided with respect to estimated natural gas reserves, which are managed, developed and delivered by Wexpro at cost-of-service pursuant to the Wexpro Agreement. The estimates of proved gas reserves were prepared by Wexpro’s reservoir engineers. Gas reserve estimates are subject to numerous uncertainties inherent in estimating quantities of proved reserves, projecting future rates or production and timing of development expenditures. The accuracy of these estimates depends on the quality of available data and on engineering and geological interpretation and judgment. Reserve estimates are imprecise and will change as additional information becomes available. Geological and engineering data demonstrate with reasonable certainty that these quantities are recoverable under existing economic and operating conditions. Since the gas reserves operated by Wexpro are delivered to Questar Gas at cost-of-service, SEC guidelines with respect to standard economic assumptions are not applicable. The SEC anticipated this potential difficulty and provides that companies may give appropriate recognition to differences because of the effect of the ratemaking process. Accordingly, Wexpro uses a minimum-producing rate or maximum well-life limit to determine the ultimate quantity of gas reserves.

Proved Reserves		Natural Gas
(bcf)
Balance at December 31, 2017		429.5
Balance at December 31, 2016		469.8
Balance at December 31, 2015		522.4