Regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Thomas Lauvaux, Zach Barkley
Kenneth Davis, Natasha Miles, Scott Richardson, Douglas Martins
Department of Meteorology, Pennsylvania State University
Yanni Cao, Eun-Kyeong Kim, Guido Cervone, Alan Taylor
Department of Geography, Pennsylvania State University
Colm Sweeney, Anna Karion, Kathryn McKain
ESRL/NOAA GMD, CIRES, Boulder
Tom Murphy
Marcellus Center for Outreach and Research, Pennsylvania State University
Penn State Extension webinar series, July 20th, 2017
Regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Project sponsored by the Department of Energy
National Energy Technology Laboratory
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Natural gas production in the United States from the major shale gas formations
since 2008 (EIA data)
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2009 2010 2011 2012 2013Na
tura
l G
as
Le
ak
Ra
te
(%)
Year
Production Processing
Bottom up estimates for the US
suggests that emissions from
production and processing of natural
gas account for less than 0.8% of total
production.
0.8%
• The NOAA mass balance estimates
from 9 different basins suggest that
the EPA estimate is too low.
• The smaller producing fields are
driving the average leak rate up.0
5
10
Na
tura
l G
as
Le
ak
Ra
te (
%) NOAA Mass Balance estimates
Karion et al. (2013;2015)
Petron et al. (2012;2014)
Peischl et al. (2015; 2016)
Smith et al. (2016)
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Project goals and objectives
Overall objective: quantify fugitive emissions of CH4 from the
Marcellus gas production region of north-central Pennsylvania over a
period of two years (2015-2017)
1. Generate maps of CH4 emissions over the northeastern region of
the Marcellus shale formation
2. Break down of the relative contribution of various regional sources
(animal agriculture, wetlands, landfills, gas production, other
regional sources identified)
3. Compare to emissions-factor, activity-data based “inventory”
regional CH4 emissions estimates, evaluating both the accuracy of
the inventory methods, and our ability to detect changes.
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Two new elements in this approach:
1. First long-term deployment (i.e. 2 years) of several
instruments to measure continuously the CH4 emissions
from the natural gas production activities (only short
aircraft or automobile campaign so far)
2. Use of 13CH4 to identify the contributions from
biogenic sources and thermogenic sources (no
calibration protocol to measure 13CH4 at high accuracy)
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Objectives:
- Regional attribution of spatial and temporal variability
- Separation of source contributions using continuous 13CH4/CH4 measurements
CH4 CH4CH4
Upwind
Downwind
Upwind
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Inventory of CH4
emissions
(Natural Gas Prod.)
Other sources of CH4
(Farming, wetlands,
industrial)
Atmospheric model
(1km resolution)
Atmospheric concentrations
of CH4
(modeled)
Atmospheric concentrations
of CH4
(observations)
Optimization
(inversion system)
- Collection of inventory data to construct the a priori CH4 emissions
1. US EPA gridded product from Maasakkers et al., (2016)
2. Updated production rates for conv. & unconv. wells for selected months
3. Compressor stations as point sources (based on air permits)
Collection of activity data for the preparation of a bottom-up CH4 emission
map, including biogenic and thermogenic sources
from Barkley et al., under review
Collection of activity data for the preparation of a bottom-up CH4 emission
map, including biogenic and thermogenic sources
Animal Agriculture Coal mines/beds Landfill / Industry
Unconventional Production Conventional Production Distribution
from Barkley et al., under review
Collection of activity data for the preparation of a bottom-up CH4 emission
map, including biogenic and thermogenic sources
Map of the CH4 emissions inventory for the extended Pennsylvania study domain in
mol.km-2.hour-1 and our domain of interest (red box)
Deployment of calibrated CRDS instruments at the four identified tower
locations
Network design of the four instrumented towers:
• Two towers instrumented to measure the background mixing ratios (independent of wind
direction)
Background: Towers N and S
• Two towers downwind of the production wells, nearby the area of interest (maximum amplitude)
Downwind: Towers C and E
Installation of instruments
- Negotiation of lease agreement for the selected towers
- Installation of sheds for the duration of the deployment (no space for instruments indoor)
- Tubing installed to the top of the towers,
- Deployment before the aircraft campaign
Deployment of calibrated CRDS instruments at the four identified tower
locations
Definitive tower locations of the 4 towers called North (N),
East (E), South (S), and Central (C). Unconventional wells
are plotted in the background.
