Methane Emissions from Process Equipment at Natural Gas Production Sites in the United States: Liquid Unloadings

Allen, David T.; Sullivan, David W.; Zavala-Araiza, Daniel; Pacsi, Adam P.; Harrison, Matthew; Keen, Kindal; Fraser, Matthew P.; Hill, A.D.; Lamb, Brian; Sawyer, Robert F.; Seinfeld, John H.

doi:10.1021/es504016r

Cited by 98 publications

(135 citation statements)

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“…1) to 43 kg CO 2 eq/bbl, and the life cycle GHG emissions decrease from 89.1 to 89.0 g CO 2 eq/MJ gasoline. Although fugitive emissions do not impact the carbon intensity of Bakken crude fuels, we believe experimental investigations of tank vapor and other crude-specific emissions akin to the investigations of Allen et al for natural gas systems (37)(38)(39) are timely.…”

Section: Discussionmentioning

confidence: 92%

Life cycle greenhouse gas emissions and freshwater consumption associated with Bakken tight oil

Laurenzi

Bergerson

Motazedi

2016

Proc. Natl. Acad. Sci. U.S.A.

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In recent years, hydraulic fracturing and horizontal drilling have been applied to extract crude oil from tight reservoirs, including the Bakken formation. There is growing interest in understanding the greenhouse gas (GHG) emissions associated with the development of tight oil. We conducted a life cycle assessment of Bakken crude using data from operations throughout the supply chain, including drilling and completion, refining, and use of refined products. If associated gas is gathered throughout the Bakken well life cycle, then the well to wheel GHG emissions are estimated to be 89 g CO 2 eq/MJ (80% CI, 87-94) of Bakken-derived gasoline and 90 g CO 2 eq/MJ (80% CI, 88-94) of diesel. If associated gas is flared for the first 12 mo of production, then life cycle GHG emissions increase by 5% on average. Regardless of the level of flaring, the Bakken life cycle GHG emissions are comparable to those of other crudes refined in the United States because flaring GHG emissions are largely offset at the refinery due to the physical properties of this tight oil. We also assessed the life cycle freshwater consumptions of Bakken-derived gasoline and diesel to be 1.14 (80% CI, 0.67-2.15) and 1.22 barrel/barrel (80% CI, 0.71-2.29), respectively, 13% of which is associated with hydraulic fracturing.life cycle assessment | unconventional resources | petroleum | hydraulic fracturing | flaring

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Section: Discussionmentioning

confidence: 92%

Life cycle greenhouse gas emissions and freshwater consumption associated with Bakken tight oil

Laurenzi

Bergerson

Motazedi

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…For example, the EPA reports that approximately 50,000 wells in the United States vent during liquid unloadings, resulting in 259 Gg/yr of methane emissions (EPA, 2015c). A small fraction of these venting wells, perhaps 3-5%, likely accounts for half of unloading emissions (Allen et al, 2015b). Similarly, multiple studies (Prasino 2013; Allen et al, 2015a;Gibbs, 2015) have found that a small subpopulation of pneumatic controllers (the largest source of greenhouse gases in the petroleum and natural gas supply chains) dominates emissions.…”

Section: Zavala Et Al 2015amentioning

confidence: 98%

“…Some short-duration events occur by design. For example, liquid unloadings can last for periods as short as a few minutes, yet during that period have emission rates equivalent to a thousand or more wells in routine operation (Allen et al, 2015b). Emissions can also be due to unplanned events.…”

Section: Spatial and Temporal Variability In Emissionsmentioning

confidence: 99%

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

Allen

2016

Journal of the Air & Waste Management Association

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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

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“…• liquids unloading for all gas wells [29,44] However, there remains a lack of representative point-source data and an understanding of emissions variation across regions and over time, in particular with regards to extraction from coal bed methane, liquids unloading and pipework leaks from transmission, storage and distribution. Perhaps the largest gap in available data is for offshore extraction emissions: only one study on offshore gas extraction emissions has been found [30].…”

Section: Data Availabilitymentioning

confidence: 99%

The Natural Gas Supply Chain: The Importance of Methane and Carbon Dioxide Emissions

Balcombe

Anderson

Speirs

et al. 2016

ACS Sustainable Chem. Eng.

128

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Natural gas is typically considered to be the cleaner-burning fossil fuel that could play an important role within a restricted carbon budget. Whilst natural gas emits less CO2 when burned than other fossil fuels, its main constituent is methane, which has a much stronger climate forcing impact than CO2 in the short-term. Estimates of methane emissions in the natural gas supply chain have been the subject of much controversy, due to uncertainties associated with estimation methods, data quality and assumptions used. This paper presents a comprehensive compilation of estimated CO2 and methane emissions across the global natural gas supply chain, with the aim of providing a balanced insight for academia, industry and policy makers by summarising the reported data, locating the areas of major uncertainty and identifying where further work is needed to reduce or remove this uncertainty. Overall, the range of documented estimates of methane emissions across the supply chain is vast amongst an aggregation of different geological formations, technologies, plant age, gas composition and regional regulation, not to mention differences in estimation methods. Estimates of combined methane and CO2 emissions ranged from 2 -42 g CO2 eq./ MJ HHV, whilst methane-only emissions ranged from 0.2% -10% of produced methane. The methane emissions at the extraction stage are the most contentious issue, with limited data available but potentially large impacts associated with well completions for unconventional gas, liquids unloading and also from the transmission stage. From the range of literature estimates, a constrained range of emissions was estimated that reflects the most recent and reliable estimates: total supply chain GHG emissions were estimated to be between 3.6 and 42.4 g CO2 eq./ MJ HHV, with a central estimate of 10.5. The presence of 'super emitters', a small number of facilities or equipment that cause extremely high emissions, is found across all supply chain stages creating a highly skewed emissions distribution. However, various new technologies, mitigation and maintenance approaches, and legislation are driving significant reductions in methane leakage across the natural gas supply chain.

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Methane Emissions from Process Equipment at Natural Gas Production Sites in the United States: Liquid Unloadings

Cited by 98 publications

References 10 publications

Life cycle greenhouse gas emissions and freshwater consumption associated with Bakken tight oil

Life cycle greenhouse gas emissions and freshwater consumption associated with Bakken tight oil

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

The Natural Gas Supply Chain: The Importance of Methane and Carbon Dioxide Emissions

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