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(4)) emissions. Our near-infrared sensor targets the 2ν(3) R(4) CH(4) transition at 6057.1 cm(−1) (1651 nm) via line-scanned tunable diode-laser absorption spectroscopy (TDLAS), with Allan deviation analysis yielding a normalized 2.0 ppmv∙Hz(−1/2) sensitivity (4.5 × 10(−6) Hz(−1/2) noise-equivalent absorption) over 5 cm open-path length. Controlled CH(4) 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(2) = 0.74) over high-flow (>60 SCFH) CH(4) releases spanning 4.4 h. In conjunction with simultaneous wind velocity measurements, the leak angle-of-arrival (AOA) is ascertained via correlation of CH(4) 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(2) = 0.74) between calculated and measured release rates.