MEASURING METHANE EMISSIONS FROM ORPHANED WELLS IN THE KEVIN-SUNBURST FIELD, TOOLE COUNTY, MONTANA

The Kevin-Sunburst Field in Toole County, Montana was first discovered in March of 1922 and more than 1,500 wells drilled in the first 5 years. Eventually, more than 6,000 wells were drilled over its century long history of oil and gas production. The earliest oil wells produced for decades until the 1990’s when wells were abandoned and orphaned because operators responsible for their maintenance declared bankruptcy. Today, dozens of orphaned wells remain open at the surface and are directly emitting methane into the atmosphere. Methane emissions from orphaned wells is a persistent and poorly parameterized problem across the United States, with only a few hundred emissions measurements available in the literature. This lack of data makes it difficult to accurately assess regional and national scale emissions from orphaned wells.

In July of 2023, the USGS and Well Done Foundation measured methane emissions and collected gas samples from orphaned wells in the Kevin-Sunburst Field and analyzed the results. We are seeking to understand why some orphaned wells continue to emit methane, even a century after they were drilled. Using an automated flux chamber for emissions measurements, a handful of wells were directly measured, and emissions were evaluated along with other measurements collected in the field. Drilling and production data for the Kevin-Sunburst Field were compiled and analyzed to identify the unique characteristics of the field and engineering factors were examined to look at drilling trends through time to determine why these wells continue to emit methane after long periods of time. This presentation represents the initial findings of this field study and will give a brief history of the field, production over time, analysis of the wells measured, emission measurements from the orphaned wells, and details concerning the progress of orphaned well plugging.