Analysis of Air Emissions in the Drilling and Completions of Marcellus andUtica Shales from 2004 to 2023

Unconventional resources, particularly the development of the Marcellus and Utica shale formations, have played a significant role in shaping the U.S. energy landscape in recent years. While air emissions from fossil fuel consumption have been extensively studied, emissions generated during the development stage, specifically drilling and completion, require further investigation. Conducting a comprehensive study ofthese emissions on a broader scale will enhance our understanding of the environmental impact of shale development activities in these regions. This study aims to estimate drilling and completion air emissions from shale gas development in the Marcellus and Utica shale regions at a basin scale. Initially this study compiled a comprehensive dataset using publicly available sources. Drilling and completion durations wereanalyzed, refined, and processed to reflect actual operational times for these activities accurately. To account for technological advancements over time, the study period (2004–2023) is divided into four intervals. Emissions from individual wells were estimated using a correlation-based bottom-up inventory approach. We defined effective parameters based on the prevailing technologies in each period. The parameter ranges were determined using multiple sources, including industry surveys, EPA-42 data, and peer-reviewed studies. The study estimates emissions of nitrogen oxides (NOₓ), sulfur di-oxides (SO2) replace "sulfur di-oxides" with the correct form "sulfur dioxide (SO2, fine particulate matter (PM2.₅), and volatile organic compounds (VOCs) from shale gas production activities. NOx is identified as the dominant pollutant during drilling and completion, primarily due to its high concentration in exhaust emissions. The analysis showsa peak in drilling-related emissions in 2010, reaching 8,000 tons from 1,800 drilled wells. This increase was driven by the rapid expansion of drilling activities and the prevailing use of diesel-powered engines, which emit high levels of pollutants. Despite an increase in drilling activity in 2014, with 2,700 wells being drilled, emissions dropped to 4,800 tons. This decline can be attributed to the industry's transition toward natural gas-powered engines and the implementation of more effective emission control technologies. For well completion, emissions peaked in 2018, reaching 90,000 tons from 1,750 completed wells, compared to 84,000 tons from 2,350 completions in 2014. This paper presents an analysis of basin-scale air emissions in the development of Marcellus and Utica over the period of 2004–2023, with a focus on the impact of technological evolution over time.