Methane Destruction Removal Efficiency Assessment in US Shale Basins Using UAV-Based TDLAS Measurements

Abstract This observational study assesses the methane combustion efficiency rates (CH4 DRE%) of 42 unique flare systems across two US shale basins: the Bakken and Permian. Employing advanced technology – unmanned aerial vehicles (UAVs) and in-situ tunable diode laser absorption spectrometer(TDLAS) methane sensors – we adopt a bottom-up approach to detect, localize, and quantify CH4 emissionsat three Oil and Gas (O&G) operators.Combustion efficiency iscalculatedusing methane sensors and mass-balance methods thatcompare the mass flux flowrate of unburnt CH4exiting the flare system (i.e., in a flare’s plume) against the mass flowrate of CH4entering the system (flowmeter). Considerations for the volumetric flowrate and the vented gas temperature and pressure are also accounted. Attention to patterned gaps of quality data catalyzed a reassessment analysis:flare systems (27) were chosen for site revisitation if they exhibited hyperbolic combustion efficiency rates (like Site-5C with CH4 DRE% of -5084)orfaced difficulties (flowmeter discrepancies)that resulted in nulldata.Our findings reveal thatout of the 71 totaled flare system observations, 32 flare systems (45%) showcased combustion efficiency rates at or above the global average of 92% (IEA, 2023). 22 of the efficient flare systems were in the Bakken and 10 were in the Permian. Overall, 39 flare system assessments (55%)failed to reach the global combustion efficiency average – a combination of flowmeter discrepancies (18 flare systems) and failed combustion efficiency rates (21 flare systems). All instances of flowmeter discrepancies were in the Bakken basin and41% of revisited flare systems (11) exhibitedCH4 efficiency reevaluations that satisfied the global average.This disproportion between same-site flare efficiency implies one of many complexities in realizing a structured, continual and cohesive, flare combustion efficiency assessment at regional playing fields.Solutions towards regional discrepancies in flare system combustion efficiency require data acquisition strategies propelled by precise measurement techniques if they are to reach global initiatives(i.e., environmental regulations) aimed at mitigatingO&GCH4 emissions. Ultimately, this observational study sheds insight on the emerging potentials of technological and operational improvements for enhancedaccuracy acrossflare system efficiency assessments, vis-à-vis a regional comparison in CH4 DRE% estimates across 42 unique (71 totaled) flare systems in the Bakken and Permian basins.