Aerial Surveys of Elevated Hydrocarbon Emissions from Oil and Gas Production Sites

“…Among the top 5% of emitters in 2018 (n = 51), the most Aggregating all tank related emissions across component types, we find that tanks contribute to 52% and 58% of total emissions in 2018 and 2019, respectively, despite only comprising 18% and 16% of total emitters. The disproportionate contribution from tanks is consistent with findings from recent studies and makes it a potential target for focused mitigation opportunities [27], [43], [44]. Furthermore, the average emission rate of tankrelated emissions in 2019 is 105 kg CH4/d (95% CI [81 -165]), which is nearly an order of magnitude (7.5x) larger than the average emission rate from non-tank related emissions, 14 kg CH4/d.…”

“…The high mixing ratios were observed at wet gas wells (>5% C 2 H 6 ) that also housed compressors and separators, used to separate raw natural gas from condensate (hydrocarbon liquids and water). These results are consistent with helicopter-based infrared camera surveys of ONG wells conducted in various US shale plays . In the Barnett, 21% of well pads with the lowest gas-to-oil ratios (GOR) showed detectable emissions, compared to less than 1% of sites with higher GORs.…”

“…Although this range is in the lower half of our emission distribution (Fig. 2), such high emission rates can only be explained by inefficient or malfunctioning flaring operations (7,34). This finding agrees with a study in the Bakken Shale, which estimated that incomplete combustion from flares contributed almost 20% of the total field emissions of methane, most of which was due to a small number of low-efficiency flares (35).…”

“…According to these numbers, extreme emissions occur 2.6 times more frequently for new facilities (those from 2018 or after) than from old facilities, and the amount of methane emitted by new facilities is twice the one emitted from the older ones. This finding agrees with the results from a large helicopter-based emission survey over seven U.S. basins, which found that well pads in their first 2 months of production were five times more likely to have detected emissions (7). This result supports the speculation that recently developed wells and infrastructure associated with these wells are the major methane emitters in the Permian basin (8), which is likely due to a faster development of gas extraction methods than of storage and processing capabilities.…”