Abstract
Natural gas comprises almost one-fourth of all energy used in the U.S. with growing importance in the global energy mix. New production techniques, including those involving hydraulic fracturing, have enabled access to expanded energy resources and to increased natural gas based power generation, which has been credited with reducing greenhouse gas emissions in the U.S. However, in 2011, the U.S. Environmental Protection Agency introduced new calculation methods for gas wells - based on limited data - causing calculated emissions from natural gas systems to more than double in the U.S. national greenhouse gas inventories for 2009 and 2010 (submitted to the United Nations in 2011 and 2012 respectively).
To provide better data about natural gas systems, the American Petroleum Institute (API), in collaboration with America’s Natural Gas Alliance (ANGA), undertook a survey of U.S. natural gas production companies resulting in a rich data base from over 90,000 natural gas wells widely distributed among different producing regions in the U.S. This paper analyzes key findings of the API/ANGA study regarding methane sources pivotal to EPA’s assessment, including completions, workovers and gas well liquids unloading operations.
While the API/ANGA findings indicate significant potential overestimations in EPA’s assessment, they also confirm the importance of understanding the key activities and conversion factors that impact the estimation of methane emissions from natural gas production. Although improving the greenhouse gas emission estimation methods may take time, a more nuanced analysis is essential for informing public debate and facilitating decisions on natural gas use and its role in mitigating overall greenhouse gas emissions.
