(CN) – Fracking – the process of pulling oil and gas from beneath Earth’s surface by injecting water into subterranean rock – not only requires a huge amount of water, it can also cause chemicals to seep into the local groundwater. In short, fracking isn’t good for the environment.
But in a study published Thursday, Chinese researchers say the oil and gas industry should look to carbon dioxide as a replacement for water fracturing.
Carbon dioxide is a more effective fracturing fluid that can yield better results than water, according to the study published in the journal Joule by a team of researchers from the Chinese Academy of Sciences and China University of Petroleum. Shifting to CO2 could cut down on the amount of chemicals left underground after the fracking process and the amount of water needed.
Fracking relies on the porosity of deep-rock formations. Water is mixed with chemicals, sand, foaming agents and chemicals, but the amount of this chemical cocktail used ranges from 7 million to 15 million liters. About 30% to 50% of the fluid remains underground after the process is done.
Seepage into the local groundwater is one of the many reasons environmental advocates oppose the process, along with the air pollution and damage to the subterranean rock formations when they are split open.
But in field tests with five wells the researchers found they were able to increase the amount of oil extraction by 4 to 20 times fracking with CO2 rather than water. They determined CO2 injection was able to generate better results because it can be forced farther into the deep-rock formations.
The oil and gas industry has relied on fracturing to pull resources from deeper beneath Earth’s surface. Onshore fracking is used in operations throughout the United States, including Texas, North Dakota and Kansas, but also in the United Kingdom’s Wytch Farm, the largest onshore oil field in western Europe.
In 2011, the U.K.’s Department of Energy and Climate Change issued a moratorium on fracking to address the link between fracking and tremors. The ban was lifted in 2018 and in December of that year a minor quake rattled residents in the seaside town of Blackpool just two months after fracking operations started in the area.
While the study from the Chinese researchers does not address the link between earthquakes and fracking it remains a sticking point for the industry.
In an interview, Earth system science professor Rob Jackson of Stanford University said the study’s results are promising and he would like to see a larger sample with a broader set of conditions.
Jackson said while the process of using CO2 could be considered a “green” form of fracking, the study did not go into detail about the chemicals the researchers combined with the CO2 for their tests.
“If we could replace water with CO2 for fracking we could gain several benefits,” said Jackson, who was not affiliated with the study. “Much of the hydraulic fracturing is done in dry areas where water is scarce. It could substantially reduce the water requirements.”
Still, CO2 is more buoyant than water, said Jackson, and if a benign set of chemicals is involved in the new process there could be less environmental concern after the fracking is done.
In a statement, researcher and study co-author Nannan Sun of the Shanghai Advanced Research Institute at the Chinese Academy of Sciences said there were several unknowns on CO2 extraction when they started. Sun also noted the process is limited by the availability of readily available CO2, and keeping costs and the impact on the environment to a minimum remain factors the researchers want to mind.
“Further investigations are needed to identify the effects of type of reservoirs, geomechanical properties and conditions, CO2 sensitivity of the formation, and so forth,” said Sun.