Experimental Study of CO2 Fracturing Behaviour in Ultralow Permeability Formations

C. P. Zhang, Z. Y. Ma, P. G. Ranjith

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


CO2 fracturing with many unique advantages has been successfully used as an alternative to water-based fracturing in unconventional gas production. However, the great difference of fracturing behaviours between water and CO2 fracturing for different gas reservoirs is still scarcely studied. The intention of this study is to investigate the fracturing mechanism and to compare the fracture geometry characters between water and CO2 fracturing, and a series of fracturing tests on sedimentary rocks was therefore conducted. Experimental results show that breakdown pressure of CO2 fracturing is much lower than that of water fracturing for siltstone samples, and the difference of breakdown pressure between water and CO2 fracturing for shale samples with much lower permeability is much greater. The much higher breakdown pressure for shale samples than siltstone samples indicates that high pore pressure within rock matrix due to the strong penetration ability can greatly decrease the breakdown pressure. CO2 fracturing creates more loose particles and discrete blocks acting like proppants, and fracture aperture of CO2 fracturing is 2-5 times that of water fracturing. Multi-parallel fractures and bigger discrete blocks contribute to the low fracture compressibility, and the secondary shear fractures along the weak bedding planes in shale samples greatly increase the complexity of the fracture network.
Original languageEnglish (US)
Title of host publication55th U.S. Rock Mechanics / Geomechanics Symposium 2021
PublisherAmerican Rock Mechanics Association (ARMA)
ISBN (Print)9781713839125
StatePublished - Jan 1 2021
Externally publishedYes


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