Field Deployment of a Portable Optical Spectrometer for Methane Fugitive Emissions Monitoring on Oil and Gas Well Pads.

We present field deployment results of a portable optical absorption spectrometer for localization and quantification of fugitive methane (CH) emissions. Our near-infrared sensor targets the 2ν R(4) CH transition at 6057.1 cm (1651 nm) via line-scanned tunable diode-laser absorption spectroscopy (TDLAS), with Allan deviation analysis yielding a normalized 2.0 ppmv∙Hz sensitivity (4.5 × 10 Hz noise-equivalent absorption) over 5 cm open-path length. Controlled CH leak experiments are performed at the METEC CSU engineering facility, where concurrent deployment of our TDLAS and a customized volatile organic compound (VOC) sensor demonstrates good linear correlation (R = 0.74) over high-flow (>60 SCFH) CH releases spanning 4.4 h. In conjunction with simultaneous wind velocity measurements, the leak angle-of-arrival (AOA) is ascertained via correlation of CH concentration and wind angle, demonstrating the efficacy of single-sensor line-of-sight (LOS) determination of leak sources. Source magnitude estimation based on a Gaussian plume model is demonstrated, with good correspondence (R = 0.74) between calculated and measured release rates.