Correlation of excess ethane and excess methane by subregion. a) Map of Southwestern PA study are with the sample track (black trace) and Marcellus Shale well locations (blue markers) displayed. The well locations are sized by the condensate liquids production (barrel) to the natural gas production (million cubic feet) ratio (Bbl/Mcf). Well area density is displayed in green. b) Scatter plot of 1-Hz molar enhancements (Δppb) of ethane and methane attributed divided into three major spatial sub-regions. Enhancement ratios are displayed as dotted lines. DOI: https://doi.org/10.1525/elementa.182.f12