Origins of Oil and Gas Sector Methane Emissions: On-Site Investigations of Aerial Measured Sources

Success in reducing
oil and gas sector methane emissions is contingent
on understanding the sources driving emissions, associated options
for mitigation, and the effectiveness of regulations in achieving
intended outcomes. This study combines high-resolution, high-sensitivity
aerial survey data with subsequent on-site investigations of detected
sources to examine these points. Measurements were performed in British
Columbia, Canada, an active oil- and gas-producing province with modern
methane regulations featuring mandatory three times per year leak
detection and repair (LDAR) surveys at most facilities. Derived emission
factors enabled by source attribution show that significant methane
emissions persist under this regulatory framework, dominated by (i)
combustion slip (compressor exhaust and also catalytic heaters, which
are not covered in current regulations), (ii) intentional venting
(uncontrolled tanks, vent stacks or intentionally unlit flares, and
uncontrolled compressors), and (iii) unintentional venting (controlled
tanks, unintentionally unlit/blown out flares, and abnormally operating
pneumatics). Although the detailed analysis shows mitigation options
exist for all sources, the importance of combustion slip and the persistently
large methane contributions from controlled tanks and unlit flares
demonstrate the limits of current LDAR programs and the critical need
for additional monitoring and verification if regulations are to have
the intended impacts, and reduction targets of 75% and greater are
to be met.