Avoiding Most Carbon-Intensive Reservoirs and Better Managing Natural Gas Could Greatly Cut Emissions

All oils do not weigh similarly on the scales of climate change.

A new study from Stanford University learned that in 2015, approximately 9,000 oilfields in 90 countries generated greenhouse gases equivalent to 1.7 gigatons of carbon dioxide (CO₂) - approximately 5% of all emissions from fuel combustion that year. On average, oil production discharged 10.3 g of emissions for every megajoule of crude, but countries with the most carbon-intensive practices produced emissions at almost twice that rate.

The study, published on August 30^th in the journal Science, quantifies emissions from when companies first explore a site through conveying crude to refineries. Accounting for as much as 98% of worldwide production, it is the most wide-ranging assessment thus far of carbon intensity and pollution by oil fields.

Yet as said by lead author Mohammad Masnadi, a postdoctoral researcher at Stanford University’s School of Earth, Energy & Environmental Sciences (Stanford Earth), total emissions from crude oil production may be greater than even these recent calculations indicate, as the present analysis does not completely capture emissions connected with leakage and venting of methane, a robust global warming gas. Masnadi collaborated with Adam Brandt, an assistant professor of energy resources engineering and the paper’s senior author.

The research proposes countries with the maximum carbon-intensity produce over 15 g of CO₂ equivalent, on average, for every megajoule of crude. That is approximately triple the average carbon intensity of oilfields in nations at the low end of the scale.

Wasted Gas

Nothing increases up carbon intensity like the practice of regularly burning, or flaring, natural gas, the scientists found. “Everybody talks about heavy crude oil, oil sands and unconventional resources,” Masnadi said. But the study shows that a country like Algeria, which produces the world’s lightest crude oil, has the maximum carbon intensity because oilfield operators regularly burn large amounts of gas. Saudi Arabia, meanwhile, has comparatively low carbon intensity as it flares little gas and has massive resources with low water content, which means less energy is required for treating and separating the oil.

The revelation proposes that investment in policies and infrastructure to better manage natural gas could deliver better climate advantages than formerly thought. “Really, the challenge with flaring is there needs to be a policy or a regulatory apparatus to say, ‘Burning gas with no purpose isn’t allowed; put it back in the ground or find something useful to do with it,’” Brandt said.

To be certain, emissions associated with a reservoir’s location and accessibility still play a vital role. The research finds Canada and Venezuela rank among the most carbon-intensive oil producers because of the high energy requirements and emissions connected with extracting heavy oil from unconventional reserves like tar sands. Furthermore, so-called improved recovery methods that use steam to loosen oil from aging wells add to the comparatively high carbon intensity of oil production in countries like Oman, Indonesia, and California.

Overall, the research proposes that eliminating regular flaring and cutting methane leaks and venting to rates already accomplished in Norway could cut nearly 700 megatons of emissions from the oil sector’s yearly carbon footprint - a reduction of approximately 43%. Moreover, over the coming century, the world could avoid about 18 gigatons of emissions from the oil production projected to continue under even aggressive situations for moving away from fossil fuels - primarily by stopping extraction of the dirtiest resources and optimizing gas management.

Estimating Emissions

The research is based on a project led by Brandt called the Oil Production Greenhouse Gas Emissions Estimator, or OPGEE, which California air regulators currently use to estimate emissions from various crudes that California imports or creates as part of the state’s low-carbon fuel standard.

But so far, large gaps remained in even the best estimates of emissions from crude oil manufacture on an international scale as they worked backward from economic data, calculating how many barrels oil companies were expected to have produced based on oil prices in a particular period. According to Masnadi, “When you do this, you’re missing lots of underlying processes that lead to emissions.”

The new simulator, by contrast, uses a bottom-up approach to calculate emissions. The scientists designed models of the physical processes involved at each stage from preliminary exploration through transport to refineries. Data-intensive calculations for a single field could require measures for equal to 50 parameters, including production rates, oil density, and the amount of natural gas that the operator burned or captured in pipelines—as well as whether a producer injects steam or water to coax crude from wells, or uses some other technique.

Collecting that kind of detail for numerous active oil fields worldwide was overwhelming. “It’s the first time we’ve been able to do this at this very resolved oil field-by-oil field level,” Brandt said. But as few as 1,000 fields account for approximately two-thirds of worldwide production, and the scientists understood they could concentrate on mining open-source data sets for those heavy hitters. For the other fields - generally smaller scale producers - they could search for information in private databases.

The team eventually investigated public sources, including technical reports, news reports, peer-reviewed research, government databases, and literature from the Society of Petroleum Engineering for one year, and then collaborated with companies to get access to two proprietary data sets. They then assigned quality scores to the various data sets, giving more importance to peer-reviewed sources and less to news reports and commercial sources that they agreed to keep private.

Societies remain greatly dependent on crude oil, which presently goes into products ranging from jet fuel and asphalt to medicine and fertilizer. “Everybody lives based on these fossil fuel resources,” Masnadi said. “It’s not very feasible to get rid of this energy resource in one night or in one year.” The question is how to speed up that transition. Part of the answer offered by this paper is to comprehend in fine detail what the present state is - and why. “Now we can move forward.”

Adam Brandt is also a center fellow, by courtesy, at the Precourt Institute for Energy. Additional co-authors are from Aramco Services Co., Ford Motor Co., University of Calgary, Carnegie Endowment for International Peace, Carnegie Mellon University, University of British Columbia, California Environmental Protection Agency, National Renewable Energy Laboratory, University of Michigan, International Energy Agency, Baker Hughes, Chalmers University of Technology, Cornell University and Argonne National Laboratory.

The study was financed by the Natural Sciences and Engineering Research Council of Canada, Aramco Services Co., Ford Motor Co., the Carnegie Endowment for International Peace, the Hewlett Foundation, the ClimateWorks Foundation and the Alfred P. Sloan Foundation.