Across North America, orphaned oil and gas wells represent a serious and growing climate risk. These unplugged, often-forgotten wells can leak methane into the atmosphere for years—or decades—without oversight or monitoring. Carbon finance offers a powerful opportunity to accelerate their cleanup, reduce emissions, and create jobs in rural energy communities.

But as more orphan well projects enter the voluntary carbon market, it’s essential that the methodologies used to credit them are grounded in real-world behavior, and are capable of holding up to public, scientific, and regulatory scrutiny.

This blog outlines the core challenges in current orphan well crediting methodologies, and offers a constructive path forward: one that improves confidence in credit quality, supports high-integrity project development, and builds long-term trust in this promising market.

Editor’s Note:
The American Carbon Registry (ACR) has recently suspended its orphan well methodology and is undertaking a full revision. We view this as a constructive step that shows registries are taking these challenges seriously.

However, similar measurement and baseline issues persist in orphan well methodologies across other registries as well. This is a broader methodological challenge—and a valuable opportunity for cross-registry improvement.

The Central Challenge: Measurement and Baseline Integrity

Methane leakage from orphan wells is unpredictable. Some wells emit small amounts intermittently; others leak heavily due to degraded seals, corroded casing, or soil saturation. It’s a stochastic process—highly sensitive to local geology, infrastructure condition, and time.

Most current methodologies allow two distinct measurement pathways. Each was designed with practical constraints in mind—but both present significant limitations:

1. The Chamber Method

This approach involves taking two direct methane measurements, spaced 30 days apart, to confirm a consistent leak rate. That leak rate is then extrapolated over a 20-year baseline scenario—crediting the project for avoiding decades of emissions at that same rate.

While this method includes some empirical validation, it still makes a large assumption: that a leak observed over one month will continue unchanged for 20 years.

But orphan well leakage is not static. It varies with subsurface pressure, seal integrity, corrosion, and temperature. Two brief observations cannot capture this complexity. It’s like trying to predict annual rainfall based on two sunny afternoons—directionally useful, but far too narrow to be reliable.

2. The Non-Chamber Method

This alternative is designed for safety but introduces even more uncertainty. Here’s how it works:

• A project developer confirms that a well is leaking (even minimally),
  
  
• Notes that high pressure levels within the well make it “unsafe to measure” directly,
  
  
• Immediately vents (blows down) and secures the well,
  
  
• Then uses a formula—based on annular pressure readings—to model the leak rate.
  
  

This formula can produce extremely high emissions estimates without measuring methane flow directly. In practice, some projects have been credited with avoiding millions of tons of CO₂e from wells that were emitting only trace amounts.

This isn’t about developer intent—it’s a function of methodology design. And while safety is paramount, it shouldn’t come at the expense of scientific rigor or public trust.

What About Using Decline Curves as Proxies?

Some institutions have proposed using terminal production decline rates as a proxy to estimate methane leakage over time. The idea is that leakage might follow the same gentle decline seen in the final years of a well’s productive life.

While the concept is intuitively appealing, there is currently no empirical evidence that supports a direct relationship between production decline and post-abandonment leakage. Production is a function of engineered flow systems and active pumping; leakage, by contrast, is driven by equipment failure, corrosion, and unpredictable subsurface behavior. Using one to model the other risks reinforcing the very issue we aim to fix: building baselines on assumption rather than observation.

A Constructive Solution: Control Group–Based Baselines

There’s a straightforward way to address these uncertainties: establish baselines using real-world comparison groups.

Rather than extrapolating from two data points—or relying on pressure-based estimations—projects could use a control group of unmanaged orphan wells in the same region and condition. Project developers use all available funding to plug every well that they can. But wells they cannot afford to plug would be monitored independently to track natural leakage and plugging trends over time.

This approach offers several key advantages:

• Realism: It reflects what orphan wells actually do—not what we assume they might do.
  
  
• Credibility: It replaces hypothetical counterfactuals with observable evidence.
  
  
• Fairness: It allows crediting to reflect true impact, while still supporting safety-first remediation.
  
  

Control group–based baselines are used successfully in other project categories, including cookstoves, forestry, and energy efficiency. There’s no reason orphan well projects—particularly those seeking long-term crediting for hard-to-predict emissions—shouldn’t benefit from the same rigor.

‍

Integrity Isn’t the Only Barrier—Scalability Remains a Structural Challenge

While improved baselines would meaningfully increase the integrity of orphan well crediting, they don’t address the deeper issue of scalability.

Yes, there are over 300,000 documented orphan wells in the U.S. alone. But only a small fraction of those are leaking enough methane to generate sufficient credits to cover the cost of plugging, monitoring, and verification.

And here’s the paradox:

• If a well is leaking heavily, it might be profitable as a carbon project—but it’s also more likely to be prioritized by state agencies or public funding programs.
  
  
• If a well is leaking only slightly, it may escape regulatory attention—but the credit revenues won’t come close to covering costs.
  
  

This creates a Goldilocks problem for developers: The well has to be leaking enough to generate credits, but not so much that a public agency intervenes.

This lends itself to a narrow, competitive window of opportunity—where developers are increasingly targeting the same high-emitting wells that regulators are also focused on. That introduces risks of duplication, unclear attribution, and limited room for meaningful market growth.

In short, even with perfect methodology, orphan well credits may remain a high-impact but niche solution, rather than a broadly scalable one.

What’s Next: Building a More Durable Carbon Market

Improving orphan well methodologies by:

• Reducing reliance on spot or proxy-based modeling,
  
  
• Using control groups to quantify baselines more credibly,
  
  
• And aligning better with public cleanup programs,
  
  

…would allow carbon finance to play a more confident and constructive role in methane mitigation.

At ClimateWells, we believe orphan well plugging deserves a place in the carbon market. But we also believe market design must match the realities of emissions behavior, public policy, and economic feasibility. Getting that right—together—will be critical to the future of climate finance.

Let’s raise the bar, and build a system that rewards what matters most: real, additional, measurable impact.

‍