Environmental risks and opportunities of orphaned oil and gas wells in the United States

Abstract

Hundreds of thousands of documented and undocumented orphaned oil and gas wells exist in the United States (U.S.). These wells have the potential to contaminate water supplies, degrade ecosystems, and emit methane and other air pollutants. Thus, orphaned wells present risks to climate stability and to environmental and human health, which can be reduced by plugging. To quantify environmental risks and opportunities of well plugging at the national level, we analyze data on 81 857 documented orphaned wells across the U.S. We find that > 4.6 million people live within 1 km of a documented orphaned well. 35% of the documented orphaned wells are located within 1 km of a domestic groundwater well, yet only 8% of the wells have groundwater quality data within a 1 km radius. Methane emissions from the documented orphaned wells represent approximately 3%–6% of total U.S. methane emissions from abandoned oil and gas wells, but this estimate is based on measurements at < 0.03% of U.S. abandoned wells. 91% of the documented orphaned wells overlie formations favorable for geologic storage of carbon dioxide and hydrogen, meaning that orphaned well plugging can reduce leakage risks from future storage projects. Finally, we estimate plugging costs for documented orphaned wells to exceed the $4.7 billion federal funding by 30%–80%, emphasizing the importance of prioritizing federal spending on wells with large remediation benefits. Overall, environmental monitoring data are not extensive enough to quantify risks, especially those related to air and water quality and human health. Plugging orphaned wells can provide opportunities for geologic storage of carbon dioxide and hydrogen and geothermal energy development, thereby facilitating efforts to transition to net-zero energy systems. Our analysis on environmental risks and opportunities of orphaned wells provides a framework that can be used to manage the millions of documented and undocumented orphaned wells in the U.S. and abroad.

Methane Emissions from Abandoned Oil and Gas Wells in Alberta and Saskatchewan, Canada: The Role of Surface Casing Vent Flows

“…Importantly, if the fluids from the surface casing vents do not become methane emissions to the atmosphere, they may be migrating in the subsurface and impacting groundwater instead . At the same time, groundwater monitoring is not comprehensive enough to identify contamination due to leaky wells …”

“…Therefore, focusing plugging and remediation efforts on wells with high methane emissions may leave wells with subsurface leakage unplugged. This is a concern since there are voluntary carbon credit methodologies and federal programs focused on plugging to mitigate methane emissions from abandoned oil and gas wells in Canada and the U.S. − …”

“…31 At the same time, groundwater monitoring is not comprehensive enough to identify contamination due to leaky wells. 32 Plugging Alone May Not Sufficiently Protect Groundwater. We found that low non-surface casing vent emissions often correspond to high surface casing vent emissions and possibly subsurface leakage and groundwater contamination.…”

“…Once plugged, subsurface leakage via the annulus may go unchecked leading to persistent groundwater impacts, emissions to the atmosphere, or other environmental risks such as explosive hazards. 7,16,37−40 Therefore, without careful consideration of all well integrity issues and subsurface leakage potential, the $4.7-billion orphaned well plugging program in the U.S., a part of the Bipartisan Infrastructure Law, 32,33…”

Methane Emissions from Non-producing Oil and Gas Wells and the Potential Role of Seismic Activity: A Case Study in Northeast British Columbia, Canada

“…Oil and gas wells pose a variety of environmental risks, including groundwater contamination and emissions of methane and other air pollutants. − Methane is a potent greenhouse gas with a global warming potential 83 times that of carbon dioxide over a 20 year time frame . Fugitive methane emissions occur at producing and non-producing wells. − Methane emissions from over 370,000 to 470,000 non-producing wells in Canada have been found to be underestimated by a factor of 2.5 in Canada’s national inventory report (NIR) of greenhouse gas emissions and remain uncertain. , Methane emissions from the oil and gas sector is a key target in Canada’s 2030 Emissions Reduction Plan and Canada’s approach to meeting the commitments in the Global Methane Pledge .…”