Measurements of methane emissions from natural gas gathering facilities and processing plants: measurement methods

Abstract

Abstract. Increased natural gas production in recent years has spurred intense interest in methane (CH4) emissions associated with its production, gathering, processing, transmission and distribution. Gathering and processing facilities (G&P facilities) are unique in that the wide range of gas sources (shale, coal-bed, tight gas, conventional, etc.) results in a wide range of gas compositions, which in turn requires an array of technologies to prepare the gas for pipeline transmission and distribution. We present an overview and detailed description of the measurement method and analysis approach used during a 20-week field campaign studying CH4 emissions from the natural gas G&P facilities between October 2013 and April 2014. Dual tracer flux measurements and onsite observations were used to address the magnitude and origins of CH4 emissions from these facilities. The use of a second tracer as an internal standard revealed plume-specific uncertainties in the measured emission rates of 20–47%, depending upon plume classification. Combining downwind methane, ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), and tracer gas measurements with onsite tracer gas release allows for quantification of facility emissions, and in some cases a more detailed picture of source locations.

Characterisation of interferences to in-situ observations of δ<sup>13</sup>CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> when using a Cavity Ring Down Spectrometer at industrial sites

“…Excluding the biogenic event, on average the 15 natural gas emissions detected have a weighted mean C2H6: CH4 ratio of 0.069 ppm C2H6 /ppm CH4 with an average uncertainty on each event of 0.006 ppm C2H6 /ppm CH4. This figure agrees well with the median value for conventional gas ratios measured by Roscioli et al, (2015).…”

“…The site topography is flat and open with the surrounding area as predominantly farm land and close proximity to a major road. FFCH4 emissions were expected to emanate from various sources on site such as the compressors, methane slip from turbines, and fugitive emissions due to the high pressure of gas [Roscioli et al, 2015]. Other possible methane sources in the nearby region were identified as traffic and agriculture.…”

Revisiting global fossil fuel and biofuel emissions of ethane

“…Ethane (C 2 H 6 ) is a hydrocarbon emitted mainly during the production, processing, and transportation of natural gas, and it has been proposed as a tracer for fugitive emissions from natural gas production [ Schwietzke et al , ; Swarthout et al , ; Vinciguerra et al , ]. In locations with multiple methane (CH 4 ) sources (e.g., cows, oil and gas, rice production, and wetlands), C 2 H 6 can be used as a tracer for fossil fuel CH 4 emissions [ McKain et al , ; Roscioli et al , ]. Natural gas leakage contributes about ~60% of C 2 H 6 emissions globally [ Xiao et al , ] and up to 70% in regions with active oil and gas development [ Gilman et al , ].…”

Possible malfunction in widely used methane sampler deserves attention but poses limited implications for supply chain emission estimates

“…Additionally, the BHFS is ill-suited for tank emission measurements due to their high concentrations of non-CH 4 hydrocarbons and airflow constraints (Brantley et al, 2015). Accurately quantifying all emissions from natural gas production sites will likely require improved measurement approaches such as site-level, downwind measurements to fully capture large emission sources that cannot be measured with the BHFS (Subramanian et al, 2015;Roscioli et al, 2015;Brantley et al, 2014;Rella et al, 2015;Lan et al, 2015;Omara et al, 2016).…”