The Yomiuri Shimbun. TOKYO — A Kyoto University research team developed a new basic technology to extract shale gas trapped deep underground by injecting carbon dioxide into shale bedrock instead of water, The Yomiuri Shimbun has learned.
The research team said it plans to start a large-scale substantiative experiment to verify the technology in autumn, aiming for practical use of the technology within several years.
In addition to securing shale gas, a new energy resource, the newly developed technology is also expected to help combat global warming as it will confine CO2 underground.
A common method to extract shale gas is to frack hard shale bedrock by injecting pressurized water into shale formations. The more finely cracked the bedrock is, the more shale gas can be obtained. However, making ideal cracks in shale formations by injecting water is difficult because the liquid has a high viscosity.
According to the research team led by Kyoto University Professor Tsuyoshi Ishida and Assistant Professor Chen Youqing, CO2 becomes a “supercritical” fluid if it is heated to 31.1 C or more and subjected to pressure of at least 73 atmospheres. A supercritical fluid is very smooth and has properties midway between a liquid and gas.
The research team confirmed that supercritical CO2 injected into shale bedrock fractured the bedrock and created finer cracks more widely in comparison to the use of pressurized water.
Last autumn, Japan Oil, Gas and Metals National Corporation, an auxiliary organization of the Economy, Trade and Industry Ministry, designated the development of this technology as a research project.
In October, the university research team will start conducting a substantiative experiment to fracture granite, the hardness of which is similar to that of shale, in a hot spring area in Toyama Prefecture.