Temporal variability largely explains top-down/bottom-up difference in methane emission estimates from a natural gas production region
Edited by Steven C. Wofsy, Harvard University, Cambridge, MA, and approved August 16, 2018 (received for review April 3, 2018)
Significance
Our results demonstrate that access to high-resolution spatiotemporal activity data and multiscale, contemporaneous measurements is critical to understanding oil- and gas-related methane emissions. Careful consideration of all factors influencing methane emissions—including temporal variation—is necessary in scientific and policy discussions to develop effective strategies for mitigating greenhouse gas emissions from natural gas infrastructure.
Abstract
This study spatially and temporally aligns top-down and bottom-up methane emission estimates for a natural gas production basin, using multiscale emission measurements and detailed activity data reporting. We show that episodic venting from manual liquid unloadings, which occur at a small fraction of natural gas well pads, drives a factor-of-two temporal variation in the basin-scale emission rate of a US dry shale gas play. The midafternoon peak emission rate aligns with the sampling time of all regional aircraft emission studies, which target well-mixed boundary layer conditions present in the afternoon. A mechanistic understanding of emission estimates derived from various methods is critical for unbiased emission verification and effective greenhouse gas emission mitigation. Our results demonstrate that direct comparison of emission estimates from methods covering widely different timescales can be misleading.
Data Availability
Data deposition: Datasets are available at https://hdl.handle.net/10217/190251.
Acknowledgments
We thank all field measurement personnel and those who aided in data compilation for their significant, coordinated efforts. This work was supported by Research Partnership to Secure Energy for America/National Energy Technology Laboratory Contract 12122-95/DE-AC26-07NT42677 to the Colorado School of Mines. Cost share for this project was provided by Colorado Energy Research Collaboratory, the National Oceanic and Atmospheric Administration Climate Program Office, Southwestern Energy, XTO Energy, a subsidiary of ExxonMobil, Chevron, Statoil and the American Gas Association, many of whom also provided operational data and/or site access. Additional data and/or site access was also provided by CenterPoint, Enable Midstream Partners, Kinder Morgan, and BHP Billiton.
Supporting Information
Appendix (PDF)
- Download
- 2.82 MB
Movie S1.
- Download
- 2.02 MB
References
1
; US EIA, Carbon intensity of energy use is lowest in U.S. industrial and electric power sectors. Today in Energy (US Energy Information Administration, Washington, DC). Available at https://www.eia.gov/todayinenergy/detail.php?id=31012. Accessed September 17, 2017. (2017).
2
; US EPA, Inventory of U.S. greenhouse gas emissions and sinks: 1990-2014 (Environmental Protection Agency, Washington, DC). (2016).
3
; US EPA, Inventory of U.S. greenhouse gas emissions and sinks: 1990-2015 (Environmental Protection Agency, Washington, DC). (2017).
4
RA Alvarez, SW Pacala, JJ Winebrake, WL Chameides, SP Hamburg, Greater focus needed on methane leakage from natural gas infrastructure. Proc Natl Acad Sci USA 109, 6435–6440 (2012).
5
S Kirschke, et al., Three decades of global methane sources and sinks. Nat Geosci 6, 813–823 (2013).
6
EG Nisbet, EJ Dlugokencky, P Bousquet, Atmospheric science. Methane on the rise–Again. Science 343, 493–495 (2014).
7
; US EIA, US natural gas gross withdrawals and production (US Energy Information Administration, Washington, DC). (2017).
8
G Heath, E Warner, D Steinberg, A Brandt, Estimating US methane emissions from the natural gas supply chain: Approaches, uncertainties, current estimates, and future studies (National Renewable Energy Laboratory, Golden, CO). (2015).
9
J Peischl, et al., Quantifying atmospheric methane emissions from oil and natural gas production in the Bakken shale region of North Dakota. J Geophys Res Atmos 121, 6101–6111 (2016).
