Speciated organic compound emissions from oil wells in Utah

This study investigates emissions total organic compound (TOC) of methane and speciated total non-methane organic compounds (TNMOC) from key components at oil well pads in Duchesne County, Utah, focusing on liquid storage tanks, separator equipment, and wellhead systems. Using a custom-built high-flow sampling system, we quantified emissions from these components and compared them to regulatory data. Measured TOC emissions from oil tanks ranged from 10 to 1,480 g h−1 (median 150 g h−1), exceeding emissions from wellheads (15–500 g h−1; median 120 g h−1) and water tanks (3.9–50 g h−1; median 30 g h−1). Thief hatches and pressure relief valves were the primary emission points on tanks, even those routed to combustors. Methane emissions from oil tanks were higher than regulatory tank emission estimates, and oil tank emissions were also the most reactive (i.e., highest ozone-forming potential). Water tank emissions were less reactive, while wellhead emissions were richer in NMOCs relative to other non-tank sources. These results provide critical quantitative data to improve air quality assessments of oil and gas infrastructure.