Fracking operations could switch from using water to CO2
By Adam Vaughan
Could a greenhouse gas be the answer to making fracking less controversial? Counterintuitive as the idea might seem, Chinese researchers claim that using carbon dioxide instead of water for fracturing rocks could be a greener way of extracting fossil fuels.
Traditional hydraulic fracturing, as the name suggests, involves pumping large volumes of water underground to create cracks in shale rock to release oil and gas. Carbon dioxide has been proposed before as an alternative that could address the fracking industry’s significant water demand in dry areas. It could also tackle problems associated with polluted water flowing back to the surface after the process.
To test how effective the gas might be, a Chinese research team drilled and fracked five wells with CO2 at Jilin oil field in north-east China, as well as conducting lab tests on rock samples from south-west China. They were “delighted” to find the wells produced up to 20 times as much oil after the fracking.
“These real world results revealed that as compared to water fracturing, CO2 fracturing is an important and greener alternative,” the researchers concluded.
Carbon dioxide could be a useful way of addressing fracking’s water consumption in arid areas of the US and even the UK, where water companies have said the fracking industry could put pressure on some local water supplies. It also holds the prospect of opening up more of China’s shale gas resource, which is the world’s largest but has not been exploited as rapidly as that in the US.
“Reservoirs in China may be more suitable to be fractured by CO2,” says Nannan Sun of the Chinese Academy of Sciences. But he added it was too early to say if it could change the speed at which China’s fracking industry develops.
While using the gas could be greener by reducing water use and potential water pollution, the research does not show CO2 fracturing is environmentally better overall. While some of the CO2 could be stored within the rocks, Nannan says it could also potentially leak out after fracking, which would add to global warming. If CO2 fracturing makes more oil and gas economically recoverable, that would add to the stock of fossil fuels we can burn too.
“This study does not include the analysis that is needed to establish whether CO2 fracking is likely to lead to an overall reduction in global greenhouse gas emissions,” said Hannah Chalmers at the University of Edinburgh in a statement.
Moreover, there are few signs of CO2 being taken up by fracking companies any time soon. Nannan says collecting and transporting the CO2 to the site is just one barrier, while UK fracking trade body UKOOG says water is still the best choice for fracking.
Journal reference: Joule, DOI: 10.1016/j.joule.2019.05.004
First published at the New Scientist – 30 May 2019. See: https://www.newscientist.com/article/2204939-could-fracking-with-carbon-dioxide-instead-of-water-be-greener/