Consistent Metrics Needed for Quantifying Methane Emissions from Upstream Oil and Gas Operations
David T. Allen, Qining Chen, Jennifer B. Dunn
Abstract
Methane emissions from oil and natural gas sources are often characterized as a methane emissions intensity, which is typically defined as methane emissions divided by natural gas production. Reporting methane emission intensities implicitly assigns all methane emissions from production activities to natural gas, but many of the regions that supply large amounts of natural gas to world markets simultaneously produce natural gas, natural gas liquids, and oil. The importance of whether methane and other greenhouse gas emissions from production activities are allocated to natural gas alone or to multiple products was examined using data from the Eagle Ford Shale production region in south central Texas. In the Eagle Ford, differences in emission allocation methods can produce differences in estimated emissions of 50–110 g CO2e/MJ of natural gas. This is comparable to the difference in combustion emissions between coal and natural gas.