Coordinates, elevations, and sampling heights of the 4
towersPhoto of temporary shed (upper) and tube
inlet at tower N, 46m AGL (lower)
Field sampling flow schematic with automatic calibration system using
four gas-phase standards of unique isotopic 13CH4 values () and CH4
(X) mixing ratios at ambient (amb) and heavy and high (HI) and low
(Lo1, Lo2) mixing ratios, respectively.
Calibration of the four CRDS CH4/13CH4 instruments:
- Four standards for 13Ch4 measurements with various levels of enrichment/depletion and concentrations
- Dry air (use of Nafion) with automated valve (flow path selector) between calibration standards and
outdoor inlet tube
from Miles et al., in prep.
Deployment of calibrated CRDS instruments at the four identified tower
locations
Comparison between continuous CRDS mixing ratio measurements and flask samples for CO2 (in ppm),
CH4 (in ppb), and 13CH4 (in permil)
Deployment of calibrated CRDS instruments at the four identified tower
locations
from Miles et al., in prep.
CH4 mixing ratio measurements over 2015-2017 from the four CRDS CH4/13CH4 instruments (in ppb)
Deployment of calibrated CRDS instruments at the four identified tower
locations
CH4 mixing ratio enhancements over 2015-2017 from the four CRDS CH4/13CH4 instruments (in ppb)
Deployment of calibrated CRDS instruments at the four identified tower
locations
Aircraft campaign to quantify CH4 emissions over the entire northern
Marcellus region
NOAA Twin Otter on the tarmac of the Williamsport airport
List of flights, conditions, and durations for the 12 flights of the
aircraft campaign
Show flight pathsFlight patterns for the 12 flights of the aircraft campaign
with the mean wind direction during the flight (red
arrows). The flight on 14 May shows highly variable
winds across the domain.Colm Sweeney, NOAA
Anna Karion, NIST
Aircraft campaign to quantify CH4 emissions over the entire northern
Marcellus region
Example of flight measurements for May 24th, 2015 with vertical profiles of meteorological and greenhouse gas
measurements (upper left), wind direction and spedd (upper right), methane (lower left), and ethane (lower right)
Aircraft campaign to quantify CH4 emissions over the entire northern
Marcellus region
Inventory of CH4
emissions
(Natural Gas Prod.)
Other sources of CH4
(Farming, wetlands,
industrial)
Atmospheric model
(1km resolution)
Atmospheric concentrations
of CH4
(modeled)
Atmospheric concentrations
of CH4
(observations)
Optimization
(inversion system)
Quantification of emissions: Data Assimilation System
WRF-CH4 atmospheric modeling system:
- WRF-Chem, modified for CH4, v3.5.1,
- Physics configuration based on previous studies (Lauvaux et al., 2012; Deng et al., in prep.)
- 3 grids in nested mode (one-way): 9km/3km/1km resolution,
- Emission fields from inventory data coupled to the 3km and 1km grids,
- 3 modes developed for the project:
- Forecast: 9km/3km resolutions,12-hour assimilation, 24-hour forecast.
- Historical: initial and boundary conditions from North American Regional Reanalysis (NARR)
- Data assimilation: Four Dimensional Data Assimilation (FDDA) mode with nudging
of WMO surface stations and radiosondes
Evaluation –Aircraft campaign of May 2015
- Simulations of flight days at 1km resolution in the three different modes
Atmospheric modeling system: WRF-CH4
Atmospheric CH4 enhancement from the various
sectors of emissions over PA (in ppm)
Atmospheric modeling system: WRF-CH4
Modeling domain to simulate the
atmospheric conditions during the
deployment period (2015-2017) using the
Weather Research and Forecasting model
NG Transmission/Distribution
Unconventional Production/Gathering
May 24th 2015 Total
Enhancement
Modeled Methane Enhancement
(in ppm)
Conventional Wells
Coal Mines
Enteric Fermentation
Landfills and Other
May 29th 2015: A good day.
