Air Toxics and Other Volatile Organic Compound Emissions from Unconventional Oil and Gas Development

Abstract

Unconventional oil and natural gas (UONG) exploration and production have grown rapidly and are expected to increase further in the United States and internationally. Direct measurements of key air pollutant emissions from UONG are limited, especially during drilling and completion (hydraulic fracturing and flowback) of new wells. Knowledge of emission rates (ERs) of air toxics and other air pollutants from these activities is urgently needed to inform public policy. To address this key knowledge gap, we use a tracer ratio method to quantify pad-level, activity-specific [drilling, hydraulic fracturing (“fracking”), flowback, and production] ERs of 46 VOCs in the Denver-Julesburg (D-J, a mixed oil and gas play) and Piceance (primarily natural gas) basins in Colorado. Large differences in ERs of individual VOCs were observed across operation types, across facilities conducting the same operation type, and over time during a single operation. ERs of benzene and most VOCs were highest in both basins during flowback, when injected fracking fluids and produced water flow to the surface. ERs from production are much lower, an important result given the significant difference in the duration of activity (days to weeks for flowback vs decades for production). Fracking ERs of light alkanes and benzene were higher in the Piceance Basin than in the D-J Basin. Findings from this study provide important new information that can be used to evaluate potential health hazards and other air quality impacts of unconventional oil and gas activities in Colorado’s two major oil and gas production basins.

Impact of U.S. Oil and Natural Gas Emission Increases on Surface Ozone Is Most Pronounced in the Central United States

“…Regulations on O&NG operation and emission controls vary by states, and the rate of controlled and fugitive emissions varies widely depending on many conditions, including the chemical composition of the petroleum reservoir, operator equipment, practices, and on the stage of well development. 84 Our modeling attributed emissions equally among all reported wells, neglecting any of these dependencies, which contribute to the uncertainty in the regional sensitivity of our findings. There is also the potential of a reduction in ozone precursor emissions in the proximity and downwind of electrical power plants that were converted from coal to gas as a consequence of the lower cost and readily available gas for power generation.…”

Seasonality and Source Apportionment of Nonmethane Volatile Organic Compounds at Boulder Reservoir, Colorado, Between 2017 and 2019

“…In addition to concerns about O 3 exposure, the intersection of urban and residential communities with intensive O&NG development has elevated concerns about exposure to air toxics (Hecobian et al., 2019; Holder et al., 2019). Benzene has been highlighted as an air toxic of concern in the region (Holder et al., 2019; McKenzie et al., 2018).…”

Identifying and quantifying source contributions of air quality contaminants during unconventional shale gas extraction

“…The majority of environmental impact studies focus on water quality impacts of unconventional natural gas development (Annevelink et al, 2016;Butkovskyi et al, 2017;Jackson et al, 2015;Torres et al, 2016). However, relatively fewer studies focus on air quality impacts (Hecobian et al, 2019;Islam et al, 2016;Ren et al, 2019;Swarthout et al, 2015;Williams et al, 2018). Some studies focus on collecting and analyzing data for the pre-operational phase of fields to provide a baseline dataset for future work that evaluates operational shale gas activities (Purvis et al, 2019).…”