10
A Karion, et al., Methane emissions estimate from airborne measurements over a western United States natural gas field. Geophys Res Lett 40, 4393–4397 (2013).
11
G Pétron, et al., A new look at methane and nonmethane hydrocarbon emissions from oil and natural gas operations in the Colorado Denver-Julesburg Basin. J Geophys Res Atmos 119, 6836–6852 (2014).
12
S Schwietzke, et al., Improved mechanistic understanding of natural gas methane emissions from spatially resolved aircraft measurements. Environ Sci Technol 51, 7286–7294 (2017).
13
A Karion, et al., Aircraft-based estimate of total methane emissions from the barnett shale region. Environ Sci Technol 49, 8124–8131 (2015).
14
SM Miller, et al., Anthropogenic emissions of methane in the United States. Proc Natl Acad Sci USA 110, 20018–20022 (2013).
15
J Peischl, et al., Quantifying atmospheric methane emissions from the Haynesville, Fayetteville, and northeastern Marcellus shale gas production regions. J Geophys Res Atmospheres 120, 2119–2139 (2015).
16
AR Brandt, et al., Energy and environment. Methane leaks from North American natural gas systems. Science 343, 733–735 (2014).
17
D Zavala-Araiza, et al., Reconciling divergent estimates of oil and gas methane emissions. Proc Natl Acad Sci USA 112, 15597–15602 (2015).
18
DR Lyon, et al., Constructing a spatially resolved methane emission inventory for the Barnett Shale region. Environ Sci Technol 49, 8147–8157 (2015).
19
D Zavala-Araiza, et al., Toward a functional definition of methane super-emitters: Application to natural gas production sites. Environ Sci Technol 49, 8167–8174 (2015).
20
TN Lavoie, et al., Spatiotemporal variability of methane emissions at oil and natural gas operations in the Eagle Ford Basin. Environ Sci Technol 51, 8001–8009 (2017).
21
DT Allen, et al., Methane emissions from process equipment at natural gas production sites in the United States: Liquid unloadings. Environ Sci Technol 49, 641–648 (2015).
22
DT Allen, Methane emissions from natural gas production and use: Reconciling bottom-up and top-down measurements. Curr Opin Chem Eng 5, 78–83 (2014).
23
S Conley, et al., Application of Gauss’s theorem to quantify localized surface emissions from airborne measurements of wind and trace gases. Atmos Meas Tech 10, 3345–3358 (2017).
24
AM Robertson, et al., Variation in methane emission rates from well pads in four oil and gas basins with contrasting production volumes and compositions. Environ Sci Technol 51, 8832–8840 (2017).
25
TI Yacovitch, et al., Natural gas facility methane emissions: Measurements by tracer flux ratio in two US natural gas producing basins. Elem Sci Anth 5, 69 (2017).
26
TL Vaughn, et al., Comparing facility-level methane emission rate estimates at natural gas gathering and boosting stations. Elem Sci Anth 5, 71 (2017).
27
DJ Zimmerle, et al., Gathering pipeline methane emissions in Fayetteville shale pipelines and scoping guidelines for future pipeline measurement campaigns. Elem Sci Anth 5, 70 (2017).
28
C Bell, et al., Comparison of methane emission estimates from multiple measurement techniques at natural gas production pads. Elem Sci Anth 5, 79 (2017).
29
SM Ross Simulation (Academic, New York, 2013).
30
; US EPA, GHG reporting program data sets. Available at https://19january2017snapshot.epa.gov/ghgreporting/ghg-reporting-program-data-sets_.html. Accessed August 31, 2018. (2016).
31
DB Turner Workbook of Atmospheric Dispersion Estimates (US Dept of Health, Education, and Welfare, Washington, DC, 1970).
32
JH Seinfeld, SN Pandis Atmospheric Chemistry and Physics: From Air Pollution to Climate Change (Wiley, Somerset, NJ, 2012).