Wind
Speed
4.8 m/s
Atmospheric CH4 enhancement (in ppm)
Enhancem
ent
(ppm
)
A B C D
A
B C
D
Observed CH4 Enhancement
(ppm)
Aircraft emissions estimate on May 29th 2015
Observed CH4 Enhancement measured during the flight (in ppm)
Enhancem
ent
(ppm
)
A
B C
D
Non-NG CH4 Enhancement (ppm)
A B C D
Aircraft emissions estimate on May 29th 2015
Observed and modeled Non-Natural Gas CH4 enhancement for the May 29th flight (in ppm)
Enh
an
cem
en
t (p
pm
)
A
B C
D
Natural Gas CH4 Enhancement
(ppm)
A B C D
Aircraft emissions estimate on May 29th 2015
Observed CH4 enhancement for the May 29th flight (in ppm)
Enhancem
ent
(pp
m)
B C
DA
Natural Gas CH4 Enhancement
(ppm)
Emission Rate = 0.13%
A B C D
Aircraft emissions estimate on May 29th 2015
Observed and modeled Natural Gas CH4 Enhancement for the May 29th flight (in ppm)
Enhancem
ent
(ppm
)
A
B C
D
Natural Gas CH4 Enhancement
(ppm)
Emission Rate = 0.26%
A B C D
Aircraft emissions estimate on May 29th 2015
Observed and optimized Natural Gas CH4 enhancement for the May 29th flight (in ppm)
CASE STUDY: MAY 24th, 2015
The Importance of a Good Methane Inventory
31
Aircraft emissions estimate on May 24th 2015
Observed CH4 enhancement for the May 24th flight at 20z (in ppm)
Importance of the inventory with the projected atmospheric enhancement from
Coal mines/beds explaining the observed spatial gradients
Coal Plume Final Result: All Emissions
UNG Emission Rate=0.29%
Aircraft emissions estimate on May 24th 2015
Best-guess upstream emission estimates
Optimal mean leakage rate based on 10 flights in May 2015: 0.39% of production
Marcellus Mass Balance: valid over 4 days out of 10
May 22nd, 2015
May 23nd, 2015 May 29th, 2015
May 29th, 2015
Best-guess upstream emission estimates
Optimal mean leakage rate based on 10 flights in May 2015: 0.39% of production
TOWER INVERSION: June to December, 2015
Time-dependent flux estimate for NE PA
Tower-based inversion for June-December 2015
Inversion
window
Diagram of the different flux sub-regions used
in the inversion. Towers (green pins) and wells
(pink dots) are plotted overtop
Map of the percent change in the posterior flux
compared to the prior flux using tower
observations from Oct-Dec 2015
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Conclusions
Successful calibration of 13CH4 continuous CRDS sensors (about 0.2 permil)
Leakage rate equivalent to 0.4% of production (wells and gathering compressors)
Site-level estimate (about 15 wells in PA), Omara et al. (2016): 0.64% of production (wells only)
EPA-derived estimate for NE PA (Maasakkers et al., 2016): 0.13% of production
Aircraft mass-balance (1 flight only) for NE PA (Peischl et al., 2013): 0.3% of production
Initial tower-based inversion results suggest lower leakage rates over June to December 2015
Future work
ACT-America study on unconventional and coal mines in SW PA and WV ongoing
Perform tower-based inversion over June 2015 to December 2016
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Publications and references
Barkley, Z. R., Lauvaux, T., Davis, K. J., Deng, A., Cao, Y., Sweeney, C., Martins, D., Miles, N. L., Richardson, S. J.,
Murphy, T., Cervone, G., Karion, A., Schwietzke, S., Smith, M., Kort, E. A., and Maasakkers, J. D.: Quantifying methane
emissions from natural gas production in northeastern Pennsylvania, Atmos. Chem. Phys. Discuss.,
https://doi.org/10.5194/acp-2017-200, in review, 2017.
Cao, Y., Cervone, G., Barkely, Z., Lauvaux, T., Deng, A., and Taylor, A.: Influence of Geographic Coordinate System on
Weather Simulations of Atmospheric Emissions, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2016-253, in
review, 2016.
Miles, N., D. K. Martins, S. J. Richardson, C. Rella, C. Arata, T. Lauvaux, K. J. Davis, Z. Barkley, K. McKain, C.
Sweeney: Calibration and Field Testing of Cavity Ring-Down Laser Spectrometers Measuring Methane Mole Fraction
and Isotopic Ratio Deployed on Towers in the Marcellus Shale Region, in prep.
Data from towers
2015-2017 data archive for CH4 and 13CH4 continuous tower measurements in northeastern PA:
http://www.datacommons.psu.edu/commonswizard/MetadataDisplay.aspx?Dataset=6134
Data from the 2015 aircraft campaign
Aircraft Campaign over the Northeastern Marcellus Shale (May 2015):
https://doi.org/10.15138/G35K54
TA [2] Continuous, regional methane emissions estimates in northern
Pennsylvania gas fields using atmospheric inversions
Publications in preparation
Barkley, Z. R., et al.: Regional inversion of methane emissions from natural gas production in northeastern Pennsylvania,
in prep.
Barkley, Z. R., et al.: Methane emissions from coal mines and natural gas production in southwestern PA, in prep.
Project Website
http://sites.psu.edu/marcellus/
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