|Measurements and Modeling to Quantify Emissions of Methane and VOCs from Shale Gas Operations
||Last Reviewed 6/22/2015
The goals of this project are to determine the leakage rates of methane and ozone-forming volatile organic carbons (VOCs) and the emission rates of air toxics from Marcellus shale gas activities at a process level. Methane emissions in the Marcellus Shale region shall be differentiated between “newer” sources associated with shale gas development and “older” sources associated with coal or conventional natural gas exploration.
Carnegie Mellon University, Pittsburgh, PA 15213
The extensive development of shale gas exploration and production in the Marcellus region has caused concern about potential environmental impacts on water resources, land, and the atmosphere. The overall effects of shale gas development have not been extensively characterized, including the nature and magnitude of the following pollutant emissions:
- Fugitive releases such as methane and/or VOC leaks at the well head, compressor stations, or gas processing facilities
- Emissions associated with support equipment such as drilling rigs or diesel trucks that service gas wells
- Emissions associated with active venting or well completion
- Discharges or migration of process water used in hydraulic fracturing
- Evaporation of additives used in hydraulic fracturing fluid from holding ponds
Emission and leak rates of methane and other gases from shale gas activities are in many cases estimated rather than directly measured. Quantifying the magnitude of these emissions and understanding their sources at a process level is important to ensure industrial compliance with regulatory agencies, promote public health, and improve public understanding of the risks associated with the shale gas industry. The magnitude of methane emissions from Marcellus shale gas operations should be compared to other possible sources of fugitive methane such as landfills, agricultural sources, abandoned coal mines, and gas wells. Quantifying the methane emissions from other regional sources will aid in understanding the net influence of shale gas operations on methane emissions.
The project will directly address uncertainties in the emissions of methane and other VOCs from shale gas operations. Analysis of direct emission rates will improve overall understanding of how shale gas development affects air quality. The analyses of methane, VOCs, and other air toxics will improve the characterization of air emissions across the spectrum of technologies and processes used in the Marcellus Shale region. Project results will help determine how fugitive emissions vary based on different technologies (i.e., “green” versus standard well completions) and if emissions vary with the age of the facility. The project will therefore provide a dataset of emission rates for use in lifecycle analyses, chemical transport models, and policy decision-making.
Accomplishments (most recent listed first)
Project results were presented at the American Geophysical Union annual meeting on December 15, 2014.
Researchers have performed sampling at 31 facilities with tracer testing. Methane emissions at producing wells were estimated at one percent of production levels. Emission measurements were highest at flowback stages than during production.
Researchers conducted calibration experiments of the tracer release technique to determine uncertainty bounds for the field measurements
Researchers conducted a literature search to compile existing data on methane emissions from traditional (non-shale) natural gas sources and shale gas operations and have begun to compile emissions data from non-gas sources of methane, including those from landfills and agriculture. Field measurements began in spring 2014. The tracer flux experiment utilizing the mobile laboratory has been planned for the spring at shale and non-shale sites. Measurements were also gathered from landfill locations.
Researchers sampled ten shale gas sites in Pennsylvania in collaboration with an industry partner. (Seven of the wells were producing and three wells were in the flowback stage.) Methane emissions were higher at flowback sites than at the producing wells. Future reports will normalize the methane emissions rates to total natural gas production at each site in order to determine the fractional leakage of methane. In addition, five conventional gas wells were sampled in West Virginia.
Researchers have contacted industry partners to identify specific unit operations at different stages of shale gas development and are arranging for on-site access to conduct direct measurements of methane emissions and tracer release experiments. A literature search of published emission rates of methane, ozone-forming VOCs, and air toxics from oil and gas activities will begin and include public data submitted to the Environmental Protection Agency or state agencies for regulatory purposes, and the resulting data will be published in the scientific literature. Researchers will obtain methane and VOC emissions data from industry partners.
Current Status (June 2015)
Seasonal sampling of wells continues in the spring and summer months. The team will be combining emission data with well population data in order to estimate emission contributions from shale and non-shale sources.
The team will sample active well and abandoned wells sites in Pennsylvania and study the results based on well age and seasonality. The latter will be tested by identifying five wells that will be sampled quarterly over the next year.
Project Start: 10/01/2013
Project End: 09/30/2016
DOE Contribution: $1,001,990
Performer Contribution: $250,498
NETL – Sandy McSurdy (email@example.com or 412-386-4533)
CMU – Albert Presto (firstname.lastname@example.org or 412-721-5203)