Integrating Wellsite Geochemical Indicators into Data-Driven Environmental Risk Screening for Abandoned U.S. Oil and Gas Wells

Abandoned oil and gas wells represent a widespread and persistent environmental challenge in the United States, posing risks to climate, groundwater resources, and public health. Many legacy wells suffer from progressive integrity degradation, enabling methane emissions and subsurface fluid migration that are difficult to identify using inventory-based or inspection-driven approaches alone. This review synthesizes current knowledge on integrating wellsite geochemical indicators into data-driven environmental risk screening frameworks for abandoned U.S. oil and gas wells. Drawing on 25 peer-reviewed studies, the review examines well integrity failure mechanisms, methane emissions and source attribution, groundwater contamination pathways, and the application of geochemical tracers such as methane isotopes, major ion chemistry, halide ratios, and organic contaminants. The findings demonstrate that environmental impacts are highly heterogeneous, with a small subset of wells responsible for disproportionate methane emissions and contamination risks. While data-driven screening approaches, including GIS-based and machine-learning methods, have improved large-scale risk identification, geochemical indicators remain underutilized within these frameworks. Integrating geochemical evidence enhances risk discrimination, reduces uncertainty associated with incomplete well inventories, and improves prioritization for monitoring and remediation. This review highlights methodological gaps, policy-relevant uncertainties, and opportunities for advancing scalable, geochemically informed screening tools. By explicitly integrating wellsite geochemical indicators into data-driven screening workflows, the proposed framework alters risk classification outcomes by reducing false negatives associated with spatial proxy-based models and improving differentiation between low- and high-risk abandoned wells. This integration enhances prioritization accuracy for methane mitigation and groundwater protection, supporting more targeted and cost-effective remediation strategies at basin to national scales.