Gas Quality Analytical and Calculation Methods and Procedures for the
following pipelines operated by Dominion Energy Questar Pipeline
Services, Inc. (DEQPS): Dominion Energy Questar Pipeline, LLC Dominion
Energy Overthrust Pipeline, LLC Questar Southern Trails Pipeline Company
White River Hub, LLC
DEQPS uses values obtained from online gas chromatograph analysis through
C9+ to determine gas quality. Calculations for Specific Gravity and BTU
are determined using compositions and physical constants for the
individual gas components. DEQPS uses the following GPA, API and AGA
standards for compositional analysis: GPA-2166, Analysis for Natural Gas
and Similar Gaseous Mixtures by Gas Chromatography (latest version) is
used to determine the compositional makeup of the gas stream using gas
chromatography GPA-2172, Calculation of Gross Heating Value, Relative
Density, and Compressibility Factor for Natural Gas Mixtures from
Compositional Analysis (latest version) is used to calculate gross heading
value and relative density. GPA-2145, Table of Physical Constants for
Hydrocarbons and Other Compounds of Interest to the National Gas Industry
(latest version) is used as the source for the physical constants for each
gas component. These values are used to calculate the properties of the
combined gas stream. API 14.1, Manual of Petroleum Measurement Standards
(latest version) is used for collecting and handling of natural gas
samples for custody transfer. AGA-8, Compressibility Factors of Natural
Gas and Other Related Hydrocarbon Gases (latest version) is used to
calculate compressibility factors. Peng-Robinson Equation of State is used
with compositional analysis values through C9+ to calculate Cricondentherm
Hydrocarbon Dew Point values (CHDP). At sites where an online gas
chromatograph is not available, gas is sampled for analysis using either a
continuous sampling bottle or a spot sample is taken. Gas samples are
collected on a monthly or quarterly basis and the compositional makeup of
the gas is determined using the chromatographic analysis that is performed
using the standards described above.