Orphaned Well Credits After ACR: How Isometric Changes the Count

At a Glance · Orphaned Well Credits

Plugging an orphaned well that is leaking methane is among the more clearly additional activities in the voluntary market, since public funding covers only part of the wells that need plugging and no owner remains to pay for the rest. The weakness has been in the quantification: ACR v1.0, under which most credits were issued, averaged two short measurements, held the result flat for 20 years and allowed all 20 years to be issued in the year the well was plugged, and developers have attributed ACR’s decision to pause it in May 2025 to concerns about over-crediting, although ACR itself cited the need for requirements that apply consistently across sites.

Isometric’s protocol addresses most of that design, by counting the lower of two measurements, applying a decline after ten years and issuing after verification, and on Climate Decode’s calculation it credits the same well at 78% to 84% of the ACR total. It is nonetheless not the most conservative approach in the market, since the Open Carbon Protocol applies a decline from the first year, and Isometric’s ten-year plateau rests on the assumption that the corrosion of the wellhead offsets the depletion of the reservoir, which field data has yet to confirm.

The market will accordingly hold credits from the same activity issued to different standards of integrity, as REDD+ and cookstoves already do, and buyers should treat the methodology version, the measurement record and the issuance schedule of each credit as part of the purchase decision, alongside the project type.

RMI’s technical explainer of March 2026 counts at least 120,000 documented orphaned wells in the United States and Canada, and estimates that undocumented wells may number about ten times as many. The Infrastructure Investment and Jobs Act set aside US$4.7 billion for states to plug orphaned wells to 2030, of which about US$1.5 billion had been disbursed and 10,257 wells plugged by June 2025, and researchers expect plugging costs to exceed that funding by 30% to 80%, which is the gap that carbon credits are intended to fill.¹

ACR has issued the largest share of orphaned well credits, about 4.9 million of the 8.3 million issued across all standards on RMI’s count, and it inactivated its Plugging Orphaned Oil and Gas Wells methodology, version 1.0, on 9 May 2025, stating that its requirements needed to apply consistently and appropriately across diverse sites and wells, while allowing projects whose measurement method it had already approved to complete verification under version 1.0.^1,2 Developers told Quantum in October 2025 that the methodology had been shelved over concerns about over-crediting, and version 2.0, which ACR planned to publish in 2026 after public comment and scientific peer review, had not been published at the time of writing.^3,4

Table 1 · ACR orphaned well plugging projects, credits retired and still available. Source: Climate Decode Canopy Market Watch registry data, ACR, as at August 2026.

Of the 1.1 Mt retired, Climate Decode’s registry data records 587,359 credits retired in the name of Tradewater, a developer, and the largest corporate retirements by Workday at 181,829, Morgan Stanley at 80,000, Marsh & McLennan at 65,500 and Maple Leaf Foods at 34,357, across 113 retiring account names in all.¹² The three Heartland projects in Oklahoma hold about 3.8 Mt of the 4.7 Mt still available, such that most of the unsold stock was issued under the inactive methodology to a single group of projects and has scarcely been retired.

Isometric opened its Orphaned Well Plugging Protocol, version 1.0, for public consultation on 15 October 2026, covering onshore orphaned oil and gas wells in the United States and Canada.^6,7 The two methodologies credit the same activity, although they differ in almost every rule that determines the number of credits.

Table 2 · The two methodologies compared. Sources: ACR, Plugging Orphaned Oil and Gas Wells v1.0 and errata, June 2025; Isometric, Orphaned Well Plugging Protocol v1.0, October 2026.

The baseline accounts for most of the difference in volume. ACR multiplied the mean of the two measurements by 20 years, whereas Isometric holds the measured rate for ten years, on the assumption that the depletion of the reservoir and the corrosion of the wellhead roughly offset each other, and applies a decline thereafter, such that on Climate Decode’s calculation the same measured rate yields 78% to 84% of the ACR total at Isometric’s default decline rates and 84% to 88% where reservoir evidence supports the lower rates.^5,6 Since Isometric also credits the lower of its two measurements where ACR took the mean, the reduction for a well whose readings vary will be larger than the curve alone indicates.

