USA offshore oil and gas platforms release more methane than previously estimated

Offshore energy producing platforms in United States (U.S.) waters of the Gulf of Mexico are emitting twice as much methane, a powerful greenhouse gas, than previously thought, according to a new study from the University of Michigan supported by the Climate and Clean Air Coalition.

Researchers conducted a first-of-its-kind study by flying aircraft to sample air over offshore oil and gas platforms in the Gulf of Mexico. Their findings suggest that U.S. federal government’s calculations are too low. The research found that, for the full U.S. Gulf of Mexico, oil and gas facilities emit approximately ½ a Teragram of methane each year, corresponding to a loss of produced gas of roughly 2.9 percent. That’s a high loss rate similar to large onshore basins primarily focused on oil.

Each year the U.S. Environmental Protection Agency (US EPA) issues its U.S. Greenhouse Gas Inventory, but its numbers for offshore emissions are not produced via direct sampling. Offshore installations account for roughly one-third of the oil and gas produced worldwide, and these facilities both vent and leak methane.  Until now, only a handful of measurements of offshore platforms have been made, and no aircraft studies of methane emissions in normal operation had been conducted.

The study identified three reasons for the discrepancy between US EPA estimates and their findings:

• Errors in platform counts:  Offshore facilities in state waters, of which there are more than 1,300, were missing from the U.S. Greenhouse Gas Inventory.
• Persistent emissions from shallow-water facilities, particularly those primarily focused on natural gas, are higher than inventoried.
• Many shallow water facilities are large, with old infrastructure and tend to produce episodic, disproportionally high spikes of methane emissions. These facilities, which have more than seven platforms apiece, contribute to nearly 40% of emissions, yet consist of less than 1% of total platforms.  If this emission process were identified, it could provide an optimal mitigation opportunity.

Eric Kort, University of Michigan Associate Professor of Climate and Space Sciences and Engineering, said EPA officials are already making adjustments to correct their count of offshore platforms operating in the Gulf of Mexico. But emissions estimates, particularly for shallow waters, still need adjustments.

“We have known onshore oil and gas production often emits more methane than inventoried. With this study we show that this is also the case for offshore production, and that these discrepancies are large.” Kort said. “By starting to identify and quantify the problem, with a particular focus on larger shallow water facilities, we can work towards finding optimal mitigation solutions.”

The shallow-water discrepancies need further investigation, Kort added, since deep water facilities may be sending some of the oil and gas they produce via pipeline to others located closer to shore.

The University of Michigan study is the second to be published in a series of peer-reviewed scientific studies supported by the Climate and Clean Air Coalition’s (CCAC) Oil and Gas Methane Science Studies. The first study in the series also looked at methane emisisons from oil and gas operations in the Gulf of Mexico but used shipped based sampling. That study, by Aerodyne Research, Inc., took downwind measurements from 103 sites, including shallow and deepwater offshore platforms and drillships. It similarly found that a small number of sites (2%) were responsible for a large number of emissions (20%) and also suggested. It was published in Environmental Science and Technology in March 2020.

Helena Molin Valdés, Head of the Climate and Clean Air Coalition Secretariat, said the studies were important to help companies prioritize work to reduce emissions and help governments target policies that do the same. She also called for urgent action to reduce methane emissions.

“We know that oil and gas is one of the largest sectors responsible for methane emissions. These new studies help us understand the extent to which offshore operations contribute to this problem, something that was previously unclear,” Ms. Molin Valdés said. “We can and must move rapidly to reduce methane leaks and venting from the oil and gas sector. It is not just technically feasible, but because methane has commercial value, reducing these emissions can result in financial savings or be carried out at low cost.”

Ms. Molin Valdés urged oil and gas producing countries to raise their climate ambition by addressing methane emissions from the sector saying that the CCAC and United Nations Environment Programme would work with countries on ways to do this. 

In addition to the Gulf of Mexico, extensive measurements of methane sources have also been done in the North Sea, Romania, Australia and over 10 European cities. These studies will be publicly available and easily accessible so a wide range of stakeholders – including civil society, scientists, companies, and governments – can use the data to make well-informed decisions and prioritize areas for action.

Methdology

The University of Michigan team conducted its sampling in 2018 with Scientific Aviation using a small research plane with enough room for a pilot and passenger in the two front seats, as well as scientific gear where there normally would be two rear two seats. Tubes along the wings of the plane drew in air that was pumped to the equipment for analysis of the amount of methane included as well as wind speed. Circling a single platform gives researchers a better idea of how much methane that single source is emitting.

In addition to 12 individual facilities, the flights also covered larger geographical areas. Flying downwind from clusters of 5 to 70 oil and gas platforms, and taking similar measurements, researchers can evaluate how well inventory estimates compare with large numbers of facilities. 

“By measuring emissions from both individual facilities as well as many dozens of facilities we can compare results, evaluate different inventories, and generate a more statistically robust estimate of total emissions from the US Gulf of Mexico,”said Alan Gorchov Negron, lead author on the study and a PhD candidate in climate sciences at the University of Michigan.

As a pilot study, Kort said the research is promising but has gaps.  Greater statistical sampling and identification of the cause of high emissions can guide mitigation and improve reported emissions. To further the work and fill in these gaps, new aerial sampling is in the works funded by the Alfred P. Sloan Foundation. The project, titled Flaring and Fossil Fuels: Uncovering Emissions & Losses (F³UEL), will mean more flights later over the next three years over the Gulf of Mexico, Alaska and California.

This study was supported by the Climate and Clean Air Coalition Oil and Gas Methane Science Studies. The Environmental Defense Fund, the European Commission, and the companies of the Oil and Gas Climate Initiative have contributed $7.2 million to this series of scientific studies. The CCAC, which calls 69 governments and many more civil society organizations members, together with the United Nations Environment Programme (UNEP) collaborates with governments relevant to each study, linking policy and action to help address methane emissions. CCAC’s Oil and Gas Methane Partnership is also helping companies systematically manage their methane emissions from upstream oil and gas operations. The Climate and Clean Air Colaition’s Secretariat is hosted by UNEP.

Contact:

University of Michigan: Jim Lynch, +1 (313) 727-5045, lynchja [at] umich.edu  

Climate and Clean Air Coalition: Tiy Chung +33 626 71 79 81, tiy.chung [at] un.org