Exploration and Production Technologies
Continuous, Regional Methane Emissions Estimates in Northern Pennsylvania Gas Fields Using Atmospheric Inversions Last Reviewed 1/5/2015


The goal of this project is to quantify fugitive and total emissions of methane from the Marcellus gas production region of north-central Pennsylvania with an emphasis on detecting changes in emissions over time caused by changing gas production activity.

The Pennsylvania State University (Penn State), University Park, PA 16802-5000
National Oceanic and Atmospheric Administration (NOAA), Boulder, CO 80305-3337
The Regents of the University of Colorado, Boulder, CO 80309-0572
Picarro, Inc., Santa Clara, CA 95054-1000

Shale gas development in many parts of the U.S. has raised concerns about the contribution of methane emissions to the greenhouse gas (GHG) footprint. Estimates of total methane leakage have been estimated from 1 to 7 percent of shale gas production with the greatest leakage occurring during the production stage. U. S. government reports of shale gas emissions have varied greatly in recent years with the U.S .Environmental Protection Agency (EPA) reporting the estimated national average production-sector leak rate as 0.16 percent of production in 2010, 1.42 percent in 2011 and 2012, and 0.88 percent in 2013. These variations were driven mainly by changes in EPA’s assumptions for calculating emissions from several stages of natural gas well operation. In particular, the main driver for the 2013 reduction in production emissions was a report prepared by the oil and gas industry, which contended that methane emissions from liquid unloading were more than an order of magnitude lower than EPA’s 2011 report estimate, and that emissions from re-fracking wells in tight sands or shale formations were less than half of EPA’s 2011 report estimate. Actual industry-wide leak rates are highly uncertain and will remain so until small-scale leakage estimates are reconciled with large-area estimates derived from atmospheric data. Accurate, regionally comprehensive, and continuous monitoring of the actual rate of leakage from shale gas production is required both to document the GHG impact of gas production and evaluate efforts to reduce emissions.

Previous measurements of fugitive emissions from gas production were based on measurements at individual components. This method has led to the creation of emissions factors which, when combined with activity data and field measurements, provide the existing emissions estimates. This approach is prone to systematic error since emissions are highly variable across production facilities, over time, and between operators. This project seeks to measure emissions over larger areas in order to address regional trends in emissions. Emissions within the Marcellus shale gas region will be sampled via aircraft, automobile, and towers in order to create a direct estimate of emissions as it relates to location and time. The shale gas methane emissions will be compared with those from other possible methane sources including landfills, wetlands, and water treatment and agricultural sources. Successful completion of the project will result in the most comprehensive set of measurements of shale gas production to date from any location, and the first long-term, large-scale emissions measurements conducted in the Marcellus shale. This new emissions measurement technology can be used to minimize fugitive emissions by quantifying leakage rates and locations, resulting in effective measures to minimize leakage. This project will reduce the current uncertainty in GHG emissions during natural gas production within the Marcellus region and provide technology suitable for continuously quantifying the GHG impact of the industry in other areas of the United States.

Mobile emission sampling campaigns were completed in three Pennsylvania counties. Results were analyzed and contributions broken down as thermogenic and biogenic sources. The results will be compared with those of future sampling campaigns in order to determine the sources of the emissions. These data are publicly available on the project webpage located at http://sites.psu.edu/marcellus/data-download/. Researchers are collecting data documenting shale gas well locations, gas production for each well, the technology used, the distribution network comprising the pipelines and storage facilities, and the location of processing facilities such as compressor stations. EPA emission factors will be used with the spatially distributed activity data to generate emission maps at 3 km resolution.

Researchers have begun to construct spatially resolved methane emission estimates from livestock farming based on agricultural data provided by Penn State’s College of Agriculture.

The Weather Research and Forecasting - Four Dimensional Data Assimilation (WRF-FDDA) atmospheric modeling system has been configured for the network design. The initial methane emissions inventory has been created at 1 km resolution and coupled to the WRF-FDDA system. The modeling system will be used to optimize the locations of the four tower-based methane sensors.

Current Status (January 2015)
Researchers are developing a GIS database that will contain information on different sources of methane in Pennsylvania and New York, including wells, landfills, and wetlands.  Four locations for methane monitoring towers have been established, and one more tower site may be added to the project (with additional cost share from a new project partner). The team continues to search for gas pipeline GIS data to incorporate into the database.

Project Start: 10/01/2013
Project End: 09/30/2016

DOE Contribution: $1,782,725
Performer Contribution: $ 445,682

Contact Information:
NETL – Sandy McSurdy (sandra.mcsurdy@netl.doe.gov or 412-386-4533)
PSU – Ken Davis (kjd10@psu.edu or 814-863-8601)

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