Air quality concerns of unconventional oil and natural gas production

Abstract

Increased use of hydraulic fracturing ("fracking") in unconventional oil and natural gas (O & NG) development from coal, sandstone, and shale deposits in the United States (US) has created environmental concerns over water and air quality impacts. In this perspective we focus on how the production of unconventional O & NG affects air quality. We pay particular attention to shale gas as this type of development has transformed natural gas production in the US and is set to become important in the rest of the world. A variety of potential emission sources can be spread over tens of thousands of acres of a production area and this complicates assessment of local and regional air quality impacts. We outline upstream activities including drilling, completion and production. After contrasting the context for development activities in the US and Europe we explore the use of inventories for determining air emissions. Location and scale of analysis is important, as O & NG production emissions in some US basins account for nearly 100% of the pollution burden, whereas in other basins these activities make up less than 10% of total air emissions. While emission inventories are beneficial to quantifying air emissions from a particular source category, they do have limitations when determining air quality impacts from a large area. Air monitoring is essential, not only to validate inventories, but also to measure impacts. We describe the use of measurements, including ground-based mobile monitoring, network stations, airborne, and satellite platforms for measuring air quality impacts. We identify nitrogen oxides, volatile organic compounds (VOC), ozone, hazardous air pollutants (HAP), and methane as pollutants of concern related to O & NG activities. These pollutants can contribute to air quality concerns and they may be regulated in ambient air, due to human health or climate forcing concerns. Close to well pads, emissions are concentrated and exposure to a wide range of pollutants is possible. Public health protection is improved when emissions are controlled and facilities are located away from where people live. Based on lessons learned in the US we outline an approach for future unconventional O & NG development that includes regulation, assessment and monitoring.

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

“…There are significant uncertainties in our knowledge of the source processes and geographical distribution of halogens and severe limitations in the databases of chemical kinetics parameters (Abbatt et al, 2014). Part of the problem is related to the difficulty in measuring halogens species at the low concentrations found in the atmosphere (Finlayson-Pitts, 2010): this area of research has been very active in recent years and many of the most recent advancements in our knowledge are related to developments in the field of analytical chemistry, particularly mass spectrometry.…”

Contribution of oil and natural gas production to renewed increase in atmospheric methane (2007–2014): top–down estimate from ethane and methane column observations

“…This has been facilitated by the development of new extraction techniques (hydraulic fracturing and horizontal drilling), which involve additional fugitive methane emissions during flowback periods compared to conventional techniques (Field et al, 2014;Howarth, 2014). Several studies report that methane emission from this industry is likely underestimated (Karion et al, 2013;Miller et al, 2013;Brandt et al, 2014;Kort et al, 2014;Schneising et al, 2014;Turner et al, 2015).…”

“…In the case of ethane three source categories are distinguished: fossil fuel extraction (oil, gas, and coal), biomass burning, and biofuel use. Initial global ethane emissions are compiled from the following emission inventories: (i) biomass burning emissions from the Global Fire Emission Database GFED4s (van der Werf et al, 2010;Giglio et al, 2013) with emission factors from Akagi et al (2011), (ii) biofuel use emissions from the linearly extrapolated activity data in Fernandes et al (2007) with appropriate emission factors (Andreae and Merlet, 2001), and (iii) fossil-fuel-related emissions provided in Schwietzke et al (2014). The latter includes annual emissions up to 2011 from the extraction of coal (EMR = 0.5 % or MER = 100), oil (EMR = 21.3 % or MER = 2.5), and natural gas (mean ethane content of 7.3 % at a global fugitive emission rate of 5 %).…”

Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement

“…Direct emissions from oil and gas operations include hydrocarbons from flowback events and well completions, on-site equipment during the routine operation of the well, such as compressors and storage tanks, and unintentional emissions such as leaks from valves and pipelines. Indirect emissions of NMVOCs, HAPs, and NO x come largely from combustion sources such as diesel engines in generators, drilling rigs, compressors, and trucks used to transport equipment, water, and petroleum (Field et al, 2014). In ad-dition, flaring is widely used in certain shale plays, including the EFS, to dispose of excess natural gas -mostly associated gas produced at oil wells (Tedesco and Hiller, 2014).…”