Assessing the Performance of Point Sensor Continuous Monitoring Systems at Midstream Natural Gas Compressor Stations

Continuous Monitoring Systems (CMS) are a promising technology to detect and quantify intermittent and high-volume methane emissions across the oil and gas supply chain. This is particularly salient at midstream compressor stations, where the contribution of short-duration emission events to total emissions makes survey-type technologies less suitable for developing accurate measurement-informed inventories. In this work, we report on the first concurrent and long-term test of five CMS technologies to detect, localize, and quantify methane emission from two major types of midstream compressor stations found in the US – a turbine-only station and an engine-only station. We find that CMS technologies can distinguish between different operational states of engine-driven compressors with large CH4 emissions contribution from compressor exhaust. Combining known events at these facilities with in situ controlled releases, we observe that all CMS technologies generally struggle in identifying short-duration (<30 min) or low emission rate (relative to baseline) events. Critically, we find that positive event detection, based on analysis of underlying methane signals, frequently did not translate to alerts sent to the operators. Deployment of CMS at midstream compressor stations must proceed with caution based on specific applications, site configuration, and the nature of baseline emissions.