Methane and Ozone Concentrations from a Plugged Abandon Gas Well in Western Pennsylvania

The first deep natural gas wells in Pennsylvania were drilled in the 1850s, and since then hundreds of thousands of wells have been drilled throughout the state. Each of these wells can act as a methane source to the atmosphere. While many of these wells do not emit sufficient methane to significantly impact climate or air quality, over the past few years there have been growing concerns over wells that are unexpectedly high emitters. Plugged wells are of particular concern as when classified as plugged - we do not expect significant emissions. However, the emissions from these wells may change over time, particularly decades after plugging. This work will focus on the impacts of an aging conventional gas well in Indiana County, Pennsylvania. We monitor a single well which has been classified as plugged in the Pennsylvania Department of Environmental Protection (PA-DEP) records. Recent flow rate measurements indicate that this well emits between 5 to 17 SLPM of gas which is mostly methane. With these levels of methane emissions, we can characterize the local methane enhancement, and determine if any in-situ ozone production can be observed. We measured ozone (O₃) and nitrogen oxide (NOx) concentrations, meteorological conditions, and methane (CH₄) and ethane (C₂H₆) concentrations. Samples were taken at a number of locations near the well, moving between locations on ten minute intervals. We used the ethane:methane ratios to determine when we were sampling air affected by the well, and then using the ratio information we characterized the observed ozone. We will report on the results of this case study, focusing on the extent of methane enhancement and overall ozone concentrations.