HIDING IN PLAIN SIGHT: ARE THERE MORE UNDOCUMENTED ORPHAN WELLS THAN WE REALIZE?

Decades of oil and gas production in the United States (US) have left millions of unplugged undocumented wells across the country, which pose significant risks to public health, safety, and the environment. Before the 1950s, most states had no laws requiring the reporting of oil and gas wells, resulting in missing records of past well drillings. This gap makes it challenging to estimate the total number of undocumented orphan wells (UOWs) in the US, which is crucial for policy analysis and implementing necessary remediation steps to ensure public safety and environmental protection by the state. Accurate estimates are also essential for securing funding and resources needed to address the issue and setting priorities in environmental and public health policies.

We develop a workflow to address this challenge, estimating the number and spatial distribution of UOWs at the county level using historical production data and undercounted digital well completion records. Our analysis reveals significant underreporting and missing records before 1950’s which is adjusted with reliable underreporting factors. We estimate well completions for years with unreliable data using statistical analysis from adjacent years with reliable data. Applying our workflow in Pennsylvania (PA) and Oklahoma (OK), we estimate 340,827 orphan wells in PA and 309,462 in OK, far exceeding current figures from the Interstate Oil and Gas Corporate Commissions (IOGCC) (100K and 105K for PA and OK, respectively). We distributed the estimated orphan wells within counties based on the percentage of wells drilled in each county in the past. Our workflow identified Osage and Creek County in OK and McKean County in PA as having some of the highest numbers of UOWs (more than 35K). Our workflow can be applied to other oil-producing states to estimate the total number of UOWs, shedding light on the total number of UOWs across the US. Methane emissions from UOWs in just two states amount to 0.7056 MMt of CH⁴, which is 14 times higher than the IOGCC's recent estimate of 0.05 MMt for UOWs across the entire US. So, this research is crucial for states as they prioritize the location and remediation of UOWs, helping to mitigate environmental hazards and improve public safety.