A new method, developed in the United States, could help improve oil output from the...
A new method, developed in the United States, could help improve oil output from the tightly packed formations of shale rock. Developed by researchers at Pennsylvania State University, the new oil extraction workflow may improve shale oil recovery up to an additional 15%.
The efficient method could also provide long-term storage for carbon dioxide (CO2) emissions.
Researchers revealed that the workflow was successfully implemented for the Texas Eagle Ford Shale, where it demonstrated improvement in oil extraction, the researchers said, explaining that it can be expanded for application in other shale reservoirs.
Method improves cyclic CO2 injection
The method focuses on improving cyclic CO2 injection, a process in which CO2 is pumped into the reservoir to enhance oil production. Also known as “CO2 huff-n-puff,” the decades-old injection method bolsters extraction from naturally occurring rock formations.
Researchers revealed that these rocks contain microscopic pores, called nanopores, where significant portions of hydrocarbons – the main component of oil — accumulate.
Published in the journal Fuel, the study indicates that a larger volume of injected CO2 leads to greater enhanced oil recovery by enabling deeper penetration into the reservoir and more effective mixing with crude oil.
Furthermore, deep reservoirs containing low gas–oil ratio black oil are especially favorable for cyclic CO2 HnP, as the injected CO2 substantially enhances oil swelling and improves production potential, according to researchers.
Leveraging CO2 to bolster oil production
Researchers compared the underground shale environment to a sponge. Similar to the tiny openings in a sponge that fill with water, nanopores effectively soak up and retain hydrocarbons until the surface is disrupted.
“I would call this one of the best recycling systems in the industry,” said Hamid Emami-Meybodi associate professor of petroleum and natural gas engineering, faculty associate in Penn State’s EMS Energy Institute and lead author.
“Leveraging CO2 to bolster oil production eases environmental impacts, helps fulfill growing energy demand and contributes to the U.S.’ energy independence and security.”
CO2 is fed into the reservoir through a well
The lead researchers revealed that during injection, CO2 is fed into the reservoir through a well. Then the well is shut to allow the injected gas to soak for a sufficient period. The gas mixes with the oil, altering its properties and improving oil mobility and extraction, according to the researchers.
By introducing CO2 in oil mixtures at different pressures, the injection process helps force hydrocarbons out of nanopores and to the surface. But the method’s effectiveness varies widely with changing operational conditions, depths and oil types, according to a press release.
“Optimizing injection is challenging due to numerous variables – including the oil properties and makeup of the shale environment – that can complicate extraction,” said Emami-Meybodi.
Researchers revealed that the workflow was successfully implemented to optimize and screen cyclic CO2 injection in the Eagle Ford Shale. The workflow can be expanded for broader applications across various types of unconventional EOR projects, according to the study.
Oil produced from shale reservoirs drove record crude output in the U.S. over the past decade, but inefficiencies in extraction often leave as much as 90% of the oil behind.