Quantification of Oil and Gas Methane Emissions in the Delaware and Marcellus Basins Using a Network of Continuous Tower-Based Measurements

Abstract

Abstract. According to the United States Environmental Protection Agency (US EPA), emissions from oil and gas infrastructure contribute 30 % of all anthropogenic methane (CH4) emissions in the US. Studies in the last decade have shown emissions from this sector to be substantially larger than bottom-up assessments, including the EPA inventory, highlighting both an increased importance of methane emissions from the oil and gas sector towards their overall climatological impact, and the need for independent monitoring of these emissions. In this study we present continuous monitoring of regional methane emissions from two oil and gas basins using tower-based observing networks. Continuous methane measurements were taken at 4 tower sites in the northeastern Marcellus basin from May 2015 through December 2016, and 5 tower sites in the Delaware basin in the western Permian from March 2020 through April 2022. These measurements, an atmospheric transport model, and prior emission fields, are combined using an atmospheric inversion to estimate monthly methane emissions in the two regions. This study finds the mean overall emission rate from the Delaware basin during the measurement period to be 146–210 Mg CH4 h-1 (energy-normalized loss rate of 1.1–1.5 %, gas-normalized rate of 2.5–3.5 %). Strong temporal variability in the emissions was present, with the lowest emission rates occurring during the onset of the COVID-19 pandemic. In the Marcellus, this study finds the overall mean emission rate to be 19–28 Mg CH4 h-1 (gas-normalized loss rate of 0.30–0.45 %), with relative consistency in the emission rate over time. These totals align with aircraft top-down estimates from the same time periods. In both basins, the tower network was able to constrain monthly flux estimates within ±20 % uncertainty in the Delaware and ±24 % uncertainty in the Marcellus. The results from this study demonstrate the ability to monitor emissions continuously and detect changes in the emissions field, even in a basin with relatively small emissions and complex background conditions.

Geospatial Life Cycle Analysis of Greenhouse Gas Emissions from US Liquefied Natural Gas Supply Chains

“…Upstream production, gathering and boosting: The upstream stage includes well drilling through gas dehydration and compression (SI section S2). In the Marcellus basin, CO2 emissions associated with fuel use including diesel and fuel gas were obtained from the XTO-operated facilities in that region, 17 and the inventory-based methane emission estimates were derived from the integration of several studies [39][40][41] and replaced by an measurement informed methane emission estimates from a field campaign in the Northeastern Marcellus basin 28 . For the Permian basin, we employed the framework of GHG emission in a recent NETL report on lifecycle analysis of US natural gas supply chains, 40 and replaced the inventory-based methane emissions data with an aggregated measurement informed emissions estimates from peer-reviewed literature 33,42 .…”

“…27 Field campaigns in the Marcellus basin show that the gas production normalized emission rate varies between 0.3 and 1.4%. [28][29][30] In the Permian basin, O&G operators are reported to emit 3.7%-9.4% of the NG normalized to gas production, which is roughly 3 to 10 times the average emission rate in other US major O&G basins. [31][32][33] Therefore, inventory-based methane emission estimates combined with sensitivity analysis is unable to meet the growing need for accurate measurement informed emission estimation, and measurements should be incorporated into LCA studies.…”

Summertime Ozone Production at Carlsbad Caverns National Park, New Mexico: Influence of Oil and Natural Gas Development

“…VOC emissions result from the venting of petroleum hydrocarbons, volatilization of hydrocarbon‐based drilling fluids, and incomplete combustion of fuels used in O&G equipment (Dix et al., 2023; Francoeur et al., 2021; Ku et al., 2024). Summertime easterly winds can transport these emissions to the west of the primary source regions (Barkley et al., 2023; Crosman, 2021; Dix et al., 2023). Consequently, concentrations of VOCs commonly associated with O&G (e.g., light alkanes) are ∼1 order of magnitude greater at CAVE than at other southwestern US national parks (Benedict et al., 2020).…”