Methane Mitigation of End-of-Life Oil and Gas Wells

The global oil and gas industry is estimated to contribute over 80 million metric tons of methane annually, or about one-fifth of global methane emissions. Of this, about 10% of emissions come from oil and gas wells near or past the end of their productive lives, though this figure is widely uncertain. All estimates put the number of end-of-life (EOL) wells that haven’t been decommissioned in the U.S. in the millions. Permanently plugging and abandoning (P&A) these wells, a process that involves sealing the wellbore with cement and mechanical plugs, removing surface equipment, and remediating the surrounding environment, is the only currently widely accepted decommissioning solution. However, P&A is costly, slow, and complicated by unclear ownership and weak incentives. In the meantime, millions of tons of methane and other pollutants continue to leak from aging wellheads, casings, and surface equipment across the U.S., adding to the climate challenge as well as posing environmental and health risks to nearby communities. Accelerating the decommissioning of the leakiest or most at-risk wells is one of the most actionable near-term opportunities in methane mitigation.

End-of-Life (EOL) wells that are low-producing, idled, abandoned, or orphaned have a high risk of emitting substantial amounts of methane when left unplugged.

Timeline

investigation

Research the obstacles and incentives that lead to wells being unplugged at the end of their lives. Research methane measurement and mitigation technologies

investigation

Scope the landscape of carbon crediting methodologies targeting EOL wells

implementation

Collaborate with registries, project developers and buyers to build trust in high integrity methodologies

investigation

Evaluate detection and measurement techniques for emissions from EOL wells and surface equipment. Assess the performance and cost effectiveness of mitigation options under different well conditions and geographies

implementation

Develop practical guidance to help operators and regulators prioritize abatement actions

Currently

Project Impact

The Carbon Containment Lab is working to build the evidence base needed to drive and support faster, more cost-effective, and higher integrity methane mitigation for end-of-life oil and gas wells.

End-of-life oil and gas wells emissions follow a heavy-tailed distribution: a small fraction of wells account for the vast majority of the problem. Identifying and acting on those highest-emitting wells could deliver well over 130 million metric tons of CO₂e reductions annually, at relatively low cost and with immediate near-term climate impact.

A significant share of this problem traces to abandoned and orphaned oil and gas (AOOG) wells. Abandoned wells are non-producing assets with a solvent operator that may or may not be plugged; orphaned wells go a step further, with no known owner or solvent operator, leaving plugging responsibilities to the state by default. Many orphaned wells are also "undocumented," meaning their locations, ownership statuses, and production histories are unknown. There are at least 120,000 documented orphaned wells in the United States and Canada, but the true number is likely far higher; some studies suggest regional databases undercount these wells by a factor of ten. These wells are scattered across public, private, and tribal lands, and over 4.6 million Americans live within one kilometer of a documented orphaned well. Existing regulations were designed to prevent wells from reaching this state, but financial assurance requirements have proven chronically inadequate, and government plugging programs face decades-long backlogs.

The problem extends beyond orphaned wells. Over 575,000 wells in the United States are classified as marginal; they produce at or less than 15 barrels of oil equivalent (BOE) per day and have a known owner and solvent operator. Also known as stripper wells, these assets are operated at the edge of profitability and make up three-quarters of all active US oil and gas producing wells. Despite contributing only about 5 percent of total US oil and gas production, marginal wells are estimated to account for roughly half of all oil and gas well-site methane emissions. Their small production volumes make their operations highly emissions-intensive, and their sheer numbers make them difficult to monitor and regulate.

Map of documented orphaned wells, reproduced from Plugging orphan wells across the United States | Environmental Defense Fund.

Leak Detection and Quantification

With hundreds of thousands of marginal and orphaned wells scattered across the country, not all can be addressed at once. Targeting investment where it delivers the greatest climate benefit means finding the highest emitters first. A range of technologies exist for this purpose, from handheld optical gas imaging cameras and ground-based sensors to aerial surveys and satellite-based detection, each with distinct trade-offs in sensitivity, spatial coverage, cost, and ease of deployment.

Methane emissions from individual wells are highly variable, intermittent, and sensitive to subsurface conditions that change over time. A single snapshot measurement may not reflect a well's true average emission rate. Funders, credit buyers, and regulators all need confidence that the well being targeted is genuinely among the worst emitters, and that the benefit of plugging it can be robustly quantified. Closing the gap between what detection technologies can see and what quantification methods can reliably measure is a central focus of this project.

Project Considerations

Funding and Institutional Fragmentation

Responsibility for end-of-life well management is split across federal agencies, state regulators, tribal governments, and private operators, with overlapping mandates and chronically insufficient funding. The $4.7 billion allocated (of which, $1.5 billion has been disbursed) under the 2021 Infrastructure Investment and Jobs Act was an unprecedented federal commitment, but is estimated to cover only a fraction of documented orphaned wells. In most states, operator bonding requirements fall well short of actual plugging costs, meaning the gap between the scale of the problem and the pace of the response is likely to keep widening without more robust funding mechanisms.

Methodology Baselines and Measurement Uncertainty

Estimating the climate benefit of plugging a well requires a credible baseline, a science backed calculation of how much methane would have continued to leak if nothing had been done. But emissions from individual wells are highly variable, intermittent, and influenced by subsurface conditions that shift over time. Existing voluntary carbon market methodologies take meaningfully different approaches to this challenge, applying different measurement techniques and assumptions about how leak rates change over the crediting period. There is currently no consensus on which approach is most accurate, and resolving these uncertainties will be essential to ensuring that credited emissions reductions reflect real-world climate benefits.

Variability in Plugging Costs

Plugging costs vary from several thousands of dollars for a shallow, accessible well to hundreds of thousands or more for one that is deep, deteriorated, or remotely located. Wellbore geometry, depth, casing condition, surface accessibility, and the presence of hazardous gases all influence the complexity and cost of a plugging job. Surrounding environmental remediation adds significantly to the cost burden.

Repurposing of Wells

A growing body of research supports the potential for repurposing decommissioned wellbores for beneficial uses, including geothermal energy production and subsurface carbon storage, which could offset plugging costs. However, technical and economic feasibility varies significantly by well type, location, and subsurface geology, and most pathways remain at an early stage of development. There is also a risk that the prospect of future repurposing, including re-drilling using modern techniques like fracking, could delay proper plugging, underscoring the need for stopgap measures to reduce interim emissions.

Rate of Plugging

While the physical plugging operation itself takes just a few days to a week, it must be preceded by well condition assessments, regulatory plan approval, contractor procurement, and the safe resolution of any wellbore hazards such as radioactive material, pressurized gases, or deteriorated casing. This long lead time means that identified high-emitting wells can continue leaking for months or years while awaiting action, underscoring the potential value of interim stopgap measures that can reduce emissions while the full P&A process works its way through the queue.

Ownership Uncertainty and Mineral Rights

Before a well can be plugged or its emissions reductions credited, it must be clear who holds the legal rights and responsibilities associated with it, and for orphaned and abandoned wells this is rarely straightforward, as surface rights, mineral rights, and pore space rights may be held by different parties under agreements that are incomplete, outdated, or disputed. In the U.S., mineral rights and surface rights are frequently severed, and on tribal lands the complexity compounds further. Overlaid on this is the still-unsettled question of who holds the "carbon rights" to emissions reductions generated by plugging, a question neither the U.S. nor Canada has resolved in law, creating legal uncertainty that can slow or deter investment in plugging projects altogether.

Partner with us

Your full name ^*

Your email address ^*

Area of Expertise ^*

Your message