Controlled Release Tests Results for the Methane Lidar Camera

Methane emissions detection using continuous monitors enables round-the-clock monitoring to quickly identify emissions from oil and gas facilities. The SLB methane lidar camera participated in Stanford University’s 2024 Methane Controlled Release Campaign to characterize its performance at detecting, localizing, and quantifying methane emissions from different sources. The camera successfully detected and localized emissions as low as 0.3 kg/h as well as super emitters as high as 310 kg/h. The camera detected all but one emission greater than 1 kg/h, resulting in a limit of detection at 90% confidence of 1.5 kg/h. In addition, the camera localized all emissions to the correct piece of equipment or to the adjacent piece of equipment, including many releases where the camera’s vantage point was suboptimal. The emission rates measured by the camera showed a systematic underestimation compared to the ground truth results. Such an underestimation is unexpected and inconsistent with the camera’s performance in previous studies. In this paper, we perform a root cause analysis to identify the cause of the underestimation. The analysis concludes that the measured methane signal was accurate and that the underestimation was caused by a wind shadow that resulted in the camera’s anemometer systematically underestimating the wind speed. Reprocessing the methane lidar camera’s data using an on-facility anemometer not affected by a wind shadow instead of the camera’s anemometer resulted in quantification that was within a factor of two 78% of the time and a systematic bias of 11%. The 90% limit of detection, the fraction of results within a factor of two, and the systematic bias (using the on-facility anemometer), are superior to any scanning/imaging system at METEC 2023 and 2024 ADED programs. As a result of this study, improvements in the camera installation workflow have been introduced to avoid wind shadows in the future.