By Kat Kerlin
It requires roughly the same level of greenhouse gas emissions to extract shale oil as it does to extract conventional crude oil, according to a pair of studies by UC Davis and Stanford University released this week by the U.S. Department of Energy’s Argonne National Laboratory.
The research analyzed the Eagle Ford shale play in Texas and the Bakken play in North Dakota. These plays are shale formations with low permeability that must be hydraulically fractured to produce oil and gas.
Eagle Ford and Bakken are the second and third largest oil-producing regions in the U.S., respectively, since 2012. Together, Bakken and Eagle Ford accounted for 54 percent of oil production and 19 percent of gas production within seven major production regions in 2014.
Until now, there has been little information about how the production method impacts greenhouse gas levels.
Both studies showed that greenhouse gas emissions associated with shale oil production are similar to levels generated at conventional crude oil reserves, even after considering the flaring and venting of natural gas during the shale oil process. The emission intensity stays consistent during the lifespan of extraction at the oil play.
This contradicts an earlier estimate that the Bakken play might produce greenhouse gas emissions 20 percent higher than for crude oil production.
The Eagle Ford study was led by Sonia Yeh, a research scientist with the Institute of Transportation Studies at UC Davis. It looked at crude oil from different production zones for 2009–2013. Some zones produced more oil while others produced more gas. The study showed that wells in the gas-rich zone used roughly twice the amount of energy as wells in the oil-rich zone, which used an average of 1.2 percent of energy for production, extraction, and processing. Water use was also generally higher at the gas-rich wells.
“It was challenging to calculate the net energy use and net greenhouse gas emissions for Eagle Ford because of the wide range of products produced at these places, and there were no publicly available tools for horizontal drilling and hydraulic fracturing,” said Yeh. “The collaboration provided greater transparency and understanding of energy and climate impacts of oil production in these important regions.”
The studies calculate energy consumption and greenhouse gas emissions associated with the crude oil and natural gas extraction using the Oil Production Greenhouse Gas Emissions Estimator (OPGEE) model, with production data collected for shale oil well operations in both plays. This model estimates energy for the lifecycle—from the initial exploration to the refinery entrance gate—and includes production, processing and transport.
The research team incorporated the OPGEE results into the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model developed at Argonne National Laboratory to determine the full life-cycle energy and emissions impacts.
The research was funded by the Vehicle Technology Office and the Bioenergy Technology Office of the Energy Efficiency and Renewable Energy Office of the U.S. Department of Energy.
The full reports can be found online at greet.es.anl.gov.
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