Abstract
Recent research suggests that important emission estimates used to populate bottom-up
methane (CH4) inventories may be missing or incorrect. Methane is a powerful greenhouse gas
and the largest component of natural gas. The most recent Greenhouse Gas inventories include
emissions from plugged and unplugged abandoned oil and gas wells, where emissions are
calculated from measurement of CH4 emissions from mainly historic wells on the east coast of
the US. Literature suggests the average emission from plugged wells in the US and Canada is 1.6
g CH4 h-1, and 7.5 g CH4 h-1 from unplugged. To investigate if these emission factors could be used
to generate representative emission estimates from abandoned wells in Colorado, we measured
CH4 emissions from 128 plugged and 206 unplugged abandoned wells in 17 counties and from 63
oil and gas fields in Colorado. Results show zero CH4 emissions from all plugged wells observed
and plugging remains effective for at least fifty years after the well has been sealed and covered
in soil. The average CH4 emission from an unplugged and abandoned wells in Colorado is 586 g
CH4 h-1, over 70 times higher than the national average and with most emissions resulting from
wells stranded by the recent removal of a gathering line instead of neglect of very old oil and gas
wells. Emissions follow a heavily left-skewed long-tailed emission distribution typically seen by
other oil and gas emission surveys, with 39% of unplugged wells not emitting. Statistical analysis
indicates that emission is uncorrelated to well characteristics and 88% of the total emission from
abandoned wells in Colorado are from a 20 x 20-mile area. Findings of this study suggest that
newly abandoned oil and gas wells present a greater environmental and safety risk than historic
wells with the largest observed emitter 200 times larger than the highest high emitting wells on
the East coast. As a result, recently producing and abandoned wells should be considered as a
priority for both screening and remediation.
methane (CH4) inventories may be missing or incorrect. Methane is a powerful greenhouse gas
and the largest component of natural gas. The most recent Greenhouse Gas inventories include
emissions from plugged and unplugged abandoned oil and gas wells, where emissions are
calculated from measurement of CH4 emissions from mainly historic wells on the east coast of
the US. Literature suggests the average emission from plugged wells in the US and Canada is 1.6
g CH4 h-1, and 7.5 g CH4 h-1 from unplugged. To investigate if these emission factors could be used
to generate representative emission estimates from abandoned wells in Colorado, we measured
CH4 emissions from 128 plugged and 206 unplugged abandoned wells in 17 counties and from 63
oil and gas fields in Colorado. Results show zero CH4 emissions from all plugged wells observed
and plugging remains effective for at least fifty years after the well has been sealed and covered
in soil. The average CH4 emission from an unplugged and abandoned wells in Colorado is 586 g
CH4 h-1, over 70 times higher than the national average and with most emissions resulting from
wells stranded by the recent removal of a gathering line instead of neglect of very old oil and gas
wells. Emissions follow a heavily left-skewed long-tailed emission distribution typically seen by
other oil and gas emission surveys, with 39% of unplugged wells not emitting. Statistical analysis
indicates that emission is uncorrelated to well characteristics and 88% of the total emission from
abandoned wells in Colorado are from a 20 x 20-mile area. Findings of this study suggest that
newly abandoned oil and gas wells present a greater environmental and safety risk than historic
wells with the largest observed emitter 200 times larger than the highest high emitting wells on
the East coast. As a result, recently producing and abandoned wells should be considered as a
priority for both screening and remediation.
| Original language | English |
|---|---|
| Publication status | Published - 2023 |