Orphaned oil and gas wells are abandoned wells for which the cost of environmental impacts usually falls on governments and the general public. Government agencies responsible for well plugging often face funding shortfalls and many orphaned wells remain unplugged. To address this and support the oil and natural gas industry, federal governments are already spending, or considering spending, billions of dollars to plug orphaned oil and gas wells. Here, we analyze oil and gas data for the United States and Canada and identify policy recommendations that can best address environmental impacts of abandoned and orphaned wells. At least 116,245 wells across 32 states and four Canadian provinces/territories are operated by companies filing for bankruptcy in the first half of 2020, which may be an indication that many wells will be orphaned in the near future. Moreover, there are 4,700,000 historic and active oil and gas wells in the United States and another 790,000 in Canada. Of these, 2,000,000 and 310,000 wells are active in the United States and Canada, respectively. Thus, three of five wells ever drilled in the United States are currently inactive (2,700,000 wells), but only one in three are plugged (1,500,000 wells). Plugging involves isolating zones containing oil, gas, and water and is the main strategy for well abandonment. If the orphaned well stimulus funding comes through, tens of thousands of wells will be plugged within a few years. Well plugging at this scale far exceeds current rates of plugging, and it is important that we work to ensure long-term environmental benefits of well abandonment to water, air, climate, ecosystems, and human health. Minimizing environmental impacts of the millions of abandoned and orphaned wells in the United States, Canada, and abroad will allow for an economically beneficial and environmentally safe transition to a carbon-neutral economy.

Orphaned oil and gas wells are unplugged nonproducing wells with no solvent owner of record to plug and mitigate them, such that the responsibility often falls on government agencies and the general public. Unplugged wells pose risks to the environment, climate, and human health. To develop a national framework to quantify the environmental benefits of plugging and optimize mitigation, we analyze oil and gas well data from state agencies across the United States to estimate the number of documented orphaned wells over time and evaluate their attributes. We find at least 81,857 documented orphaned wells as of September 2021 and 123,318 as of April 2022, representing 2% and 3%, respectively, of all estimated abandoned wells in the United States. We identify at least 20,286 potentially documented orphaned wells as of September 2021 (0.5% of all estimated abandoned wells in the country), of which 8% became documented orphaned wells as of April 2022. We estimate annual methane emissions to average 0.016 ± 0.001 MMt of CH 4 for the 123,318 documented orphaned wells as of April 2022, corresponding to 5−6% of the total methane emissions estimated by the U.S. EPA for all abandoned wells. Although well type (i.e., oil vs gas) is generally available (83% of the 81,857 documented orphaned wells as of September 2021), only 49% and 16% of the wells have information on depth and last production date, respectively. Overall, documented orphaned wells and their attributes, including location, well type, depth, and last production date, require additional characterization and studies to constrain the uncertainties. Nevertheless, our identification and analysis of documented orphaned wells represent the first steps toward characterizing the full set of wells eligible to be plugged and remediated with the federal funding available in the U.S. via the Infrastructure Investment and Jobs Act. Our results can also be useful for the management of the hundreds of thousands, potentially a million, undocumented orphaned wells likely to exist across the nation.

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.

&lt;p&gt;Millions of oil and gas wells are abandoned and orphaned in Canada and the United States. These well sites can be repurposed for wind and solar energy, while the wells access itself can be redeveloped for geothermal energy production. To identify opportunities for repurposing abandoned and orphaned wells and well sites for renewable energy development, we analyze public oil and gas well data from state, provincial, and territorial agencies to estimate the number and geospatial distribution of abandoned and orphaned wells in Canada and the United States. As of March 2022, we identify 4,724 orphaned wells and 420,113 abandoned wells in Canada and identify 123,318 orphaned wells (as of March 2022) and 3,151,700 abandoned wells (as of August 2022) in the United States. Using this dataset, we analyze geographic locations of abandoned and orphaned wells with national maps of renewable energy potential (geothermal, wind, and solar) and land cover/land use in Canada and the United States. We then evaluate how the potential to repurpose wells/well sites vary across Canada and the United States. Due to funding shortfalls, many abandoned and orphaned wells remain unplugged and are negatively impacting the environment and contributing to greenhouse gas emissions. Repurposing wells and well sites can provide an additional funding stream to manage the millions of abandoned and orphaned wells around the world.&lt;/p&gt;

&lt;p&gt;Measurements have shown that abandoned oil and gas wells emit methane to the atmosphere, but the estimates of methane emissions at the national scales remain highly uncertain. Here, we provide an overview of available measurement data and studies investigating factors linked to high methane-emitting abandoned wells. We then analyze abandoned oil and gas well data in Canada and the United States to estimate methane emissions for both countries and evaluate uncertainties in the national estimates. Available measurement data indicate that average methane emission rates used as emission factors vary by 3 orders of magnitude or more, even after accounting for plugging status. Plugging status has been shown to be an important predictor of high methane emitting wells; however, there may be other important factors such as age, depth, fluid type and geographical region. Such well attribute data are not consistently available for many abandoned and orphaned oil and gas wells in Canada and the United States. Overall, there is a need for additional measurements of methane emissions from abandoned oil and gas wells and compilation of well attributes to reduce uncertainties in national estimates.&lt;/p&gt;