An astonishingly high rate of methane is emitting from the shallow water zones of the offshore oil and gas production in Gulf of Mexico. The emission rates detected were much higher than typical onshore oil production.
According to a new study, the methane emissions were 23-66% high from shallow offshore Gulf of Mexico operations compared to 3.3-3.7% reported by other studies of operations in the Permian basin. The study, conducted by researchers at Carbon Mapper, University of Arizona, NASA’s Jet Propulsion Laboratory, University of Michigan, and Arizona State University, observed 151 shallow water offshore oil and gas platforms in US state and federal waters in the Gulf of Mexico.
Offshore platforms were mapped using the Global Airborne Observatory – a plane equipped with a 432-band visual and shortwave infrared imaging spectrometer with a 34 degree field of view and a bore-sighted high resolution context camera. This 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.
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Why is it so important?
Methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere, and such undetected emissions disproportionally contributes to global warming. Offshore oil and natural gas platforms are responsible for about 30% of global oil and natural gas production. Despite the large share of global production there are few studies that have directly measured atmospheric methane emanating from these platforms.
“Top-down atmospheric measurements of methane in the offshore environment is notoriously hard so the fact that we were able to systematically measure the areas we wanted to measure was a huge success,” says Riley Duren, CEO, Carbon Mapper, adding that “this really opens the door for what is possible in the future in terms of sustained, operational offshore monitoring.”
Carbon Mapper is a non-profit with a mission to deliver and guide the adoption of digital public goods that facilitate timely action to mitigate human impacts to Earth’s climate and ecosystems. It is planning to launch a hyperspectral satellite constellation that will be designed to pinpoint and track 90% of global high emission methane point sources. The first two satellites are scheduled to be launched in summer-fall 2023.
The organization plans to conduct periodic near-global surveys for persistent high emission methane sources (for example, see gold areas in the figure below) and more frequent monitoring of priority areas to detect intermittent activity (purple areas) – including most of the major offshore oil and gas production fields around the world. The monitoring cadence for these surveys will depend on the number of satellites in the constellation.
The ‘super-emitter’ activity observed in the Gulf of Mexico is likely due to a combination of leaks and malfunctions from older equipment and intentional venting of gas, says Duren. “One hypothesis is that routine “cold venting” of gas might be more prevalent at relatively low production shallow water oil platforms than many onshore basins like the Permian where flaring is widespread,” he adds.
Onshore oil and gas production is undoubtedly contributing a large share to overall methane emissions but owing to their remote location posing technological challenges in conducting studies these areas have not been included in a large number of studies. Natural hindering factors like dark surface areas limiting solar reflection limit overall methane measurements in such locations. Such limitations may lead to gaps in overall methane emission measurement and thus undermine Global Methane Pledge goals.
Remote sensing via aircraft or satellite—adapted for offshore conditions—may provide a powerful way to close this observational gap.
“Bottom-up estimates and gaps in observational data can result in significant undercounting of emissions from offshore oil and gas infrastructure,” says Dr. 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,” she adds.
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Multiple visits by the researchers to many of these platforms in Spring and Fall of 2021 showed that the offshore sources measured in this study were highly persistent. Further observations to be done will evaluate whether there is a long-term trend.
Another observation was that the high emissions were being released by specific types of equipment which were visually easy to identify- tanks, satellite wells, pipelines, and vent booms.
The study found that the methane emissions from the measured platforms exhibit highly skewed ‘super emitter behavior’.
Although the study area was centered on the Gulf of Mexico, based on the study patterns Carbon Mapper predicted that these skewed distributions are generally not limited to this section of the Gulf of Mexico and probably occur in other offshore production regions globally. To further broaden the area of study scientists in this program are planning to conduct broader airborne methane surveys of the Gulf of Mexico including deeper waters later in Fall 2022.
What were the challenges?
Even with high resolution images of methane plumes observed from high-altitude aircraft, it can be challenging to relate those emissions to specific equipment and operations within complex facilities like offshore oil and gas platforms, explains Duren.
“In an ideal world, we would have access to operational data or direct on-site confirmation by facility operators. In this case, our study was limited to using high- resolution images to assess probable causes—for example, whether a methane plume appears to originate from storage tanks or vent booms,” he adds.
For instance, the fact that the team detected methane emanating multiple times from the same locations over several months helped improve the confidence in its assessments, but there were always some residual uncertainty regarding attribution.
According to Dr. Ayasse, one of the biggest challenge was the limited scope. “We were not able to measure everything, and we did not measure deep water platforms. This means that our results are likely limited to shallow state and federal waters,” she explains.
Carbon Mapper hopes to fill these gaps with future studies and once its satellite constellation is in place that will provide persistent monitoring of offshore oil and gas fields globally starting late next year.
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