UAV-based aeromagnetic surveys for orphaned well location: Emerging best practices

Abstract

Historical oil and gas exploration and development in the northeastern United States left behind hundreds of thousands of orphaned oil and gas wells in areas where hydrocarbon extraction predated state and federal regulations on well abandonment. Abandoned by their original operators with incomplete records of location and well status, orphaned wells pose significant economic and environmental challenges associated with possible emissions of formation liquids and gases. Effective location and assessment of orphaned wells is a key first step in well site remediation; however, the task of locating orphaned wells has proven to be a formidable challenge in some of the most impacted areas. Specifically, in key areas of the northeastern United States, where the oil and gas industry first emerged in the late 19th and early 20th centuries, historical lease maps have proven largely inaccurate, and wide-area terrestrial geophysical surveys in difficult terrain characteristics and dense vegetation were found to be cost-prohibitive. In recent years, integration of miniaturized magnetic sensors with low-altitude uncrewed aerial vehicles (UAVs) facilitated successful implementation of wide-area aeromagnetic surveys targeting orphaned well identification in areas where piloted aeromagnetic surveys were previously infeasible due to challenging terrain and canopy conditions. Aeromagnetic data sets collected by ultra-low-altitude UAV surveys and processed to highlight magnetic anomalies associated with orphaned well casings have the potential to drastically reduce search areas for orphaned wells and complement ground surveys, thus helping turn the tide in orphaned well remediation efforts. As UAV-based aeromagnetic surveys gain recognition as a dependable wide-area surveying tool for remote identification of orphaned well sites, we highlight key advantages and important limitations of this methodology, underscore key practical challenges to successful implementation, and outline best practices in effective survey design and execution.