Figure 1 · Credits for the same measured leak rate under each approach, as a share of the ACR v1.0 total; Climate Decode calculation on each methodology’s published baseline shape, excluding differences in measurement and deductions. Sources: ACR; Isometric; Payne Institute, June 2026.

The treatment of public funding is the second difference. ACR v1.0 required a regulatory surplus test and a performance standard that any eligible orphaned well passes, and set no rule for wells already funded or scheduled for plugging by government, whereas Isometric excludes wells on state funding lists by default and requires a financial additionality test for wells funded under the IIJA, which matters since regulators that prioritise high emitters will tend to fund the wells that would otherwise generate the most credits.^1,5,6

Climate Decode screens methane credits by methodology version, measurement record and issuance schedule, so credits of the same project type can be compared on one basis.

Isometric enters a field in which each standard has drawn the baseline differently, and the Payne Institute’s review of June 2026 sets out the range.⁸

Table 3 · Other orphaned well crediting approaches. Sources: Payne Institute, June 2026; Climate Action Reserve, October 2025.

The Payne Institute concludes that the haircuts across the active methodologies are likely, taken together, to keep total credits from overstating the climate benefit, although the timing of the avoided emissions remains the weak point, since methods based on expected emissions cannot show when a well would have leaked and may therefore overstate the near-term benefit.^8,9 Isometric’s option of annual issuance after verification addresses that problem most directly among the current standards, while its ten-year plateau places it above the Open Carbon Protocol on volume per well and below ACR v1.0 and CarbonPath.¹⁰

ACR’s version 2.0, the work of the Climate Action Reserve and any assessment by the ICVCM will determine whether a common standard emerges, and ACR’s wider position is covered in our ACR analysis.

Three risks remain under every methodology, the first being measurement, since emissions from orphaned wells vary with wellhead configuration, weather and time and are often intermittent, such that a reading taken over two or three hours can overstate or understate the rate that is then credited for 20 years, a risk that Isometric reduces by crediting the lower reading without removing it.¹

The second is the durability of the plug, since plugs can fail years after plugging through cement bond failure and geological, thermal or chemical stress, whereas RMI notes that current methodologies typically require one or two tests within 12 to 18 months of plugging.¹ The issuance schedule accordingly decides who carries that risk: under ACR v1.0 the buyer could hold a credit for 20 years of avoided methane from the year of plugging, whereas under Isometric part of the volume waits for a permanence check or is issued only as each year is verified.

The third is price, a US non-profit having relaunched its well plugging credits at US$7 a tonne in the week Isometric opened its protocol.¹¹ In Climate Decode’s view, the experience of REDD+ suggests that credits issued under a superseded methodology will trade at a discount once a stricter alternative is available.

Four developments will determine how the market prices orphaned well credits:

1. Whether ACR’s version 2.0 adopts a declining baseline and staged issuance, and how ACR treats the 4.7 Mt issued under version 1.0 that remains available.
2. The outcome of Isometric’s consultation, in particular the evidence it accepts for the ten-year plateau and the lower decline rates.
3. Any assessment of a well plugging methodology by the ICVCM, without which none of these credits carries the CCP label.
4. Whether buyers distinguish credits by methodology version and issuance schedule, given the scrutiny on legacy credits described in our analysis of the CFTC inquiry.

Buyers should accordingly request the measurement record of each well, the methodology version and the share of credits issued before a permanence check, and should price ACR version 1.0 stock against the volume the same wells would earn under a declining baseline.

Climate Decode Platform

The registry figures in this analysis come from Canopy Market Watch, which tracks issuance, retirements and buyers across ten registries.

Climate Decode · Advisory

Buying, or developing, methane credits

Climate Decode compares methodologies on volume, risk and buyer acceptance, and screens credits by version, measurement and issuance schedule.

Notes

Sources

Isometric’s protocol is described as opened for consultation and may change. The comparison in Figure 1 is a Climate Decode calculation on each methodology’s baseline shape for the same measured rate, and excludes differences in measurement and deductions.