A new study, led jointly by University College London and Tsinghua University has provided the first global inventory of abandoned oil and gas wells and their associated methane emissions, addressing a significant gap in current climate data.
While previous research focused on national or regional methane estimates for specific years, this work delivers a broader, more comprehensive picture, crucial for accurately assessing historical emissions and informing mitigation strategies.
The research took in 4.5 million abandoned wells across 127 countries, finding that in 2022, global well emissions totalled 400,000 tonnes of methane, 98% of which was emitted by just ten countries – 70% from the USA alone.
90% of these emissions were found to be coming from unplugged wells.
The team also raise concerns about offshore ‘super-emitter’ wells, where emissions can be up to 11 times higher than onshore wells due to easier gas transfer from water to air.
The UK and the Netherlands host long-standing super-emitter wells in the North Sea, where the team say high-integrity plugging and transparency in reporting are urgently needed. Developing countries in Asia and Africa also face growing well challenges, compounded by the historic operations of multinational oil firms.
The challenge of incomplete records is exemplified in Romania, where detailed data is available for just 57 out of an estimated 60,000 wells.
The team also estimated the historical release of methane from abandoned wells, dating back decades. Using the detailed sample of 420,000 wells, they calculated that cumulative global emissions to be in the range of 11.2 to 12.6 million tonnes of methane as of 2022. These emissions occurred gradually, often undetected and unrecorded in official greenhouse gas inventories.
Prof. Dabo Guan from Tsinghua University explains the importance of this work: ‘Methane is short-lived in the atmosphere – only about a decade – but its warming power is intense. That’s why sustained emissions from sources like abandoned wells matter: they can maintain a persistent near-term warming pressure that is often overlooked in official inventories and policy frameworks.’
UCL’s Dr. Tianyang Lei added: ‘This is the first time the world has a comprehensive map of where these forgotten wells are, how much methane they release, and what we can do about it. Many of these wells have been leaking unnoticed for decades.’
The research found that the average length of time between a well being decommissioned and being plugged is 22 years, leading the team to calculate that earlier action would prevent 1.6 million tonnes of methane from being released between 2023 and 2050.
Prof. Guan said: ‘We’re in a decade that demands fast-acting mitigation. If we want to slow warming quickly, methane is the lever – and abandoned wells are a place we can pull that lever right now.’
The team call for action on both the high-risk wells – such as those that remain unplugged or are offshore – and the 2.5 million ‘orphan’ wells around the world without responsible operators or proper documentation.
Key to effective action is the development of high-integrity plugging standards to ensure the wells are completely sealed.
The study identifies technologies such as satellite monitoring, AI-based detection drone inspections as tools to collect data accurately.
Dr. Lei says: ‘Abandoned oil and gas wells are out of sight – but they don’t have to be out of control. With the right data and fast action, we can turn these overlooked sources into fast wins for the climate.’
The full research can be downloaded as a PDF here.
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