A global inventory of methane emissions from abandoned oil and gas wells and possible mitigation pathways.

Methane emissions from abandoned oil and gas (AOG) wells are significant but poorly quantified, contributing to uncertainties in global greenhouse gas inventories and hindering progress toward net-zero emission targets. In fact, the actual level of methane emissions from AOG wells worldwide and the geological characteristics of the wells remain poorly understood. Here, we develop a resource-type-specific, comprehensive inventory of methane emissions from 4.5 million AOG wells across 127 countries as of 2022, including detailed well-level data for 420 000 wells (9% of the total). We estimate global methane emissions from AOG wells at 0.4 Mt in 2022. Historical cumulative emissions are estimated at 11.2-12.6 Mt, of which 90% originate from unplugged wells. Over the period 2023-50, methane emissions from the AOG wells included in our inventory are projected to be 9.9 Mt in the absence of any decarbonization intervention (slightly higher than Spain's annual greenhouse gas emissions in 2019). Plugging abandoned wells is critical to reducing emissions, with potential mitigation of 53%-61% over 2023-50. High-emitting wells-particularly those tied to major oil and gas producers-should be prioritized. This study provides refined estimates of methane emissions and possible mitigation pathways for global AOG wells at well/country levels that have been overlooked in global greenhouse gas emissions inventories.