A new study has suggested that offshore oil and gas production in the U.S. Gulf of Mexico has substantially higher methane emissions than those from typical onshore production.
Non-profit organization Carbon Mapper released the findings of airborne observations in the spring and fall of 2021 of 151 shallow water offshore oil and gas platforms in U.S. state and federal waters in the Gulf of Mexico.
Researchers found that the methane loss rate from these shallow water sources is significantly higher than typical onshore production and disproportionally contributes to climate change – providing a potential focus for sustained monitoring and mitigation efforts.
Specifically, the team calculated a methane loss rate of 23-66 percent from shallow offshore Gulf of Mexico operations compared to 3.3-3.7 percent reported by other studies of operations in the Permian basin. The team plans to conduct additional surveys of the broader population of platforms in the Gulf and selected international offshore production areas with aircraft and satellites to assess overall methane loss rates.
Carbon Mapper collaborated on the research with the University of Arizona, NASA’s Jet Propulsion Laboratory, the University of Michigan, and Arizona State University. It is the first systematic application of a remote emissions-sensing technology that can detect methane emissions over water, and attribute methane emissions to specific infrastructure.
Offshore oil and natural gas platforms are responsible for about 30 percent of global oil and gas production. Despite the large share, few studies have directly measured atmospheric methane emanating from these platforms due to their remote location compared to onshore production, and the technological challenges of observing methane emissions over water. These factors present unique challenges for oil and gas leak detection and repair programs and may undermine society’s ability to meet methane reduction targets such as the Global Methane Pledge.
“Bottom-up estimates and gaps in observational data can result in significant undercounting of emissions from offshore oil and gas infrastructure,” said Alana Ayasse, Research Scientist with Carbon Mapper, and the University of Arizona. “This study underscores the importance of increased transparency and sustained remote monitoring in offshore oil- and gas-producing regions to inform mitigation action.”
Many observed shallow-water offshore platforms and surrounding infrastructure exhibited super-emitter activity. Of the 151 targeted platforms and surrounding areas surveyed between the spring and fall, 62 pieces of infrastructure had an observable methane plume – over 10 kg/hr.
According to Carbon Mapper, emissions from observed offshore sources were highly persistent. The offshore sources measured in this study were over twice as persistent – meaning how frequently emissions were detected at a given location – as methane emissions from onshore oil and gas infrastructure reported by other studies. Researchers revisited many of these platforms multiple times in the spring and fall of 2021 which provided an initial characterization of source persistence, and further observations will evaluate whether there is a long-term trend.
Also, specific types of equipment were responsible for a disproportionate number of emissions. Using high-resolution imaging, the researcher attributed observed emissions primarily to tanks, satellite wells, pipelines, and vent booms that were visually identifiable – showing that a small number of observable emissions sources were responsible for most of the methane released into the atmosphere. The infrastructure observed was distributed evenly across state and federal waters, allowing the team to sample different regulatory structures.
“Remote sensing of methane over onshore oil and gas fields has transformed our understanding of emissions and highlighted mitigation possibilities,” said Eric Kort, Associate Professor of Climate and Space Sciences and Engineering University of Michigan. “By demonstrating these similar remote sensing capabilities for offshore infrastructure, this work opens the door to similarly impactful advances for this large and often neglected segment of the fossil fuel industry.”
Demonstrating the technical capabilities to remotely observe methane emissions from offshore oil and gas infrastructure is an important precursor to the future launch of the hyperspectral satellite constellation being developed in partnership with Carbon Mapper, Planet Labs PBC, and NASA JPL which will be able to provide more sustained and high-frequency observations over wider geographic areas.
According to the organization, insights from emissions data captured from offshore oil and gas platforms will be increasingly relevant as global demand for LNG grows, and offshore oil and gas leases are expanded.
The imaging spectrometer used in the study, Arizona State University’s Global Airborne Observatory, can pinpoint methane sources to within about 15 feet while flying at 18,000 feet. When methane emission plumes were detected, researchers used a high-resolution camera to relate the plumes to individual pieces of equipment.
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