33
AR Brandt, GA Heath, D Cooley, Methane leaks from natural gas systems follow extreme distributions. Environ Sci Technol 50, 12512–12520 (2016).
34
D Zavala-Araiza, et al., Super-emitters in natural gas infrastructure are caused by abnormal process conditions. Nat Commun 8, 14012 (2017).
35
AL Mitchell, et al., Measurements of methane emissions from natural gas gathering facilities and processing plants: Measurement results. Environ Sci Technol 49, 3219–3227 (2015).
36
AJ Marchese, et al., Methane emissions from United States natural gas gathering and processing. Environ Sci Technol 49, 10718–10727 (2015).
37
DJ Zimmerle, et al., Methane emissions from the natural gas transmission and storage system in the United States. Environ Sci Technol 49, 9374–9383 (2015).
38
; AOGC, Production & well data (Arkansas Oil & Gas Commission, Little Rock, AK). (2016).
39
; Scientific Aviation, Our fleet. Available at https://scientificaviation.com/our-fleet/. Accessed June 28, 2018. (2018).
40
; USDA, 2012 Census Volume 1, Chapter 2: County level (National Agricultural Statistics Service, US Dept of Agriculture, Washington, DC). Available at https://www.agcensus.usda.gov/Publications/2012/Full_Report/Volume_1,_Chapter_2_County_Level/. Accessed February 17, 2017. (2012).
41
; US Fish & Wildlife Service, National Wetlands Inventory. Available at https://www.fws.gov/wetlands/data/state-downloads.html. Accessed February 19, 2017. (2018).
42
; Energy Information Administration, Documentation of the oil and gas supply module (OGSM) (Energy Information Administration, US Dept of Energy, Washington, DC). (2001).
Information & Authors
Information
Published in
Cover image: Pictured is a cluster of trees growing among houses in Port-au-Prince, Haiti. S. Blair Hedges et al. analyzed time-series satellite images and found that the proportion of Haiti's primary forests declined from 4.4% of total land area in 1988 to 0.32% in 2016. During this time, Haiti lost all primary forest from 42 of its 50 highest and largest mountains. According to the authors, deforestation and habitat loss may lead to the extinction of most of Haiti's endemic species by 2035. See the article by Hedges et al. on pages 11850–11855. Image courtesy of Eladio Fernández (photographer).
Classifications
Copyright
Copyright © 2018 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Data Availability
Data deposition: Datasets are available at https://hdl.handle.net/10217/190251.
Submission history
Published online: October 29, 2018
Published in issue: November 13, 2018
Keywords
Acknowledgments
We thank all field measurement personnel and those who aided in data compilation for their significant, coordinated efforts. This work was supported by Research Partnership to Secure Energy for America/National Energy Technology Laboratory Contract 12122-95/DE-AC26-07NT42677 to the Colorado School of Mines. Cost share for this project was provided by Colorado Energy Research Collaboratory, the National Oceanic and Atmospheric Administration Climate Program Office, Southwestern Energy, XTO Energy, a subsidiary of ExxonMobil, Chevron, Statoil and the American Gas Association, many of whom also provided operational data and/or site access. Additional data and/or site access was also provided by CenterPoint, Enable Midstream Partners, Kinder Morgan, and BHP Billiton.
Notes
This article is a PNAS Direct Submission.
2Retired.
Authors
Competing Interests
The authors declare no conflict of interest.
Metrics & Citations
Metrics
Citation statements
Altmetrics
Citations
Cite this article
115 (46) 11712-11717,
Export the article citation data by selecting a format from the list below and clicking Export.
Cited by
Loading...
View Options
View options
PDF format
Download this article as a PDF file
DOWNLOAD PDFLogin options
Check if you have access through your login credentials or your institution to get full access on this article.
Personal login Institutional LoginRecommend to a librarian
Recommend PNAS to a LibrarianPurchase options
Purchase this article to access the full text.