Emissions from oil and gas operations in the United States and their air quality implications

Abstract

The energy supply infrastructure in the United States has been changing dramatically over the past decade. Increased production of oil and natural gas, particularly from shale resources using horizontal drilling and hydraulic fracturing, made the United States the world's largest producer of oil and natural gas in 2014. This review examines air quality impacts, specifically, changes in greenhouse gas, criteria air pollutant, and air toxics emissions from oil and gas production activities that are a result of these changes in energy supplies and use. National emission inventories indicate that volatile organic compound (VOC) and nitrogen oxide (NO x ) emissions from oil and gas supply chains in the United States have been increasing significantly, whereas emission inventories for greenhouse gases have seen slight declines over the past decade. These emission inventories are based on counts of equipment and operational activities (activity factors), multiplied by average emission factors, and therefore are subject to uncertainties in these factors. Although uncertainties associated with activity data and missing emission source types can be significant, multiple recent measurement studies indicate that the greatest uncertainties are associated with emission factors. In many source categories, small groups of devices or sites, referred to as super-emitters, contribute a large fraction of emissions. When super-emitters are accounted for, multiple measurement approaches, at multiple scales, produce similar results for estimated emissions. Challenges moving forward include identifying super-emitters and reducing their emission magnitudes. Work done to date suggests that both equipment malfunction and operational practices can be important. Finally, although most of this review focuses on emissions from energy supply infrastructures, the regional air quality implications of some coupled energy production and use scenarios are examined. These case studies suggest that both energy production and use should be considered in assessing air quality implications of changes in energy infrastructures, and that impacts are likely to vary among regions. Implications: The energy supply infrastructure in the United States has been changing dramatically over the past decade, leading to changes in emissions from oil and natural gas supply chain sources. In many source categories along these supply chains, small groups of devices or sites, referred to as super-emitters, contribute a large fraction of emissions. Effective emission reductions will require technologies for both identifying super-emitters and reducing their emission magnitudes. PAPER HISTORY

Visibility impacts at Class I areas near the Bakken oil and gas development

“…Modern techniques of oil and gas extraction, including horizontal drilling and hydraulic fracturing (fracking), have facilitated cost-effective recovery of previously untapped oil and gas reserves in the Bakken region of western North Dakota, eastern Montana, southeastern Saskatchewan, and southwestern Manitoba (Figure 1). Production of oil in North Dakota increased from a few million barrels per month in 2000 to over 35 million barrels in 2015 (Allen 2016; North Dakota Industrial Commission, Department of Mineral Resources, Oil and Gas Division 2016; Prenni et al 2016). More recently, there was a decline in the number of new wells drilled as the oil industry reacted to price reductions beginning in late 2014, with oil production leveling off and then beginning to decline in 2015.…”

Emissions in the stream: estimating the greenhouse gas impacts of an oil and gas boom

“…Other approaches use aircraft or satellite measurements of regions to produce 'top-down' estimates. Comparisons of the two approaches suggest that the 'bottom-up' approach understates total emissions in many cases (Allen 2016).…”

Constraining the accuracy of flux estimates using OTM 33A

“…are thought to contribute the bulk of emissions within the O&G sector (Alvarez et al, 2012;Zavala-Araiza et al, 2015;Alvarez et al, 2018). However, attempts to quantify O&G methane emissions are hindered by inaccurate emission inventories, a lack of measurements, and variability between basins (Allen, 2016;Schwietzke et al, 2017;Robertson et al, 2017;Alvarez et al, 2018;Omara et al, 2018). For example, basin-wide aircraft measurements of methane emissions from different O&G basins find emissions are generally higher than official inventories published by the U.S. Environmental Protection Agency (EPA; e.g., Karion et al, 2013;Pétron et al, 2014;Brandt et al, 2014;Karion et al, 2015;Schwietzke et al, 2017;Peischl et al, 2018), but the scale of aircraft measurements give little insight into the exact source of emissions on the ground.…”