Quantification of natural gas and other hydrocarbons from production sites in northern West Virginia using tracer flux ratio methodology

Abstract

Tracer flux ratio (TFR) methodology performed downwind of 15 active oil and natural gas production sites in Ohio County, West Virginia sought to quantify air pollutant emissions over two weeks in April 2018. In coordination with a production company, sites were randomly selected depending on wind forecasts and nearby road access. Methane (CH₄), ethane (C₂H₆), and tracer gas compounds (acetylene and nitrous oxide) were measured via tunable infrared direct absorption spectroscopy. Ion signals attributed to benzene (C₆H₆) and other volatile gases (e.g., C₇ – C₉ aromatics) were measured via proton-transfer reaction time-of-flight mass spectrometry. Short-term whole facility emission rates for 12 sites are reported. Results from TFR were systematically higher than the sum of concurrent on-site full flow sampler measurements, though not all sources were assessed on-site in most cases. In downwind plumes, the mode of the C₂H₆:CH₄ molar ratio distribution for all sites was 0.2, which agreed with spot sample analysis from the site operator. Distribution of C₆H₆:CH₄ ratios was skew but values between 1 and 5 pptv ppbv^-1 were common. Additionally, the aromatic profile has been attributed to condensate storage tank emissions. Average ratios of C₇ – C₉ to C₆H₆ were similar to other literature values reported for natural gas wells.