Methane emissions from underground gas storage in California

Abstract

Accurate and timely detection, quantification, and attribution of methane emissions from Underground Gas Storage (UGS) facilities is essential for improving confidence in greenhouse gas inventories, enabling emission mitigation by facility operators, and supporting efforts to assess facility integrity and safety. We conducted multiple airborne surveys of the 12 active UGS facilities in California between January 2016 and November 2017 using advanced remote sensing and in situ observations of near-surface atmospheric methane (CH 4 ). These measurements where combined with wind data to derive spatially and temporally resolved methane emission estimates for California UGS facilities and key components with spatial resolutions as small as 1-3 m and revisit intervals ranging from minutes to months. The study spanned normal operations, malfunctions, and maintenance activity from multiple facilities including the active phase of the Aliso Canyon blowout incident in 2016 and subsequent return to injection operations in summer 2017. We estimate that the net annual methane emissions from the UGS sector in California averaged between 11.0±3.8 GgCH 4 yr −1 (remote sensing) and 12.3±3.8 GgCH 4 yr −1 (in situ). Net annual methane emissions for the 7 facilities that reported emissions in 2016 were estimated between 9.0±3.2 GgCH 4 yr −1 (remote sensing) and 9.5±3.2 GgCH 4 yr −1 (in situ), in both cases around 5 times higher than reported. The majority of methane emissions from UGS facilities in this study are likely dominated by anomalous activity: higher than expected compressor loss and leaking bypass isolation valves. Significant variability was observed at different time-scales: daily compressor duty-cycles and infrequent but large emissions from compressor station blow-downs. This observed variability made comparison of remote sensing and in situ observations challenging given measurements were derived largely at different times, however, improved agreement occurred when comparing simultaneous measurements. Temporal variability in emissions remains one of the most challenging aspects of UGS emissions quantification, underscoring the need for more systematic and persistent methane monitoring.

Characterizing Methane Emission Hotspots From Thawing Permafrost

“…The remote measurement used a matched filter approach presented in Thompson et al. (2015), and deployed in multiple subsequent campaigns (Cusworth et al., 2020; Duren et al., 2019; Elder, Thompson, et al., 2020; Frankenberg et al., 2016; Thorpe et al., 2020). A complete description appears in the Methods in Supporting Information S1.…”

Quantifying Global Power Plant Carbon Dioxide Emissions With Imaging Spectroscopy

“…An identical instrument, the Global Airborne Observatory (GAO) (Asner et al., 2012), can also provide trace gas retrievals. Fine spatial scale mapping allows for direct attribution of CH 4 plumes to sub‐facility level infrastructure elements, which in the case of AVIRIS‐NG, has led operators to use this information to help guide emission mitigation (Cusworth et al., 2020; Thorpe et al., 2020). Imaging spectrometers are also sensitive to elevated CO 2 concentrations (Dennison et al., 2013; Thorpe et al., 2017), but have not previously been used for retrieval of emission rates.…”

Multisatellite Imaging of a Gas Well Blowout Enables Quantification of Total Methane Emissions

“…Similarly, the GHGSat‐D satellite, with its finer 50 m spatial resolution, detected prolonged venting (10–43 t h −1 ) operations at a gas compressor station in Turkmenistan from June 2018 to January 2019 (Varon et al., 2019), results which were consistent with TROPOMI estimates. Airborne remote sensing surveys imaged and quantified emissions from the Aliso Canyon blowout January–February 2016 in California (20 t h −1 ; Thorpe et al., 2020) with results consistent with airborne in situ methods for the same period (Conley et al., 2016). The Hyperion EO‐1 satellite imaging spectrometer (2000–2017; Folkman et al., 2001) also imaged plumes three times during the event at 30 m spatial resolution and detected significant CH 4 emissions (Thompson et al., 2016).…”